Selective amplification of x-rays in the energy range 50-65 keV

We report the result of direct measurements of x-ray spectra performed using both, CdTe and CZT, diode detectors and narrow collimation. It was observed that a needle type collimator placed far away from the x-ray source (near 2 m) produced a huge deformation of the x-ray spectrum showing a significant amplification shoulder towards the high end of the energy distribution. The enhancement due to the collimator was recorded at different x-ray operating voltages and currents, and was compared with similar measurements using a slit collimator. The amplification can be explained as Rayleigh scattering by means of the Monte Carlo code MCSHAPE which takes into account the polarization effects in photon transport