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Prep for Gain Tests: Some Progress, Some Setbacks

Overcoming LEMO connector issues, gas and pad plane modifications, disaster recovery, and GEM cleaning using ultrasonics. Valuable lessons learned for the future.

karina-fuentes
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Prep for Gain Tests: Some Progress, Some Setbacks

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  1. Prep for Gain Tests:Some Progress, Some Setbacks TKH for the Stony Brook Crew

  2. 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…

  3. 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

  4. 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??

  5. 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!!

  6. 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.

  7. 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…

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