Prep for Gain Tests:Some Progress, Some Setbacks

TKH for the Stony Brook Crew

Box Preparation: Vacuum & Source

Some trouble with mis-manufactured LEMOs: Did not seat flush to surface. Leaked badly. ~1/3 of the LEMO connectors did not have full

threads up the body…bottomed out before sealing.

Stony Brook Shop Counter-bores holes. Leaks gone (w/ He leak Checker) Source mounted using battery clip.

Was 10 mCi 55Fe Now 2 ½ lives later…

Box Preparation: Pad Plane & Gas

Small mods: Pad plane initially sized for prototype GEMs Holes put into it for final sized GEMs Solder pads interfere with final GEM frames.

Solution: Solder underside Raise pad plane.

Done and ready. Gas/pump:

Done

DAMMIT!!!

On Saturday, while heat-shrinking tubing onto HV divider chain, DISASTER: Heat Gun and Scroll pump on same breaker. Breaker trips. Chamber under vacuum “refills” though pump

exhaust line (i.e. from the floor outside of tent) GEMs/Grid in use have lots of dust on them “Necessity is the Mother of Invention”:

Need GEM cleaning procedure to recover these GEMs for test use…maybe success??

Step-by-Step Cleaning Tests

Look at GEMs under low (magnifying visor) and high (microscope) magnification: LOTS of dust (particularly top GEM).

Blow off with Bottle Gas: Removes ~90% of dust Not close to good enough.

Normal cleaning not good enough: Wash with flow of deionized water. Chase with ethanol. Blow dry with bottle gas. Little improvement…GEM looks bad.

UltraSonics!!

UltraSonic Equipment from DCH Pulled out equipment from storage. UltraSonics in warmed deionized water bath:

40 kHz, 70 kHz, 104 kHz, 170 kHz Rough Cleaning Fine cleaning. Continual resistivity measurement

Tested one corner of one GEM dipped into UltraSonic bath: US-off…swish around: no change dust remains. US-on (40 kHz), “untouchable” dust gone in 30 sec.

Put whole GEM in tank: 10 min at 40 kHz. 1 min each at 70, 104, 170 kHz.

Quick look: GEM looks pretty good Used microscope on 1 strip…zero dust. Resistors look really clean and pretty.

Lessons Learned:

Scroll Pumps Leak when off! Need electric gate valve. Exhaust flapper (like on main chamber pump)

MAYBE (learn today) UltraSonic cleaning can successfully remove dust from a dirty GEM. 1 strip from bad looking to looking perfect. Good to know if there is a way. Better to learn now than later.

Test one GEM for voltage holding before touching others I’m encouraged But keep your fingers crossed…