Design and Initial Tests of a Gas Scattering Energy Monitor in the PEFP RFQ and DTL

We have developed a gas scattering energy monitor to measure the energy spectrum of the proton beam from 3 MeV to 20 MeV at the four-vane PEFP (Proton Engineering Frontier Project) RFQ and the DTL tank exit as a function of RF drive power. The energy monitor is comprised of a Xe scattering chamber, two collimators to reduce the beam intensity, and a surface barrier detector for measuring the proton energy. In order to measure the beam current simultaneously, a faraday cup is incorporated into the energy monitor. The calculated flux attenuation through the 0.2 mm diameter collimator is 2.7 x 10^-3and the energy loss is 72 keV. We report on design details and multiple gas scattering of proton beams in Xe gas by using a SRIM code.