Effect of plasma formation on beam position measurements in air*

The interaction of high-energy charged particle beams with gaseous medium has been of interest to the physics community for a long time. We plan to perform experiments to measure the beam properties of a high energy charged particle beam (800 MeV protons) at different gas pressures in an experimental facility at the LANSCE particle accelerator, located at Los Alamos National Laboratory. Beam properties will be measured by beam position monitors (BPM)  located in ambient air. One of the  BPMs will be located inside a chamber where the gas pressure can be varied. The time structure of the proton beam pulse will be varied and its effect at atmospheric pressure will be monitored. The pressurized gas chamber will have electrically isolated plates at bias voltages to collect and measure plasma particles produced by beam gas interactions. Numerical simulations  and analytical theory  are being performed in support of experimental observations to determine limits when produced plasma can strongly affect the BPM signal.