1 Stony Brook Update Cross Roads T.K. Hemmick for himself

2 The Glovebox Water Spiked Our intuition that the purifier was filling due to the long time with a heavy water load was correct. The glovebox spiked to about 40 ppm before the windows could be applied over the HBD. All GEMs put inside HBD along with two chicklets to monitor conditions. We’ll use the chicklets to assess whether the other GEMs have lost QE.

3 No progress on making a GEMstack. New production GEMs are completely different from last year: –No charge-up curve. –Requires nearly 3800 V for a gain of After two full weeks of never sustaining 5000 gain for more than a few minutes, the bottom GEM finally began a current draw of 5 microamps at 500 V (completely stable at that point) and is now done.

4 Personal Opinion We are wasting our time trying to build the HBD to the original design. Even if we get a few stacks operating now they will fail during long term use. Don’t use the “success” of last year’s voltage holding as evidence of anything. –The “success” was only after most strips had their resistor chain modified. –The loss of single strips compromises the performance of every blob (in arm or partner) that overlaps it. –A repeat of last year’s performance over the whole surface of the HBD will make a detector will poor performance.

5 Dust Dust Dust I volunteer to wear a tee-shirt to every QM for 5 year stating that: –The original design was perfect. –Stony Brook is dusty. –The only failure ever was Stony Brook dust. –A perfect design that anyone else in the world should use was changed because of SB dust. I will do this ONLY if we give up in the present design and make changes so that the detector will work. If we make no changes I have zero confidence in the detector.

6 The proposed changes: Make a 4-GEM stack. Use the body of the HBD as a field cage to get the bias in either forward or reverse. Independently power each level with CAEN power supplies which internal logic drops the whole stack when any single channel trips. – 55 Fe source illuminates all pads. –Gain photo-electrons by losing grid. –All stacks will work easily at low gain/GEM. –Some loss of Blindness. –Need to make top surface of all stacks equal V.

7 Field Cage The HBD is basically a cylinder. Potential (Volts) Field (Volts/cm)

8 Field Cage Preliminary Design Match both end walls to the ln(r/r 0 ) profile. Match the face to same profile. Bingo…bias with uniform field HBD works.