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Un Rivelatore a Tripla-GEM per le Camere a Muoni di LHCb M. Alfonsi 1, G. Bencivenni 1, W. Bonivento 2, A. Cardini 2, P. de Simone 1, F. Murtas 1, D. Pinci.

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Presentation on theme: "Un Rivelatore a Tripla-GEM per le Camere a Muoni di LHCb M. Alfonsi 1, G. Bencivenni 1, W. Bonivento 2, A. Cardini 2, P. de Simone 1, F. Murtas 1, D. Pinci."— Presentation transcript:

1 Un Rivelatore a Tripla-GEM per le Camere a Muoni di LHCb M. Alfonsi 1, G. Bencivenni 1, W. Bonivento 2, A. Cardini 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 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari2  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 M1R1

3 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari3 Conversion & A Triple-GEM detector is built by inserting three GEM foils between two planar electrodes, which act as the cathode and the anode. The volume between the cathode and the first GEM is usually referred to as the DRIFT gap. This is also the sensitive gap in the detector. The TRANSFER gaps are the volumes between the GEMs. The volume between the last GEM and the anode is usually called the INDUCTION gap. The anode is segmented in pads to provide the spatial information and these electrodes are readout with charge/current preamplifiers.

4 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari4 Large (20x24 cm 2 ) GEM foils, divided in 6 sectors, are stretched with the tool shown above and then glued on frames.

5 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari5 Sensitive gaps ASDQ FEE Boards M1R1 Full Size Prototype

6 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari6 Considerable improvement with respect to the Ar/CO 2 =70/30 gas mixture, which exhibits a poor time resolution of about 10 ns RMS, is obtained with the new CF 4 and iso-C 4 H 10 based gas mixtures, which allow to reach time resolutions better than 5 ns RMS Our Choice: Ar/CO 2 /CF 4 45/15/40 Fast & Non-flammable 9.7 ns5.3 ns 4.5 ns Single Chamber Time Spectra

7 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari7 Working region, upper limited by Cluster Size = 1.2, is found to be 70-80 V wide, a large plateau for a micro- pattern gaseous detector! Cluster Size OR Efficiency in 20 ns 2.0 fC 3.0 fC G~4000 G~20000 Working region

8 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari8 Discharge probability per incident particle Recenti misure suggeriscono che un rivelatore possa tollerare fino a circa 1000 scariche/cm 2  P < 5.4 10 -11  G < 2.7 10 4

9 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari9 Local Aging Test high intensity X-rays detector active area 10х10 cm 2 irradiated area ~1mm 2 G=2.5·10 4 Ar/CO 2 /CF 4 (60/20/20) Δ G/G < 5% ΣV GEM = 1230 V G=6·10 3 Ar/CO 2 /CF 4 (45/15/40) Δ G/G < 5% ΣV GEM = 1280 V G=10 4 Ar/CF 4 /C 4 H 10 (68/25/7) Δ G/G ~10% ΣV GEM = 1030 V 10 LHCb Years 6.6 C/cm 2 10 LHCb Years 1.8 C/cm 2 Φ gas =166.6 cc/min Φ gas =200 cc/minΦ gas =154 cc/min I G3_Dw +I Pad ~270 nAI G3_Dw +I Pad ~160 nA 10 LHCb Years 3 C/cm 2

10 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari10  Gas mixture:Ar/CO 2 /CF 4 = 45/15/40;  Large chamber A, B + small D in test position ~ 16 Gy/hour;  Large chamber C in monitor position ~ 0.5 Gy/hour;  Large chamber E in low irradiation position ~ 0.1-0.2 Gy/hour;  HV(“reference”) = 1280 V, G ~ 6x10 3 ;  H 2 O/T/ P = ± 1ppm / ± 0.1 ° K / ± 0.1mb (Panametrics/MKS probe systems) PC 60 Co 25 kCi GAS BOTTLES HV 4.5m GEM A,B,D GEM-C GEM-E Aging set-up at Casaccia

11 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari11 Casaccia / Big Detector A / 16 Gy/h Casaccia / Big Detector B / 16 Gy/h Casaccia / Big Detector C / 0.5 Gy/h Casaccia / Small Detector D / 16 Gy/h X-Ray / Small Detector / Local Aging Normalized Currents (%) 11 LHCb years 2 clearly different trends ! PSI CO 2 problem H 2 O injection

12 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari12  G/G ~ 0  G/G ~ -10% for 0.15 C/cm 2 Normalized Currents (%) 1.2 LHCb years Casaccia / Big Detector A / 16 Gy/h Casaccia / Big Detector B / 16 Gy/h Casaccia / Big Detector C / 0.5 Gy/h Casaccia / Small Detector D / 16 Gy/h X-Ray / Small Detector / Local Aging 2 clearly different trends ! Integration time: 3  35 days

