title: Energy Stability in a High Intensity Pulsed SC Proton Linac

abstract:
  Spallation source dedicated for neutron scattering experiments, as well as
multi-purpose facilities serving several applications call for pulsed mode
operation of a high intensity proton linac. There is general agreement on the
superconducting technology for the high-energy part, which offers some
advantages, like higher gradient capabilities or operational costs reduction,
as compared to room-temperatures accelerating structures. This mode of
operation however could spoil the energy stability of the proton beam and needs
thus to be carefully studied. First, transient beam-loading effects, arising
from the large beam phase slippage along a multi-cell cavity and associated
with the finite RF energy propagation, can induce significant energy modulation
with a too small cell-to-cell coupling or a too large number of cells. Second,
due to beam phase slippage effects along the linac, energy spread exhibits a
larger sensitivity to cavity fields fluctuations than relativistic particles. A
computer code, initially developed for electron beams has been extended to
proton beams. It solves the 6xN coupled differential equations, needed to
describe cavity fields and beam-cavity interactions of a high-energy linac
composed of N cavities. Simulation examples on a typical pulsed accelerator are
given with various error sources, like Lorentz forces or microphonics detuning,
beam injection energy offsets, intensity jitters ...


title:
The Low Energy Beam Transport System of the New GSI High Current
  Injector

abstract:
  The UNILAC was improved for high current performance by replacing the Wideroe
prestripper accelerator by an RFQ and an IH-type DTL. In addition, one of two
ion source terminals was equipped with high current sources of MUCIS- and
MEVVA-type. Therefore, a redesign of the LEBT from the ion source to the RFQ
entrance was necessary. The new LEBT was installed at the beginning of 1999.
The commissioning was carried mainly with a high intense argon beam. The
achieved 17 emA Ar+ are 6 emA above the RFQ design intensity. The expected
performance of the new LEBT was achieved: full transmission for high current
beams, preservation of brilliance along the beam line, isotope separation for
all elements, transverse phase space matching to the RFQ linac, and macropulse
shaping. In particular, the high degree of space charge compensation was
confirmed.


title: Commissioning of the 1.4 Mev/u High Current Heavy Ion Linac at Gsi

abstract:
  The disassembly of the Unilac prestripper linac of the Wideroe type took
place at the beginning of 1999. An increase of more than two orders of
magnitude in particle number for the most heavy elements in the SIS had to be
gained. Since that time the new High Current Injector (HSI) consisting of
H-type RFQ and DTL-structures for dual beam operation was installed and
successfully commissioned. The High Charge Injector (HLI) supplied the main
linac during that time. Simultaneously conditioning and running in of the
rf-transmitters and rf-structures were done. The HSI commissioning strategy
included beam investigation after each transport and acceleration section,
using a versatile diagnostic test stand. Results of the extensive commissioning
measurements (e.g. transverse emittance, bunch width, beam transmission) behind
LEBT, RFQ, Super Lens, IH tank I and II and stripping section will be
discussed. An 40Ar1+ beam coming from a MUCIS ion source was used to fill the
linac up to the theoretical space charge limit. Routine operation started in
November 1999.


title:
The New Gas Stripper and Charge State Separator of the Gsi High Current
  Injector

abstract:
  The GSI Unilac was upgraded as a high current injector for the SIS in 1999.
Therefore, the stripping section [1] at 1.4 MeV/u, where a beam transport under
highest space charge conditions and multi beam operation had to be established,
was completely new designed. Results of the commissioning of the stripper
section will be presented. The beam transport to the new gas stripper, and the
charge state analysis under space charge conditions confirmed the calculations.
A 238U4+ beam - coming from a MEVVA ion source and accelerated by the new
injector linac- was stripped (with the expected stripping efficiency) to the
charge state 28+ and successfully separated by the new spectrometer (15 degree
and 30 degree kicker magnets). The transport and matching to the poststripper
accelerator under highest space charge conditions was investigated with a 15
emA 40Ar10+ beam. Especially space charge and charge state dependent emittance
growth effects in 6d-phase space will be discussed.


title: High-power Circulator Test Results at 350 MHz and 700 MHz

abstract:
  The high-power RF systems for the Accelerator Production of Tritium (APT)
program require high-power circulators at 350 MHz and 700 MHz to protect 1 MW
Continuous Wave (CW) klystrons from reflected power. The 350 MHz circulator is
based on the CERN, ESRF, and APS designs and has performed very well. The 700
MHz circulator is a new design. Prototype 700 MHz circulators have been
high-power tested at Los Alamos National Laboratory (LANL). The first of these
circulators has satisfied performance requirements. The circulator
requirements, results from the testing, and lessons learned from this
development are presented and discussed.


title:
Industrial Fabrication of Medium-Beta SCRF Cavities for a High-Intensity
  Proton Linac

abstract:
  During 1999, four 700-MHz, medium-beta (b = 0.64), superconducting radio
frequency (SCRF) cavities for a high-intensity proton linac project at Los
Alamos National Laboratory (LANL) were manufactured by industry. The SCRF
cavities were designed by a LANL team in Los Alamos, New Mexico, USA, and
manufactured at a CERCA plant in Romans, France. The cavities were made of
4-mm-thick, solid niobium sheets with a residual resistivity ratio (RRR)
greater than 250. These niobium sheets were supplied by Wah Chang (USA),
Heraeus AG (Germany), and Tokyo Denkai (Japan). The SCRF cavities were shipped
to LANL for performance testing. This paper describes the experience gained
during the manufacturing process at CERCA.


title: The Diffraction Model and its Applicability for Wakefield Calculations

abstract:
  The operation of a Free Electron Laser (FEL) in the ultraviolet or in the
X-ray regime requires the acceleration of electron bunches with an rms length
of 25 to 50 micro meters. The wakefields generated by these sub picosecond
bunches extend into the frequency range well beyond the threshold for Cooper
pair breakup (about 750 GHz) in superconducting niobium at 2 K. It is shown,
that the superconducting cavities can indeed be operated with 25 micro meter
bunches without suffering a breakdown of superconductivity (quench), however at
the price of a reduced quality factor and an increased heat transfer to the
superfluid helium bath. This was first shown by wakefield calculations based on
the diffraction model. In the meantime a more conventional method of computing
wake fields in the time domain by numerical methods was developed and used for
the wakefield calculations. Both methods lead to comparable results: the
operation of TESLA with 25 micro meter bunches is possible but leads to an
additional heat load due to the higher order modes (HOMs). Therefore HOM
dampers for these high frequencies are under construction. These dampers are
located in the beam pipes between the 9-cell cavities. So it is of interest, if
there are trapped modes in the cavity due to closed photon orbits. In this
paper we investigate the existence of trapped modes and the distribution of
heat load over the surface of the TESLA cavity by numerical photon tracking.


title:
Spectroscopic investigations of a dielectric-surface-discharge plasma
  source

abstract:
  Spectroscopic investigations of the properties of a plasma produced by a
flashboard plasma source, commonly used in pulsed plasma experiments, are
presented. The plasma is used to prefill a planar 0.4-ms-conduction time plasma
opening switch (POS). A novel gas-doping technique and a secondary surface
flashover plasma source are used to locally dope the plasma with gaseous and
solid materials, respectively, allowing for spatially-resolved measurements.
The electron density, temperature, and plasma composition are determined from
spectral line intensities and line profiles. Detailed collisional-radiative
modeling is used to analyze the observed line intensities. The propagation
velocity and divergence angle of various ions are determined from
time-of-flight measurements and Doppler broadening of spectral lines,
respectively. This allows for distinguishing the secondary plasma ejected from
the POS electrodes from the plasma of the flashboard source.


title:
Automated Operation of the APS LINAC using the Procedure Execution
  Manager

abstract:
  The Advanced Photon Source (APS) linear accelerator has two thermionic
cathode rf guns and one photocathode rf gun. The thermionic guns are used
primarily for APS operations while the photocathode gun is used as a
free-electron laser (FEL) driver. With each gun requiring a different lattice
and timing configuration, the need to change quickly between guns puts great
demands on the accelerator operators. Using the Procedure Execution Manager
(PEM), a software environment for managing automated procedures, we have made
start-up and switch-over of the linac systems both easier and more reliable.
The PEM is a graphical user interface written in Tcl/Tk that permits the user
to invoke "machine procedures" and control their execution. It allows
construction of procedures in a hierarchical, parallel fashion, which makes for
efficient execution and development. In this paper, we discuss the features and
advantages of the PEM environment as well the specifics of our procedures for
the APS linac.


title:
The quantum vacuum, fractal geometry, and the quest for a new theory of
  gravity

abstract:
  In this letter recent developments are shown in experimental and theoretical
physics which brings into question the validity of General Relativity. This
letter emphasizes the construction of a fractal 3+\phi^3 spacetime, in
N-dimensions in order to formalize a physical and consistent theory of `quantum
gravity.' It is then shown that a `quantum gravity' effect could arise by means
of the Strong Equivalence Principle. Which is made possible through a pressure
of the form -kappa(R^{ca}_{b}-{1\over 2}g^{c sigma}_{ab}R^c)=kappa T^{c
sigma}_{ab}. Where it is seen that nuclear pressures can be added to rethe
gravitational field equations by means of twistor spaces.


title: Beam Position-Phase Monitors for SNS Linac

abstract:
  Electromagnetic modeling with MAFIA of the combined beam position-phase
monitors (BPPMs) for the Spallation Neutron Source (SNS) linac has been
performed. Time-domain 3-D simulations are used to compute the signal
amplitudes and phases on the BPPM electrodes for a given processing frequency,
402.5 MHz or 805 MHz, as functions of the beam transverse position. Working
with a summed signal from all the BPPM electrodes provides a good way to
measure accurately the beam phase. While for an off-axis beam the signal phases
on the individual electrodes can differ from those for a centered beam by a few
degrees, the phase of the summed signal is found to be independent of the beam
transverse position inside the device. Based on the analysis results, an
optimal BPPM design with 4 one-end-shorted 60-degree electrodes has been
chosen. It provides a good linearity and sufficient signal power for both
position and phase measurements, while satisfying the linac geometrical
constrains and mechanical requirements.


title: Bridge Coupler for APT

abstract:
  The Coupled Cavity Drift Tube Linac (CCDTL) used in the Accelerator for the
Production of Tritium (APT) is fully described elsewhere [1]. The modules are
composed of several machined and brazed segments that must account for the
accumulation of dimensional tolerances in the build up of the stack. In
addition, space requirements dictate that power fed to the accelerator cannot
be through the accelerating cavities. As well, we would like to remove a single
segment of the accelerator without removing additional segments. These
requirements combined with phasing relationships of the design and space
limitations have resulted in a different bridge coupling method used in the
module comprising 3-gap segments. The coupling method, phasing relationships
and other features that enhance the flexibility of the design will be
discussed.


