We have an installed field emission sem which is exhibiting unstable
emission currents.  Vacuum levels in all parts are at acceptable
levels (gun chamber and int chamber are in the 10^-8 and 10^-7 Pa
respectively.  The specimen chamber is at 8x10^-7 Torr.) When the
accelerating voltage is turned on, the extraction voltage ramps up and
the emission current fluctuates wildly.  Pressing 'emission current
reset' results in a request to 'flash' the emitter.  Flashing the
emitter does not improve the stability.  I know the emitter element is
less than a year old (so it should still be good).  Any ideas?

A much better place for this type of question would be the engeneering tips forum;
http://www.eng-tips.com/index.cfm

Sounds like there may be a contamination problem. Look carefully in
emitter area for "whiskers" or other contamination. Do not rule out a
failed emitter.