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Micromegas for the Central Tracker

Micromegas for the Central Tracker. Sébastien Procureur CEA-Saclay. Micromegas and CLAS12. - 3 double layers of cylindrical MM (Barrel). ~ 4 m². - 3 double layers of flat MM ( Forward ). Micromegas CLAS collaboration meeting, 09 /03/2011 S.Procureur.

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Micromegas for the Central Tracker

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  1. Micromegas for the Central Tracker Sébastien Procureur CEA-Saclay

  2. Micromegas and CLAS12 - 3 double layers of cylindrical MM (Barrel) ~ 4 m² - 3 double layers of flat MM (Forward) Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  3. Build cylindrical detectors with similar performance as flat ones The MM challenges (Cerchi dell'Inferno) “Abandon all hope, you who enter here” Achieve good spatial resolution in a 5 T transverse B field Build large area detectors (~0.3m²) operating at high efficiency Develop off-detector electronics (~1.5 m) Estimate the spark rate (and make it ALARA) Find some space for detectors & electronics Get money Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  4. Mini: 4 mm 128 mm 2 to 4 mm Cylindrical Micromegas Make use of the « bulk » technology (2006) Photoresist border → more robust → PCB canbethin Photoresist amplification spacer (~300 µm) Mesh PCB with strips Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  5. Cylindrical Micromegas Performance compared to thick flat MM usingcosmics Thick detector Thin detector → similar performance as thick detectors Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  6. Spatial resolution in 5 T X tiles of Barrel Micromegas are sensitive to the Lorentz angle of driftingelectrons x = h tanθ = h v B / E h → minimize h (but less signal) → use heaviergas (but more sparks) x → increase E field (but lowertransparency) →  ~ 220 µm if  canbelowered down to 20° Garfield simulation Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  7. Spatial resolution in 5 T Test to validate Garfield simulation with a Micromegas in dvcsmagnet (Hall B) → use of a focused UV laser to extractelectrons from the drift electrode Garfield validated,  canbe as low as 20° P. Konczykowskiet al., NIM A612 (2010), 274 Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  8. Large area detectors Full size Y prototypes have been builtat CERN → doubled area compared to COMPASS → Cdet ~ 25 nF, Cstripfrom 90 to 120 pF (canbereduced) 50x60 cm² 1400 channels → 90% of strips OK (1st proto!) Scan with Fe55 source → ready to buildthemat Saclay Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  9. Electronics The limitedspacerequires an off-detector electronics → long cables → initial cableswere 160 pF/m (FLEX) → Iraklifound 70 pF/m (Hitachi) → Ccab = 105 pF ~ Cstrip → Significanteffect on S/B (~50%) → Needs 10 V more to becompensated Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  10. Electronics - recent developments • Detector cables: Hitachi 50 pF/m cables expected on March 15th • check ability to withstand sparks • Goal: 40 pF/m cables • Dream: reworked input stage adapted to high detector capacitances up to 200 pF • ENC of 2200e for 150 ns peaking time • Expected S/N : 30 – 40 depending on gain • Test bench: Dream carrier board in place & route • Up to 7 Dreams • One Dream on a remote board • Firmware: in progress • Test bench and front-end unit firmware • Goal: estimate FPGA resources needed Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  11. DREAM and test bench schedule • February: Dream carrier board place & route started • End of March • Submission of Dream • Backup date: end of April • Production of the Dream carrier board • April: Dream carrier board in test • May: Dream test bench ready • Final adjustments for firmware and software • June: packaged Dream ready for tests • T2-T3 – Dream tests Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  12. Spark rate studies Activitystarted in 2009 → simulation: try to relate sparkswith large energydepositswith Geant4 (Gemc) → spark condition: Nel ~ 107 (Raether) → Quantitativelyreproduces (few) existing data → Explainsgaseffect & givepredictions (bulk) S. Procureur et al., NIM A621 (2010), 177 Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  13. Spark rate studies Tests at CERN/SPS, October 2009 → 6 different detectors in 150 GeV pion beams → Effect of a 1.5 T  magneticfield → 1st test of a MM+GEM detector (D. Neyret) → 1 week of data → bulk ~ non-bulk → No strongeffect of B field S. Procureur et al., submitted to NIM (Feb. 1st 2011) Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  14. Spark rate studies Tests atJLab/Hall B, July 2010 → 1 MM & 1 MM+GEM in FROST setup → Effect of a 5 T // magneticfield → 2.5 days of data → simulation ~ OK → 100 with GEM foil → x10 with 5 T field B. Moreno et al., submitted to NIM (Mar. 8th 2011) Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  15. Spark rate studies Tests at CERN/PS, August 2010 → 12 detectors in π+ or π-beam → beammomentumtunablebetween 0.2 and 3 GeV/c → 2 MM+GEM to understandspark rate suppression → 2 weeks of data → peaks in spark rates withπ+ → confirms GEM effects G. Charles et al., submitted to NIM (Feb. 25th 2011) Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  16. Spark rate – last mysteries 2 observations cannotbereproduced by the naive simulation → effect of the longitudinal 5 T field → spark suppression with the MM-GEM detectors → stronghint for significanteffect of transverse diffusion  new spark condition: critical surface charge density → explains all effectsseenwith MM-GEM: → large suppression withmoderate GEM gains → effect of trans. diff. onlyathigh GEM gains → change of slopeathigh GEM gain Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  17. Integration Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  18. Forward Tagger with Micromegas? Project to equip the FMT with central pixels for small angle e- detection - add ~ 6k channels to the FMT (electronics?) - add 2-4 MM layers in front of calo  Trackfindingeff > 95% in pFMT φ p Very large background due to Moeller All hits Selected hits z Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  19. Schedule

  20. Build cylindrical detectors with similar performance as flat ones Conclusion Achieve good spatial resolution in a 5 T transverse B field Build large area detectors (~0.3m²) operating at high efficiency Develop off-detector electronics (~1.5 m) Estimate the spark rate (and make it ALARA) Find some space for detectors & electronics Get money Micromegas CLAS collaboration meeting, 09/03/2011 S.Procureur

  21. Additional slides

  22. Working point

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