- Email: [email protected]
Test beam and irradiation test results of Triple-GEM detector prototypes for the upgrade of the muon system of the CMS experiment
Nuclear Instruments and Methods in Physics Research A 824 (2016) 586–588
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Test beam and irradiation test results of Triple-GEM detector prototypes for the upgrade of the muon system of the CMS experiment I. Vai a,b,n, On behalf of the CMS GEM Collaboration a b
Dipartimento di Fisica, Universitá degli Studi di Pavia, Pavia, Italy INFN Sezione di Pavia, Pavia, Italy
art ic l e i nf o
a b s t r a c t
Available online 4 December 2015
The CMS Collaboration is developing GEM detectors for the upgrade of the CMS muon system. Their performance will be presented, analyzing the results of several test beams and an irradiation test performed in the last years. & 2015 Elsevier B.V. All rights reserved.
Keywords: GEM Micro-pattern gas detectors CMS
1. Introduction The Compact Muon Solenoid (CMS) Collaboration is improving the muon system to maintain the high level of performance achieved during Run 1 [1] also in the harsh environment of High Luminosity LHC (HL-LHC). The installation of additional detectors in the endcap muon stations is foreseen to maintain high trigger efficiency and muon reconstruction performance and achieve redundancy in the forward region beyond j η j ¼1.6. The Gas Electron Multiplier (GEM) technology achieved significant relevance, as the installation of a GEM station in the region 1:6 o j η j o 2:2 (GEM Endcap 1/1, GE1/1 in the following) is expected to fulfill the requirements in spatial, angular and time resolutions as well as in rate capability and radiation hardness [6]. GEM is a well-known technology, detailed information on their operational principle can be found in [5]. The work of the CMS GEM Collaboration focused therefore on the development of a Triple-GEM detector prototype fitting the HL-LHC requirements, improving the stretching technique, the mechanics, the assembly procedure and so on.
results of these tests show that the detection efficiency for charged hadrons reaches values of 97–98% (Fig. 1 for Ar/CO2/CF4 (Top) and Ar/CO2 (Bottom) results), the angular resolution is in the range 100–160 μrad, the timing resolution is of the order of few ns with both the gas mixtures employed. A spatial resolution of the order of 200–300 μm has been achieved, as shown in Fig. 2. During a test performed at CERN with muon and pion beams, it has been demonstrated that the presence of a strong magnetic field (up to 1.5 T) does not deteriorate the performance of a GE1/1 detector. The gain has been measured with all the prototypes using a X-Ray source, up to values of the order of 104–105. Moreover, tests performed on GE1/1-III show an overall gain uniformity with variation less than 15% among different sectors. Rate capability tests have been performed with an Ag X-Ray source (peak energy 22 keV), whose data are reported in Fig. 3, and a high-intensity Cu X-Ray source (peak energies 8 and 8.9 keV): the gain is measured to be constant over four orders of magnitude of incident particle rate up to 100 MHz/cm2 [6].
3. Results from irradiation test 2. Results from test beams The performance of the various prototypes (named as GE1/1-I, GE1/1-II, etc.) has been measured in test beams at CERN and at Fermilab. At CERN the chambers were operated with Ar/CO2/CF4 45:15:40 gas mixture and read-out with binary-output VFAT2 front-end chips [2]; and at Fermilab, with Ar/CO2 70:30 gas mixture and read-out with analog APV25 front-end chips [3,4]. The n Correspondence address: Dipartimento di Fisica, Universitá degli Studi di Pavia, Pavia, Italy. E-mail address: [email protected]
http://dx.doi.org/10.1016/j.nima.2015.11.133 0168-9002/& 2015 Elsevier B.V. All rights reserved.
Aging tests were performed at the Gamma Irradiation Facility (GIF) at CERN, with a 137Cs source of 566 GBq (Gamma rays 662 keV). A GE1/1-IV prototype, operated at a gas gain of 2 104, was subjected to an incident gamma rate of the order of 100 kHz/ cm2. The mixture employed was the standard Ar/CO2/CF4 45:15:40 at 0.5 l/h. The system was also equipped with counters that monitor the cleanliness of the gas. Possible aging of the detector could be identified monitoring the readout current of the GE1/1-IV detector: a polymer deposit would indeed affect the gas gain. The normalized gain of the irradiated sectors of the GE1/1-IV prototype shows no drop after accumulating about 10 mC/cm2 of charge, corresponding to about two years of GE1/1 operation at
I. Vai / Nuclear Instruments and Methods in Physics Research A 824 (2016) 586–588
587
Fig. 2. GE1/1-IV spatial resolution, here defined as the sigma of the track-hit residuals (difference between the measured hit positions and the points where the fitted track impacts the chamber) distribution. Data obtained with a pion beam at CERN for the central sector of the detector, operated with Ar/CO2/CF4 45:15:40 and read-out with binary output VFAT2 chips [6].
14000
Ag Xray 22 keV GE1/1-IV Ar-CO2-CF4 45:15:40
Effective Gas Gain
12000 10000 8000 6000 4000 2000 0 1.0E-01
2
10 kHz/cm equivalent MIP 1.0E+00
1.0E+01
1.0E+02
1.0E+03
Rate (kHz/cm2) Fig. 3. Effective gas gain as a function of the incident photon rate measured in a GE1/1-IV detector operated with Ar/CO2/CF4 45:15:40 and irradiated with a 22 keV X-Ray source. The dashed line represents the expected rate in the CMS muon system [6].
