Particle accelerator

A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams.
Large accelerators are used for basic research in particle physics. The largest accelerator currently operating is the Large Hadron Collider (LHC) near Geneva, Switzerland, operated by the CERN. It is a collider accelerator, which can accelerate two beams of protons to an energy of 6.5 TeV and cause them to collide head-on, creating center-of-mass energies of 13 TeV. Other powerful accelerators are, RHIC at Brookhaven National Laboratory in New York and, formerly, the Tevatron at Fermilab, Batavia, Illinois. Accelerators are also used as synchrotron light sources for the study of condensed matter physics. Smaller particle accelerators are used in a wide variety of applications, including particle therapy for oncological purposes, radioisotope production for medical diagnostics, ion implanters for manufacture of semiconductors, and accelerator mass spectrometers for measurements of rare isotopes such as radiocarbon. There are currently more than 30,000 accelerators in operation around the world.
There are two basic classes of accelerators: electrostatic and electrodynamic (or electromagnetic) accelerators. "Electrostatic" accelerators use static electric fields to accelerate particles. The most common types are the Cockcroft–Walton generator and the Van de Graaff generator. A small-scale example of this class is the cathode ray tube in an ordinary old television set. The achievable kinetic energy for particles in these devices is determined by the accelerating voltage, which is limited by electrical breakdown. "Electrodynamic" or "electromagnetic" accelerators, on the other hand, use changing electromagnetic fields (either magnetic induction or oscillating radio frequency fields) to accelerate particles. Since in these types the particles can pass through the same accelerating field multiple times, the output energy is not limited by the strength of the accelerating field. This class, which was first developed in the 1920s, is the basis for most modern large-scale accelerators.
Rolf Widerøe, Gustav Ising, Leó Szilárd, Max Steenbeck, and Ernest Lawrence are considered pioneers of this field, conceiving and building the first operational linear particle accelerator, the betatron, and the cyclotron.
Because the target of the particle beams of early accelerators was usually the atoms of a piece of matter, with the goal being to create collisions with their nuclei in order to investigate nuclear structure, accelerators were commonly referred to as atom smashers in the 20th century. The term persists despite the fact that many modern accelerators create collisions between two subatomic particles, rather than a particle and an atomic nucleus.
Uses.
Beams of high-energy particles are useful for fundamental and applied research in the sciences, and also in many technical and industrial fields unrelated to fundamental research. It has been estimated that there are approximately 30,000 accelerators worldwide. Of these, only about 1% are research machines with energies above 1 GeV, while about 44% are for radiotherapy, 41% for ion implantation, 9% for industrial processing and research, and 4% for biomedical and other low-energy research.
High-energy physics.
For the most basic inquiries into the dynamics and structure of matter, space, and time, physicists seek the simplest kinds of interactions at the highest possible energies. These typically entail particle energies of many GeV, and interactions of the simplest kinds of particles: leptons (e.g. electrons and positrons) and quarks for the matter, or photons and gluons for the field quanta. Since isolated quarks are experimentally unavailable due to color confinement, the simplest available experiments involve the interactions of, first, leptons with each other, and second, of leptons with nucleons, which are composed of quarks and gluons. To study the collisions of quarks with each other, scientists resort to collisions of nucleons, which at high energy may be usefully considered as essentially 2-body interactions of the quarks and gluons of which they are composed. This elementary particle physicists tend to use machines creating beams of electrons, positrons, protons, and antiprotons, interacting with each other or with the simplest nuclei (e.g., hydrogen or deuterium) at the highest possible energies, generally hundreds of GeV or more.
The largest and highest-energy particle accelerator used for elementary particle physics is the Large Hadron Collider (LHC) at CERN, operating since 2009.
Nuclear physics and isotope production.
Nuclear physicists and cosmologists may use beams of bare atomic nuclei, stripped of electrons, to investigate the structure, interactions, and properties of the nuclei themselves, and of condensed matter at extremely high temperatures and densities, such as might have occurred in the first moments of the Big Bang. These investigations often involve collisions of heavy nucleiof atoms like iron or goldat energies of several GeV per nucleon. The largest such particle accelerator is the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory.
Particle accelerators can also produce proton beams, which can produce proton-rich medical or research isotopes as opposed to the neutron-rich ones made in fission reactors; however, recent work has shown how to make 99Mo, usually made in reactors, by accelerating isotopes of hydrogen, although this method still requires a reactor to produce tritium. An example of this type of machine is LANSCE at Los Alamos.
Synchrotron radiation.
Electrons propagating through a magnetic field emit very bright and coherent photon beams via synchrotron radiation. It has numerous uses in the study of atomic structure, chemistry, condensed matter physics, biology, and technology. A large number of synchrotron light sources exist worldwide. Examples in the U.S. are SSRL at SLAC National Accelerator Laboratory, APS at Argonne National Laboratory, ALS at Lawrence Berkeley National Laboratory, and NSLS at Brookhaven National Laboratory. In Europe, there are MAX IV in Lund, Sweden, BESSY in Berlin, Germany, Diamond in Oxfordshire, UK, ESRF in Grenoble, France, the latter has been used to extract detailed 3-dimensional images of insects trapped in amber.
Free-electron lasers (FELs) are a special class of light sources based on synchrotron radiation that provides shorter pulses with higher temporal coherence. A specially designed FEL is the most brilliant source of x-rays in the observable universe. The most prominent examples are the LCLS in the U.S. and European XFEL in Germany. More attention is being drawn towards soft x-ray lasers, which together with pulse shortening opens up new methods for attosecond science. Apart from x-rays, FELs are used to emit terahertz light, e.g. FELIX in Nijmegen, Netherlands, TELBE in Dresden, Germany and NovoFEL in Novosibirsk, Russia.
Thus there is a great demand for electron accelerators of moderate (GeV) energy, high intensity and high beam quality to drive light sources.
Low-energy machines and particle therapy.
Everyday examples of particle accelerators are cathode ray tubes found in television sets and X-ray generators. These low-energy accelerators use a single pair of electrodes with a DC voltage of a few thousand volts between them. In an X-ray generator, the target itself is one of the electrodes. A low-energy particle accelerator called an ion implanter is used in the manufacture of integrated circuits.
At lower energies, beams of accelerated nuclei are also used in medicine as particle therapy, for the treatment of cancer.
DC accelerator types capable of accelerating particles to speeds sufficient to cause nuclear reactions are Cockcroft-Walton generators or voltage multipliers, which convert AC to high voltage DC, or Van de Graaff generators that use static electricity carried by belts.
Radiation sterilization of medical devices.
Electron beam processing is commonly used for sterilization. Electron beams are an on-off technology that provide a much higher dose rate than gamma or X-rays emitted by radioisotopes like cobalt-60 (60Co) or caesium-137 (137Cs). Due to the higher dose rate, less exposure time is required and polymer degradation is reduced. Because electrons carry a charge, electron beams are less penetrating than both gamma and X-rays.
Electrostatic particle accelerators.
Historically, the first accelerators used simple technology of a single static high voltage to accelerate charged particles. The charged particle was accelerated through an evacuated tube with an electrode at either end, with the static potential across it. Since the particle passed only once through the potential difference, the output energy was limited to the accelerating voltage of the machine. While this method is still extremely popular today, with the electrostatic accelerators greatly out-numbering any other type, they are more suited to lower energy studies owing to the practical voltage limit of about 1 MV for air insulated machines, or 30 MV when the accelerator is operated in a tank of pressurized gas with high dielectric strength, such as sulfur hexafluoride. In a "tandem accelerator" the potential is used twice to accelerate the particles, by reversing the charge of the particles while they are inside the terminal. This is possible with the acceleration of atomic nuclei by using anions (negatively charged ions), and then passing the beam through a thin foil to strip electrons off the anions inside the high voltage terminal, converting them to cations (positively charged ions), which are accelerated again as they leave the terminal.
The two main types of electrostatic accelerator are the Cockcroft-Walton accelerator, which uses a diode-capacitor voltage multiplier to produce high voltage, and the Van de Graaff accelerator, which uses a moving fabric belt to carry charge to the high voltage electrode. Although electrostatic accelerators accelerate particles along a straight line, the term linear accelerator is more often used for accelerators that employ oscillating rather than static electric fields.
Electrodynamic (electromagnetic) particle accelerators.
Due to the high voltage ceiling imposed by electrical discharge, in order to accelerate particles to higher energies, techniques involving dynamic fields rather than static fields are used. Electrodynamic acceleration can arise from either of two mechanisms: non-resonant magnetic induction, or resonant circuits or cavities excited by oscillating RF fields.
Electrodynamic accelerators can be "linear", with particles accelerating in a straight line, or "circular", using magnetic fields to bend particles in a roughly circular orbit.
Magnetic induction accelerators.
Magnetic induction accelerators accelerate particles by induction from an increasing magnetic field, as if the particles were the secondary winding in a transformer. The increasing magnetic field creates a circulating electric field which can be configured to accelerate the particles. Induction accelerators can be either linear or circular.
Linear induction accelerators.
Linear induction accelerators utilize ferrite-loaded, non-resonant induction cavities. Each cavity can be thought of as two large washer-shaped disks connected by an outer cylindrical tube. Between the disks is a ferrite toroid. A voltage pulse applied between the two disks causes an increasing magnetic field which inductively couples power into the charged particle beam.
The linear induction accelerator was invented by Christofilos in the 1960s. Linear induction accelerators are capable of accelerating very high beam currents (>1000 A) in a single short pulse. They have been used to generate X-rays for flash radiography (e.g. DARHT at LANL), and have been considered as particle injectors for magnetic confinement fusion and as drivers for free electron lasers.
Betatrons.
