It is important to estimate the dose due to neutrons emitted by negative pion irradiation. Calculations of neutron kerma distribution are performed. Measured time of flight spectra of neutrons emitted from plateau of depth-dose curve as well as the peak of it in tissue material are used for the calculations. The present calculated results explain the feature of the long range component of neutron dose.

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In high energy x-ray beams, neutrons are produced due to photo - d isintegration in the target material, beam flattening filter and collimator. Neutron dose equivalents from a Mevatron were measured using two kinds of detectors. One of the detectors was a neutton dose rate meter, generally called a rem counter. The other was a track-etch detector made up of 10B and polycarbonate plates for detecting alpha-track from 10B(n, a) reaction. The track-etch detector as well as BF3 counter of remcounter is mounted inside a moderator. After the irradiation at the level of 2 to 10 mrem, polycarbonate plates are electrochemically etched to record only alpha-track as etch pits.
Neutron dose equivalents were measured as a function of the distance away from the isocenter. This relation may be represented by an exponential function. The distances of every 1.3 in and 1.4 m decrease the neutron dose equivalent about one half for 10 MV and 15 MV x-ray beams respectively. It can be concluded that these two dosimetry combination provides a new approach with a number of advantages compared to some other existing techniques for such measurements of neutron dose equivalent in high energy x-ray beams.

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A study of the output-shape for the pulsed radiations was carried out by means of a Cerenkov-light detection. The electron output-shapes of the Betatron were single- or double-peak distributions and varied with electron intensity. For the 10 MV Linac (105 degrees bended beam) x-rays its shapes showed triple-peak distributions and varied with magnetron frequency. The output-shape of the 6 MV Linac (straight beam) x-rays was a rectangular-like wave. And, the observed pulse-width was about 2 micro-second for the all.
The Cerenkov-light detector is easily con s t r acted and measurement can be simply carried out. Therefore, it is seemed that this method is useful for an adjustment of the pulsed radiation output of the therapy machines.

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The stopping powers due to collision energy loss for electrons have been. calculated from 10 keV to 1000 MeV. Values are given for 30 elements, i. e., H, He, Li, Be, B, C, N, O, F, Ne, Na, Mg, Al, Si, P, S, Cl, Ar, K, Ca, Fe, Co, Ni, Cu, Zn, Ge, Cd, Sn, W, and Pb, and 40 dosimetric materials, i. e., Muscle, Standard man, Tissue approximation, Bone, Water, Mix-D, Mix-DP, Mix-R, TE Plastic(A-150), TEPNIRS, TEP-Air Equivalent, TC-Hiraoka, TE Liquid-Frigerio, TEL-Goodman, Air, TE Gas-Rossi, A-150 Gas, Carbon Dioxide, Methane, Ethylene, Propane, LiF, Bea, Mg2SiO4, CaF2, CaSO4, NaI, CsI, ZnS, CdS, AgBr, Anthracene, Stilbene, Nylon 6/6, Polyethylene, Polystyrene, Lucite, Paraffin, Alaldite, and Fricke Solution.

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