title:
LEDA Beam Operations Milestone and Observed Beam Transmission
  Characteristics

abstract:
  Recently, the Low-Energy Demonstration Accelerator (LEDA) portion of the
Accelerator Production of Tritium (APT) project reached its 100-mA, 8-hr CW
beam operation milestone. LEDA consists of a 75-keV proton injector, 6.7-MeV,
350-MHz CW radio-frequency quadrupole (RFQ) with associated high-power and
low-level rf systems, a short high-energy beam transport (HEBT) and high-power
(670-kW CW) beam dump. During the commissioning phase it was discovered that
the RFQ field level must to be approximately 5-10% higher than design in order
to accelerate the full 100-mA beam with low losses. Measurements of a
low-duty-factor, 100-mA beam show the beam transmission is unexpectedly low for
RFQ field levels between ~90 and 105% of design. This paper will describe some
aspects of LEDA operations critical to achieving the above milestone.
Measurement and simulation results for reduced RFQ beam transmission near
design operating conditions are also presented.


title: RF Control System for the NLC Linacs

abstract:
  The proposed Next Linear Collider contains a large number of linac RF systems
with new requirements for wideband klystron modulation and accurate RF vector
detection. The system will be capable of automatically phasing each klystron
and compensating for beam loading effects. Accelerator structure alignment is
determined by detection of the beam induced dipole modes with a receiver
similar to that used for measuring the accelerator RF and is incorporated into
the RF system topology. This paper describes the proposed system design, signal
processing techniques and includes preliminary test results.


title: RF Cell Modeling and Experiments for Wakefield Minimization in DARHT-II

abstract:
  Electron beams of linear induction accelerators experience deflective forces
caused by RF fields building up as a result of accelerating cavities of finite
size. These forces can significantly effect the beam when a long linac composed
of identical cells is assembled. Recent techniques in computational modeling,
simulation, and experiments for 20 MeV DARHT-II (Dual Axis Radiographic
Hydrodynamic Test) accelerator cells were found to reduce the wakefield
impedance of the cells from 800 ohms/meter to 350 ohms/meter and experimental
results confirm the results of the modeling efforts. Increased performance of
the cell was obtained through a parametric study of the accelerator structure,
materials, material tuning, and geometry. As a result of this effort, it was
found that thickness-tuned ferrite produced a 50% deduction in the wakefield
impedance in the low frequency band and was easily tunable based on the
material thickness. It was also found that shaped metal sections allow for
high-Q resonances to be de-tuned, thus decreasing the amplitude of the
resonance and increasing the cell s performance. For the geometries used for
this cell, a roughly 45 degree angle had the best performance in affecting the
wakefield modes.


title: Test of accelerating structure for VEPP-5 preinjector

abstract:
  Preinjector VEPP-5 electron linac consists of two linear accelerators on
energy 300 MeV and 510 MeV and includes 14 accelerating structures [1]. First
accelerating structures both linacs have increased average rate of acceleration
25-30 MeV/m, and other regular sections up to 17-20 MeV/m. This paper presents
the results of basic test of 3-meter long accelerating structure. Average rate
of acceleration of an electron beam 35 MeV/m was achieved. The electron beam
energy up to 105 MeV was obtained.


title: The CLIC Main Linac Accelerating Structure

abstract:
  This paper outlines the RF design of the CLIC (Compact Linear Collider) 30
GHz main linac accelerating structure and gives the resulting longitudinal and
transverse mode properties. The critical requirement for multibunch operation,
that transverse wakefields be suppressed by two orders of magnitude within 0.7
ns (twenty fundamental mode cycles), has been demonstrated in a recent ASSET
experiment. The feasibility of operating the structure at an accelerating
gradient of 150 MV/m for 130 ns has yet to be demonstrated. Damage of the
internal copper surfaces due to high electric fields or resulting from metal
fatigue induced by cyclic surface heating effects are a major concern requiring
further study.


title: Tests of the CERN Proton Linac Performance for LHC-Type Beams

abstract:
  As the pre-injector of the LHC injector chain, the proton linac at CERN is
required to provide a high-intensity (180mA) beam to the Proton Synchrotron
Booster. The results of measurements at this intensity will be presented.
Furthermore, the linac is now equipped with bunch shape monitors from INR,
Moscow, which have allowed the comparison of the Alvarez tank RF settings with
simulations.


title:
Measurement of the six Dimensional Phase Space at the New GSI High
  Current Linac

abstract:
  For the characterization of the 10 mA ion beam delivered by the new High
Current Linac at GSI, sophisticated, mainly non-intersepting diagnostic devices
were developed. Besides the general set-up of a versatile test bench, we
discuss in particular bunch shape and emittance measurements. A direct
time-of-flight technique with a diamond particle detector is used to observe
the micro-bunch distribution with a resolution of $\sim 25 $ ps equals
0.3$^{o}$ in phase. For the determination of the energy spread a coincidence
technique is applied, using secondary electrons emitted by the ion passing
through an aluminum foil 80 cm upstream of the diamond detector. The transverse
emittance is measured within one macro pulse with a pepper-pot system equipped
with a high performance CCD camera.


title: Superconducting Superstructure for the TESLA Collider: New Results

abstract:
  A new cavity-chain layout has been proposed for the main linac of the TESLA
linear collider. This superstructure-layout is based upon four 7-cell
superconducting standing-wave cavities, coupled by short beam pipes. The main
advantages of the superstructure are an increase in the active accelerating
length in TESLA and a saving in rf components, especially power couplers, as
compared to the present 9-cell cavities. The proposed scheme allows to handle
the field-flatness tuning and the HOM damping at sub-unit level, in contrast to
standard multi-cell cavities. The superstructure-layout is extensively studied
at DESY since 1999. Computations have been performed for the rf properties of
the cavity-chain, the bunch-to-bunch energy spread and multibunch dynamics. A
copper model of the superstructure has been built in order to compare with the
simulations and for testing the field-profile tuning and the HOM damping
scheme. A "proof of principle" niobium prototype of the superstructure is now
under construction and will be tested with beam at the TESLA Test Facility in
2001. In this paper we present latest results of these investigations.


title: Beam Dynamics Studies for a High Current Ion Injector

abstract:
  Recent ion source developments resulted in the generation of high brilliance,
high current beams of protons and light ions. After extraction and transport
the beams with large internal space charge forces have to be captured, bunched
and preaccelerated for the injection into the following driver part of a new
generation of high intensity beam facilities for neutron sources, energy
production, transmutation e.g. A combination of RFQ and DTL is considered to be
a good solution for such a high current ion injector. Some preliminary beam
dynamics layouts have been investigated by multiparticle simulations. Basic
parameters like frequency, ion energy and sparking have been varied for the
International Fusion Material Irradiation Facility (IFMIF) scenario as an
example. The main interest was directed to high transmission, low losses and
emittance conservation. The beam matching to the RFQ is shortly discussed as
well as the matching between RFQ and DTL.


title: High Current Beam Dynamics in an Ess SC Linac

abstract:
  Three alternative designs of the European Spallation Source (ESS) high energy
linac are described. The most promising ones are either a normalconducting (nc)
coupled cavity linac (CCL) up tofinal energy or a change at 407 MeV to only one
group of 6 cell superconducting (sc) elliptical cavities.
  Fully 3d Monte Carlo simulations are presented for both options, optimized
for reduced halo formation at the linac end. For the error free matched case,
especially the halo formation in the longitudinal plane is more pronounced for
the hybrid solution with its superconducting cavities, caused by the
unavoidable phase slippage, but still quite well acceptable for loss free ring
injection. Simulations however for a 30% mismatched dense core, surrounded in
addition by 1.5% halo particles are showing few particles with very large
amplitudes even in real space. This case represents halo formation in front to
end simulations, caused by current fluctuations, filamented RFQ output
distribution and enhanced by accumulated field errors.


title:
Studies of Coupled Cavity Linac (CCL) Accelerating Structures with 3-D
  Codes

abstract:
  The cw CCL being designed for the Accelerator Production of Tritium (APT)
project accelerates protons from 96MeV to 211MeV. It consists of 99 segments
each containing up to seven accelerating cavities. Segments are coupled by
intersegment coupling cavities and grouped into supermodules. The design method
needs to address not only basic cavity sizing for a given coupling and pi/2
mode frequency, but also the effects of high power densities on the cavity
frequency, mechanical stresses, and the structure's stop band during operation.
On the APT project, 3-D RF (Ansoft Corp.'s HFSS) and coupled RF/structural
(Ansys Inc.'s ANSYS) codes are being used to develop tools to address the above
issues and guide cooling channel design. The code's predictions are being
checked against available low power Aluminum models. Stop band behavior under
power will be checked once the tools are extended to CCDTL structures that have
been tested at high power. A summary of calculations made to date and agreement
with measured results will be presented.


title: Estimates of dispersive effects in a bent NLC main linac

abstract:
  An alternative being considered for the Next Linear Collider (NLC) is not to
tunnel in a straight line but to bend the Main Linac into an arc so as to
follow an equipotential. We begin here an examination of the effects that this
would have on vertical dispersion, with its attendant consequences on
synchrotron radiation and emittance growth by looking at two scenarios: a
gentle continuous bending of the beam to follow an equipotential surface, and
an introduction of sharp bends at a few sites in the linac so as to reduce the
maximum sagitta produced.


title: Analyses of klystron modulator approaches for NLC

abstract:
  Analyze of experimental results shows that the energy discharge efficiency of
the modern modulators is 0.92-0.93. The energy transfer efficiency can be
reached up to 0.7 for 1.5 usec pulse width and up to 0.8 for 3.0 usec
accordingly. The geometry and core material of the transformer is one element
of modulator, which limits the efficiency due to limitation if transmission
band of the pulse power. Ways of the rise of energy transfer efficiency had
been discussed. The use of features of coupled transmission lines lies in the
base of an idea how the energy transfer efficiency can be improved up to 0.85
in the frame of the conventional approach. In the second part of the paper the
transformerless modulator approaches are presented upon a modified Marx method
of voltage multiplication using on/off IGBT instead of on switches.