The Betatron is a circular magnetic induction accelerator, invented by Donald Kerst in 1940 for accelerating electrons. The concept originates ultimately from Norwegian-German scientist Rolf Widerøe. These machines, like synchrotrons, use a donut-shaped ring magnet (see below) with a cyclically increasing B field, but accelerate the particles by induction from the increasing magnetic field, as if they were the secondary winding in a transformer, due to the changing magnetic flux through the orbit.
Achieving constant orbital radius while supplying the proper accelerating electric field requires that the magnetic flux linking the orbit be somewhat independent of the magnetic field on the orbit, bending the particles into a constant radius curve. These machines have in practice been limited by the large radiative losses suffered by the electrons moving at nearly the speed of light in a relatively small radius orbit.
Linear accelerators.
In a linear particle accelerator (linac), particles are accelerated in a straight line with a target of interest at one end. They are often used to provide an initial low-energy kick to particles before they are injected into circular accelerators. The longest linac in the world is the Stanford Linear Accelerator, SLAC, which is long. SLAC is an electron-positron collider.
Linear high-energy accelerators use a linear array of plates (or drift tubes) to which an alternating high-energy field is applied. As the particles approach a plate they are accelerated towards it by an opposite polarity charge applied to the plate. As they pass through a hole in the plate, the polarity is switched so that the plate now repels them and they are now accelerated by it towards the next plate. Normally a stream of "bunches" of particles are accelerated, so a carefully controlled AC voltage is applied to each plate to continuously repeat this process for each bunch.
As the particles approach the speed of light the switching rate of the electric fields becomes so high that they operate at radio frequencies, and so microwave cavities are used in higher energy machines instead of simple plates.
Linear accelerators are also widely used in medicine, for radiotherapy and radiosurgery. Medical grade linacs accelerate electrons using a klystron and a complex bending magnet arrangement which produces a beam of 6-30 MeV energy. The electrons can be used directly or they can be collided with a target to produce a beam of X-rays. The reliability, flexibility and accuracy of the radiation beam produced has largely supplanted the older use of cobalt-60 therapy as a treatment tool.
Circular or cyclic RF accelerators.
In the circular accelerator, particles move in a circle until they reach sufficient energy. The particle track is typically bent into a circle using electromagnets. The advantage of circular accelerators over linear accelerators ("linacs") is that the ring topology allows continuous acceleration, as the particle can transit indefinitely. Another advantage is that a circular accelerator is smaller than a linear accelerator of comparable power (i.e. a linac would have to be extremely long to have the equivalent power of a circular accelerator).
Depending on the energy and the particle being accelerated, circular accelerators suffer a disadvantage in that the particles emit synchrotron radiation. When any charged particle is accelerated, it emits electromagnetic radiation and secondary emissions. As a particle traveling in a circle is always accelerating towards the center of the circle, it continuously radiates towards the tangent of the circle. This radiation is called synchrotron light and depends highly on the mass of the accelerating particle. For this reason, many high energy electron accelerators are linacs. Certain accelerators (synchrotrons) are however built specially for producing synchrotron light (X-rays).
Since the special theory of relativity requires that matter always travels slower than the speed of light in a vacuum, in high-energy accelerators, as the energy increases the particle speed approaches the speed of light as a limit, but never attains it. Therefore, particle physicists do not generally think in terms of speed, but rather in terms of a particle's energy or momentum, usually measured in electron volts (eV). An important principle for circular accelerators, and particle beams in general, is that the curvature of the particle trajectory is proportional to the particle charge and to the magnetic field, but inversely proportional to the (typically relativistic) momentum.
Cyclotrons.
The earliest operational circular accelerators were cyclotrons, invented in 1929 by Ernest Lawrence at the University of California, Berkeley. Cyclotrons have a single pair of hollow "D"-shaped plates to accelerate the particles and a single large dipole magnet to bend their path into a circular orbit. It is a characteristic property of charged particles in a uniform and constant magnetic field B that they orbit with a constant period, at a frequency called the cyclotron frequency, so long as their speed is small compared to the speed of light "c". This means that the accelerating D's of a cyclotron can be driven at a constant frequency by a radio frequency (RF) accelerating power source, as the beam spirals outwards continuously. The particles are injected in the center of the magnet and are extracted at the outer edge at their maximum energy.
Cyclotrons reach an energy limit because of relativistic effects whereby the particles effectively become more massive, so that their cyclotron frequency drops out of sync with the accelerating RF. Therefore, simple cyclotrons can accelerate protons only to an energy of around 15 million electron volts (15 MeV, corresponding to a speed of roughly 10% of "c"), because the protons get out of phase with the driving electric field. If accelerated further, the beam would continue to spiral outward to a larger radius but the particles would no longer gain enough speed to complete the larger circle in step with the accelerating RF. To accommodate relativistic effects the magnetic field needs to be increased to higher radii as is done in isochronous cyclotrons. An example of an isochronous cyclotron is the PSI Ring cyclotron in Switzerland, which provides protons at the energy of 590 MeV which corresponds to roughly 80% of the speed of light. The advantage of such a cyclotron is the maximum achievable extracted proton current which is currently 2.2 mA. The energy and current correspond to 1.3 MW beam power which is the highest of any accelerator currently existing.
Synchrocyclotrons and isochronous cyclotrons.
A classic cyclotron can be modified to increase its energy limit. The historically first approach was the synchrocyclotron, which accelerates the particles in bunches. It uses a constant magnetic field formula_1, but reduces the accelerating field's frequency so as to keep the particles in step as they spiral outward, matching their mass-dependent cyclotron resonance frequency. This approach suffers from low average beam intensity due to the bunching, and again from the need for a huge magnet of large radius and constant field over the larger orbit demanded by high energy.
The second approach to the problem of accelerating relativistic particles is the isochronous cyclotron. In such a structure, the accelerating field's frequency (and the cyclotron resonance frequency) is kept constant for all energies by shaping the magnet poles so to increase magnetic field with radius. Thus, all particles get accelerated in isochronous time intervals. Higher energy particles travel a shorter distance in each orbit than they would in a classical cyclotron, thus remaining in phase with the accelerating field. The advantage of the isochronous cyclotron is that it can deliver continuous beams of higher average intensity, which is useful for some applications. The main disadvantages are the size and cost of the large magnet needed, and the difficulty in achieving the high magnetic field values required at the outer edge of the structure.
Synchrocyclotrons have not been built since the isochronous cyclotron was developed.
Synchrotrons.
To reach still higher energies, with relativistic mass approaching or exceeding the rest mass of the particles (for protons, billions of electron volts or GeV), it is necessary to use a synchrotron. This is an accelerator in which the particles are accelerated in a ring of constant radius. An immediate advantage over cyclotrons is that the magnetic field need only be present over the actual region of the particle orbits, which is much narrower than that of the ring. (The largest cyclotron built in the US had a magnet pole, whereas the diameter of synchrotrons such as the LEP and LHC is nearly 10 km. The aperture of the two beams of the LHC is of the order of a centimeter.) The LHC contains 16 RF cavities, 1232 superconducting dipole magnets for beam steering, and 24 quadrupoles for beam focusing. Even at this size, the LHC is limited by its ability to steer the particles without them going adrift. This limit is theorized to occur at 14TeV.
However, since the particle momentum increases during acceleration, it is necessary to turn up the magnetic field B in proportion to maintain constant curvature of the orbit. In consequence, synchrotrons cannot accelerate particles continuously, as cyclotrons can, but must operate cyclically, supplying particles in bunches, which are delivered to a target or an external beam in beam "spills" typically every few seconds.
Since high energy synchrotrons do most of their work on particles that are already traveling at nearly the speed of light "c", the time to complete one orbit of the ring is nearly constant, as is the frequency of the RF cavity resonators used to drive the acceleration.
In modern synchrotrons, the beam aperture is small and the magnetic field does not cover the entire area of the particle orbit as it does for a cyclotron, so several necessary functions can be separated. Instead of one huge magnet, one has a line of hundreds of bending magnets, enclosing (or enclosed by) vacuum connecting pipes. The design of synchrotrons was revolutionized in the early 1950s with the discovery of the strong focusing concept. The focusing of the beam is handled independently by specialized quadrupole magnets, while the acceleration itself is accomplished in separate RF sections, rather similar to short linear accelerators. Also, there is no necessity that cyclic machines be circular, but rather the beam pipe may have straight sections between magnets where beams may collide, be cooled, etc. This has developed into an entire separate subject, called "beam physics" or "beam optics".
More complex modern synchrotrons such as the Tevatron, LEP, and LHC may deliver the particle bunches into storage rings of magnets with a constant magnetic field, where they can continue to orbit for long periods for experimentation or further acceleration. The highest-energy machines such as the Tevatron and LHC are actually accelerator complexes, with a cascade of specialized elements in series, including linear accelerators for initial beam creation, one or more low energy synchrotrons to reach intermediate energy, storage rings where beams can be accumulated or "cooled" (reducing the magnet aperture required and permitting tighter focusing; see beam cooling), and a last large ring for final acceleration and experimentation.
Electron synchrotrons.
Circular electron accelerators fell somewhat out of favor for particle physics around the time that SLAC's linear particle accelerator was constructed, because their synchrotron losses were considered economically prohibitive and because their beam intensity was lower than for the unpulsed linear machines. The Cornell Electron Synchrotron, built at low cost in the late 1970s, was the first in a series of high-energy circular electron accelerators built for fundamental particle physics, the last being LEP, built at CERN, which was used from 1989 until 2000.
