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Stony Brook Update

Stony Brook Update. T.K. Hemmick for the Tent Crew. Miscellaneous items 1. Our crew is expanding again: T. Videbaek will return. G. Wille is already back L. Makdisi joining 3 REU and one Simons fellow

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Stony Brook Update

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  1. Stony Brook Update T.K. Hemmick for the Tent Crew

  2. Miscellaneous items 1 • Our crew is expanding again: • T. Videbaek will return. • G. Wille is already back • L. Makdisi joining • 3 REU and one Simons fellow • Our glove box scrubber that we predicted would fill with the large water load did fill Thursday last week. • Scrubbing it requires loss of flow for more than 12 hours. • Back on now, water levels good again.

  3. LEGS Gas System Running • Jack Mahon has reworked the LEGS system for us: • Removed three restrictions. • Installed higher capacity flow controllers • Purchased new scrubbers • Running on Nitrogen • An empty cylinder acts as a buffer volume (smaller than HBD but OK). • System working in recirculation mode. • Running at 1.75 torr overpressure. • Stable now for two weeks. • Emergency system designed: • Simple standby system with bottle & bubbler. • Latches into standby immediately on power loss, overpressure, or underpressure. • Parts on order…expect parts this week.

  4. HV Preamp Amp HV Scope GEM HV HV Preamp Amp GEM GEM Some simple tests for charge collection. • Starting to address questions from last week. • Flash Lamp pulsing through MgF2 window. • Simple system: • Two Modes: • GEMS same;collect charge on the Grid • Grid && Top-Top same • Adjust dV of GEM • Adjust dV of 1st gap • Collect charge on mid GEM

  5. Some First Results • Rise of the effective QE with voltage difference to the grid: • Looks just like you might expect. • Extraction field is an important component in effective QE.

  6. Charge Collected on the Middle GEM • GRAIN OF SALT REQUIRED (see next slide) • All curves show “saturation-like” behavior. • All charges collected are small fraction of grid charge (3.5 V). • Collection fraction seems to fall with dV on the GEM.

  7. The Grain of Salt • Using the GEM as the charge collection electrode is bad. • There is a large series resistance (protection resistors). • There is a large parallel capacitance through GEM. • RC of the GEM is 21 milli-seconds. • Pulse shape collected by GEM is really ugly. • Need to repeat using pads for charge collection. • Results suspect until measurement improved.

  8. Field from Sauli • Here is a calculationabout field lines inforward bias. • Notice that ALL linesfrom the top drift gapgo through the hole. • Notice that there aremore field lines below. • This is because the fieldbelow the GEM is higher. • The extra lines come fromthe top of the GEM. • QUESTION: • Do we get ALL the field lines from the top of the top GEM into the transfer field, or do we lose some? • We must lose some of the lines, the loss will have these lines terminate on the bottom of the top GEM. • What fraction of field lines from the top of the top GEM are landing on the bottom of the top GEM in reverse bias field?

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