Beams Of Different Energies Research Articles

Pulsed Bending Magnet System for the Stanford Two-Mile Accelerator

The electron beam from the Stanford two-mile linear accelerator is analyzed by a high-quality magnetic deflection system in the beam switchyard. The first magnet element in this system is a pulsed switching magnet capable of switching beams of different energies and intensities to either transport system on a pulse-to-pulse basis. This magnet actually consists of five one-meter sections and is powered by pulsed high-voltage supplies (modulators). Each magnet section is excited with two modulators because it must pulse in either polarity in order to switch the beam left or right; the pulse height should be continuously variable to accommodate any beam energy. The magnetic field in these magnets rises sinusoidally 360 times a second and has a peak value at 1700 gauss. In this paper the optical properties of pulsed magnet will be discussed briefly. Detailed descriptions of the pulsed magnet modulators, the instrumentation for the magnet, and the test results will be given. The problems connected with high-power switching at high repetition rates will be discussed.

Modification of HeLa cell survival by 250-kvp and cobalt-60 radiation: variation with depth in tissue-equivalent phantom.

Numerous attempts have been made to evaluate relative biological effectiveness (RBE) of radiation beams of different energies. Biological approaches to this problem have usually consisted in the determination of surface effects on large animals or man, or lethal effects on small animals. In every case the RBE has been measured with little or no attenuation of the radiation beam by overlying tissue or tissue-equivalent material. It is known that beams of radiation are degraded in passing through tissue-equivalent material, and it is of interest, therefore, to determine whether there is a variation of biological effectiveness of a given type of radiation with depth in tissue or phantom. It is further known that the more energetic radiations (for example, gamma rays from cobalt 60) are degraded more rapidly than are radiations from lower energy sources (as 250-kvp x-rays). One might then expect to find greater modification of biological effectiveness with depth for cobalt-60 radiation than for 250-kvp radiat...