A large number of electron synchrotrons have been built in the past two decades, as part of synchrotron light sources that emit ultraviolet light and X rays; see below.
Storage rings.
For some applications, it is useful to store beams of high energy particles for some time (with modern high vacuum technology, up to many hours) without further acceleration. This is especially true for colliding beam accelerators, in which two beams moving in opposite directions are made to collide with each other, with a large gain in effective collision energy. Because relatively few collisions occur at each pass through the intersection point of the two beams, it is customary to first accelerate the beams to the desired energy, and then store them in storage rings, which are essentially synchrotron rings of magnets, with no significant RF power for acceleration.
Synchrotron radiation sources.
Some circular accelerators have been built to deliberately generate radiation (called synchrotron light) as X-rays also called synchrotron radiation, for example the Diamond Light Source which has been built at the Rutherford Appleton Laboratory in England or the Advanced Photon Source at Argonne National Laboratory in Illinois, USA. High-energy X-rays are useful for X-ray spectroscopy of proteins or X-ray absorption fine structure (XAFS), for example.
Synchrotron radiation is more powerfully emitted by lighter particles, so these accelerators are invariably electron accelerators. Synchrotron radiation allows for better imaging as researched and developed at SLAC's SPEAR.
Fixed-Field Alternating Gradient Accelerators.
Fixed-Field Alternating Gradient accelerators (FFA)s, in which a magnetic field which is fixed in time, but with a radial variation to achieve strong focusing, allows the beam to be accelerated with a high repetition rate but in a much smaller radial spread than in the cyclotron case. Isochronous FFAs, like isochronous cyclotrons, achieve continuous beam operation, but without the need for a huge dipole bending magnet covering the entire radius of the orbits. Some new developments in FFAs are covered in.
History.
Ernest Lawrence's first cyclotron was a mere 4 inches (100 mm) in diameter. Later, in 1939, he built a machine with a 60-inch diameter pole face, and planned one with a 184-inch diameter in 1942, which was, however, taken over for World War II-related work connected with uranium isotope separation; after the war it continued in service for research and medicine over many years.
The first large proton synchrotron was the Cosmotron at Brookhaven National Laboratory, which accelerated protons to about 3 GeV (1953–1968). The Bevatron at Berkeley, completed in 1954, was specifically designed to accelerate protons to sufficient energy to create antiprotons, and verify the particle-antiparticle symmetry of nature, then only theorized. The Alternating Gradient Synchrotron (AGS) at Brookhaven (1960–) was the first large synchrotron with alternating gradient, "strong focusing" magnets, which greatly reduced the required aperture of the beam, and correspondingly the size and cost of the bending magnets. The Proton Synchrotron, built at CERN (1959–), was the first major European particle accelerator and generally similar to the AGS.
The Stanford Linear Accelerator, SLAC, became operational in 1966, accelerating electrons to 30 GeV in a 3 km long waveguide, buried in a tunnel and powered by hundreds of large klystrons. It is still the largest linear accelerator in existence, and has been upgraded with the addition of storage rings and an electron-positron collider facility. It is also an X-ray and UV synchrotron photon source.
The Fermilab Tevatron has a ring with a beam path of . It has received several upgrades, and has functioned as a proton-antiproton collider until it was shut down due to budget cuts on September 30, 2011. The largest circular accelerator ever built was the LEP synchrotron at CERN with a circumference 26.6 kilometers, which was an electron/positron collider. It achieved an energy of 209 GeV before it was dismantled in 2000 so that the tunnel could be used for the Large Hadron Collider (LHC). The LHC is a proton collider, and currently the world's largest and highest-energy accelerator, achieving 6.5 TeV energy per beam (13 TeV in total).
The aborted Superconducting Super Collider (SSC) in Texas would have had a circumference of 87 km. Construction was started in 1991, but abandoned in 1993. Very large circular accelerators are invariably built in tunnels a few metres wide to minimize the disruption and cost of building such a structure on the surface, and to provide shielding against intense secondary radiations that occur, which are extremely penetrating at high energies.
Current accelerators such as the Spallation Neutron Source, incorporate superconducting cryomodules. The Relativistic Heavy Ion Collider, and Large Hadron Collider also make use of superconducting magnets and RF cavity resonators to accelerate particles.
Targets.
The output of a particle accelerator can generally be directed towards multiple lines of experiments, one at a given time, by means of a deviating electromagnet. This makes it possible to operate multiple experiments without needing to move things around or shutting down the entire accelerator beam. Except for synchrotron radiation sources, the purpose of an accelerator is to generate high-energy particles for interaction with matter.
This is usually a fixed target, such as the phosphor coating on the back of the screen in the case of a television tube; a piece of uranium in an accelerator designed as a neutron source; or a tungsten target for an X-ray generator. In a linac, the target is simply fitted to the end of the accelerator. The particle track in a cyclotron is a spiral outwards from the centre of the circular machine, so the accelerated particles emerge from a fixed point as for a linear accelerator.
For synchrotrons, the situation is more complex. Particles are accelerated to the desired energy. Then, a fast acting dipole magnet is used to switch the particles out of the circular synchrotron tube and towards the target.
A variation commonly used for particle physics research is a collider, also called a "storage ring collider". Two circular synchrotrons are built in close proximityusually on top of each other and using the same magnets (which are then of more complicated design to accommodate both beam tubes). Bunches of particles travel in opposite directions around the two accelerators and collide at intersections between them. This can increase the energy enormously; whereas in a fixed-target experiment the energy available to produce new particles is proportional to the square root of the beam energy, in a collider the available energy is linear.
Higher energies.
At present the highest energy accelerators are all circular colliders, but both hadron accelerators and electron accelerators are running into limits. Higher energy hadron and ion cyclic accelerators will require accelerator tunnels of larger physical size due to the increased beam rigidity.
For cyclic electron accelerators, a limit on practical bend radius is placed by synchrotron radiation losses and the next generation will probably be linear accelerators 10 times the current length. An example of such a next generation electron accelerator is the proposed 40 km long International Linear Collider.
It is believed that plasma wakefield acceleration in the form of electron-beam "afterburners" and standalone laser pulsers might be able to provide dramatic increases in efficiency over RF accelerators within two to three decades. In plasma wakefield accelerators, the beam cavity is filled with a plasma (rather than vacuum). A short pulse of electrons or laser light either constitutes or immediately precedes the particles that are being accelerated. The pulse disrupts the plasma, causing the charged particles in the plasma to integrate into and move toward the rear of the bunch of particles that are being accelerated. This process transfers energy to the particle bunch, accelerating it further, and continues as long as the pulse is coherent.
Energy gradients as steep as 200 GeV/m have been achieved over millimeter-scale distances using laser pulsers and gradients approaching 1 GeV/m are being produced on the multi-centimeter-scale with electron-beam systems, in contrast to a limit of about 0.1 GeV/m for radio-frequency acceleration alone. Existing electron accelerators such as SLAC could use electron-beam afterburners to greatly increase the energy of their particle beams, at the cost of beam intensity. Electron systems in general can provide tightly collimated, reliable beams; laser systems may offer more power and compactness. Thus, plasma wakefield accelerators could be used – if technical issues can be resolved – to both increase the maximum energy of the largest accelerators and to bring high energies into university laboratories and medical centres.
Higher than 0.25 GeV/m gradients have been achieved by a dielectric laser accelerator, which may present another viable approach to building compact high-energy accelerators. Using femtosecond duration laser pulses, an electron accelerating gradient 0.69 Gev/m was recorded for dielectric laser accelerators. Higher gradients of the order of 1 to 6 GeV/m are anticipated after further optimizations.
Black hole production and public safety concerns.
In the future, the possibility of a black hole production at the highest energy accelerators may arise if certain predictions of superstring theory are accurate. This and other possibilities have led to public safety concerns that have been widely reported in connection with the LHC, which began operation in 2008. The various possible dangerous scenarios have been assessed as presenting "no conceivable danger" in the latest risk assessment produced by the LHC Safety Assessment Group. If black holes are produced, it is theoretically predicted that such small black holes should evaporate extremely quickly via Bekenstein-Hawking radiation, but which is as yet experimentally unconfirmed. If colliders can produce black holes, cosmic rays (and particularly ultra-high-energy cosmic rays, UHECRs) must have been producing them for eons, but they have yet to harm anybody. It has been argued that to conserve energy and momentum, any black holes created in a collision between an UHECR and local matter would necessarily be produced moving at relativistic speed with respect to the Earth, and should escape into space, as their accretion and growth rate should be very slow, while black holes produced in colliders (with components of equal mass) would have some chance of having a velocity less than Earth escape velocity, 11.2 km per sec, and would be liable to capture and subsequent growth. Yet even on such scenarios the collisions of UHECRs with white dwarfs and neutron stars would lead to their rapid destruction, but these bodies are observed to be common astronomical objects. Thus if stable micro black holes should be produced, they must grow far too slowly to cause any noticeable macroscopic effects within the natural lifetime of the solar system.
Accelerator operator.
The use of advanced technologies such as superconductivity, cryogenics, and high powered radiofrequency amplifiers, as well as the presence of ionizing radiation, pose challenges for the safe operation of accelerator facilities. An accelerator operator controls the operation of a particle accelerator, adjusts operating parameters such as aspect ratio, current intensity, and position on target. They communicate with and assist accelerator maintenance personnel to ensure readiness of support systems, such as vacuum, magnets, magnetic and radiofrequency power supplies and controls, and cooling systems. Additionally, the accelerator operator maintains a record of accelerator related events.


