=== Cryogenics ==
Frost forming on the outside of the cryogenics chamber indicates a leak in the system and can potentially be very damaging to the system and the sample.  First, turn off the compressor and //slowly// heat the chamber back up to room temperature.  Possible causes:
    * Water inside the chamber due to not applying the vacuum long enough.  Pressures inside the chamber should be around 10^-6 Torr or less.
    * Improperly closed vacuum valve: check to see if the the vacuum valve was sufficiently closed.  
    * Insufficient seal: clean all of the seals, especially the bottom of the stainless steal casing covering the apparatus.  Dust and dirt will often create difficulties in creating a vacuum seal inside the chamber.  Also, clean the o-ring, being careful not to damage it upon removal (it is best not to use blunt objects or metal tools to remove the o-ring.  A tiny amount of vacuum grease may then be applied to the o-ring.  (The o-ring does not need more than a small pinch of grease and grease must be spread evenly on all parts of the ring).
    * Hydrogen leak: it is possible that a hydrogen leak has occurred (see Dr. Tate for dealing with a hydrogen leak).