Slit scattering effects in a well aligned pepper pot

A pepper pot is a device used to measure a medium energy (<20 MeV) electron beam´s transverse emittance by sampling its transverse phase space. This is accomplished by blocking most of the incident electron beam, while allowing small ´beamlets´ to pass through openings in a mask. The accuracy of the transverse emittance measured by a pepper pot is limited by several factors including, electrons leaking through the solid region of the mask, the imaging system resolution and dynamic range, scattering, etc. While the noise contributions from the prior quantities can be easily estimated, scattering effects have previously been neglected due to the difficulty in estimating the effect. In this paper, EGS4 simulations are presented to determine the affect of scattering on emittance measurements for an 8 MeV electron beam.