WA70 experiment

The WA70 experiment was a collaboration between the Universities of Geneva, Glasgow, Liverpool, Milan and Neuchatel using the facilities of the OMEGA spectrometer at CERN.
The purpose of the experiment was to study direct photons produced in proton-proton and proton-pion collisions within a fixed target of liquid hydrogen at the CERN SPS. The experiment was proposed on 6 August 1980 and formally approved on 22 October 1981. Preliminary data was taken in 1983 with physics runs in 1984, 1985 and 1986.
A novel feature of the experiment was a liquid scintillator calorimeter, which was built in quadrants and designed to measure the energy of direct photons and other particles produced by the collisions. This was situated downstream of the liquid hydrogen target.
Results were presented at scientific conferences and published in scientific journals. The measured cross section for direct photon production was in agreement with predictions from perturbative QCD.
The spokesperson for the experiment was Professor Michel Martin, and participants included Dr. Fabiola Gianotti (who went on to become CERN's first woman Director General).


William Valentine Mayneord

William Valentine Mayneord, CBE FRS (14 February 1902 – 10 August 1988) was a British physicist and pioneer in the field of medical physics.
He was born in Redditch, Worcestershire to Walter and Elizabeth Mayneord but after the early death of his mother was adopted by an aunt in Evesham. He was educated at Prince Henry's School, Evesham and gained a Bachelor of Science at the University of Birmingham
He entered the field of medical physics in 1924 at St Bart's Hospital in London. In 1927 he moved to the Cancer Hospital, now the Royal Marsden Hospital. There he was involved in pioneering work with Izrael Hieger.
During World War II he was seconded by the government to work in Canada on the radiological aspects of atomic energy development.
It has been said that such was his renown, especially for bringing in the use of the radiological unit the rad, that the SI unit may well have been called the mayneord instead of the gray (2). It was during a meeting in 1946 with a young Harold Elford Johns, inventor of the cobalt-60 teletherapy unit, that Johns was prompted to go into medical physics. His department subsequently developed one of the world's first radioisotope scanners.
He was elected a Fellow of the Royal Society in 1965. His candidacy citation read: ""Distinguished for his applications of physics to medical sciences. He was responsible for the use of fluorescence spectroscopy in the collaborative study of carcinogenic agents in coal-tar which led to the discovery of the activity of 3:4 - benzopyrene. He was among the first to measure gamma-radiation in "r" units. His precision measurements have stood the test of time. He is recognised as the leading authority in the United Kingdom on the applications of radiation dosimetry to medical radiology and to the problems of radiation hazards"."
He was awarded a CBE in 1965.


David B. Cline

David Bruce Cline (December 7, 1933 – June 27, 2015) was an American particle physicist known for his contributions to the discovery of the Higgs boson and the W and Z intermediate bosons. After receiving his Ph.D. from the University of Wisconsin-Madison, he went on to join the University's physics faculty and founded the “Pheno Group”. Shorthand for phenomenology, the group consisted of particle physicists designing and running experiments alongside developing theoretical models that went beyond the current standard model of particle physics. He later moved to UCLA where he became a Distinguished Professor of Physics & Astronomy for his contributions to the growth of the UCLA Physics & Astronomy Department.
Rather than working in a U.S. based particle accelerator, the Superconducting Supercollider, Cline chose to work on CERN’s Large Hadron Collider. While there, he and others founded the Compact Muon Solenoid (CMS) experiment, which is still active today in investigating the Standard Model and is one of the largest international scientific collaborations in history. Cline was also involved in the development of the ICARUS neutrino detector. When assembled, it would be the largest detector of its time, built with the purpose of detecting neutrinos from the sun and the beams from CERN.
In the later part of his career, Cline shifted his interests towards astroparticle physics. He pioneered the use of liquified noble gases in particle detectors to enhance the detection through the use of a Time Projection Chamber. Not only did this facilitate work in investigating neutrino oscillations, the introduction of noble gases into detectors could be exploited to detect dark matter. Dark matter’s elusive nature inspired Cline to organize a biannual international conference for dark matter research, which will go on to have its 14th meeting in March 2020.
Early life and education.
Cline was born on December 7, 1933, in Rosedale, Kansas. He attended and graduated from Rosedale High School in the same city, and after being discharged from the Army, attended Kansas State University, where he received a BS in Physics in 1959 and MS in Physics in 1961 in physics. He continued his studies and pursued a PhD at the University of Wisconsin - Madison under the guidance of Dr. William Fry. He completed his PhD thesis in 1965, titled “A Study of Some Rare Decay Modes of the Positive Kaon”. His PhD work investigated the existence of the then undiscovered electrically charged W boson and electrically neutral Z boson. His observations of decaying kaons dismissed the existence of the neutral weak force carrier, but he would later go on to withdraw this belief when experiments at CERN claimed to require the existence of the Z boson for certain interactions.
Career.
In 1967, Cline was appointed to the faculty at the University of Wisconsin. Once there, he co-founded the “Pheno Group”, which consisted of physicists dedicated to pursuing a broad range of particle physics research in both theory and phenomenology.
The same year, Cline began working at CERN, and with Alfred E. Mann of the University of Pennsylvania and Carlo Rubbia of Harvard, the team produced a document that launched the first experiments to study the weak force using neutrino beams at the new Fermilab accelerator complex. After a period of uncertainty, Cline and collaborators agreed with the claim coming from the CERN laboratory in Geneva that certain neutrino interactions required the existence of weak neutral currents. In 1976, the group proposed upgrading the single-beam proton accelerator at CERN to a dual-beam proton-antiproton collider. The installation of this 270 GeV antiproton-proton collider, along with the implementation of more advanced beam-cooling techniques, prompted the investigation for intermediate vector bosons (IVB). With a theorized mass of 80-90 GeV, it was expected that the high energy of the collider would lead to the first observations of these particles. The experiment at CERN proved successful, and in 1983 IVBs were detected and differentiated the weak force from the electromagnetic force for the first time. The discovery warranted the 1984 Nobel Prize in Physics, awarded to Dr. Carlo Rubbia and Dr. Simon van der Meer for the discovery of the W and Z bosons.
Following his involvement in the discovery of the W and Z boson, Cline moved to the UCLA Physics Department in 1986. Once there, he began actively pursuing efforts to grow the university's particle physics department and incorporate new areas of research. He was focused on hiring faculty with a specialization in accelerator physics, which was a rapidly growing field at the time. Cline became a Distinguished professor of Physics and Astronomy for his contributions to the growth of astroparticle physics and accelerator physics with the support of the UCLA Physics & Astronomy department that gained him global recognition in the field. He proposed investigations into the mass of the νΤ & νe neutrinos using terrestrial solar and supernova neutrino sources, nucleon decay using the ICARUS detector in Italy, and neutrino oscillations. To accomplish his projects, Cline and a small group of US physicists proposed the new design of a supernova neutrino detector large enough to observe extra-galactic supernova bursts.
Cline was part of the experiment that made their discovery in 1983 at CERN which first implemented the scheme they proposed in 1976. Later Cline was also a member of the Fermilab experiment that discovered the top quark and of one of the CERN experiments that discovered the Higgs boson in 2012.
At UCLA he was also one of the pioneers of the use of liquefied noble gases as particle detectors and made innovative contributions to the development of the use of liquid argon and xenon to detect dark matter.
In the early 1990s, the U.S. had plans to build the Superconducting Supercollider. Cline was among many other U.S. scientists who chose to work on a competing European based supercollider, CERN's Large Hadron Collider . He continued working at CERN's LHC and was a cofounder of the Compact Muon Solenoid (CMS) experiment. The goal was to detect and measure the stable particles that remain after colliding protons at nearly the speed of light, in an effort to investigate physics beyond the Standard Model and identify the conditions of the early universe.
The CMS was constructed and is located at one of the four collision points that make up the LHC and is designed to detect muons with high accuracy and be the most powerful solenoid magnet of its time, being capable of producing a magnetic field of 4 Tesla. The international collaboration that was CMS would come to be one of the largest of its kind, incorporating over 200 institutes and 50 countries. The collaboration proved to be successful, as the CMS was involved in the first 7 TeV proton-proton collisions, the discovery of the Xib baryon, and the discovery of the Higgs Boson. David Cline is listed as a contributor to these experiments for his contribution to the creation of CMS.
Cline was also involved in a collaboration between over 25 universities across the globe who proposed the construction of a neutrino detector in Fermilab in 2005. The proposed detector would be a 30 Kiloton Off-Axis Detector, with the purpose of studying  νμ → νe Oscillations in the NuMI Beamline. The NuMI Off-axis νe Appearance, or NOvA, collaboration brings together over 240 scientists from 51 institutions to study the effects neutrinos may have had on the evolution of the universe
Notable Involvements.
Super Proton-Antiproton Synchrotron & Compact Muon Solenoid.
Although Cline is not credited for the discovery of the W and Z bosons, Cline and Rubbia'sproposal of the installation of a proton-antiproton collider has led to advances in particle physics through the investigation of heavy bosons. Cline's role as a co-founder of the CMS experiment has also earned him the status of a contributor to the first 7 & 8 TeV proton-proton collisions, as well as the discovery of the Higgs Boson and Xib baryon.
Investigation of Dimuon Events.
In the early 70s, Cline investigated the production of dimuons from neutrinos and antineutrinos. These neutrino events require the generation and decay of intermediate particles that did not agree with models that predicted the intermediate particles to be heavy leptons and semi-weak vector bosons.
In February 1975, Cline and others reported on their observation of a new particle produced by high energy neutrino and antineutrino interactions. 14 dimuon events were observed, and due to the characteristics of the event and the absence of any trimuon events, the interaction seemed to require the presence of a new massive particle. The theorized particle, which was expected to have a previously unobserved quantum number, would need to decay weakly in order to have two muons in the final state.
The source of the second muon was argued to be due to the decay of pions and kaons. Cline and others provided evidence against this by observing “(i) the rate of dimuon events, (ii) the opposite signs of their electric charges, (iii) the different densities of the target materials in which they were produced, and (iv) the distributions in muon momentum and transverse momentum.”
The neutrino interactions leading to dimuon events required the existence of a new particle that they called the y particle. The group theorized that, if the particle was a hadron, the mass is between 2 and 4 GeV and the lifetime would have to be less than 10−10s. The alternate theory was that the neutrino interaction produced a neutral heavy lepton that decayed into two muons and a neutrino/antineutrino.
Physics potential of a few 100-GeV mu+ mu- collider.
Cline's most cited single-author paper describes the potential applications of " a few 100-GeV μ+μ− collider". His proposal was inspired by the evidence that the Standard Model and SUSY Model should exhibit a resonance at a mass just under 2Mz. At this energy range, it was very difficult to accurately detect and measure interactions at the LHC. Reaching such high energies was needed to search for the Higgs. The μ+μ− collider would have also had applications in investigating TeV interactions with higher resolution than colliders at the time.
High-Transverse-Momentum Secondaries and Rising Total Cross Sections in Cosmic-Ray Interactions.
While he was still at UW - Madison, Cline worked with Dr. Francis Halzen and studied hadron collisions from cosmic ray interactions. Their observations showed evidence for high-transverse-momentum secondaries in excess of the predicted exponential cutoff, which matched data from CERN at the time. Experiments at CERN ISR had shown that the cross sections of hadron collisions had been larger than expected. The data supported the quark model of the proton, where small momentum collisions would scatter at the “surface”, leading to an exponential cutoff of the transverse-momentum. High momentum collisions, however, lead to interactions with the quarks and produce high-transverse momentum along with a jet of hadrons. Their study concluded that the rise in the total cross section of the interactions of cosmic rays and the detection of hadron jets supports the theory of a composite model of the proton.
Observation of Elastic Neutrino-Proton Scattering.
Cline spent time exploring weak neutral current interactions by scattering neutrinos by protons. Previously, the exploration of this interaction was difficult due to the high neutron background and poor pion-proton separation. Cline mitigated these hindrances by using a detector that was sufficiently large enough to capture neutrino induced neutrons, which could be absorbed or detected through their interactions in the outer regions of the detector. Using a wide-band horn-focused neutrino beam at Brookhaven National Laboratory, Cline and others observed 30 events of neutrino-proton elastic scattering, which gave results consistent with most broken-gauge-symmetry models involving the weak neutral current.
Experimental Observation of Plasma Wake-Field Acceleration.
At Argonne National Laboratory Advanced Accelerator Test Facility, Cline and group created a plasma-wake field by exciting 21 MeV electrons through a dense plasma to measure the accelerated and deflected wake-field. This was one of the first instances of an experiment having performed a direct measurement of plasma wake fields by accelerating an injected witness-beam pulse in the wake of an intense driver-beam pulse in a plasma. They also demonstrated the existence of strong transverse wake fields using the witness beam.
The Search for Dark Matter.
The XENON100 project was a large collaboration dedicated to finding dark matter particles that Cline was involved in. Conducted at Laboratori Nazionali del Gran Sasso (LNGS) for 13 months during 2011 and 2012. The experiment featured an ultra-low electromagnetic background of (5.3 ± 0.6) × 10−3 events/(kg day keVee) in the energy region of interest. The resulting data provided the most stringent limit for the mass of WIMPs, mχ>8  GeV/c2, with a minimum nucleon cross section of σ=2.0×10−45  cm2 at mχ=55  GeV/c2.
Detection of Energy Deposition Down to the KeV Region Using Liquid Xenon Scintillation.
Cline was part of a collaboration to detect cosmic energy depositions in the KeV range in 1993. The group proposed a liquid xenon detector that could detect energies low enough to provide evidence for WIMPs. The proposed detector would also be able to distinguish alpha particles from gamma rays using scintillation and charge signal techniques. Previous detectors were not able to differentiate between background radioactivity and electrical noise, but by the utilization of an active chamber with high charge detection efficiency and liquid xenon scintillation, Cline and others suggested and believed that this type of detector would be the most effective method of directly measuring WIMPs.
Detection of Primordial Black Holes.
When primordial black holes explode at the end of their life, they send a myriad of particles flying across the universe. In 1992, Cline set out to investigate how accurately the current models described the hadronic and leptonic spectrum of these bursts, and predicted values for the upper limit of the particle densities. He suggested methods to detect gamma and neutrino bursts by utilizing the SuperNova Burst Observatory set to be constructed in New Mexico's WIPP site.
Published Works.
Papers.
David B. Cline has over 1400 published papers, and is cited over 90,000 times in various journals for high energy and astroparticle physics. He participated in numerous collaborations including, but not limited to, the ICARUS project, CMS at CERN, and UA1 collaboration. Below are some of the most cited and influential works that he contributed to.
Articles.
Cline wrote a total of seven articles for the Scientific American magazine. They are summarized below.
References in Media.
Last Documented Interview.
David Cline's last documented interview was a part of director Vincent Tran's movie "One Under the Sun" (2017), a science-fiction movie in which “The sole survivor of a doomed space mission attempts to reunite with her terminally ill daughter. The government, however, believes she's returned to earth with an extraordinary power and orders her confined to a secret facility”. The movie captured Cline's last documented interview, in which he discusses religion, the origin of the universe and how it relates to the origin of life, and the Higgs boson. He most notably considers the journey of a universe consisting only of elementary particles, and how we can study these elementary particles to investigate the origins of the universe and the big bang. He ponders on the idea that the universe was self-created, following Stephen Hawking’s argument which he popularized in his book “The Grand Design”. Cline argued that the Higgs boson must be present at the beginning of the universe in order to account for the mass of matter, and without it, the universe could not have been self-created. He admits that this topic borders on the line of religion because of the lack of proof and its ability to undermine other theories.
Concerning the origin of life, Cline sets out on connecting the Higgs boson to the big bang. He begins by stating the coincidence that all amino acids are left handed molecules and all nucleic acids are right handed molecules. He argues that life could have been created by any combinations of the amino-acids found on earth, but life settled on the 21 acids by chance. Cline mentions a meteor found in Australia, referencing the Murchison meteorite. He explains that because the meteor had a large volume, the core of the meteor was left unharmed from the radiation that had damaged the outer layers. This led to the great discovery of over 70 new amino acids, different from the ones previously found on earth. He uses this example to illustrate how many different combinations of amino-acids could have led to the formation of life, leading to the necessity of a common origin of life. Supernova explosions emit 1057 neutrinos, which can induce a left-handedness in the surrounding matter, and due to the Supernova Neutrino Amino Acid Processing model, leading to the generation of left-handed amino acids, dubbing them amino-acid factories. Cline concludes by stating his belief that all amino acids in our body came from outer space, connecting the origin of life to the early days of the universe.
Books.
Telescope in the Ice.
"The Telescope in the Ice: Inventing a New Astronomy at the South Pole", by Mark Bowen draws on his involvement in the IceCube project in Antarctica. David Cline was mentioned in the book due to his role in the project as well. Cline was involved in the search for high-energy cosmic neutrinos through the IceCube Neutrino Observatory at the Amundsen-Scott South Pole Station. He was brought on the project for his expertise in neutrino interactions, and was said to be one of the project's founder's, Francis Halzen, most important mentors.
Nobel Dreams.
"Nobel Dreams: Power, Deceit and the Ultimate Experiment", by Gary Taubes mentions Cline for his contributions as a collaborator to the UA1 and UA2 experiments; the former eventually found the W and Z bosons, and then won the award the book was named after.
Personal life.
David Cline married twice. He died on June 27, 2015 at UCLA Medical Center, following a heart attack on campus the previous afternoon. He is survived by five children and eight grandchildren.


