Linear accelerator, radiation from

Acknowledgement We are deeply indebted to Mr. Tadao Takada and Mrs. Sachiko Tojo who have contributed to the experiment. We also thank the members of the Radiation Laboratory of SANKEN, Osaka University, for running the linear accelerator. This work has been partly supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sport and Culture of Japan. 

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... 

Improvements in the physical selectivity, from orthovoltage x-ray to cobalt-60 and high-energy linear accelerators, combined with more powerful diagnostic tools and radiation delivery methods have continuously improved the results of photon therapy (3-D or inverse planning, conformal- and intensity-modulated radiation therapy, and stereotactic methods). The safety and the reliability of photon therapy are well established. 

The adiabatic character of EB energy deposition is used in calorimetry, which is the primary absolute method of measuring the absorbed dose (energy per unit mass).1 It measures the amount of heat produced by the absorption of the ionizing radiation. An example is the water calorimeter developed by Risp National Laboratory in Denmark.2-3 This instrument is reported to be suitable for electrons from a linear accelerator with energies higher than 5 MeV and shows accuracy of 2%.4... 

A direct synthesis of N2F2 in low yield and admixed with other nitrogen fluorides has been reported from the irradiation of N2-F2 mixtures with ra-y-radiation from a nuclear reactor admixed with other high-energy radiation from uranium fission products (85). There is also a radiochemical synthesis of N2F2 (1.5%) and NF3 (42%) when an N2-F2 mixture is irradiated with 30-MeV electrons in an electron linear accelerator (86). Reaction of fluorine diluted with N2 and NH3 also gives some N2F2 (159,213). 

Accidental exposure of a maintenance technician to radiation from an industrial linear accelerator. 

Very few investigations of the radiolysis of nitroalkanes have been reported, and no systematic study of their radiation chemistry has been made. Low molecular weight nitroparaffins were irradiated with y-rays from a cobalt-60 source using dose rates between 0.5 and 2.5 x 10" rad.h and the products analyzed by gas chromatography and mass spectrometry . The yield of gaseous products from irradiated nitromethane was drastically reduced if after a short irradiation, such as is obtained with a linear accelerator, the samples were immediately quenched in liquid nitrogen. Inder these conditions [Pg.668]

The main differences between pulse radiolysis and flash photolysis arise from the use in the former of ionizing radiation instead of light to initiate the reaction. Thus a pulse of electrons from a linear accelerator (or, less commonly, an X-ray pulse)... 

The basic principle is to observe the change in absorbance after an intense radiation pulse has created a significant population of short-lived reactive intermediates. Early experiments used xenon flash lamps as excitation sources and were able to detect intermediates with lifetimes >10 second. Modern experiments use pulsed lasers as excitation sources. The monochromatic output of a laser allows selective excitation the narrow pulse width allows detection of species with lifetimes as low as 10 second. A complementary experiment uses a pulse of electrons from a linear accelerator to generate the reactive species. More experimental detail is available in many reviews [139]. 

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... 

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