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A Triple GEM Detector for the central Region of Muon Station 1

A Triple GEM Detector for the central Region of Muon Station 1. M. Alfonsi 1 , G. Bencivenni 1 , W. Bonivento 2 , A.Cardini 2 , C. Deplano 2 , P. de Simone 1 , F. Murtas 1 , D. Pinci 3 , M. Poli-Lener 1 , D. Raspino 2 and B. Saitta 2.

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A Triple GEM Detector for the central Region of Muon Station 1

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  1. A Triple GEM Detector for the central Region of Muon Station 1 M. Alfonsi1, G. Bencivenni1,W. Bonivento2, A.Cardini2, C. Deplano2, P. de Simone1, F. Murtas1, D. Pinci3, M. Poli-Lener1, D. Raspino2 and B. Saitta2 • Laboratori Nazionali di Frascati - INFN, Frascati , Italy • Sezione INFN di Cagliari – Cagliari, Italy • Sezione INFN di Roma 1, Roma, Italy

  2. This is the proposal for using a Triple-GEM Detector for the inner region (R1) of the first Station (M1) of the LHCb Muon Detector. • Triple-GEM detectors are very interesting devices with the following main characteristics: • High rate capability • Very good spatial resolution • Extremely low spark probability • Intrinsically radiation hard • Good time performances • Light detector A. Cardini / INFN Cagliari

  3. These characteristics make GEM-based detector an attractive device for M1R1 (~0.6m2), for which the requirements are: • Rate Capability up to 0.5 MHz/cm2 • Station Efficiency > 96% in a 20 ns time window(*) • Cluster Size < 1.2 for a 10x25 mm2 pad size • Radiation Hardness 1.6 C/cm2 in 10 years(**) • Chamber active area 20x24 cm2 (*)A station is made of two detectors “in OR”. This improves time resolution and provides some redundancy (**) Estimated with 50 e-/particle at 184 kHz/cm2 with a gain of ~ 6000 • In this presentation we will show thatTriple-GEM detectors with pad readout are the appropriate choice for M1R1 A. Cardini / INFN Cagliari

  4. 10x10 cm2 GEM foils are stretched and then glued on frames The Triple-GEM prototype is assembled inside a gas tight box. FEE electronics is connected to the pads. A. Cardini / INFN Cagliari

  5. Large (20x24 cm2) GEM foils, divided in 6 sectors, are stretched with the tool shown above and then glued on frames. A. Cardini / INFN Cagliari

  6. M1R1 Full Size Prototype ASDQ FEE Boards Sensitive gaps A. Cardini / INFN Cagliari

  7. In these 3 years of R&D a large amount of measurements were performed on many different Triple-GEM prototypes. • With radioactive sources: • gain (55Fe), charge-transfer optimization (90Sr), sparking (137Am), global aging (60Co) • With 5.9 keV X-ray tubes: • Local aging, gain, charge-transfer optimization • With low intensity hadron beam (CERN PS, Frascati BTF): • Time resolution, efficiencies, cluster size, cross-talk • With high intensity hadron beam (PSI): • Spark probability, large-area aging, time resolution, efficiencies • With cosmic rays: • Time resolution, cluster size, cross-talk, electronics optimization, grounding studies A. Cardini / INFN Cagliari

  8. Gain & Gain Uniformity Gain uniformity ~ 10-15 % A. Cardini / INFN Cagliari

  9. Single Chamber Time Spectra 9.7 ns 5.3 ns 4.5 ns 4.5 ns A. Cardini / INFN Cagliari

  10. Working region, upper limited by Cluster Size = 1.2, is found to be 70 V wide, a large plateau for a micro-pattern gaseous detector! OR Efficiency in 20 ns Working region 2.0 fC Cluster Size 3.0 fC G~20000 G~4000 A. Cardini / INFN Cagliari

  11. Discharge Studies Working region At PSI we exposed three detectors to a particle flux up to 300 MHz. Each detector integrated, without any damage, about 5000 discharges. In order to have no more than 5000 discharges in 10 years in M1R1 the discharge probability has to be kept below 2.5 10-12 (G < 17000). This limit is conservative because up to 5000 discharges no damage was observed. G~17000 G~4000 A. Cardini / INFN Cagliari

