Plasma Chemistry in a High Pressure Gas Filled RF Test Cell for use in a Muon Cooling Channel

Abstract

Current muon collider schemes call for significant six dimensional (6D) cooling of the muon beam before it is accelerated [1]. One cooling scheme, the Helical Cooling Channel (HCC), employs RF cavities filled with high pressure hydrogen gas [2]. The gas acts both as an energy loss mechanism to allow for ionization cooling [3, 4], and as a buffer in order to prevent RF breakdown [5]. When a beam of particles passes through a HPRF cavity, it will ionize the gas. The amount of plasma generated is dependent on the beam energy, the stopping power of the gas, and the density of the gas. The resulting plasma will gain energy from the RF electric field and transfer it through collisions to the gas. This effect is called plasma loading. An experiment performed at theMuCool Test Area at Fermilab studied the formation of plasma created by a proton beam and its evolution over the course of many 805 MHz RF cycles [6].