William George Fastie

William George Fastie (6 December 1916 – 14 July 2000) was an American optical physicist and spectroscopist who played a part in the Johns Hopkins University space program of the late 1950s.
Early years.
Fastie was one of four children of William Ferdinand and Carolyn Fastie. He attended Johns Hopkins University between 1934 and 1941, initially at evening classes and later as a graduate student in physics, supervised by August Herman Pfund, Robert W. Wood, and Gerhard Heinrich Dieke.
Career.
During World War II, Fastie work in the department of physics involved the development of infrared detectors. At the end of the War he joined Leeds & Northrup as a research physicist, but was lured back to Hopkins in 1951 by the professor of physics, John D. Strong.
Fastie's first publication described a new design of spectrometer which today bears his name. With the launch of Sputnik 1, Fastie saw the potential of spectroscopy from space, and started a program at Hopkins to develop this idea. Initially concentrating on spectroscopic analysis of the Earth's upper atmosphere, it soon broadened into a full-fledged astronomy program, using accurately pointed telescopes.
He contributed to the Mariner 5 flyby of Venus in 1967, and the Mariner 6 and 7 flybys of Mars in 1969, as well as heading the ultraviolet spectrometer experiment on Apollo 17 in 1972 - the missions using ultraviolet spectrometers designed by Fastie in 1952. Known today as the Ebert-Fastie spectrometer, it has a design similar to that described by in the early 1900s. Fastie's interests also moved to astronomy in the 1960s, and he designed a number of precision-pointing telescopes whose designs are still used in sounding rockets.
In 1977 NASA appointed Fastie as a member of the Hubble Space Telescope (HST) science working group. In 1979, the
Association of Universities for Research in Astronomy Inc suggested Hopkins as the home for the Space Telescope Science Institute. Fastie provided a detailed formulation for the proposal. The bio-luminescence of Chesapeake Bay was added to his list of interests, as was the development of new designs of spectroscope.
Fastie retired from Hopkins in 1982, but continued to work on campus for another 15 years. He contributed to the design of the Hopkins Ultraviolet Telescope, used on the Space shuttle in December 1990 and March 1995.
The 'Fastie Finger', a device in the Advanced Camera for Surveys used for masking unwanted bright astronomical light sources used, is named after him.
Personal life.
Fastie and his wife Frances raised two sons and a daughter.
Fastie died in Baltimore of pneumonia on July 14, 2000.


Lawrence Biedenharn

Lawrence Christian Biedenharn, Jr. (18 November 1922, Vicksburg, Mississippi – 12 February 1996, Austin, Texas) was an American theoretical nuclear physicist and mathematical physicist, a leading expert on applications of Lie group theory to physics.
Biedenharn studied at MIT with an interruption in World War II from 1942 to 1946 as a lieutenant in the Signal Corps in the Pacific theater, where in 1946 he was stationed in Tokyo for a year as a radio officer. He received his bachelor's degree in absentia from MIT. After World War II, he returned to MIT where he received his PhD in physics under Victor Weisskopf in 1950. As an MIT graduate student he shared an office with J. David Jackson, then a graduate student, and John Blatt, then a post-doc. Biedenharn was employed at Oak Ridge National Laboratory, became an assistant professor at Yale University, and then an associate professor at Rice University. From 1961 he was a professor at Duke University, where he became in 1987 "James B. Duke Professor", and then retired in 1992 as professor emeritus. He remained active in teaching and research as an adjunct professor at the University of Texas, Austin. In 1996 he died from kidney cancer.
Biedenharn is known for his contributions to the quantum theory of angular momentum, especially the theory of nuclear reactions and Coulomb excitations (excitations of atoms by the scattering of charged particles and the Coulomb interaction with the nucleus). In the later part of his career, he worked on representation of quantum groups. From 1985 to 1993 he was the chief editor of the "Journal of Mathematical Physics". For many years Hendrik van Dam was his co-editor.
In 1958 Biedenharn was a Fulbright Fellow and a Guggenheim Fellow. He received the Jesse W. Beams Award in 1979 and twice received (1976 and 1987) the Humboldt Prize.
In 1950 he married Sarah Willingham, who became a lawyer; they had a son and a daughter.


