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Digital Hadron Calorimetry using Gas Electron Multiplier Technology Andy White

Digital Hadron Calorimetry using Gas Electron Multiplier Technology Andy White ALCPG, Victoria BC, July 2004. GEM/DHCAL development. Started with Research Enhancement Grant from UTA. Supported by U.S. Department of Energy ADR and LCRD programs.

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Digital Hadron Calorimetry using Gas Electron Multiplier Technology Andy White

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  1. Digital Hadron Calorimetry using Gas Electron Multiplier Technology Andy White ALCPG, Victoria BC, July 2004

  2. GEM/DHCAL development • Started with Research Enhancement Grant from UTA. • Supported by U.S. Department of Energy ADR and LCRD programs. • Important contributions from UTA Electrical Engineering, and UTA Computer Science Engineering. • Working with ANL HEP DHCAL/RPC group on readout electronics. • Working with CALICE collaboration.

  3. Digital Hadron Calorimeter Development Linear Collider calorimetry development path at UTA: - Motivated by the physics potential! - Can digital + energy flow approach work ?? - Gas Electron Multipliers offer robust/low- cost/flexible technology to implement digital calorimetry STEPS: - Understand/operate GEM systems (done) - Develop GEM/DHCAL design (done) - Build/test large-scale GEM active DHCAL layer(s) - Develop full calorimeter design for test beam stack

  4. Digital calorimetry – counting cells

  5. 140mm 70mm GEM foil etching GEM field and multiplication From CERN-open-2000-344, A. Sharma

  6. Double GEM schematic Create ionization Multiplication Signal induction From S.Bachmann et al. CERN-EP/2000-151

  7. Embeded onboard readout Ground to avoid cross-talk Design for DHCAL using Triple GEM

  8. GEM/DHCAL cross-talk studies • - High digital “hit” efficiency essential for tracking charged particles in/through calorimeter. • plusminimal crosstalk to reduce confusion and mistakes in track following, pattern recognition. • Need crosstalk information to set threshold(s) for “hit” definition. • Examine hits from source particles in prototype on two adjacent pads. • Study nature of crosstalk signal with generated signals.

  9. Recent cross-talk studies Pad examined for crosstalk Main pad UTA GEM/DHCAL prototype

  10. 32-channel board from Fermilab

  11. UTA GEM Calorimeter prototype - typical signal Single cosmic event: upper = trigger, lower = preamp output

  12. Typical signal - source

  13. Typical crosstalk signal (prototype)

  14. Crosstalk study Signal generator scope Insulator Copper pads

  15. Crosstalk simulation (pulse generator) Study by Dr. Jia Li

  16. Crosstalk derives from edges

  17. Effect of rise time

  18. Bigger pads = larger effect BigPad

  19. …and vice-versa SmallPad

  20. Effect of gap between adjacent pads Large Gap

  21. Effect of gap between adjacent pads Small Gap

  22. Usual situation – no crosstalk visible

  23. Rare example of large crosstalk

  24. Effect of sharing signal between adjacent pads Trigger=252 Thr.=110mV, V=2000V.

  25. Development of module concepts TESLA – HCAL Layout

  26. DHCAL/GEM Module concepts GEM layer slides into gap between absorber sheets Side plates alternate in adjacent modules Include part of absorber in GEM active layer - provides structural integrity

  27. Development of GEM sensitive layer Requirements: - minimize overall thickness - develop robust design - maintain 1mm, 3mm gaps in GEM structure - maintain active layer flatness – absorber slice - minimize “dead” boundary areas - maintain integrity of gas volume - design for ease of construction!

  28. Development of GEM sensitive layer Absorber strong back Gas inlet/outlet (example) Cathode layer 3 mm Non-porous, double-sided adhesive strips 1 mm 1 mm 9-layer readout pc-board Anode(pad) layer Fishing-line spacer schematic (NOT TO SCALE) GEM foils

  29. Development of GEM sensitive layer - Identified materials for layer construction - Specified interlayer spacings/spacers - Tried out assembly ideas - Built large (1ft x 2ft) mechanical prototypes - Iterating on assembly procedures - Specify/document final procedure prior to assembly of large, working active layer(s).

  30. Details of GEM active layer construction (Tests using Kapton foil only for now)

  31. Coating the absorber slice with adhesive for the cathode layer

  32. Stretching the “GEM” layer with frame Note the need to be able to grip the edges of the kapton (but not the copper)

  33. “GEM” layer ready for laying down

  34. One form of 3mm spacer 3mm side walls and spacers installed

  35. “GEM” foil laid down over side walls and sides weighted

  36. 1mm side walls installed plus spacers and gas in/outlets Gas in/oulet

  37. Sealing corners of walls

  38. Installing 2nd 1mm walls and fishing line spacers

  39. Final “GEM” foil installed, “PC board” installed, and whole assembly weighted

  40. Development of large-scale GEM layer • Original plans were to use “existing” roll of 3M 10cm x 10cm foils… • However, the roll no longer exists! • Discussions on new run to produce what we actually need. • Several other customers for GEM foils for various studies (La Tech., U.Washington, IHEP-Beijing,…)

  41. 3M GEM foil production • Aim for 3 GEM foil strips/layer for ~1m3 prototype. • Need subdivision of GEM’s into separate voltage segments – minimal “no-copper” gap. • Other issues: • - use of Mylar for masks -> hole “slewing” • => glass phototool better but more costly • - pattern repetition/kapton gap for gripping edge • - New layout (with 15cm x 15cm subunits -> U.W. etc.)

  42. Mass Production is based on a 3M Proprietary Flex Circuit Manufacturing Technique • 3M Microinterconnect Systems Division Reel-to-reel process, rolls of 16”’x16” templates of detachable GEMs in any pattern. Optional processes possible. • First batch of 1,980 GEMs recently produced. Low cost per unit! (~2 USD/GEM not counting R&D) • Two fabrication techniques (additive, substractive) tested. Reel to reel flex circuit manufacture in clean room conditions Single roll of ~1,000 GEMS hep-ex/0304013

  43. 3M GEM foil – new layout

  44. 3M GEM foil – new layout (detail) Gap in copper (both sides) for HV sector isolation Issue: providing copper-free strip to grip GEM layer

  45. 3M GEM foil production - issues • Quotation - $10K for glass phototool • cost per length of roll or per 15cm x 15cm unit? • Refine layout…develop cost sharing with other users • Specify QC at 3M and UTA – physical inspection, standing current (nA),… • Delivery?

  46. GEM/DHCAL test beam stack issues GEM active layer – three sections • Minimizing walls • Joining GEM foils(?) • One strongback/layer? • Gas flow/supports (post vs. line) • 3 PCB’s or single pad layers? 305mm GEM strip from 3M roll …progress towards test beam design

  47. Conclusions • Progress on understanding prototype signals and associated crosstalk. • Progress on large-scale GEM active layers. • Working with ANL/Fermilab on readout electronics (GEM mods to RPC design). • Working with 3M Corp. on GEM foil production. • Issue now is the funding/timescale for test beam stack.

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