Prototype Progress…

The Stony Brook Crew &Bob Azmoun, Craig Woody.

How to Clean a GEM…

• Last meeting, we reported a vacuum accident that “heavily dusted 3 GEMs”.

• “Ordinary cleaning” insufficient.• Ultrasonics worked!

– Individual GEMS tested at 450 V (stable).

– Triple running at 360 V (stable)

Something Old, Something New, Something Borrowed, Something Blue…

• For tests fully functional Data Acquisition & Analysis system:

• DAQ system is Canberra MCA “printing” the spectrum as into laptop.

• Analyze text file with perl script and feed spectra into root.

• For a 1-channel system it is actually quite fast to get and analyze data.

• Good results from gain tests.

Row Scan (A5J5)

• 55Fe peak in all channels.

• Variation in gain similar to WIS reports.

• Sigma/Mean ~0.14 0

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Peak Channel

a5 b5 c5 d5 e5 f5 h5 j5

Pad Number

Row Scan

Column Scan c1c7

• 55Fe looks good.• Rates good (~20 kHz)• Some 2-stage gain seen

– Rate consistent w/ holes.

• Very stable operation. 0

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Peak Channel

c1 c2 c3 c4 c5 c6 c7

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Column Scan

BTW…we know how dirt got into cryo!

• DUH…the cryo pump has been vacuuming the floor through a rough pump the same way we vacuumed dust onto the GEMs.

• Decided to open & clean:– Cloud for dust from blowing gas on cold head.– Small handful of STONES/SAND.

• Now pumping is clean…• Added thermocouple to

Evaporation Box.• Radiant heating NOT

effective…adding heatersto evaporation box.

Prototype to be done in Italian Box• Only box we have, so we’ll use it for p’type.• Nitrogen Flow from re-pressurizing dewar.• Cleaning up:

– Gloves removed for cleaning.– Box itself thoroughly cleaned.

Strategy for keeping clean• Boxes within Boxes…• Flow through HBD using Bob’s gas system.• Flow through Evaporation box (rapid purge)• Flow through Glove Box.• GloveBox exposure minimal

– Just during transfer…

Evap Box

HBD

Main Glove Box

Schedule:• Evaporate CsI this week and set photo-

sensitivity baseline using flash lamp.• Next week is contingency on this.• After end of next week BNL:

– Full electronics chain…when?– Transparency, Gain, etc…

• Install during April 21 access.• Should be enough time to see signals from

real interactions.• Success as BNL seeing Flash Lamp light

source using small GEM…

Xe Flash Lamp: Monitor Relative QE of GEM

• Test: Illuminated 4x4cm CsI PC in vacuum

• Raw Output from pad 7mV into 50ohm, width~1usec 70pC 4.4x108 pe’s 1.5x109 photons (assuming ~30% avg. QE across spectrum)

• Lamp Output intensity can be regulated, and attenuated.• RF noise preceding pe signal can be a problem if using a

preamp to record signal signal is integrated over noise lose pe signal

• Can use GEM amplification to amplify pe signal, while noise amplitude remains fixed, or can devise an optical delay and gate over pe signal only.

Xe Lamp/MgF2 window

Ar Filled Diffuser: Spectralon diffuser (disc) + Tyvec reflector (inside surface)

RF Noise(from lamp power supply) pe pulse

2 RF pulses

Aperture