13 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari13  Clarify aging mechanism: Physical/Chemical analysis of irradiated detectors  Understanding different chamber behavior: Investigation on the Gas-flow effect  Absolute Gain Measurement  Gain Uniformity  Gain/Efficiency Recovery by voltage increase: A gain recovery by a factor 2 has already been performed during the Casaccia test @ Settembre 2003

14 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari14 W.Witzeling (Tech. Coord.) in the Zürich Sept. ’03 LHCb-week:  “Ageing is a delicate issue in this region and recent ageing results on the GEM require further clarification before a final decision can be taken.”  “The TB congratulates the GEM team to the results achieved and encourages them to pursue the work with the aim of coming to a positive decision in March 04.”

15 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari15 Chamber A (nA/pad)Chamber B (nA/pad) Good uniformity on the chambers X-ray test : Uniformity (Pad Current)

16 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari16 We tried to reproduce the Casaccia test results, irradiating with X-rays a 10x10 cm 2 chamber (total current ~2  A on ~ 1 cm 2 irradiation spot) flushed with a low gas flow (20 cc/min). A current drop of ~ 40% for a 0.55 C/cm 2 integrated charge (~3 LHCb years) is found on the low gas flow measurement. NO current drop is observed on the high gas flow measurement. High gas flow Low gas flow Aging induced by low gas flow

17 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari17 Ch A G1 down sample 5  Inner → 44 µm  Outer → 76 µm G1: No fluorine No etching - No damage on gold-plated drift cathode and Pad PCB. They are perfectly clean. - Fluorine found on G2 and G3 could be present as Cu-F compound, forming a thin insulating layer (no carbon deposits observed on the surfaces). Ch A G3 down sample 11  Inner → 64÷65 µm  Outer → 77÷78 µm G3:Large fluorine etching Ch A G2 down sample 9  Inner → 47 µm  Outer → 79 µm G2:Small fluorine,etching started SEM analysis on Casaccia chambers

18 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari18 The fluorine strongly etched the third GEM, not only widening the copper holes but also etching the kapton inside hole (from the bottom to the top), changing the hole shape. The effective inner hole diameter, from the standard 45-50  m becomes 60-65  m. Cross section of the first GEM foil of the aged chamber A. Cross section of the third GEM foil of the aged chamber A. SEM analysis on Casaccia chambers

19 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari19 ~50% Gain @ 1280 VAB Reference Xray LNF 6. 10 3 Casaccia drop @ 15-20 MHz/cm 2 -89% (11.5 Y)-80% (8.5 Y) X-Ray 1.6 MHz/cm 2 -55%-32% Gain Chamber A current drop (~89%) ~ gain drop(~55%) + rate capability (~30%) Gain and rate capability on aged chambers Rate capability reduced due to charging down LHCb X-Ray Casaccia B Rate Capability Casaccia A ~30%

20 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari20 old new After Casaccia, chambers A and B were tested at CERN PS-T11. Time and efficiency performances are similar to those found before Casaccia aging test, except for a 20-25 V shift in the working point, and practically unaffected working regions. 96% old new Beam test results on aged chambers

21 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari21  Casaccia results seem to be understood : the etching observed is correlated with bad gas flow rate condition;  No corrosion effect observed on the cathode and anode;  Etching effects mainly on the third gem with fluorine deposits near the copper holes edges;  No aging occurs if the gas flow is properly set, as in the LHCb running condition;  Detectors, even after a severe irradiation in bad conditions, exhibit good time and efficiency performances. Conclusioni

22 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari22 Conclusion of the Muon Group on the M1R1 Technology (Feb. ’04)  “We are satisfied with the understanding of the ageing process in GEM detectors and recommend them to be adopted for M1R1.”  Addendum-2 to the Muon TDR is under preparation

23 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari23 Final approval of the GEM chambers for Region 1 of the Muon Station 1 (Cagliari+LNF) “After the preliminary decision in September 03, more studies on ageing were performed, the effects seen in the Casaccia tests are now understood (gas flow). TB supported proposal by Muon group to adopt GEM chambers for the M1 R1 region.” (W. Witzeling) Technical Board on 25 February ’04

24 CSN1, 5 aprile 2004A. Cardini / INFN Cagliari24 Cosa viene ora? Maggio 2004: programma dettagliato sulla costruzione e costi M1R2: ci è stato chiesto di studiare la fattibilità –Ci sono indicazioni che sia una scelta “saggia” –Problemi di manpower: necessari almeno 2 tecnici a tempo pieno –Costi da valutare –Sistema GAS da studiare –…


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