title: Operational Aspects of the High Current Upgrade at the Unilac

abstract:
  With the new GSI High Current Injector, the beam pulse intensity will be
increased by more than two orders of magnitude. The high beam power and the
short stopping range at particle energies below 12 MeV/u can destroy
accelerator components even during a single beam pulse. Therefore, the
operation of the whole accelerator facility has required major changes in
hardware, software and operating strategy. A sophisticated beam diagnostic
system is indispensable for a safe operation. Preferably non-destructive
devices were installed. Destructive elements, e.g. beam stoppers, slits,
apertures, were improved in order to withstand the high beam power. Automatic
damage prevention was realised by beam loss monitors comparing and evaluating
very fast beam current transformer signals. Additionally, the component status
will be controlled permanently. For foil stripping at 11.4 MeV/u, a magnetic
beam sweeping system was installed Thereby, the hit area will be increased
during one 100 micro sec pulse. During operation, manual variation of
parameters has to be reduced. Set-up and automatic beam adjustment procedures
have to exclude uncontrolled beam loss. The versatility of the UNILAC is
enhanced by the possible three-beam operation on a pulse-to-pulse basis. Since
November 1999 the upgraded UNILAC is serving the experiments.


title: Looking Forward to Pricing Options from Binomial Trees

abstract:
  We reconsider the valuation of barrier options by means of binomial trees
from a "forward looking" prospective rather than the more conventional
"backward induction" one used by standard approaches. This reformulation allows
us to write closed-form expressions for the value of European and American put
barrier-options on a non-dividend-paying stock.


title:
Design and Performance Simulations of the Bunch Compressor for the APS
  LEUTL FEL

abstract:
  A magnetic bunch compressor has been designed and is being commissioned for
the APS linac to provide higher peak current for the LEUTL FEL. Of primary
concern is control of emittance growth due to coherent synchrotron radiation
(CSR). In addition, tolerances must be carefully evaluated in order to choose
the most stable operating conditions and ensure that the system can meet
operational goals. The computer code ELEGANT was used to design the bunch
compressor, set tolerances, and simulate likely performance. This 6-D code
includes a fast, simple simulation of CSR effects as well as longitudinal and
transverse wakefields. It also is believed to be unique in allowing
optimization of actual tracking results, such as bunch length, energy spread,
and emittance. Automated setup and analysis of matching and tolerance
simulations allowed consideration of numerous configurations without excessive
effort. This permitted choosing configurations that reduce sensitivity to
errors. Simulations indicate that emittance growth should be tolerable for up
to 600 A peak current, for which the normalized emittance will increase from 5
to about 6.8 pi-um. The simulations also provide predictions of emittance
variation with chicance parameters, which we hope to verify experimentally. *
Work supported by the U.S. Department of Energy, Office of Basic
  Energy Sciences, under Contract No. W-31-109-ENG-38.


title: Design of the SNS Normal Conducting Linac RF Control System

abstract:
  The Spallation Neutron Source (SNS) is being designed for operation in 2004.
The SNS is a 1 GeV machine consisting of a combination normal-conducting and
super-conducting linac as well as a ring and target area. The linac front end
is a 402.5 MHz RFQ being developed by Lawrence Berkeley Lab. The DTL (at 402.5
MHz) and the CCL (at 805 MHz) stages are being developed by Los Alamos National
Laboratory. The expected output energy of the DTL is 87 MeV and that of the CCL
is 185 MeV. The RF control system under development for the linac is based on
the Low Energy Demonstration Accelerator (LEDA) control system with some new
features. This paper will discuss the new design approach and its benefits.
Block diagrams and circuit specifics will be addressed. The normal conducting
RF control system will be described in detail with references to the
super-conducting control system where appropriate.


title: A Highly Flexible Bunch Compressor for the APS LEUTL FEL

abstract:
  The LEUTL FEL at the APS has achieved gain at 530 nm with peak beam current
\~100 A. In an effort to push to 120 nm and beyond, we have designed and are
commissioning a bunch compressor to increase the peak current to 600 A or more.
The bunch compressor uses a four-dipole chicane at an energy of 100 to 210 MeV.
To provide options for control of emittance growth due to coherent synchrotron
radiation (CSR), the chicane has variable R56. The central pair of dipoles is
movable, accommodating variable R56 with less concern about emittance dilution
from nonuniformity of the dipole field. The symmetry of the chicane is also
variable via longitudinal motion of the final dipole, which is predicted to
have an effect on emittance growth. Following the chicane, a three-screen
emittance measurement system should permit resolution of the difference in
emittance growth between various chicane configurations. A vertical bending
magnet analysis line is present to permit imaging of correlations between
transverse and energy coordinates. This paper reviews the features and expected
performance of the chicane. A companion paper discusses the physics design in
detail.
  Work supported by the U.S. Department of Energy, Office of Basic Energy
Sciences, under Contract No. W-31-109-ENG-38.


title: Space Charge Effects in Bunch Shape Monitors

abstract:
  The operation and parameters of Bunch Shape Monitors using coherent
transformation of time structure of an analyzed beam into a spatial one of low
energy secondary electrons emitted from a wire target is influenced by the
characteristics of a beam under study. The electromagnetic field of a bunch
disturbs the trajectories of secondary electrons, thus resulting in a
degradation of phase resolution and in errors of phase reading. Another effect
is the perturbation of the target potential due to the current in the wire
induced by a bunch as well as due to current compensating emission of the
secondary electrons. The methods, the models and the results of simulations are
presented.


title:
Use of Coherent Transition Radiation to Set Up the APS RF Thermionic Gun
  to Produce High-Brightness Beams for SASE FEL Experiments

abstract:
  We describe use of the Advanced Photon Source (APS) rf thermionic gun, alpha
magnet beamline, and linac to produce a stable high-brightness beam in excess
of 100 amperes peak current with normalized emittance of 10 pi mm-mrad. To
obtain peak currents greater than 100 amperes, the rf gun system must be tuned
to produce a FWHM bunch length on the order of 350 fs. Bunch lengths this short
are measured using coherent transition radiation (CTR) produced when the rf gun
beam, accelerated to 40 MeV, strikes a metal foil. The CTR is detected using a
Golay detector attached to one arm of a Michelson interferometer. The alpha
magnet current and gun rf phase are adjusted so as to maximize the CTR signal
at the Golay detector, which corresponds to the minimum bunch length. The
interferometer is used to measure the autocorrelation of the CTR radiation. The
minimum phase approximation is used to derive the bunch profile from the
autocorrelation. The high-brightness beam is accelerated to 217 MeV and used to
produce SASE in five APS undulators installed in the Low- Energy Undulator Test
Line (LEUTL) experiment hall. Initial optical measurements showed a gain length
of 1.3 m at 530 nm. * Work supported by U. S. Department of Energy, Office of
Basic Energy Sciences, under Contract No. W-31-109-ENG-38.


title:
Coherent Synchrotron Radiation Measurements in the CLIC Test Facility
  (CTF II)

abstract:
  Bunches of high charge (up to 10 nC) are compressed in length in the CTF II
magnetic chicane to less than 0.2 mm rms. The short bunches radiate coherently
in the chicane magnetic field, and the horizontal and longitudinal phase space
density distributions are affected. This paper reports the results of beam
emittance and momentum measurements. Horizontal and vertical emittances and
momentum spectra were measured for different bunch compression factors and
bunch charges. In particular, for 10 nC bunches, the mean beam momentum
decreased by about 5% while the FWHM momentum spread increased from 5% to 19%.
The experimental results are compared with simulations made with the code
TraFiC4.


title: Physics Design Considerations of Diagnostic X Beam Transport System

abstract:
  Diagnostic X (D-X) transport system would extract the beam from the
downstream transport line of the second- axis of the Dual Axis Radiographic
Hydrodynamic Test facility (DARHT-II) and transport this beam to the D-X firing
point via four branches of the beamline in order to provide four lines of sight
for x-ray radiography. The design goal is to generate four DARHT-II-like x-ray
pulses on each line of sight. In this paper, we discuss several potential beam
quality degradation processes in the passive magnet lattice beamline and
indicate how they constrain the D-X beamline design parameters, such as the
background pressure, the pipe size, and the pipe material


title: Physics Design of the ETA-II/Snowtron Double Pulse Target Experiment

abstract:
  We have modified the single pulse target experimental facility[ ] on the
Experimental Test Accelerator II (ETA-II) to perform the double pulse target
experiments to validate the DARHT-II[, ] multi-pulse target concept. The 1.15
MeV, 2 kA Snowtron injector will provide the first electron pulse. The 6 MeV, 2
kA ETA-II beam will be used as the probe beam. Our modeling indicates that the
ETA-II/Snowtron experiment is a reasonable scaling experiment.


title: A New Linear Inductive Voltage Adder Driver for the Saturn Accelerator

abstract:
  Saturn is a dual-purpose accelerator. It can be operated as a large-area
flash x-ray source for simulation testing or as a Z-pinch driver especially for
K-line x-ray production. In the first mode, the accelerator is fitted with
three concentric-ring 2-MV electron diodes, while in the Z-pinch mode the
current of all the modules is combined via a post-hole convolute arrangement
and driven through a cylindrical array of very fine wires. We present here a
point design for a new Saturn class driver based on a number of linear
inductive voltage adders connected in parallel. A technology recently
implemented at the Institute of High Current Electronics in Tomsk (Russia) is
being utilized[1].
  In the present design we eliminate Marx generators and pulse-forming
networks. Each inductive voltage adder cavity is directly fed by a number of
fast 100-kV small-size capacitors arranged in a circular array around each
accelerating gap. The number of capacitors connected in parallel to each cavity
defines the total maximum current. By selecting low inductance switches,
voltage pulses as short as 30-50-ns FWHM can be directly achieved.


title: Toutatis, the Cea-Saclay RFQ code

abstract:
  A CW high power linear accelerator can only work with very low particles
losses and structure activation. At low energy, the RFQ is a very sensitive
element to losses. To design the RFQ, a good understanding of the beam dynamics
is requested. Generally, the reference code PARMTEQM is enough to design the
accelerator. TOUTATIS has been written with goals of cross-checking results and
obtaining a more reliable dynamics. This paper relates the different numerical
methods used in the code. It is time-based, using multigrids methods and
adaptive mesh for a fine description of the forces without being time
consuming.
  The field is accurately calculated through a Poisson solver and the vanes are
fully described, allowing to properly simulate the coupling gaps and RFQs
extremities. Differences with PARMTEQM and LIDOS.RFQ are shown.


title:
RF System Upgrades to the Advanced Photon Source Linear Accelerator in
  Support of the Fel Operation

abstract:
  The S-band linear accelerator, which was built to be the source of particles
and the front end of the Advanced Photon Source injector, is now also being
used to support a low-energy undulator test line (LEUTL) and to drive a
free-electron laser (FEL). The more severe rf stability requirements of the FEL
have resulted in an effort to identify sources of phase and amplitude
instability and implement corresponding upgrades to the rf generation chain and
the measurement system. Test data and improvements implemented and planned are
described


title: Status of Superconducting RF Linac Development for APT

abstract:
  This paper describes the development progress of high current superconducting
RF linacs in Los Alamos, performed to support a design of the linac for the APT
(Accelerator Production of Tritium) Project. The APT linac design includes a CW
superconducting RF high energy section, spanning an energy range of 211 to 1030
MeV, and operating at a frequency of 700 MHz with two constant beta sections
(beta of 0.64 and 0.82). In the last two years, we have progressed towards
build a cryomodule with beta of 0.64. We completed the designs of the 5 cell
superconducting cavities and the 210 kW power couplers. We are scheduled to
begin assembly of the cryomodule in September 2000. In this paper, we present
an overview of the status of our development efforts and a report on the
results of the cavity and coupler test program.