  12. Aging Studies Local Aging: performed with a high intensity 5.9 keV X-ray tube, irradiated area of about 1 cm2(~ 5000 GEM holes). Integrated charge 4 C/cm2 25 LHCb years. Large Area Aging: performed by means of the PSI M1 positive hadron beam, with an intensity up to 300 MHz and an irradiated area of about 15 cm2. Integrated charge 0.5 C/cm2 3 LHCb years. Global Aging: performed at Casaccia with a 25 kCi 60Co source. Detectors were irradiated at 0.5  16 Gray/h. Integrated charge up to 2 C/cm2 12.5 LHCb years. A. Cardini / INFN Cagliari

  13. Casaccia / Big Detector A / 16 Gray/h Casaccia / Big Detector B / 16 Gray/h Casaccia / Big Detector C / 0.5 Gray/h Casaccia / Small Detector D / 16 Gray/h X-Ray / Small Detector / Local Aging Normalized Currents (%) G/G ~ 0 G/G ~ -10% for 0.15 C/cm2 Integration time: 3  35 days 1.4 LHCb years 2 clearly different trends ! A. Cardini / INFN Cagliari

  14. PSI Normalized Currents (%) Casaccia / Big Detector A / 16 Gray/h Casaccia / Big Detector B / 16 Gray/h Casaccia / Big Detector C / 0.5 Gray/h Casaccia / Small Detector D / 16 Gray/h X-Ray / Small Detector / Local Aging Good timing performances were also measured at the PS after the PSI test  No significant aging effects H2O injection CO2 problem 2 clearly different trends ! 12.5 LHCb years A. Cardini / INFN Cagliari

  15. There is a clear inconsistency between data taken under very high global irradiation rate (16 Gray/h) and those taken at a lower irradiation rate (0.5 Gray/h), with X-Rays and at PSI. This systematic effect could be due to the fact that for the highly irradiated detectors the gas flow was not increased proportionally with the irradiation rate, due to a limitation in the detector gas-output impedance. A. Cardini / INFN Cagliari

  16. Aging Summary • X-Rays, PSI and Low-irradiated chamber at Casaccia show similar trend, the detector current reduction is negligible. • Tests on heavily-irradiated chambers at Casaccia are not compatible with previous results. This might indicate that an accelerated aging test requires an increased gas flow. • According to X-Ray, PSI and low-irradiation tests Triple-GEM Detectors can stand 10 years in M1R1 at LHCb without detector performances being affected. A. Cardini / INFN Cagliari

  17. After 17/9 LHCb Tech. Board A. Cardini / INFN Cagliari

  18. Work in progress • Clarify aging mechanism: Physical/Chemical analysis of irradiated detectors in progress • Understanding different chamber behavior: Investigation on the Gas-flow effect • Absolute Gain Measurement: in progress • Gain Uniformity: in progress • Gain/Efficiency Recovery by voltage increase: A gain recovery by a factor 2 has already been performed during the Casaccia test • Casaccia aging test at lower rate A. Cardini / INFN Cagliari

  19. Conclusions The 2000-2003 Triple-GEM Detector R&D has shown that these detectors fulfill the requirements for M1R1: • Good time resolution & efficiency in 20 ns • Cluster size below 1.2 in a large HV range • Very low discharge probability • Very robust against sparks • Good radiation hardness Triple-GEM technology appears to be adequate to be used for the central region of the first Muon Station A. Cardini / INFN Cagliari

  20. According to the Buddhism precepts: “Following the ancient tradition, people take refuge in the triple-Gem” (see, for example, “Going for the refuge, taking the precepts”, by Bhikkhu Bodhi) A. Cardini / INFN Cagliari

  21. Altre Trasparenze A. Cardini / INFN Cagliari

  22. Simulation • Maxwell 3D GEM electric field model • Garfield tools: Heed (ionization mechanism) + Magboltz (drift velocity and diffusion) Imonte 4.5 (Townsend and attachment • Electronics simulated with SPICE s(t) = 1/nv n: clust/mm v: e- velocity Ar/CO2/CF4 (45/15/40) Ed Optimal value A. Cardini / INFN Cagliari

  23. Low THR ~ 2 fC Efficiency in 20 ns Single chamber Efficiency Curve A. Cardini / INFN Cagliari

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