Tent Update 5 Feb 2008 Matt Durham for tent crew

Washing Ilia has washed dozens of GEMs at our DI water station Some previously damaged GEMs have be recovered, notably the gold GEM from the latest stack in the gain test box (drew current after trip) GEMs which are washed twice and don’t recover are “BAD” – set aside and assumed dead forever Ten GEM stacks have been assembled and their pre-CsI gain curves measured Next evaporation can happen as soon as evaporator is ready

Latest QE Results

The “Scrapes” When doing the QE scans, the cathode current would suddenly peg the picoammeter to 7.33V (typically ~1.3V) We attributed this to the ammeter – this system is homemade and has always been a little bit shaky The second time this happened, we saw a correlation between this huge signal and the position of the grid, but no correlation to where the light was shining The ammeters test fine (with our tiny current source) So it must be something inside the evaporator I remember seeing defects on the surface of a gold GEM from the last evaporation (now in WS3)…BINGO I’ll load up some “Bad GEMs” in transport box for a test run and fix this

Upgrades to Glovebox Precision input capacitor (blue box) installed so calibration can be completed with all cabling in situ – more precise calibration Signal Pulser New P and T sensor logging by LabView (thanks Bob)

Gain Test Box Flow System Manifold set up for different gases (right now Ar/CO2 and CF4) Flow meter and bypass for pump out All stainless steel lines Bubbler and flow meter (through window) are in view of operator for checking flow

HBD Status: 2 Stacks Installed Gold GEM from “Test Stack 2” has ~60 MOhm short (??) Taken out for washing and recovered 4 Gold GEMs with CsI were moved into glovebox yesterday

Gain vs. Time Stack installed in WS2 Gain may be saturating at ~25000 – HUGE

Gain vs Time – WS3 Had 45 trips over cycle – This was the first stack to be tested under flow Storm came in, so air pressure drops and thus gain rises – trip! After storm passed, operated without trips for ~5.5 hours Gain saturating around ~ HUGE

Gain vs dV WS3 composed entirely of NEW production GEMs WS2 composed entirely of OLD production GEMs Both stacks end up at roughly the same gain, versus Note: Most of our old production gold GEMs were fried in the HBD. We have a surplus of old copper GEMs that must be paired with new gold GEMs – but the mixing effects may not be as drastic as we thought

Conclusions As much as it pains me to admit, I think we had dust problems at SB, which are now a thing of the past (washing doesn’t hurt either) We are now able to hold much higher voltages than before and observe much higher gains This round of assembly has its setbacks, but is proceeding at a reasonable pace.