title: Analysis of longitudinal bunching inan FEL driven two-beam accelerator

abstract:
  Recent experiments [1] have explored the use of a free-electron laser (FEL)
as a buncher for a microwave two-beam accelerator, and the subsequent driving
of a standing-wave rf output cavity. Here we present a deeper analysis of the
longitudinal dynamics of the electron bunches as they are transported from the
end of the FEL and through the output cavity. In particular, we examine the
effect of the transport region and cavity aperture to filter the bunched
portion of the beam.
  [1] T. Lefevre, et. al., Phys. Rev. Lett. 84 (2000), 1188.


title:
Progress on the 140 KV, 10 Megawatt Peak, 1 Megawatt Average Polyphase
  Quasi-Resonant Bridge, Boost Converter/Modulator for the Spallation Neutron
  Source (SNS) Klystron Power System

abstract:
  This paper describes electrical design and operational characteristics of a
zero-voltage-switching 20 kHz polyphase bridge, boost converter/modulator for
klystron pulse application. The DC-DC converter derives the buss voltages from
a standard 13.8 kV to 2300 Y substation cast-core transformer. Energy storage
and filtering is provided by self-clearing metallized hazy polypropylene
traction capacitors. Three "H-Bridge" IGBT switching networks are used to
generate the polyphase 20 kHz transformers primary drive waveforms. The 20 kHz
drive waveforms are chirped the appropriate duration to generate the desired
klystron pulse width. PWM (pulse width modulation) of the individual 20 kHz
pulses is utilized to provide regulated output waveforms with adaptive
feedforward and feedback techniques. The boost transformer design utilizes
amorphous nanocrystalline material that provides the required low core loss at
design flux levels and switching frequencies. Resonant shunt peaking is used on
the transformer secondary to boost output voltage and resonate transformer
leakage inductance. With the appropriate transformer leakage inductance and
peaking capacitance, zero-voltage-switching of the IGBT's is attained,
minimizing switching losses. A review of these design parameters and a
comparison of computer calculations, scale model, and first article results
will be performed.


title:
The RTA Betatron-Node Experiment: Limiting Cumulative BBU Growth In A
  Linear Periodic System

abstract:
  The successful operation of a Two-Beam accelerator based on extended
relativistic klystrons hinges upon decreasing the cumulative dipole BBU growth
from an exponential to a more manageable linear growth rate. We describe the
theoretical scheme to achieve this, and a new experiment to test this concept.
The experiment utilizes a 1-MeV, 600-Amp, 200-ns electron beam and a short
beamline of periodically-spaced rf dipole-mode pillbox cavities and solenoid
magnets for transport. Descriptions of the beamline are presented, followed by
theoretical studies of the beam transport and dipole-mode growth.


title: Simulation of Returning Electrons from a Klystron Collector

abstract:
  Spurious oscillations in klystrons due to returning electrons from the
collector into the drift tube were observed and studied at KEK. Simulations of
returning electrons using EGS4 Monte Carlo method have been performed. And the
oscillation conditions are described in this paper.


title:
Simulation of an Intra-Pulse Interaction Point Feedback for Future
  Linear Colliders

abstract:
  In future normal-conducting linear colliders, the beams will be delivered in
short bursts with a length of the order of 100 ns. The pulses will be separated
by several ms. In order to maintain high luminosity, feedback is necessary on a
pulse-to-pulse basis. In addition, intra-pulse feedback that can correct beam
positions and angles within one pulse seem technically feasible. The likely
performances of different feedback options are simulated for the NLC (Next
Linear Collider) and CLIC (Compact Linear Collider).


title:
Towards Reliable Acceleration of High-energy and High-intensity Electron
  Beams

abstract:
  KEK electron linac was upgraded to 8 GeV for the KEK B-Factory (KEKB)
project. During the commissioning of the upgraded linac, even continuing SOR
ring injections, we had achieved a primary electron beam with 10-nC (6.24 x
10^10) per bunch up to 3.7-GeV for positron generation. This could be
classified as one of the brightest S-band linac's.
  Since the KEKB rings were completed in December 1998, those 3.5-GeV position
and 8-GeV electron beams have been injected with an excellent performance.
Moreover, we have succeeded in switching among the high-intensity beams for
KEKB and beams for two SOR rings with sufficient reproducibility.
  After the commissioning of the KEKB ring started, we have launched a project
to stabilize the intensity and quality of the high-current beams furthermore,
and have accomplished it investigating every conceivable aspect.


title:
A Low Charge Demonstration of Electron Pulse Compression for the CLIC RF
  Power Source

abstract:
  The CLIC (Compact Linear Collider) RF power source is based on a new scheme
of electron pulse compression and bunch frequency multiplication using
injection by transverse RF deflectors into an isochronous ring. In this paper,
we describe the modifications needed in the present LEP Pre-Injector (LPI)
complex at CERN in order to perform a low-charge test of the scheme. The design
of the injector (including the new thermionic gun), of the modified linac, of
the matched injection line, and of the isochronous ring lattice, are presented.
The results of preliminary isochronicity measurements made on the present
installation are also discussed.


title: Beam Dynamics Simulation for the CTF3 Drive-Beam Accelerator

abstract:
  A new CLIC Test Facility (CTF3) at CERN will serve to study the drive beam
generation for the Compact Linear Collider (CLIC). CTF3 has to accelerate a 3.5
A electron beam in almost fully-loaded structures. The pulse contains more than
2000 bunches, one in every second RF bucket, and has a length of more than one
microsecond. Different options for the lattice of the drive-beam accelerator
are presented, based on FODO-cells and triplets as well as solenoids. The
transverse stability is simulated, including the effects of beam jitter,
alignment and beam-based correction.


title: Beam Loading Compensation in the Main Linac of CLIC

abstract:
  Compensation of multi-bunch beam loading is of great importance in the main
linac of the Compact Linear Collider (CLIC). The bunch-to-bunch energy
variation has to stay below 1 part in 1000. In CLIC, the RF power is obtained
by decelerating a drive beam which is formed by merging a number of short bunch
trains. A promising scheme for tackling beam loading in the main linac is based
on varying the lengths of the bunch trains in the drive beam. The scheme and
its expected performance are presented.


title: Double Kicker system in ATF

abstract:
  A double kicker system which extracts the ultra-low emittance multi-bunch
beam stably from ATF damping ring was developed. The performance of the system
was studied comparing an orbit jitter with single kicker extraction in single
bunch mode. The position jitter reduction was estimated from the analysis of
the extraction orbits. The reduction was confirmed for the double kicker system
within a resolution of BPMs. More precise tuning of the system with a wire
scanner has been tried by changing a beta function at the second kicker to get
more reduction of kick angle jitter. The results of these studies are described
in detail.


title: Beam Switching and Beam Feedback Systems at KEKB Linac

abstract:
  The KEK 8-GeV electron / 3.5-GeV positron linac has been operated with very
different beam specifications for downstream rings, KEKB, PF and PF-AR. For the
reliable operation among these beam modes intelligent beam switching and beam
feedback systems have been developed and used since its commissioning.
  A software panel is used to choose one of four beam modes and a switching
sequence is executed in about two minutes. Most items in a sequence are simple
operations followed by failure recoveries. The magnet standardization part
consumes most of the time. The sequence can be re-arranged easily by
accelerator operators. Linac beam modes are switched about fifty times a day
using this software.
  In order to stabilize linac beam energy and orbits, as well as some
accelerator equipment, about thirty software beam feedback loops have been
installed. They have been utilized routinely in all beam modes, and have
improved its beam quality. Since its software interfaces are standardized, it
is easy to add new feedback loops simply defining monitors and actuators.


title:
The RF-System of the New Gsi High Current Linac Hsithe RF-System of the
  New Gsi High Current Linac Hsi

abstract:
  The RF part of the new high current injector-linac HSI consists of five
cavities with the new operating frequency of 36 MHz instead of 27 MHz of the
removed Wideroe type injector. The calculated power requirements of the
cavities including beam load in three structures were between 110 kW for a
rebuncher and 1.75 MW pulse-power for the two IH-cavities. The beam load is up
to 150 kW for the RFQ and up to 750 kW for the two drift tube tanks. An
additional 36 MHz debuncher in the transfer line to the Synchrotron (SIS) will
need 120 kW pulse power. We decided to fulfil these demands with amplifiers of
only two power classes, namely three amplifiers with 2 MW and six amplifiers
with 200 kW pulse output power. The latter ones are also used as drivers for
the 2 MW stages. The 200 kW amplifiers were specified in detail by GSI and
ordered in the industry. The three 2 MW final amplifiers were designed,
constructed and built by GSI. The paper gives an overview of the complete RF
system and the operating performance of amplitude and phase control with beam
load. It further describes some specialities of the new 2 MW amplifiers like
the simplicity of the anode circuit, a very sophisticated socket for a cathode
driven amplifier with cathode on dc ground, the parasitic mode-suppression,
shielding and filtering of unallowable RF-radiation and operating experience
since October 1999.


title: Commissioning of Ih-RFQ and Ih-DTL for the Gsi High Current Linac

abstract:
  The new 1.4 MeV/u front end HSI (HochStromInjektor) of the Unilac accelerates
ions with A/q ratios of up to 65 and with beam intensities in emA of up to 0.25
A/q. The maximum beam pulse power is up to 1300 kW. During the stepwise linac
commissioning from April to Septem-ber 1999 the beam behind of each cavity was
analysed within two weeks. A very stable Ar1+ beam out of a vol-ume plasma
source MUCIS was used mainly. The meas-ured norm. 80 % emittance areas around
0.45 pi mm mrad are close to the results from beam simulations. Up to 80 % of
the design intensity at the linac exit were achieved. In February 2000 an U4+
beam from the MEVVA source was accelerated for the first time.


title: Main steps for the fabrication of IPHI RFQ

abstract:
  The RFQ of the project IPHI is a 8 meter long, high power, very precise
tolerances (0.01 mm on 1 meter long for example) device to accelerate protons.
This RFQ is similar to the RFQ of the LEDA project. So, we realize a thermal
and mechanical studies followed by different tests for machining and brazing
copper. We describe in this paper those different steps and the way we proceed
to supply the fabrication itself by an independent company.