Sekazi Mtingwa

Sekazi Kauze Mtingwa: (born Michael Von Sawyer; October 20, 1949) is an American theoretical high-energy physicist. He is a co-recipient of the 2017 Robert R. Wilson Prize for Achievement in the Physics of Particle Accelerators. He is the first African-American to be awarded the prize. Mtingwa was elected a Fellow of the American Physical Society (APS) in 2008 for "his definitive treatment of Intrabeam scattering, his contributions to the wakefield acceleration, and his early recognition of the fixed target physics potential of the next generation electron-positron collider." He also co-founded the National Society of Black Physicists in 1977 and served in various other national and international initiatives.
Biography.
Mtingwa was born in Atlanta, Georgia. He studied physics and pure mathematics at the Massachusetts Institute of Technology (MIT), where he received B.S. degrees in both subjects in 1971. While an undergraduate, he helped found the Interphase EDGE (then Project Interphase) program to prepare incoming students in subjects such as physics and math. Afterwards, he joined graduate school at Princeton University, where he was awarded a Ph. D. degree in theoretical high energy physics in 1976. The title of his PhD thesis is "Asymptotic chiral invariance and its consequences." While in graduate school, he changed his name from Michael Von Sawyer to Sekazi Kauze Mtingwa, a Tanzanian name.
After graduating from Princeton, Mtingwa took a research associate position, which turned into a part-time assistant professorship including some teaching duties, from Susumu Okubo at the University of Rochester. There in Rochester, Mtingwa met and soon married Estella Johnson. In 1978, he took a post-doctoral research position at the University of Maryland, College Park in the Center for Theoretical Physics.
Mtingwa received a Ford Foundation fellowship in 1980 and took it to Fermilab in Illinois for a one-year postdoctoral position, and became a research physicist there in 1981. In joint work with James Bjorken, an American theoretical physicist who is Emeritus Professor at the Stanford Linear Accelerator Center, he developed a theory of "intrabeam scattering" in particle accelerators.
 For this work, he was awarded the 2017 Robert R. Wilson Prize for Achievement in the Physics of Particle Accelerators, since that theory "empowered major discoveries in a broad range of disciplines by a wide variety of accelerators, including hadron colliders, damping rings/linear colliders, and low emittance synchrotron light sources."
While at Fermilab, he also contributed in a significant way to two of the antiproton source accelerator systems, which were instrumental in particle discoveries, including that of the top quark.
In 1988–1991, Mtingwa worked at Argonne National Laboratory, where he developed theory of advanced wakefield and plasma acceleration and of the photon colliders. Starting in 1991, he joined the faculty at North Carolina A&T State University (with a brief stint at Morgan State University in 1997–1999). He has been a visiting professor at MIT and Harvard University.
Sekazi Mtingwa is a founder of the African Laser Centre and a cofounder of Triangle Science, Education & Economic Development, a consulting company that supports underrepresented groups in STEM. Mtingwa is a cofounder and former president of the National Society of Black Physicists.
He is a Fellow of the American Physical Society (elected in 2008) and of the American Association for the Advancement of Science (elected in 2015).


Melissa Franklin

Melissa Eve Bronwen Franklin (born September 30, 1956) is an experimental particle physicist and the Mallinckrodt Professor of Physics at Harvard University. In 1992 Professor Franklin became the first woman to receive tenure in the Physics department at Harvard University and she served as Chair of the department from 2010 to 2014. While working at Fermi National Accelerator Laboratory in Chicago, her team found some of the first evidences for the existence of the top quark. In 1993, Franklin was elected a fellow of the American Physical Society. She is currently member of the CDF (Fermilab) and ATLAS (CERN) collaborations.
Early life and education.
Franklin was born in Edmonton, Alberta and grew up first in Vancouver, British Columbia and then Toronto, Ontario, where her family moved in 1962. Her father, Stephen Franklin, was a British-born journalist who worked as drama critic for the "Ottawa Journal" and later as staff writer and editor for "Weekend" magazine. Her mother, Elsa, was a television producer as well as Canadian author Pierre Berton's manager and literary agent. Melissa Franklin dropped out of high school to form an alternative school with friends. After attending SEED Alternative School and the Lycee Francais Charles de Gaulle in London, she studied physics at the University of Toronto and graduated in 1977. In the summer of 1977, while Melissa Franklin was a student at CERN, she was part of a legendary bar-room bet with John Ellis which in part led to the naming of Penguin diagrams.
Career.
Franklin was a student at CERN in 1978, where she met John Ellis. According to Ellis, he coined the name penguin diagrams following a bet he had made with her in a pub. Franklin earned her physics PhD from Stanford University in 1982 with a thesis titled "Selected studies of charmonium decay" under the supervision of Gary Feldman, working with the school's linear accelerator, SLAC. She did postdoctoral work at the University of California at Berkeley in the Lawrence Berkeley Laboratory. In 1988 she became an assistant professor at the University of Illinois, and worked at Fermilab in Chicago. In 1987 she joined Harvard University, later becoming the physics department's first tenured woman professor. For over a decade, Franklin traveled between Boston and Chicago every few weeks, to check on and fix equipment at Fermilab. In 1995, her team proved the existence of the top quark.
At Harvard, Franklin co-directs the Laboratory for Particle Physics and Cosmology (LPPC), alongside Gary Feldman, John Huth, Masahiro Morii and Christopher Stubbs. The LPPC studies topics on the Energy Frontier, the Intensity Frontier and the Cosmic Frontier.
Since the 1990s, Franklin has been a frequent guest on the CBC Radio science program "Quirks and Quarks". Franklin has also been a frequent lecturer and "dramatic read[er]" in the annual Ig Noble Prize Ceremonies and other events of the "Annals of Improbable Research".


Thiago David Olson

Thiago David Olson (born 1989) is a venture capitalist, electrical engineer and entrepreneur. Olson is the co-founder and CEO of Stratos Technologies, Inc., creators of the Stratos Card. As an electrical engineer Olson became known as a teenager for his research in Nuclear Fusion and Neutron Sciences. As a 17-year-old, attending Stoney Creek High School in Rochester Hills, Michigan, Olson created a homemade nuclear fusion reactor. In his article "Neutron activation analysis using an inertial electrostatic confinement fusion device" he indicated that his apparatus did not produce surplus energy.
For this work, he received a first place Special Award given by the AVS/VTD in 2007 in connection with a second place prize in the Intel International Science and Engineering Fair 2007, section Physics and Astronomy
He studied at Vanderbilt University and Princeton University. In 2009, he was one of three students to receive a Department of Defense "SMART" Fellowship, which supports students who demonstrate interest in conducting applied research.
Olson previously worked as an electrical engineer at the U.S. Department of Defense.
The minor planet 23262 Thiagoolson has been named after Olson for his research in nuclear fusion and neutron sciences.
External links.
https://www.fastcompany.com/3043133/genius-who-built-a-nuclear-fusion-reactor-at-17-takes-on-the-payments-industry


Jiming Bao

Jiming Bao is a Chinese physicist.
Bao studied physics at Zhejiang University, where he earned his bachelor's and master's degrees. He then completed a doctorate in applied physics at the University of Michigan. Bao teaches at the University of Houston. In 2018, Bao was elected a fellow of the Optical Society of America. In 2019, he was granted an equivalent honor by the American Physical Society, "[f]or the discovery of photoacoustic laser streaming, for seminal contributions to the understanding of basic electronic and optical properties of nanostructured materials, and the development of new nanomaterials for applications in solar energy conversions and optoelectronic devices."


Unit generator

Unit generators (or "ugens") are the basic formal units in many MUSIC-N-style computer music programming languages. They are sometimes called opcodes (particularly in Csound), though this expression is not accurate in that these are not machine-level instructions.
Unit generators form the building blocks for designing synthesis and signal processing algorithms in software. For example, a simple unit generator called OSC could generate a sinusoidal waveform of a specific frequency (given as an input or argument to the function or class that represents the unit generator). ENV could be a unit generator that delineates a breakpoint function. Thus ENV could be used to drive the amplitude envelope of the oscillator OSC through the equation OSC*ENV. Unit generators often use predefined arrays of values for their functions (which are filled with waveforms or other shapes by calling a specific generator function).
The unit generator theory of sound synthesis was first developed and implemented by Max Mathews and his colleagues at Bell Labs in the 1950s.
Code example.
In the SuperCollider language, the .ar method in the SinOsc class is a UGen that generates a sine wave. The example below makes a sine wave at frequency 440, phase 0, and amplitude 0.5.


Optical phenomena

Optical phenomena are any observable events that result from the interaction of light and matter. See also list of optical topics and optics. A mirage is an example of an optical phenomenon.
Common optical phenomena are often due to the interaction of light from the sun or moon with the atmosphere, clouds, water, dust, and other particulates. One common example is the rainbow, when light from the sun is reflected and refracted by water droplets. Some phenomena, such as the green ray, are so rare they are sometimes thought to be mythical. Others, such as Fata Morganas, are commonplace in favored locations.
Other phenomena are simply interesting aspects of optics, or optical effects. For instance, the colors generated by a prism are often shown in classrooms.
List.
Optical phenomena include those arising from the optical properties of the atmosphere; the rest of nature (other phenomena); of objects, whether natural or human-made (optical effects); and of our eyes (Entoptic phenomena). Also listed here are unexplained phenomena that could have an optical explanation and "optical illusions" for which optical explanations have been excluded.
There are many phenomena that result from either the particle or the wave nature of light. Some are quite subtle and observable only by precise measurement using scientific instruments. One famous observation is of the bending of light from a star by the Sun observed during a solar eclipse. This demonstrates that space is curved, as the theory of relativity predicts.
Unexplained phenomena.
Some phenomena are yet to be conclusively explained and may possibly be some form of optical phenomena. Some consider many of these "mysteries" to simply be local tourist attractions that are not worthy of thorough investigation.


