A thin-walled cyrogenic gas target for electron-scattering experiments

A cryogenic target system for gaseous 4He at an operating temperature of 20 K is discussed. Dictated by the experiments, which involve among others recoil particle detection, the target window is made either of Mylar with a thickness of 1.5 μm or Kapton of 7.0 μm. The corresponding upper limits for the working pressure are 25 and 400 kPa, respectively. The heat exchanger can handele up to 10 W of heat dissipated by the electron beam. The maximum value for the luminosity amounts to 2500 μA mg/cm2. The effective target thickness which is a function of dissipated beam power can reliably be determinded. (orig.)