title:
Results on Plasma Focusing of High Energy Density Electron and Positron
  Beams

abstract:
  We present results from the SLAC E-150 experiment on plasma focusing of high
energy density electron and, for the first time, positron beams. We also
discuss measurements on plasma lens-induced synchrotron radiation, longitudinal
dynamics of plasma focusing, and laser- and beam-plasma interactions.


title:
Frequency dependent hyperpolarizabilities of atoms; calculations using
  density-functional theory

abstract:
  Using the orbitals generated by the van Leeuwen-Baerends potential, we
calculate frequency dependent response properties of noble gas atoms of He, Ne
and Ar and alkaline earth atoms Be and Mg, with particlar emphasis on their
nonlinear polarizabilities. For this we employ time-dependent Kohn-Sham
formalism with adiabatic local-density aproximation (ALDA) for exchange and
correlation. We show that results thus obtained for frequency dependent
polarizabilities of the inert gas atoms are highly acurate. On the other hand,
polarizabilities of the alkaline earths are not given with the same accuracy.
In light of this, we make an assessment of ALDA for obtaining linear and
nonlinear response properties by employing time-dependent density-functional
theory.


title: A 3.0mev Komac/KTF RFQ Linac

abstract:
  The Radio-Frequency Quadrupole (RFQ) linac that will accelerate a 20mA proton
beam from 50keV to 3MeV has been designed and is being fabricated as the first
phase, KOMAC Test Facility (KTF), of the Korea Multipurpose Accelerator Complex
(KOMAC) project at the Korea Atomic Energy Research Institute (KAERI). The
physical, engineering designs and fabrication status of the RFQ are described.


title: Development of the Low Energy Accelerator for Komac

abstract:
  KAERI (Korea Atomic Energy Research Institute) has been performing the
project named KOMAC (Korea Multi-purpose Accelerator Complex) within the frame
work of national mid and long term nuclear research plan. The final objectives
of KOMAC is to build a 20-MW (1 GeV and 20 mA) cw (100% duty factor) proton
linear accelerator. As the first stage, the low energy accelerator up to 20 MeV
is being developed in KTF (KOMAC Test Facility). The low energy accelerator
consists of an injector, RFQ, CCDTL, and RF systems. The proton injector with
Duoplasmatron ion source has been developed, and the LEBT with solenoid lens is
under development. The RFQ linac that will accelerate a 20mA proton beam from
50keV to 3MeV has been designed and is being fabricated. The RF system for RFQ
is being developed, and the CCDTL up to 20MeV is being designed. The status of
the low energy accelerator will be presented.


title: A High-Intensity H- Linac at CERN Based on LEP-2 Cavities

abstract:
  In view of a possible evolution of the CERN accelerator complex towards
higher proton intensities, a 2.2 GeV H- linac with 4 MW beam power has been
designed, for use in connection with an accumulator and compressor ring as
proton driver of a muon-based Neutrino Factory. The high-energy part of this
linac can use most of the RF equipment (superconducting cavities and klystrons)
from the LEP collider after its decommissioning at the end of 2000. Recent
results concerning low-beta superconducting cavities are presented, and the
main characteristics of the linac design are described. The complete
linac-based proton driver facility is outlined, and the impact on the linac
design of the requirements specific to a Neutrino Factory is underlined.


title: An ECR hydrogen negative ion source at CEA/Saclay: preliminary results

abstract:
  The development of a high intensity negative ion source is part of a
considerably larger activity presently undergoing at CEA Saclay in the field of
high intensity linear accelerators. Preliminary studies toward the construction
of a 2.45 GHz ECR H- ion source have been performed for few months. This new
test bench takes advantage of our experience on the French high intensity
proton source SILHI. In the new source, the high-energy electrons created in
the ECR zone are trapped by a dipole magnetic filter. A rectangular 200 mm long
plasma chamber and an intermediate iron shield are used to minimize the
magnetic field in the extraction region. A second magnetic filter separates
electrons and negative ions in a 10 kV extraction system. To reduce the
electron/H- ratio, the plasma electrode is slightly polarized. The design
allows future evolutions such as cesium injection, higher energy extraction and
plasma diagnostics. The installation of the source is now in progress. The
first helium plasma has been produced for few weeks to verify the electron
separator behavior. The design, computations and the first results of the
source are presented.


title: Design of the Ess RFQs and Chopping Line

abstract:
  The chopping line is a critical part of the ESS linac in term of technical
realisation of the choppers and preservation of the beam qualities. A new
optimised design of the ESS RFQs and chopping lines is reported. The beam
dynamics has been optimised with H- beam currents up to 100-mA to have safety
margin with respect to the ESS goals. The first RFQ transmits almost 99.7% of
the beam up to 2 MeV. The line with two choppers allows a perfect chopping
between 2 bunches. The second RFQ accelerates the particles up to 5 MeV with a
transmission close to 100%.


title: Status Report on the 5 Mev Iphi RFQ

abstract:
  A 5-MeV RFQ designed for a proton current up to 100-mA CW is now under
construction as part of the High Intensity Proton Injector project (IPHI). Its
computed transmission is greater than 99 %. The main goals of the project are
to verify the accuracy of the design codes, to gain the know-how on
fabrication, tuning procedures and operations, to measure the output beam
characteristics in order to optimise the higher energy part of the linac, and
to reach a high availability with minimum beam trips. A cold model has been
built to develop the tuning procedure. The present status of the IPHI RFQ is
presented.


title:
Continued Monitoring of the Conditioning of the Fermilab Linac 805 MHz
  Cavities

abstract:
  We have reported previously on the conditioning of the high-gradient
accelerating cavities in the Fermilab Linac. Automated measurements of the
sparking rate have been recorded since 1994 and are reported here. The sparking
rate has declined since the beginning, but there are indications that this rate
may have leveled off now. The X-rays emitted by the cavities are continuing to
decrease.


title: The FaBrE Project at Trieste

abstract:
  A program to design a high brilliance electron source suitable for a short
wavelength Linac-based FEL is presented. The goal of the project is to develop
a multi-cell integrated photoinjector capable of delivering 1 nC bunches with
emittance below 1 mm mrad. This will be the first step toward a possible
development of a IV generation light source test facility based on the existing
Trieste Linac. For this purpose a common program between Sincrotrone Trieste
and INFN-Milano has been undertaken. Here a brief description of the program
and the first results of the RF Gun electromagnetic structure with the beam
dynamics on the ELETTRA Linac are presented.


title:
Design of the 7 MeV/u, 217 MHz Injector Linac for the Proposed Ion Beam
  Facility for Cancer Therapy at the Clinic in Heidelberg

abstract:
  A dedicated clinical synchrotron facility for cancer therapy using energetic
proton and ion beams (C, He and O) has been designed at GSI for the
Radiologische Universitaetsklinik at Heidelberg, Germany. The design of the
injector linac is presented. Suitable ion sources are discussed and results of
ion source test measurements are reported. The LEBT allows for switching
between two ion sources. A short RFQ accelerates the ions from 8 keV/u to 400
keV/u. It is followed by a very compact beam matching section and a 3.8 m long
IH-type drift tube linac for the acceleration to 7 MeV/u. Both rf structures
are designed for a resonance frequency of 216.816 MHz and for ion
mass-to-charge ratios up to A/q = 3 (12C4+, (H_3)+, 3He+, 16O6+).


title: A Real-Time Energy Monitor System for the IPNS Linac

abstract:
  Injected beam energy and energy spread are critical parameters affecting the
performance of our rapid cycling synchrotron (RCS). A real-time energy
monitoring system is being installed to examine the H- beam out of the Intense
Pulsed Neutron Source (IPNS) 50 MeV linac. The 200 MHz Alvarez linac serves as
the injector for the 450 MeV IPNS RCS. The linac provides an 80 ms macropulse
of approximately 3x1012 H- ions 30 times per second for coasting-beam injection
into the RCS. The RCS delivers protons to a heavy-metal spallation neutron
target for material science studies. Using a number of strip-line beam position
monitors (BPMs) distributed along the 50 MeV transport line from the linac to
the RCS, fast signals from the strip lines are digitized and transferred to a
computer which performs an FFT. Corrections for cable attenuation and
oscilloscope bandwidth are made in the frequency domain. Rectangular pulse
train phasing (RPTP) is imposed on the spectra prior to obtaining the inverse
transform (IFFT). After the IFFT, the reconstructed time-domain signal is
analyzed for pulse width as it progresses along the transport line.
Time-of-flight measurements of the BPM signals provide beam energy. Finally,
using the 3-size measurement technique, the longitudinal emittance and energy
spread of the beam are determined.


title:
Optical Transition Radiation (OTR) Measurements of an Intense Pulsed
  Electron Beam

abstract:
  We present the first time resolved OTR angular distribution measurements of
an intense pulsed electron beam (1.7 kA, 60 ns). These initial experiments on
the first axis of the Dual Axis Radiographic Hydro-Testing (DARHT) facility and
subsequent analysis, demonstrate the possibility to extract, from the data, the
energy and the divergence angle of a 3.8 and 20 MeV electrons.


title:
Development of a Smart Modulator and Efficiency Evaluation of 500-GeV
  e+e- C-Band Linear Collider

abstract:
  An e+e- linear collider at 500-GeV C.M. (center of mass) has been proposed as
a future accelerator. The C-band linear collider has more than a thousand
klystrons and matching modulators. The linear colliders require smart
modulators with high reliability, compact and simple configuration, and good
power efficiency. This study suggests solutions to problems expected in the
future linear colliders. A C-band smart modulator has been developed using a
constant-current inverter power supply. The smart modulator provides 350-kV
pulses of the pulse-to-pulse stability of 0.35%, the pulse-width of 4.35
microseconds, and the repetition rate of 50 Hz. We also investigated the power
efficiency for the C-band scheme. A pulse efficiency of 75% can be achieved by
an optimized pulse transformer and the RF phase modulation. With pulsed
klystrons of 60% power efficiency, it is possible to achieve the RF system
efficiency of 32% with the wall-plug power of 170 MW.


title: RF Cavities For The Muon and Neutrino Factory Collaboration Study

abstract:
  A multi-laboratory collaboration is studying the feasibility of building a
muon collider, the first phase of which maybe a neutrino factory. The phase
space occupied by the muons is very large and needs to be cooled several orders
of magnitude for either machine, 100,000 to 1 million for the collider and ten
to 100 for the factory. Ionization cooling is the base line method for muon
cooling. This scheme uses hydrogen absorbers and rf re-acceleration in a long
series of magnetic focusing channels to cool the muons. At Fermilab two rf
cavity types are under study to provide the required cooling rf
re-acceleration, a 805 MHz high gradient cavity for the collider and a 201 MHz
high gradient cavity for the neutrino factory. The 805 MHz cavity currently
under going cold testing is a non-periodic pi-mode cavity with the iris
openings shaped to follow the contour of the beam. The 201 MHz cavity uses
hollow thin metal tubes over the beam aperture to terminate the field in a
pill-box type mode to increase its shunt impedance. This is possible because
muons have little interactions with thin metal membranes. Details of these
cavities and cold measurement data will be presented.