Maurice Tweedie

Maurice Charles Kenneth Tweedie, British medical physicist and statistician from the University of Liverpool, was born in Reading, England September 30, 1919 and died March 14, 1996.
He read physics at the University of Reading and attained a B.Sc. (general) and B.Sc. (special) in physics in 1939 followed by a M.Sc. in physics 1941. He found a career in radiation physics, but his primary interest was in mathematical statistics where his accomplishments far surpassed his academic postings. This included pioneering work with the Inverse Gaussian distribution. Arguably his major achievement rests with the definition of a family of exponential dispersion models characterized by closure under additive and reproductive convolution as well as under transformations of scale that are now known as the Tweedie exponential dispersion models.
As a consequence of these properties the Tweedie exponential dispersion models are characterized by a power law relationship between the variance and the mean which leads them to become the foci of convergence for a central limit like effect that acts on a wide variety of random data. The range of application of the Tweedie distributions is wide and includes:
Tweedie's Formula
An additional area of Tweedie's work was the development of a formula which Efron (2011) described as offering "a simple empirical Bayes approach to correcting selection bias".


Patrice Cellario

Patrice Cellario (born November 21, 1953) is a Monegasque nuclear physicist and civil servant. He serves as Monaco's Interior Minister.
Early life.
Patrice Cellario was born on November 21, 1953 in Monaco. He was educated in Monaco, attended prep school in Marseille, and graduated from the Grenoble Institute of Technology. He earned a PhD in Physics.
Career.
Cellario started his career at the Centre d'études nucléaires in Grenoble.
Cellario became a civil servant in Monaco in 1982, where he worked on telecommunications. He was engineering manager of the Stade Louis II from 1985 to 1988. He was the deputy director of Monaco Public Works from 1990 to 1992, and its director from 1992 to 1998. He then served as the director of Monaco's Environment, Urban Affairs and Construction from 1998 to 2000, followed by Monaco's Foresight and Studies on Urban Affairs form 2001 to 2008, and Monaco's Foresight, Urban Affairs and Mobility from 2008 to 2009. He served as the chief executive of Monaco's Department of the Interior from 2009 to 2015.
Cellario has served as Monaco's Interior Minister since April 4, 2015.
Personal life.
Cellario is married, and he has three children.


John R. Kirtley

John Robert Kirtley (born August 27, 1949) is an American condensed matter physicist and a Consulting Professor at the Center for Probing the Nanoscale in the Department of Applied Physics at Stanford University. He shared the 1998 Oliver E. Buckley Prize of the American Physical Society, and is a Fellow of both the American Physical Society and the American Association for the Advancement of Sciences.
Early life and education.
He received his BA in Physics in 1971 and his PhD in Physics in 1976, both from the University of California, Santa Barbara. His PhD topic was inelastic electron tunneling spectroscopy, with Paul Hansma as his thesis advisor. He was then a Research Assistant Professor at the University of Pennsylvania from 1976–1978, working in the group of Donald N. Langenberg on non-equilibrium superconductivity. From 1978 to 2006 he was a Research Staff Member at the IBM Thomas J. Watson Research Center in Yorktown Heights, New York. Since 2006 he has worked at the University of Twente in the Netherlands, been an Alexander von Humboldt Foundation Forschungspreis winner at the University of Augsburg in Germany, a Jubileum Professor at Chalmers University of Technology in Sweden, and currently holds a Chaire d'Excellence from the NanoSciences Fondation in Grenoble, France.
Career.
He has worked in the fields of Surface Enhanced Raman scattering, light emission from tunnel junctions and electron injection devices, noise in semiconducting devices, scanning tunneling microscopy and scanning SQUID microscopy. He is married to Kathryn Barr Kirtley, who received her PhD from UCSB in quantum chemistry in 1977. They have one son, the writer David Barr Kirtley.
Kirtley shared the 1998 Oliver E. Buckley Prize with C.C. Tsuei, Donald Ginsberg, and D.J. van Harlingen. The citation was for "using phase-sensitive experiments in the elucidation of the orbital symmetry of the pairing function in high-Tc superconductors". Kirtley, Tsuei, and co-workers used scanning SQUID imaging of the half-integer flux quantum effect in tricrystal samples
 to demonstrate that cuprate high temperature superconductors have predominantly d-wave pairing symmetry.


Reality Is Not What It Seems

Reality Is Not What It Seems: The Journey to Quantum Gravity () is an illustrated book by Italian physicist Carlo Rovelli.
The book discusses quantum gravity. It was first published in Italian in 2014 (before the author's best-seller "Seven Brief Lessons on Physics"). It was published in English in 2016 by which time the English translation of "Seven Brief Lessons" had already appeared.
Structure.
The book's opening chapters trace the history and evolution of quantum gravity. Starting with pre-socratic philosopher Democritus through to the ideas of Sir Isaac Newton and, eventually, Albert Einstein, Rovelli puts forward a theory that quantum gravity brings great unity to the universe. Rovelli then states that space and time, waves and particles, energy and matter are all the same. Rovelli then seeks to disprove the concepts of continuity and infinity.


John Hopps

John H. Hopps (1939 – May 14, 2004) was an American physicist and politician. A native of Dallas, Texas, Hopps was a Ford Scholar to Morehouse College, also receiving degrees from the Massachusetts Institute of Technology (where he was a member of Omega Psi Phi fraternity) and Brandeis University. After his graduation in 1971, Hopps joined the faculty at Ohio State University, and later accepted a research position in nuclear engineering at MIT, and was a member of leadership at the Charles Stark Draper Laboratory.
In 1992, Hopps joined the National Science Foundation, where he was director of the division of materials sciences, and in 1995 returned to Morehouse, where he became provost and senior vice-president. Hopps was appointed by President George W. Bush as deputy Undersecretary of Defense, in 2001, where he oversaw research for defense and engineering, a position he held until his death on 14 May 2004 in Potomac, Maryland.


Swapan Chattopadhyay

Swapan Chattopadhyay CorrFRSE (born December 26, 1951) is an Indian American physicist. Chattopadhyay completed his PhD from the University of California (Berkeley) in 1982.
Currently, Chattopadhyay holds the Presidential Chair of Research, Scholarship and Artistry at Northern Illinois University (NIU) where he is Professor of Physics and Director of Accelerator Research. Concurrently he holds a joint appointment with Fermi National Accelerator Laboratory (Fermilab) where he is a distinguished scientist, member of the director's senior leadership team and director of the Cooperative Research and Development Agreement between Fermilab and NIU.
Chattopadhyay is a Fellow of the American Physical Society, American Association for the Advancement of Science, Institute of Physics (UK), Royal Society of Arts, Manufactures and Commerce (UK) and Corresponding Fellow of the Royal Society of Edinburgh and a member of many international panels and committees, including the "International Committee for Future Accelerators" and the DESY Science Council (2008–2013).
Early life and education.
Early childhood.
Swapan Chattopadhyay was born in Calcutta, India and spent his early childhood years in the Himalayan hill town of Darjeeling. The Indo-China conflict over the disputed territory of Tibet led the family to relocated to the metropolitan mega-city of Calcutta in the early 1960s, where he received high school and university education. He was awarded a high school diploma in 1967 as a National Scholar, graduating from Ballygunge Government High School and was selected a National Science Talent Scholar in a nationwide competition. It was in this high school, that he was the beneficiary of the gifted mentorship of the school's physics teacher, Pramatha Nath Patra.
Higher education and early career.
Chattopadhyay completed his B.Sc. degree from Calcutta University in 1970 in physics. He continued his studies at the Indian Institute of Technology at Kharagpur, for his post-graduate studies, completing his M.Sc. degree with specialization in Particle Physics in 1972.
Chattopadhyay then joined in 1972 the Physics department of the University of Oregon. However, over time, the draw towards the University of California at Berkeley got stronger and he joined the University of California at Berkeley in 1974, as a Ph.D. student in the Department of Physics. After flirting for two years (1974–1976) with the inimitable Berkeley brand of theoretical particle physics, then known as the "S-matrix" and "Bootstrap" theories of "strong interactions", under tutelage of Prof. Geoffrey Chew, Chattopadhyay was attracted away by accelerator physics dealing with charged particle and light beams. After having completed his PhD, he moved to CERN as an "attaché scientifique" in the Super Proton-Antiproton Synchrotron, contributing to program of stochastic cooling of antiproton beams.
Career.
Chattopadhyay is noted for his pioneering contributions of innovative concepts, techniques and developments in high energy particle colliders, coherent and incoherent light sources, ultrafast sciences in the femto- and atto- second regimes, superconducting linear accelerators and various applications of interaction of particle and light beams. He has directly contributed to the development of many accelerators around the world, e.g. the Super Proton-Antiproton Synchrotron at CERN, the Advanced Light Source at Berkeley, the asymmetric-energy electron-positron collider PEP-II at Stanford, the Continuous Electron Beam Accelerator facility (CEBAF) at Jefferson Lab and the Free-Electron Lasers at Jefferson and Daresbury Laboratories.
He was formerly the Sir John Cockcroft Chair of Physics jointly at the Universities of Liverpool, Manchester and Lancaster—the First Chair of accelerator physics in UK, named after the British Nobel Laureate credited with creating the field. In this role he was the Inaugural Director of the Cockcroft Institute (UK), having been appointed in April 2007. Prior to this he served as Associate Director of Thomas Jefferson National Accelerator Facility (2001–2007), Staff/ Senior Scientist and Founding Director of the Centre for Beam Physics at Lawrence Berkeley National Laboratory (1984–2001); and Scientific Attaché at CERN (1982–1984).
After the period spent at CERN, Chattopadhyay returned to Lawrence Berkeley National Laboratory in 1984, where he led and defined the accelerator physics of the Advanced Light Source (ALS) and contributed to the conceptual design of the Superconducting Super Collider (SSC), pioneered the accelerator physics which underpinned the Berkeley-Stanford asymmetric B-factory (PEP-II) for CP-violation studies, and initiated the Berkeley FEL/Femtosecond X-ray Source and Laser-Plasma Acceleration development. He was a Senior Scientist, a Guest Professor, and the Founder/Director of the Center for Beam Physics at Berkeley, until his move to Thomas Jefferson National Accelerator Facility in 2001 as the Associate Laboratory Director for Accelerators. At Thomas Jefferson National Accelerator Facility, he made critical advancements in microwave superconducting linear accelerators leading the way to current and future grand instruments of science such as the high precision CEBAF and its 12 GeV upgrade for precision research in hadronic physics, Spallation Neutron Source at Oak Ridge National Laboratory, USA to advance neutron sciences and novel materials research, and the current superconducting version of the International Linear Collider, to name a few.
His research at the Cockcroft Institute in UK included development of sources of "ultra-cold" relativistic free electron beams to advance coherent electron diffraction techniques; production of novel coherent and ultra-short pulses of photons (e.g. x-ray FELs); novel acceleration methods; investigation of photonic crystals and metamaterial structures for charged particle acceleration; novel high energy colliders; cavity search for "dark matter" and laboratory investigation of "dark energy" via atom interferometer techniques. Chattopadhyay is currently working for Fermilab and Northern Illinois University (NIU) acting as a distinctive professor and director of accelerator research.
Having contributed to the conception, design, construction, commissioning and operation of numerous accelerators for particle and nuclear physics, photon and neutron sciences around the world, with significant research accomplishments in advanced particle and photon beam physics, and mentoring scientists around the world, in the developing nations in particular, in accelerator developments as a unifying global force among nations, Swapan Chattopadhyay is a frequently invited speaker and advisor at professional societies and government research agencies, serving on numerous editorial, advisory and review committees throughout the world.
He served as the Vice-Chair, Chair-elect, Chair and Past-Chair of the American Physical Society's Division of Physics of Beams (2007–2011). Chattopadhyay has delivered lectures throughout the world e.g. Saha Memorial Lecture, Homi Bhabha Lecture, Raja Ramanna Memorial Lecture, and Cavendish Lecture among many.


