in a preferred set of embodiments , free radicals created to kill tumor cells have their lifetimes extended by a weak magnetic field ( in the range of 10 to 100 gauss ), shaped and timed to extend free radical lifetimes in the tumor , while avoiding to the extent possible , extending free radical lifetimes in surrounding tissue . in one preferred embodiment tumor cells are exposed to levels of 2 to 6 gy of co - 60 gamma radiation ( ir ) stimulus , with simultaneous exposure to dc field strengths ranging from 10 to 100 gauss ( 1 to 10 millitesla ), with the dc electromagnetic field exposure continuing for up to one hour after cessation of the ir . in other preferred embodiments other forms of stimulus for producing free radicals are used , including chemotherapy , other forms of radiation and exposure to induced ultrasound , ultraviolet , thermal , or sonic cavitation energy . magnetic field persistence after cessation of stimulus is between 1 minute and 10 hours . referring to fig5 , in one preferred embodiment , a machine 110 is used to provide the tumor treating radiation and magnetic field . a control computer 112 , controls an electromagnetic current source 114 , which controls the electromagnets 116 , including turning them off and / or rapidly sequencing a planned variable strength field . the computer 112 also controls the radiation beam level control 118 , which controls the intensity of the radiation beam 122 , from the radiation beam source 120 . radiation beam 122 travels through a human body 124 and reaches and travels through a tumor 126 . an electromagnetic field , having axis 130 helps to perpetuate free radicals produced by the radiation beam 122 . fig6 shows a machine that is the same as that of fig5 , except for that permanent magnets 130 are used , in order to produce a very thin magnetic field , to restrict the magnetic field effects as much as possible to the tumor . because it is beneficial for magnets 130 to be very accurately aligned , in one embodiment they are not moved , but the patient is moved upwardly by a bed lift mechanism 132 , so that magnets 130 can be laser aligned prior to a patient being treated , without having to be moved into position after alignment , which could cause some of the precision of the alignment to be lost during this movement . a magnetic field interrupting mechanism 134 ( in one embodiment mounted on a rotating shaft ) can be used to block the magnetic field , in one embodiment in a periodic manner coordinated with the radiation beam source 120 and contoured to conform to tumor shape . referring to fig7 , showing a preparation and treatment scheme 150 begins with a determination , based on tumor location , of the positioning of magnets 116 ( fig5 ) and radiation beam source 120 ( block 152 ). then , given these locations , the maximum permissible radiation exposure for the interposed tissue is computed ( block 154 ). next , given these limits , the maximum effectiveness scheme of exposure to a radiation beam and a magnetic field is determined ( block 156 ). as it is impossible to expose only the tumor to the magnetic field , the effect of the magnetic field on the radiation beam effect on interposed tissue must be taken into consideration in this determination . after this , the magnets and radiation sources are physically positioned relative to the body ( block 158 ) and treatment is undertaken , according to the scheme ( block 160 ). the increase in the efficacy of the treatment , for the case of a radiation is given by : where int is the integral over the volume indicated in the superscript and tt = tumor tissue ; and it + ptt = interposed tissue and post tumor tissue ; and ebs = effective beam strength the amount of time that the tumor tissue can be irradiated will be limited by the effective strength of the beam as it crosses the tissue that is interposed between the body exterior surface and the effective strength of the beam as it passes through the tissue interposed between the tumor ( on the backside relative to the beam source ) and the body exterior surface . accordingly , in a preferred embodiment , the difference between the increase in beam strength between the tumor tissue and the interposed tissue and post tumor tissue is maximized . in one method of doing this a pair of permanent magnets that have been laser aligned are provided and the patient is moved into position between them . with this method the magnets do not have to be moved to be positioned correctly relative to the patient . such movement could reduce the alignment of the magnets . also , the magnetic field between the two magnets can be measured while no patient is interposed , to verify alignment and magnetic field strength . although the presence of a human body will change the field characteristics , it is still helpful to know the magnetic field when no body is interposed . in one preferred embodiment , after the patient is moved into position , while maintaining alignment