INFLUENCE OF INTENSE BEAM IN HIGH PRESSURE HYDROGEN GAS FILLED RF CAVITIES

The influence of an intense beam in a high-pressure gas filled RF cavity has been measured by using a 400 MeV proton beam in the Mucool Test Area at Fermilab. The ionization process generates dense plasma in the cavity and the resultant power loss to the plasma is determined by measuring the cavity voltage on a sampling oscilloscope. The energy loss has been observed with various peak RF field gradients (E), gas pressures (p), and beam intensities in nitrogen and hydrogen gases. Observed RF energy dissipation in single electron (dw) in N2 and H2 gases was 2 10 -17 and 3 10 -17 Joules/RF cycle at E/p = 8 V/cm/Torr, respectively. More detailed dw measurement have been done in H2 gas at three different gas pressures. There is a clear discrepancy between the observed dw and analytical one. The discrepancy may be due to the gas density effect that has already been observed in various experiments.