Tent Update5 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 ~33000 - 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, 33200 versus 28700

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.