The effects of beam parameters on bremsstrahlung exposure angular distribution

The effects of electron beam parameters, including beam radius, emittance and its energy, on the bremsstrahlung exposure angular distribution of a meter away from the target are researched in this paper. The analytic theory is described in detail. T. H. Martin experience formula is used to get the forward bremsstrahlung exposure in front of the target. Three kinds of typical electron transverse distribution are used, and they are the Ka-pachinsky-Vlajimersky distribution (KV), the waterbag distribution (WB), and the Gaussian (GS). From these distributions, the incident angles of the beamlets, which are in different radial positions, are calculated. The Monte-Carlo method is used to find the incident angle and position of each sample electron. It is showed that the following fit formula about the radius Rb and the emittance E of electron-beam (in kms unit) e(mrad) = 1.4 R²b(m) should be meeted in order to obtain the maximal forwrad exposure. The higher the beam energy and the less the emittance, the better the distribution of exposure. The calculated results for three distributions are in agreement with each other, when two methods are used.