title: Reliability History and Improvements to the ANL 50 MEV H- Accelerator

abstract:
  The H- Accelerator consists of a 750 keV Cockcroft Walton preaccelerator and
an Alvarez type 50 MeV linac. The accelerator has been in operation since 1961.
Since 1981, it has been used as the injector for the Intense Pulsed Neutron
Source (IPNS), a national user facility for neutron scattering. The linac
delivers about 3.5x1012 H- ions per pulse, 30 times per second (30 Hz), for
multi-turn injection to a 450 MeV Rapid Cycling Synchrotron (RCS). IPNS
presently operates about 4,000 hours per year, and operating when scheduled is
critical to meeting the needs of the user community. For many years the IPNS
injector/RCS has achieved an average reliability of 95%, helped in large part
by the preaccelerator/linac which has averaged nearly 99%. To maintain and
improve system reliability, records need to show what each subsystem
contributes to the total down time. The history of source and linac subsystem
reliability, and improvements that have been made to improve reliability, will
be described. Plans to maintain or enhance this reliability for at least
another ten years of operation, will also be discussed.


title:
Testing and Implementation Progress on the Advanced Photon Source (APS)
  Linear Accelerator (Linac) High-Power S-band Switching System

abstract:
  An S-band linear accelerator is the source of particles and the front end of
the Advanced Photon Source injector. In addition, it supports a low-energy
undulator test line (LEUTL) and drives a free-electron laser (FEL). A
waveguide-switching and distribution system is now under construction. The
system configuration was revised to be consistent with the recent change to
electron-only operation. There are now six modulator-klystron subsystems, two
of which are being configured to act as hot spares for two S-band transmitters
each, so that no single failure will prevent injector operation. The two
subsystems are also used to support additional LEUTL capabilities and off-line
testing. Design considerations for the waveguide-switching subsystem, topology
selection, control and protection provisions, high-power test results, and
current status are described


title:
GRECP/MRD-CI calculations of the spin-orbit splitting in the ground
  state of Tl and of the spectroscopic properties of TlH

abstract:
  The generalized relativistic effective core potential (GRECP) approach is
employed in the framework of multireference single- and double-excitation
configuration interaction (MRD-CI) method to calculate the spin-orbit (SO)
splitting in the $^2P^o$ ground state of the Tl atom and spectroscopic
constants for the $0^+$ ground state of TlH. The 21-electron GRECP for Tl is
used and the outer core 5s and 5p pseudospinors are frozen with the help of the
level shift technique. The spin-orbit selection scheme with respect to
relativistic multireference states and the corresponding code are developed and
applied in the calculations. In this procedure both correlation and spin-orbit
interactions are taken into account. A [4,4,4,3,2] basis set is optimized for
the Tl atom and employed in the TlH calculations. Very good agreement is found
for the equilibrium distance, vibrational frequency, and dissociation energy of
the TlH ground state ($R_e=1.870 \AA, \omega_e=1420 cm^{-1}, D_e=2.049 eV$) as
compared with the experimental data ($R_e=1.868 \AA, \omega_e=1391 cm^{-1},
D_e=2.06 eV$).


title: The DARHT Phase 2 Linac

abstract:
  The second phase accelerator for the Dual Axis Hydrodynamic Test facility
(DARHT) is designed to provide an electron beam pulse that is 2 microsec long,
2kA, and 20 MeV in particle energy. The injector provides 3.2 MeV so that the
linac need only provide 16.8 MeV. The linac is made with two types of induction
accelerator cells. The first block of 8 cells have a 14 in. beam pipe compared
to 10 in. in the remaining 80 cells. The other principal difference is that the
first 8 cells have reduced volt-sec in their induction cores as a result of a
larger diameter beam pipe. The cells are designed for very reliable high
voltage operation. The insulator is Mycalex. Results from prototype tests are
given including results from solenoid measurements. Each cell contains a
solenoid for beam transport and a set of x-y correction coils to reduce
corkscrew motion. Details of tests to determine RF mode impedances relevant to
BBU generation are given. Blocks of cells are separated by "intercells" some of
which contain transport solenoids. The intercells provide vacuum pumping
stations as well. Issues of alignment and installation are discussed.


title: Optimized Wakefield Computations Using A Network Model

abstract:
  During the course of the last decade, traveling wave accelerating structures
for a future Linear Collider have been the object of intense R&D efforts. An
important problem is the efficient computation of the long range wakefield with
the ability to include small alignment and tuning errors. To that end, SLAC has
developed an RF circuit model with a demonstrated ability to reproduce
experimentally measured wakefields. The wakefield computation involves the
repeated solution of a deterministic system of equations over a range of
frequencies. By taking maximum advantage of the sparsity of the equations, we
have achieved significant performance improvements. These improvements make it
practical to consider simulations involving an entire linac ($\sim 10^3$
structures). One might also contemplate assessing, in real time, the impact of
fabrication errors on the wakefield as an integral part of quality control.


title: High Power Operations of LEDA

abstract:
  The LEDA RFQ, a 350-MHz continuous wave (CW) radio-frequency quadrupole
(RFQ), successfully accelerated a 100-mA CW proton beam from 75 keV to 6.7 MeV.
We have accumulated 111 hr of beam on time with at least 90 mA of CW output
beam current. The 8-m-long RFQ accelerates a dc, 75-keV, ~106-mA H+ beam from
the LEDA injector with ~94% transmission. When operating the RFQ at the RF
power level for which it was designed, the peak electrical field on the vane
tips is 33 MV/m. However, to maintain the high transmission quoted above with
the CW beam, it was necessary to operate the RFQ with field levels ~10% higher
than design. The RFQ dissipates 1.5 MW of RF power when operating with this
field. Three klystrons provide the 2.2 MW of RF power required by the RFQ to
accelerate the 100-mA beam. The beam power is 670 kW. Some of the challenges
that were met in accelerating a 100-mA CW proton beam to 6.7 MeV, will be
discussed.


title: The Beam Halo Experiment at the LEDA Facility

abstract:
  Due to the potentially adverse effects of the generation of halo particles in
intense proton beams, it is imperative to have a clear understanding of the
mechanisms that can lead to halo formation for current and proposed high-
intensity linacs. To this end a theoretical model has been developed, which
indicates that protons under the combined influence of strong space charge
forces and periodic focussing in a linear transport channel can be kicked into
halo orbits. However, no experimental measurements of beam halo in proton beams
have yet been carried out. In this paper we report the progress of an effort to
carry out an experiment to measure beam-halo using the existing high- intensity
proton beam of the LEDA facility. A linear transport channel has been assembled
with the appropriate diagnostics for measuring the expected small beam
component in the beam halo as a function of beam parameters. The experiment is
based on the use of an array of high-dynamic-range wire and beam scrapers to
determine the halo and core profiles along the transport channel. Details of
the experimental design, the expected halo measurement properties will be
presented.


title:
Generalized Relativistic Effective Core Potential Method: Theory and
  calculations

abstract:
  In calculations of heavy-atom molecules with the shape-consistent
Relativistic Effective Core Potential (RECP), only valence and some outer-core
shells are treated explicitly, the shapes of spinors are smoothed in the atomic
core regions and the small components of four-component spinors are excluded
from calculations. Therefore, the computational efforts can be dramatically
reduced.
  However, in the framework of the standard nodeless radially local RECP
versions, any attempt to extend the space of explicitly treated electrons more
than some limit does not improve the accuracy of the calculations. The errors
caused by these (nodeless) RECPs can range up to 2000 $cm^{-1}$ and more for
the dissociation and transition energies even for lowest-lying excitations that
can be unsatisfactory for many applications. Moreover, the direct calculation
of such properties as electronic densities near heavy nuclei, hyperfine
structure, and matrix elements of other operators singular on heavy nuclei is
impossible as a result of the smoothing of the orbitals in the core regions.
  In the present paper, ways to overcome these disadvantages of the RECP method
are discussed. The developments of the RECP method suggested by the authors are
studied in many precise calculations of atoms and of the TlH, HgH molecules.
The technique of nonvariational restoration of electronic structure in cores of
heavy atoms in molecules is applied to calculation of the P,T-odd
spin-rotational Hamiltonian parameters including the weak interaction terms
which break the symmetry over the space inversion (P) and time-reversal
invariance (T) in the PbF, HgF, BaF, and YbF molecules.


title: SNS Superconducting Cavity Modeling -Iterative Learning Control

abstract:
  The SNS SRF system is operated with a pulsed beam. For the SRF system to
track the repetitive reference trajectory, a feedback and a feedforward
controllers has been proposed. The feedback controller is to guarantee the
closed loop system stability and the feedforward controller is to improve the
tracking performance for the repetitive reference trajectory and to suppress
the repetitive disturbance. As the iteration number increases, the error
decreases.


title:
Energy Transfer Mechanisms and Equipartitioning in non-Equilibrium
  Space- Charge-Dominated Beams

abstract:
  A process of energy transfer is demonstrated in non-equilibrium charged
particle beams with anisotropy and space charge. Equipartitioning of energy
between available degrees of freedom occurs in just a few betatron wavelengths,
without halo formation. Collective space charge modes similar to those observed
in recent experiments provide the underlying coupling mechanism. Since
laboratory beams are commonly far from equilibrium, the traditional K-V
stability analysis does not necessarily apply, implying that selection of an
operating point based on theory does not necessarily avoid equipartitioning.
Furthermore, the rate of equipartitioning is shown to depend on a single free
parameter related space charge content of the final (equipartitioned) beam, and
does not depend on how the kinetic energy is initially distributed between the
two planes.


title: Analysis and Synthesis of the SNS Superconducting RF Control System

abstract:
  The RF system for the SNS superconducting linac consists of a superconducting
cavity, a klystron, and a low-level RF (LLRF) control system. For a proton
linac like SNS, the field in each individual cavity needs to be controlled to
meet the overall system requirements. The purpose of the LLRF control system is
to maintain the RF cavity field to a desired magnitude and phase by controlling
the klystron driver signal. The Lorentz force detuning causes the shift of the
resonant frequency during the normal operation in the order of a few hundreds
hertz. In order to compensate the Lorentz force detuning effects, the cavity is
pre-tuned into the middle of the expected frequency shift caused by the Lorentz
force detuning. Meanwhile, to reduce the overshoot in the transient response, a
feed-forward algorithm, a linear parameter varying gain scheduling (LPV-GS)
controller, is proposed to get away a repetitive noised caused by the pulsed
operation as well as the Lorentz force detuning effects.