Channelling (physics)

Channelling is the process that constrains the path of a charged particle in a crystalline solid.
Many physical phenomena can occur when a charged particle is incident upon a solid target, e.g., elastic scattering, inelastic energy-loss processes, secondary-electron emission, electromagnetic radiation, nuclear reactions, etc. All of these processes have cross sections which depend on the impact parameters involved in collisions with individual target atoms. When the target material is homogeneous and isotropic, the impact-parameter distribution is independent of the orientation of the momentum of the particle and interaction processes are also orientation-independent. When the target material is monocrystalline, the yields of physical processes are very strongly dependent on the orientation of the momentum of the particle relative to the crystalline axes or planes. Or in other words, the stopping power of the particle is much lower in certain directions than others. This effect is commonly called the "channelling" effect. It is related to other orientation-dependent effects, such as particle diffraction. These relationships will be discussed in detail later.
History.
The channelling effect was first discovered in binary collision approximation computer simulations in 1963 to explain exponential tails in experimentally observed ion range distributions that did not conform to standard theories of ion penetration. The simulated prediction was confirmed experimentally the following year by measurements of ion penetration depths in single-crystalline tungsten. First transmission experiments of ions channeling through crystals were performed by Oak Ridge National Laboratory group showing that ions distribution is determinated by crystal rainbow channeling effect.
Mechanism.
From a simple, classical standpoint, one may qualitatively understand the channelling effect as follows: If the direction of a charged particle incident upon the surface of a monocrystal lies close to a major crystal direction (Fig. 1), the particle with high probability will only do small-angle scattering as it passes through the several layers of atoms in the crystal and hence remain in the same crystal 'channel'. If it is not in a major crystal direction or plane ("random direction", Fig. 2), it is much more likely to undergo large-angle scattering and hence its final mean penetration depth is likely to be shorter. If the direction of the particle's momentum is close to the crystalline plane, but it is not close to major crystalline axes, this phenomenon is called "planar channelling".
Channelling usually leads to deeper penetration of the ions in the material, an effect that has been observed experimentally and in computer simulations, see Figures 3-5.
Negatively charged particles like antiprotons and electrons are attracted towards the positively charged nuclei of the plane, and after passing the center of the plane, they will be attracted again, so negatively charged particles tend to follow the direction of one crystalline plane.
Because the crystalline plane has a high density of atomic electrons and nuclei, the channeled particles eventually suffer a high angle Rutherford scattering or energy-losses in collision with electrons and leave the channel. This is called the "dechannelling" process.
Positively charged particles like protons and positrons are instead repelled from the nuclei of the plane, and after entering the space between two neighboring planes, they will be repelled from the second plane. So positively charged particles tend to follow the direction between two neighboring crystalline planes, but at the largest possible distance from each of them. Therefore, the positively charged particles have a smaller probability of interacting with the nuclei and electrons of the planes (smaller "dechannelling" effect) and travel longer distances.
The same phenomena occur when the direction of momentum of the charged particles lies close to a major crystalline, high-symmetry axis. This phenomenon is called "axial channelling".
At low energies the channelling effects in crystals are not present because small-angle scattering at low energies requires large impact parameters, which become bigger than interplanar distances. The particle's diffraction is dominating here. At high energies the quantum effects and diffraction are less effective and the channelling effect is present.
Applications.
There are several particularly interesting applications of the channelling effects.
Channelling effects can be used as tools to investigate the properties of the crystal lattice and of its perturbations (like doping) in the bulk region that is not accessible to X-rays.
The channeling method may be utilized to detect the geometrical location of interstitials. This is an important variation of the Rutherford backscattering ion beam analysis technique, commonly called Rutherford backscattering/channeling (RBS-C).
The channeling may even be used for superfocusing of ion beam, which can be used for sub-atomic microscopy.
At higher energies (tens of GeV), the applications include the channelling radiation for enhanced production of high energy gamma rays, and the use of bent crystals for extraction of particles from the halo of the circulating beam in a particle accelerator.


Antoine Georges

Antoine Georges (born 14 April 1961) is a French physicist. He is director of the Center for Computational Quantum Physics of the Flatiron Institute, professor at Collège de France and also at Ecole polytechnique.
Biography.
Georges' passion for science began during his teen age years at his father's laboratory where he used to capture mice for his father's experiments at the French Institute of Health and Medical Research.
In 1983 he graduated from the École Polytechnique and joined École Normale Supérieure. He obtained his Ph.D. in 1988 from Pierre-Gilles de Gennes.
In 1989, he became a postdoc at the Princeton University in order to work on high-critical-temperature superconductors in the lab of Phil Anderson and worked there till 1991. In autumn of 1990 he along with Gabriel Kotliar joined Rutgers University where they developed today's formulation of dynamical mean field theory by mapping it onto the self-consistent solution of a quantum impurity model. He also worked with Anirvan Sengupta on Kondo effects and performed theoretical work on spin glasses and quantum spin liquids along with Olivier Parcollet and Subir Sachdev.
In 2003 he relocated to the Centre de Physique Théorique, a division of École Polytechnique, and as of 2009 holds chairman position at the Collège de Frances' condensed matter physics. In February of the same year he became a teacher and professor at the Collège de France. In 2010 he was named Sommerfeld lecturer by the Ludwig Maximilian University and in 2011 became Schrödinger lecturer at the ETH Zurich. The same year he became a part-time professor at the University of Geneva and prior to all of it, he was a recipient of the "Dargelos Prize" in 2004 from his alma mater. In 2006 he was awarded the "Europhysics Prize" in condensed matter and next year he was honoured with a CNRS Silver medal.


William E. Forsythe

William Elmer Forsythe (August 22, 1881 — June 30, 1969) was an American physicist and President of the Optical Society of America.
Forsythe received his bachelor's degree from Denison University and went on to obtain a Master's and PhD at the University of Wisconsin. He was awarded the honorary degree of doctor of science from Kenyon College in 1926. In 1924 he was appointed Director of the NELA Research Laboratory in Cleveland, Ohio. During World War II he was associated with the Office of Scientific Research and Development as well as the National Defense Research Committee. He was elected member emeritus and fellow of the Illuminating Engineering Society. He served as president of the Optical Society of America from 1926 to 1927.
He died on June 30, 1969.


Marilyn Gunner

Marilyn Gunner is a physics professor at the City College of New York (CUNY) and a Fellow of the American Physical Society. She is known for her work on molecular biophysics and structural biology.
Education.
Gunner received her B.A. from the State University of New York (Binghamton). She completed her Ph.D. in 1988 at the University of Pennsylvania, where she worked on topics such as electron transfer in proteins with Leslie Dutton.
Career and Research.
Gunner previously worked in the lab of Barry Honig at Columbia University, where she studied electrostatic control of proteins. She is now a Professor in the Physics Department at CUNY where she has continued to study protein interactions. As of 2021, her 140 publications have been cited over 5,800 times. She is the lead investigator of the Multi-Conformation Continuum Electrostatics (MCCE) project, which is "a biophysics simulation program combining continuum electrostatics and molecular mechanics." Gunner was also part of a collaboration which measured the efficiency of energy storage in cyanobacteria, work that could have implications for astrobiology.
In 2006, Gunner served as the chair of the Division of Biological Physics in the American Physical Society. She currently serves as a member of the Editorial Board for both the Journal of the Royal Society Interface and Biochimica et Biophysica Acta - Bioenergetics. Gunner has also served as both a general member and as a member of the Board of Directors for the Telluride Science Research Center.