A liquid helium immersion <a
href="pGe_electromag.html">cryostat</a>(Janis 8DT) with windowless tail
stock
fits within the 2 inch magnet bore.  The beam is conducted out the top
using a light-pipe.  At the top of the light pipe is a teflon lens for
focusing the beam onto the Schottky detector.  Alternatively, a Ge:Ga
detector can be inserted down the light pipe and immersed in the liquid
helium above the laser. Triaxial cables conduct the high voltage and UHF
pulses to the crystal using the outer two conductors to give a low
impedance transmission line (~5 ohm) that matches the load. <P>