title: Electronic coherence in mixed-valence systems: Spectral analysis

abstract:
  The electron transfer kinetics of mixed-valence systems is studied via
solving the eigen-structure of the two-state non-adiabatic diffusion operator
for a wide range of electronic coupling constants and energy bias constants.
The calculated spectral structure consists of three branches in the
eigen-diagram, a real branch corresponding to exponential or multi-exponential
decay and two symmetric branches corresponding to population oscillations
between donor and acceptor states. The observed electronic coherence is shown
as a result of underdamped Rabi oscillations in an overdamped solvent
environment. The time-evolution of electron population is calculated by
applying the propagator constructed from the eigen-solution to the
non-equilibrium initial preparation, and it agrees perfectly with the result of
a direct numerical propagation of the density matrix. The resulting population
dynamics confirms that increasing the energy bias destroys electronic
coherence.


title:
Faraday Cup Measurements of Ions Backstreaming into a Electron Beam
  Impinging on a Plasma Plume*

abstract:
  The next generation of radiographic machines based on induction accelerators
is expected to generate multiple, small diameter x-ray spots of high intensity.
Experiments to study the interaction of the electron beam with plasmas
generated at the x-ray converter and at beamline septa are being performed at
the Lawrence Livermore National Laboratory (LLNL) using the 6-MeV, 2-kA
Experimental Test Accelerator (ETA) electron beam. The physics issues of
concern can be separated into two categories. The interaction of subsequent
beam pulses with the expanding plasma plume generated by earlier pulses
striking the x-ray converter or a septum, and the more subtle effect involving
the extraction of light ions from a plasma by the head of the beam pulse. These
light ions may be due to contaminants on the surface of the beam pipe or
converter, or, for subsequent pulses, in the material of the converter. The
space charge depression of the beam could accelerate the light ions to
velocities of several mm/ns. As the ions moved through the body of the incoming
pulse, the beam would be pinched resulting in a moving focus prior to the
converter and a time varying x-ray spot. Studies of the beam-generated plasma
at the x-ray converter have been previously reported. In this paper we describe
Faraday cup measurements performed to detect and quantify the flow of
backstreaming ions as the ETA beam pulse impinges on preformed plasma.
  * This work was performed under the auspices of the U.S. Department of Energy
by University of California Lawrence Livermore National Laboratory under
contract No. W-7405-Eng-48.


title: Overview of the Heavy Ion Fusion Program

abstract:
  The world Heavy Ion Fusion (HIF) Program for inertial fusion energy is
looking toward the development and commissioning of several new experiments.
Recent and planned upgrades of the facilities at GSI, in Russia, and in Japan
greatly enhance the ability to study energy deposition in hot dense matter.
Worldwide target design developments have focused on non-ignition targets for
nearterm experiments and designs which, while lowering the energy required for
ignition, tighten accelerator requirements. The U.S program is transitioning
between scaled beam dynamics experiments and high current experiments with
power-plant-driver-scale beams. Current effort is aimed at preparation for the
next-step large facility, the Integrated Research Experiment (IRE)-- an
induction linac accelerating multiple beams to a few hundred MeV, then focusing
to deliver tens of kilojoules to a target. The goal is to study heavy ion
energy deposition, and to test all of the components and physics needed for an
engineering test of a power plant driver and target chamber. This paper will
include an overview of the Heavy Ion Fusion program abroad and a more in-depth
view of the progress and plans of the U.S. program.


title: Dipole Mode Detuning in the NLC Injector Linacs

abstract:
  The injector linacs of the JLC/NLC comprise the e+ booster, the e- drive
linac, the e+ booster, and the two prelinacs. These four systems together
transport the two types of beams from the 80 MeV point at the end of their
respective bunchers up to the storage rings, and then from the storage rings to
the 10 GeV point at the beginning of the bunch compressors. Nominally, the e+
booster structure will be L-band and the others S-band. In transport through
these linacs it is important that the emittances and particle losses stay
within specified tolerances. In particular, the effects of the dipole
wakefield-especially the long-range dipole wakefield-need to be carefully
considered. We present designs of the injector linac structures that employ
simple mode detuning, without damping, and that allow us to satisfy our
tolerance requirements, for both the nominal (2.8 ns) and alternate (1.4 ns)
bunch spacing options.


title:
Collective Acceleration of Ions by Means of Plasmoids in RF Wells of
  Frequency-Modulated Laser Field

abstract:
  The proposed linear accelerator ("scanator") consists of a terawatt table-top
laser and a set of passive elements - beam splitters, dispersion elements for
stretching of the laser pulse and chirping of the splitted beams, and
dispersion elements for angle scanning of crossed frequency-modulated laser
beams. Ions are trapped and accelerated in RF wells by the electron component
of plasmoids in the intersection zone of the scanning laser beams.
Computational studies give encouraging results. A proof-of-principle experiment
on the base of a table-top laser is outlined.


title:
Analysis of Thermally Induced Frequency Shift for the Spallation Neutron
  Source RFQ

abstract:
  The Spallation Neutron Source (SNS) Front-End Systems Group at Lawrence
Berkeley National Lab (LBNL) is developing a Radio Frequency Quadrupole (RFQ)
to accelerate an H- beam from 65 keV to 2.5 MeV at the operating frequency of
402.5 MHz. The 4 section, 3.7 meter long RFQ is a 4 vane structure operating at
6% duty factor. The cavity walls are made from OFE Copper with a GlidCop outer
layer to add mechanical strength. A set of 12 cooling channels in the RFQ
cavity walls are fed and controlled separately from 4 channels embedded in the
vanes. An ANSYS finite-element model has been developed to calculate the
deformed shape of the cavity for given RF heat loads and cooling water
temperatures. By combining the FEA results with a SUPERFISH RF cavity
simulation, the relative shift in frequency for a given change in coolant
temperature or heat load can be predicted. The calculated cavity frequency
sensitivity is -33 kHz per 1 degC change in vane water temperature with
constant-temperature wall water. The system start-up transient was also studied
using the previously mentioned FEA model. By controlling the RF power ramp rate
and the independent wall and vane cooling circuit temperatures, the system
turn-on time can be minimized while limiting the frequency shift.


title: Status Report on the Low-Energy Demonstration Accelerator (LEDA)

abstract:
  The 75-keV injector and 6.7-MeV RFQ that comprise the first portion of the
cw, 100-mA proton linac for the accelerator production of tritium (APT) project
have been built and operated. The LEDA RFQ has been extensively tested for
pulsed and cw output-beam currents <=100 mA. Up to 2.2 MW of cw rf power from
the 350-MHz rf system is coupled into the RFQ, including 670 kW for the cw
proton beam. The emittance for a 93-mA pulsed RFQ output beam, as determined
from quadrupole-magnet-scan measurements, is ex x ey = 0.25 x 0.31 (pi mm
mrad)2 [rms normalized]. A follow-on experiment, to intentionally introduce and
measure beam halo on the RFQ output beam, is now being installed.


title: SLAC Linac RF Performance for LCLS

abstract:
  The Linac Coherent Light Source (LCLS) project at SLAC uses a dense 15 GeV
electron beam passing through a long undulator to generate extremely bright
x-rays at 1.5 angstroms. The project requires electron bunches with a nominal
peak current of 3.5kA and bunch lengths of 0.020mm (70fs). The bunch
compression techniques used to achieve the high brightness impose challenging
tolerances on the accelerator RF phase and amplitude. The results of
measurements on the existing SLAC linac RF phase and amplitude stability are
summarised and improvements needed to meet the LCLS tolerances are discussed.


title: JLC Progress

abstract:
  The JLC is a linear collider project pursued in Japan by researchers centered
around KEK. The R&D status for the JLC project is presented, with emphasis on
recent results from ATF concerning studies of production of ultra-low emittance
beams and from manufacturing research on X-band accelerator structures.


title: Observation of a H- Beam Ion Instability

abstract:
  We report the results of observations of H- beam instabilities at the
Fermilab Linac. By intentionally creating "high" background pressure with
different gases in the 750 keV transport line we observed coherent transverse
beam oscillations. The minimal pulse length required to observe oscillations
and the frequency of oscillations are functions of pressure and mass of the
background gas. The oscillations are present in both transverse planes and very
quickly reach saturation in amplitude growth. The observed characteristics of
beam oscillations are in quantitative agreement with "fast beam-ion
instability" described by Raubenheimer and Zimmermann. Effects described here
are occur far from the normal operating range of the Fermilab Linac but may be
important for many future high intensity accelerators.


title: 2GeV Superconducting Muon Linac

abstract:
  A muon collider as well as a neutrino factory requires a large number of
muons with a kinetic energy of 50GeV or more. Muon survival demands a high
gradient linac. The large transverse and longitudinal emittance of the muon
beam coming from a muon cooling system implies the need for a large acceptance,
acceleration system. These two requirements point clearly to a linac based on
superconducting technology. The design of a 2GeV Superconducting muon Linac
based on computer programs developed at LANL will be presented. The design is
based on the technology available today or components that will be avaible in
the very near future.


title: Beam Energy Stabilization of the Kek 40mev Proton Linac

abstract:
  The new method to stabilize the beam energy of the KEK 40MeV proton linac, is
developed now. In this method, the signal of the velocity monitor installed
upstream the debuncher in the 40MeV beam line, is processed and then fed to the
phase shifter of the debuncher rf system so as to cancel the fluctuation of the
beam energy. In this article, the beam tests to prove the validity of this
method and the system are described.


title: High Current Proton Tests of the Fermilab Linac

abstract:
  The peak current limit for the Fermilab Linac was recently studied. The
purpose was to learn what components of the present Linac can be used for the
first stage of a proposed proton driver[1]. For this application the Linac must
provide a H- beam in excess of 5000 mA-msec per pulse. The original Fermilab
Linac was designed for protons with a peak current of 75 mA and a pulse length
of four Booster turns (~10 msec). The high energy replacement was designed for
a peak current of 35 mA and a beam pulse length of 50 msec. The present H-
source cannot deliver more than ~80 mA which produces 55 mA in the Linac. Using
a proton source allows the system to be tested to currents of ~100 mA and pulse
lengths long enough to observe the effects of long pulses. This test has shown
that the present Linac can accelerate beam having a peak current up to ~85 mA
with beam loss comparable to the present Linac operation (~45 mA). The results
of the test will be presented.


