Ion Gun trouble

Doing Auger alignment tests on Cu110 single crystal. Lots of carbon, system has been baked, maybe vented, since sample was clean. 64 V LVV peak hard to see.

Manifold

• Ar sample cylinder open, Ar supply valve open, manifold pumping disconnected. This was done when bypass valve connected to air lock pumping some months back.
• Ar supply probably contaminated, maybe missing, i.e. air not Ar
• Disconnect bypass 2.75" VCR flange, add 2.75" tee, reconnect bypass and manifold pump. 
• Turbo pumps down to low 1e-5 in airlock, 14 W turbo, at least no major leak
• Reconnect Ar cylinder/regulator. 
• manifold arrangement bad, no way to isolate Ar supply, need to fix

Electronics

• Electronics start up, software connects, gun to standby, initially ~ 11 mPa, pumps down to zero in ~ hour or less (did not watch)
• Analysis chamber 1.3e-10, after FIG5 pump running a while, ionizer degassed, to 6e-11
• Pressure controller stuck at current limit with software running
• verify cables connected
• verify voltage from ~ 10x10x4 cm USB DAC box on top of 3com switch, voltage 2 V for 20 mPa, etc.
• check output pressure ref from 20-066. Stuck at 10 V, so no pressure control.
• Switch gun briefly from standby to run and back. Now pressure reference works!
• Problem seems to be emission current. Controller cannot maintain 25 mA. 
• Could be result of filament O2 exposure. 
• Can get 20 mA by increasing grid to 180 V from 150 V (range is 120 to 200)
• When emission current out of "green" range, pressure ref goes to 10 V. This may be "fail safe" design...
• Open leak valve 2 full turns, pressure to 4.2 mPa, 
• supply ~ 1 bar relative (regulator), 2 bar absolute
• 2.25 turns, now 33 mPa before controller regulates
• Electronics "click", relay like sound, no clear reason why, its always done this, seems to be associated with cut in ion current.

Test

• 30 degree tilt near center of Cu110 large hole sample holder, excellent auger down to ~ 40 eV. 
• sputter 20 mA "20 mPa" 3 kV 30 sec raster 1x1
• old "scan squares are gone
• Cl peak 180 gone, also O, C reduced
• Cu MVV clear, double peak
• after 6 min C gone