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

Transcription

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 1. Laboratori Nazionali di Frascati - INFN, Frascati, Italy 2. Sezione INFN di Cagliari Cagliari, Italy 3. 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 CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 2

3 These characteristics make GEM-based detector an attractive device for M1R1 (~0.6m 2 ), for which the requirements are: Rate Capability up to 0.5 MHz/cm 2 Station Efficiency > 96% in a 20 ns time window (*) Cluster Size < 1.2 for a 10x25 mm 2 pad size Radiation Hardness 1.6 C/cm 2 in 10 years (**) Chamber active area 20x24 cm 2 (*) 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/cm 2 with a gain of ~ 6000 In this presentation we will show that Triple-GEM detectors with pad readout are the appropriate choice for M1R1 CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 3

4 10x10 cm 2 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. CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 4

5 Large (20x24 cm 2 ) GEM foils, divided in 6 sectors, are stretched with the tool shown above and then glued on frames. CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 5

6 M1R1 Full Size Prototype ASDQ FEE Boards Sensitive gaps CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 6

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 ( 55 Fe), charge-transfer optimization ( 90 Sr), sparking ( 137 Am), global aging ( 60 Co) 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 CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 7

8 Gain & Gain Uniformity Gain uniformity ~ % CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 8

9 Single Chamber Time Spectra 9.7 ns 5.3 ns 4.5 ns 4.5 ns CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 9

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! Cluster Size OR Efficiency in 20 ns 2.0 fc 3.0 fc Working region G~4000 G~20000 CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 10

11 Discharge Studies 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 (G < 17000). This limit is conservative because up to 5000 discharges no damage was observed. Working region G~4000 G~17000 CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 11

12 Aging Studies Local Aging: performed with a high intensity 5.9 kev X-ray tube, irradiated area of about 1 cm 2 (~ 5000 GEM holes). Integrated charge 4 C/cm 2 25 LHCb years. Large Area Aging: performed by means of the PSI πm1 positive hadron beam, with an intensity up to 300 MHz and an irradiated area of about 15 cm 2. Integrated charge 0.5 C/cm 2 3 LHCb years. Global Aging: performed at Casaccia with a 25 kci 60 Co source. Detectors were irradiated at Gray/h. Integrated charge up to 2 C/cm LHCb years. CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 12

13 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 G/G ~ 0 G/G ~ -10% for 0.15 C/cm 2 Integration time: 3 35 days 2 clearly different trends! 1.4 LHCb years CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 13

14 Normalized Currents (%) PSI 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 H 2 O injection CO 2 problem Good timing performances were also measured at the PS after the PSI test No significant aging effects 2 clearly different trends! 12.5 LHCb years CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 14

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. Aging Test Gas Flow (cc/min) Current (µa) Current/gas flow Lab. Tests ~ 0 X-rays PSI Casaccia big Casaccia small Casaccia monitor Sauli (Hamburg) M1R1 (peak) (@ 184 khz/cm 2 ) 0.09 CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 15

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. CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 16

17 After 17/9 LHCb Tech. Board CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 17

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 CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 18

19 Conclusions The 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 CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 19

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) CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 20

21 Altre Trasparenze CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 21

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 σ(t) = 1/nv n: clust/mm v: e - velocity Ar/CO 2 /CF 4 (45/15/40) E d Optimal value CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 22

23 Single chamber Efficiency Curve Efficiency in 20 ns Low THR ~ 2 fc CSN1. Lecce, 24/09/2003 A. Cardini / INFN Cagliari 23