Linear accelerator, electron beam from

Using a 60 MeV electron beam from a linear accelerator, Farber (Ref 217) subjected Pb azide, Pb styphnate, TNT, HMX and PETN to total doses up to 3.65. x 10 R (3.2. x 10 rads). The results as shown in Table 12 indicate that ionizing radiation from 60 MeV electron irradiation will completely desensitize Pb azide, according to impact and heat tests conducted on the irradiated samples. The type of Pb azide was not given. A total dose of 3.65 x 10 R appears to be the threshold level for dudding of Pb styphnate Pulsed Electrons... 

Pulse radiolysis has been used with great success in studies of the hydrated electron e (aq). If the pulse of electrons from a linear accelerator (5-15 MeV) is passed through an aqueous solution, several chemical species are produced. The spectral changes in solution can be followed spectrophotomet-rically, either at a definite time after the electron pulse with a spectroscopic flash and a spectrograph, or continously at a fixed wavelength with a steady light source and a photomultiplier. Instead of the electron beam of an accelerator, X-rays pulse can be applied for one or two microseconds. ... 

Particles emitted from radioactive isotopes are generally too low in energy to provide the penetration required for conventional treatments of tumors with external radiation beams. Most external beam radiation therapies are performed with high-energy x-rays or electrons produced with compact linear accelerators with accelerating potentials between about 4 and 20 MeV. One notable exception is certain devices designed for stereotactical radiosurgery or radiation therapy of superficial tumors that use cobalt-60 y-rays. The... 

Pulse radiolysis was performed using e from a linear accelerator at Osaka University [42 8]. The e has an energy of 28 MeV, single-pulse width of 8 nsec, dose of 0.7 kGy, and a diameter of 0.4 cm. The probe beam for the transient absorption measurement was obtained from a 450-W Xe lamp, sent into the sample solution with a perpendicular intersection of the electron beam, and focused to a monochromator. The output of the monochromator was monitored by a photomultiplier tube (PMT). The signal from the PMT was recorded on a transient digitizer. The temperature of the sample solution was controlled by circulating thermostated aqueous ethanol around the quartz sample cell. Sample solution of M (5 x 10 -10 M) was prepared in a 1 x 1 cm rectangular Suprasil cell. 

The major steps involved were first the move from 200-kV x-rays to cobalt-60 and then to modern electron linear accelerators providing x-ray beams of about 20 MV (and electrons when needed for some patients). Improvements in the beam penetration were, in general, combined with improvements in beam delivery systems, e.g., isocentric gantries, variable collimators, later on multileaf collimators, etc. 

Any dosimeter used to determine absorbed dose in an irradiated product has to be calibrated. The adiabatic character of electron beam deposition is used in calorimetry, which is the primary absolute method of measuring the absorbed dose (energy per unit mass). An example of the instrument for this purpose is the water calorimeter developed in Ris0 National Laboratory in Denmark. " This calorimeter is reported to be suitable for electrons from a linear accelerator with energies higher than 5 MeV and... 

Fig. 3. Principle of linear accelerator (linac). Partially accelerated electrons from a source, such as a Cockcroft-Walton generator, arc further accelerated by stages as rhe electrons pass through radio-frequency cavities, powered by if oscillators. Each paiticle receives a small push as it passes from one cavity to the next until the final desired accelerated beam is produced Tile machine must be carefully synchronized CSG = Cockcroft-Walton generator, RFO = radio-frequency oscillator RFC = radio-frequency cavity...

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