Cryogenic Sample Stage

In order to suppress sample outgassing in the secondary ion source still further , we have designed, constructed and installed a cryogenic sample stage for our Cameca ims 6f.   By keeping the sample at circa -196C while it is in the secondary ion source, the rate of sample outgassing is significantly reduced.  Using this technique, we have achieved total chamber pressures in the e-10 Torr range even with epoxy-bearing samples present.  The system is based on two swagelok Liquid Nitrogen (LN2) feedthroughs mounted where previously the sample HV feedtrhogh flange was positioned.  Inside the vacuum chamber each LN2 line connects to a ceramic tube which can hold the 10kV sample potential.  The original Cameca sample stage has been replaced by a copper tank.  During a measurement a continuous stream (a few ml/min) of LN2 passes from a 120 l cryogenic tank, through a vacuum clad hose, through a swagelock connector and into the tank.  A continual dripping of LN2 out of the second swagelok connector assures that the cyogenic stage is maintained at LN2 temperature.