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Stony Brook UpdateJason Kamin…the Cleaning Machine!

T.K. Hemmick

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Cleaning Success

• At SB, we excellent de-ionized water:– typically 18 M-cm, alarmed below 16 M-cm– Delivered at “faucet pressure”– Can be sprayed forcefully like a rambunctious

kid with a garden hose:

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Cleaning success rate: 6 for 6!• FIX: GEM 218 (was ok up to 350V but drew non-ohmic current

higher than that)

• FIX: Au#206 dead short strip 15 washed once, no change. second wash + dry Ar at 500V, fixed.

• FIX: Cu#152: dead short, strip9.

• FIX: Cu#172: two SST (strips shorted together), strips 2&3 and 24&25.

• FIX: Au#221: two separate dead shorts. this is the gem that is part of "Test Stack 1". (Story follows…)

• FIX: Au#230: CsI coated GEM with no resistance.

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Ooops on Test Stack #1.

• Fumble-fingers (TKH) arrived back in the lab just in time to mess up a precious GEM.

• While handing the GEM between people, the GEM guy moved Forward-Backward, while the pizza-box guy moved Side-Side (miscommunication).

• The result was that the GEM was poked TWICE by a sharp SS corner and developed TWO shorted strips (uggg…).

• After a single HARD-wash in the HBD Spa, both strips recovered and the GEM is back to 100%.

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A funny thing happened on the way to…

• The next GEM was the CsI-coated GEM that had been delivered to BNL for the single GEM tests, but then returned unused.

• GEM has been in air since Thanksgiving.• EVERY SINGLE STRIP(!!!!) on this GEM

showed 1.2~1.6 M to ground.• This would presumably be from the fact that

heavily contaminated CsI is a bad insulator and made resistive path through nearly every hole.

• This GEM was also recovered by HARD-wash in the HBD Spa.

Does this indicate a potential trouble that could happen to cathodes?

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Summary

• Good news:– HARD cleaning (forceful spray) works great and every

GEM tested so far has recovered.– We will continue to clean through everything we presently

have.

• Not as Good News:– Since TKH mishandled the top GEM, we did not today get

the final gain test measurement and will only begin that tomorrow after the overnight vacuum pumping is done.

• Suggestion:– Old: “If trouble try cleaning.”– New: “Clean all GEMs before testing as STD procedure.”– Paraphrasing Rui (via Jason):

Hard Spray Washing NEVER hurts and usually helps.