by the use of a track or guide , the magnets are moved so that they approach or touch the patient &# 39 ; s skin on either side . the magnets may be placed slightly toward the anterior of the tumor , referenced to the beam source . in a preferred embodiment , the magnetic field at its maximum point within the tumor , is at the low end of the effective range , so that the magnetic field in the non - tumor areas is below the effective range . although the magnetic field in these areas may still have some positive effect on the effective beam strength , it is not as great as the effect within the tumor . in a preferred embodiment , a first radiation beam strength is applied for long enough to raise the concentration of free radicals to a desired level . then a second radiation beam strength may be applied to maintain the free radical concentration and reactivity at near optimal levels . sequential fractionation may be employed to maximize the compounding benefits of sequential magnetic field exposures or variable radiation beam strength exposure or exposures designed to optimize for a given free radical composition . that is , the magnetic field strength and / or the radiation beam strength may be varied over time . in one preferred embodiment the radiation beam producing device produces a rapidly sequenced magnetic field that , in the tumor , coincides with the exposure to a radiation field of planned strength , variation over time and contour and conforms to a preplanned and contoured electromagnetic field . in one method , the magnetic field continues after the pulse has passed through the tumor , but turns off for a brief period of time , as the beam is passing through interposed tissue . if electromagnets are used , the magnetic field is varied by varying the strength of the electric current through the electromagnets . in the case of permanent magnets ( or electromagnets ) a rotating shielding can be periodically interposed between the magnets , thereby disrupting the magnetic field . in an alternative preferred embodiment there is no time coincidence between exposure to radiation and application of a magnetic field . rather , the patient is first exposed to radiation , and then exposed to a magnetic field . one advantage of this technique is that the room used for radiation does not have to be modified to include magnets . further the patient can be removed from the room in which the exposure to radiation takes place , to another room where the application of the magnetic field can occur . this frees the radiation room for greater patient throughput . referring to fig8 , in a preferred embodiment a treatment modeling station 200 , having a display screen 202 ; a standard keyboard and mouse set of input devices 206 ; and a processor and memory assembly 204 , is provided to aid a health care provider in planning treatment . in one embodiment , this device is a standard computer , such as a standard windows ® os , linux ® os or apple ® computer , running specialty software . x - ray or ultrasound imagery , in the instance shown , showing a patient &# 39 ; s abdomen 212 and a tumor 214 in the abdomen 212 , may be loaded onto the device memory 204 and displayed , as shown . the health care provider is able to move symbolic shapes indicating magnet 216 and radiation source 218 positions , and increase or decrease magnet and radiation source intensity . a false color map 220 shows the effective beam strength , and a reading of total tumor effective radiation and healthy tissue effective radiation is provided 222 , for a given time progression of treatment events , which may be entered and modeled . the time progression can be displayed at either real time or faster than real time , to indicate the effects of treatment . after the radiation source is turned off , a beam may still be shown indicating the continuing effects of free radicals that continue to exist . a time gap between the cessation of radiation exposure and the beginning of exposure to a low strength magnetic field , may be set by a user through use of the user controls . in one embodiment station 200 is enabled to recommend a treatment sequence . fig9 is a bar graph that shows the effectiveness of 4gy of gamma radiation in the case where it is not accompanied by a magnetic field , when accompanied by a 15 gauss electromagnetic field ( middle column ) and when accompanied by a 15 gauss magnetic field that is continued for 15 minutes after the gamma radiation is discontinued . the present invention finds industrial applicability in the manufacturing of machinery for treating a tumor . while a number of exemplary aspects and embodiments have been discussed above , those possessed of skill in the art will recognize certain modifications , permutations , additions and sub - combinations thereof . it is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications , permutations , additions and sub - combinations as are within their true spirit and scope .