title: 2D Simulation of High-Efficiency Cross-Field RF Power Sources

abstract:
  An efficient method for frequency domain analysis of 2D cross-field devices
is presented. This work was done to analyze and design high efficiency
magnetrons. Arbitrary device-geometries are described by a piecewise planar
boundary. The method is based on an expansion of the electromagnetic fields
into a set of cavity eigenmodes. In order to obtain the self-consistent
solution, iterations are performed until the energy balance is reached. A
boundary integration method is used to take into account space charge effects.
The cavity eigenmodes are found by a method based on the scattering matrix
technique. The geometry is divided into regions. The boundary contour
mode-matching method is used to obtain the scattering matrices for each region.
Electromagnetic fields in each region are expanded into a series of plane
waves. Due to choice of plane wave expansion, all integration in the
mode-matching process is carried out analytically. The scattering matrices of
the regions are combined using a generalized scattering matrix technique to
obtain the scattering matrix for the full geometry, and then the eigenmode
resonance frequencies and the fields. Periodic boundary condition is used for
the field calculation and the particle tracking.


title: Development of the 50-Mev DTL for the Jaeri/Kek Joint Project

abstract:
  An Alvaretz-type DTL, to accelerate the H- ion beam from 3 to 50 MeV, is
being constructed as the injector for the JAERI/KEK Joint Project. The
following components of the DTL have been developed: (1) a cylindrical tank,
made by copper electroforming; (2) rf contactors; (3) a pulse-excited
quadrupole magnet with a hollow coil made by copper electroforming; (4) a
switching-regulator-type pulsed-power supply for the quadrupole magnet.
High-power tests of the components have been conducted using a short-model
tank. Moreover a breakdown experiment of the copper electrodes has been carried
out in order to study the properties of several kinds of copper materials.


title:
Development of a DTL Quadrupole Magnet with a New Electroformed Hollow
  Coil for the Jaeri/Kek Joint Project

abstract:
  Quadrupole electromagnets have been developed with a hollow coil produced
using an improved periodic reverse electroforming. These will be installed in
each of the drift tubes of the DTL (324 MHz) as part of the JAERI/KEK Joint
Project at the high-intensity proton accelerator facility. Measurements of the
magnets' properties were found to be consistent with computer-calculated
estimated. The details of the design, the fabrication process, and the
measurement results for the quadrupole magnet are described.


title: Development of Superconducting Linac for the Kek/Jaeri Joint Project

abstract:
  The JAERI/KEK Joint Project for the high-intensity proton accelerator
facility has been proposed with a superconducting (SC) linac option from 400
MeV to 600MeV. System design of the SC linac has been carried out based on the
equipartitioning concept. The SC linac is planned to use as an injector to a
3GeV rapid cycling synchrotron (RCS) for spallation neutron source after it
meets requirement to momentum spread less than +-0.1%. In the R&D work for SC
cavities, vertical tests of single-cell and 5 cell cavities were performed.
Experiments on multi-cell (5 cell) cavities of b=0.50 and b=0.89 at 2K were
carried out with values of maximum electric surface peak fields of 23MV/m and
31MV/m, respectively. A model describing dynamic Lorentz detuning for SC
cavities has been developed for pulse mode operation. Validity of the model was
confirmed experimentally to simulate the performance.


title: Study of Nonlinearities and Small Particle Losses in High Power Linac

abstract:
  The conception of High Power Linac developed in Russian accelerator centres
is based on the use of independently phased SC resonators with quadrupole
lenses between them. The type and parameters of the resonators as well as
focusing structure are varied along the linac to optimise beam dynamics and the
characteristics of the linac. The beam evolution in the linac was studied by
simulation in 3D accelerating and focusing fields by computer code DYNAMION.
  The simulation includes all nonlinearities of external fields and space
charge forces. Estimations of particle losses in the beam based on analysis of
the spectral properties of particle trajectories were carried out.


title: Control System for the LEDA 6.7-MeV Proton Beam Halo Experiment

abstract:
  Measurement of high-power proton beam-halo formation is the ongoing
scientific experiment for the Low Energy Demonstration Accelerator (LEDA)
facility. To attain this measurement goal, a 52-magnet beam line containing
several types of beam diagnostic instrumentation is being installed. The
Experimental Physics and Industrial Control System (EPICS) and commercial
software applications are presently being integrated to provide a real-time,
synchronous data acquisition and control system. This system is comprised of
magnet control, vacuum control, motor control, data acquisition, and data
analysis. Unique requirements led to the development and integration of
customized software and hardware. EPICS real-time databases, Interactive Data
Language (IDL) programs, LabVIEW Virtual Instruments (VI), and State Notation
Language (SNL) sequences are hosted on VXI, PC, and UNIX-based platforms which
interact using the EPICS Channel Access (CA) communication protocol.
Acquisition and control hardware technology ranges from DSP-based diagnostic
instrumentation to the PLC-controlled vacuum system. This paper describes the
control system hardware and software design, and implementation.


title: Multiple-Charge Beam Dynamics in an Ion Linac

abstract:
  There is demand for the construction of a medium-energy ion linear
accelerator based on superconducting rf (SRF) technology. It must be capable of
producing several hundred kilowatts of CW beams ranging from protons to
uranium. A considerable amount of power is required in order to generate
intense beams of rare isotopes for subsequent acceleration. At present,
however, the beam power available for the heavier ions would be limited by ion
source performance. To overcome this limit, we have studied the possibility of
accelerating multiple-charge-state (multi-Q) beams through a linac. We show
that such operation is made feasible by the large transverse and longitudinal
acceptance which can be obtained in a linac using superconducting cavities.
Multi-Q operation provides not only a substantial increase in beam current, but
also enables the use of two strippers, thus reducing the size of linac
required. Since the superconducting (SC) linac operates in CW mode, space
charge effects are essentially eliminated except in the ECR/RFQ region.
Therefore an effective emittance growth due to the multi-charge beam
acceleration can be minimized.


title: Heavy-Ion Beam Acceleration of Two-Charge States from an Ecr Ion Source

abstract:
  This paper describes a design for the front end of a superconducting (SC) ion
linac which can accept and simultaneously accelerate two charge states of
uranium from an ECR ion source. This mode of operation increases the beam
current available for the heaviest ions by a factor of two. We discuss the 12
MeV/u prestripper section of the Rare Isotope Accelerator (RIA) driver linac
including the LEBT, RFQ, MEBT and SC sections, with a total voltage of 112 MV.
The LEBT consists of two bunchers and electrostatic quadrupoles. The
fundamental frequency of both bunchers is half of the RFQ frequency. The first
buncher is a multiharmonic buncher, designed to accept more than 80% of each
charge state and to form bunches of extremely low longitudinal emittance (rms
emittance is lower than 0.2 keV/u nsec) at the output of the RFQ. The second
buncher is located directly in front of the RFQ and matches the velocity of
each charge-state bunch to the design input velocity of the RFQ. We present
full 3D simulations of a two-charge-state uranium beam including space charge
forces in the LEBT and RFQ, realistic distributions of all electric and
magnetic fields along the whole prestripper linac, and the effects of errors,
evaluated for several design options for the prestripper linac. The results
indicate that it is possible to accelerate two charge states while keeping
emittance growth within tolerable limits.


title: Multiple Charge State Beam Acceleration at Atlas

abstract:
  A test of the acceleration of multiple charge-state uranium beams was
performed at the ATLAS accelerator. A 238U+26 beam was accelerated in the ATLAS
PII linac to 286 MeV (~1.2 MeV/u) and stripped in a carbon foil located 0.5 m
from the entrance of the ATLAS Booster section. A 58Ni9+ 'guide' beam from the
tandem injector was used to tune the Booster for 238U+38. All charge states
from the stripping were injected into the booster and accelerated. Up to 94% of
the beam was accelerated through the Booster linac, with losses mostly in the
lower charge states. The measured beam properties of each charge state and a
comparison to numerical simulations are reported in this paper.


title: Determining Phase-Space Properties of the LEDA RFQ Output Beam

abstract:
  Quadrupole scans were used to characterize the LEDA RFQ beam. Experimental
data were fit to computer simulation models for the rms beam size. The codes
were found to be inadequate in accurately reproducing details of the wire
scanner data. When this discrepancy is resolved, we plan to fit using all the
data in wire scanner profiles, not just the rms values, using a 3-D nonlinear
code.


title:
Concept of Staged Approach for International Fusion Materials
  Irradiation Facility

abstract:
  The intense neutron source for development of fusion materials planned by
international collaboration makes a new step to clarify the technical issues
for realizing the 40 MeV, 250 mA deuteron beam facility. The baseline concept
employs two identical 125 mA linac modules whose beams are combined at the
flowing lithium target. Recent work for reducing the cost loading concerns the
staged deployment of the full irradiation capability in three steps. The
Japanese activity about the design and development study about IFMIF
accelerator in this year is presented and the schedule of next several years is
overviewed.


title: Inductive-Adder Kicker Modulator for Darht-2

abstract:
  An all solid-state kicker modulator for the Dual-Axis Radiographic
Hydrodynamic Test facility (DARHT-2) has been designed and tested. This kicker
modulator uses multiple solid-state modules stacked in an inductive-adder
configuration where the energy is switched into each section of the adder by a
parallel array of MOSFETs. The modulator features very fast rise and fall
times, pulse width agility and a high pulse-repetition rate in burst mode. The
modulator can drive a 50* cable with voltages up to 20 kV and can be easily
configured for either positive or negative polarity. The presentation will
include test data collected from both the ETA II accelerator kicker and
resistive dummy loads.


title: Review of Solid-State Modulators

abstract:
  Solid-state modulators for pulsed power applications have been a goal since
the first fast high-power semiconductor devices became available. Recent
improvements in both the speed and peak power capabilities of semiconductor
devices developed for the power conditioning and traction industries have led
to a new generation of solid-state switched high power modulators with
performance rivaling that of hard tube modulators and thyratron switched
line-type modulators. These new solid-state devices offer the promise of higher
efficiency and longer lifetimes at a time when availability of standard
technologies is becoming questionable. A brief discussion of circuit topologies
and solid-state devices is followed by examples of modulators currently in use
or in test. This presentation is intended to give an overview of the current
capabilities of solid-state modulators in various applications.


title: Analysis and Simulation on the Enhancement of the CSR Effects

abstract:
  Recent measurements of the coherent synchrotron radiation (CSR) effects
indicated that the observed beam emittance growth and energy modulation are
often bigger than previous predictions based on Gaussian longitudinal charge
distributions. In this paper, by performing a model study, we show both
analytically and numerically that when the longitudinal bunch charge
distribution involves concentration of charges in a small fraction of the bunch
length, enhancement of the CSR self-interaction beyond the Gaussian prediction
may occur. The level of this enhancement is sensitive to the level of the local
charge concentration.


title:
Ground Motion Studies and Modeling for the Interaction Region of a
  Linear Collider

abstract:
  Ground motion may be a limiting factor in the performance of future linear
colliders. Cultural noise sources, an important component of ground motion, are
discussed here, with data from the SLD region at SLAC.