Fig. 1. Measured detection efficiency for GE1/1 prototypes for charged particles. Top: Efficiency vs HV applied to the drift electrode for a GE1/1-IV operated with Ar/ CO2/CF4 45:15:40 and read out with VFAT2 chips, configured with a threshold of 0.8 – 1.2 fC charge per strip. Bottom: Efficiency vs HV applied to the drift electrode for the central sector of a GE1/1-III operated with Ar/CO2 70:30 and read out with APV25 chips. Three different cuts are applied offline to the strip charges to simulate VFAT2 threshold behavior. The resulting efficiency curves are fitted to sigmoid functions [6].
the HL-LHC (Fig. 4). The test setup has been moved to the new higher-intensity Gamma Irradiation Facility (GIF þ þ ) at CERN, where the aging test will continue with the aim of reaching an accumulated charge higher than 100 mC/cm2 [6].
4. Summary The results of several test beams and an irradiation test demonstrate that GEM technology is capable of sustaining the harsh conditions of HL-LHC and then it is a good candidate for the upgrade of the CMS muon system. For this reason, a first installation of a GEM demonstrator is foreseen for 2016–2017, while the installation of the full GE1/1 station is planned for 2018.
Fig. 4. Corrected and normalized gain in the sector of GE1/1-IV which was irradiated, as a function of the total charge accumulated in the detector during the GIF aging test: the flat curve takes into account the fluctuations due to temperature and pressure; the other one shows the gain only normalized to its initial measured value. No aging effects have been observed after a total accumulated charge of about 10 mC/cm2 [6].
Acknowledgments We gratefully acknowledge the support of FRS-FNRS (Belgium), FWO-Flanders (Belgium), BSF-MES (Bulgaria), BMBF (Germany),
588
I. Vai / Nuclear Instruments and Methods in Physics Research A 824 (2016) 586–588
DAE (India), DST (India), INFN (Italy), NRF (Korea), QNRF (Qatar), and DOE (USA).
References [1] The CMS Collaboration, Journal of Instrumentation 8 (2013) P11002. [2] P. Aspell, et al., VFAT2: a front-end system on chip providing fast trigger information, digitized data storage and formatting for the charge sensitive readout of multi-channel silicon and gas particle detectors, in: Proceedings of TWEPP-07, 2007, 〈http://cdsweb.cern.ch/record/1069906〉.
[3] M. Raymond, et al., The APV25 0.25 μm CMOS readout chip for the CMS tracker, in: Proceedings of the IEEE Nuclear Science Symposium Conference Record, vol. 2, 2000 pp. 9/113–9/118. [4] V. Bhopatkar, M. Hohlmann on behalf of the CMS GEM Collaboration, Performance of a large-area GEM detector prototype for the upgrade of the cms muon endcap system, in: 2014 IEEE Nuclear Science Symposium Conference Record (N50-5), 〈arXiv:1126499〉. [5] F. Sauli, Nuclear Instrumentation and Methods A386 (1997) 531. [6] CMS GEM Collaboration, CMS-TDR-013, CERN-LHCC-2015-012.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Test beam and irradiation test results of Triple-GEM detector prototypes for the upgrade of the muon system of the CMS experiment I. Vai a,b,n, On behalf of the CMS GEM Collaboration a b
Dipartimento di Fisica, Universitá degli Studi di Pavia, Pavia, Italy INFN Sezione di Pavia, Pavia, Italy
art ic l e i nf o
a b s t r a c t
Available online 4 December 2015
The CMS Collaboration is developing GEM detectors for the upgrade of the CMS muon system. Their performance will be presented, analyzing the results of several test beams and an irradiation test performed in the last years. & 2015 Elsevier B.V. All rights reserved.
Keywords: GEM Micro-pattern gas detectors CMS
1. Introduction The Compact Muon Solenoid (CMS) Collaboration is improving the muon system to maintain the high level of performance achieved during Run 1 [1] also in the harsh environment of High Luminosity LHC (HL-LHC). The installation of additional detectors in the endcap muon stations is foreseen to maintain high trigger efficiency and muon reconstruction performance and achieve redundancy in the forward region beyond j η j ¼1.6. The Gas Electron Multiplier (GEM) technology achieved significant relevance, as the installation of a GEM station in the region 1:6 o j η j o 2:2 (GEM Endcap 1/1, GE1/1 in the following) is expected to fulfill the requirements in spatial, angular and time resolutions as well as in rate capability and radiation hardness [6]. GEM is a well-known technology, detailed information on their operational principle can be found in [5]. The work of the CMS GEM Collaboration focused therefore on the development of a Triple-GEM detector prototype fitting the HL-LHC requirements, improving the stretching technique, the mechanics, the assembly procedure and so on.
results of these tests show that the detection efficiency for charged hadrons reaches values of 97–98% (Fig. 1 for Ar/CO2/CF4 (Top) and Ar/CO2 (Bottom) results), the angular resolution is in the range 100–160 μrad, the timing resolution is of the order of few ns with both the gas mixtures employed. A spatial resolution of the order of 200–300 μm has been achieved, as shown in Fig. 2. During a test performed at CERN with muon and pion beams, it has been demonstrated that the presence of a strong magnetic field (up to 1.5 T) does not deteriorate the performance of a GE1/1 detector. The gain has been measured with all the prototypes using a X-Ray source, up to values of the order of 104–105. Moreover, tests performed on GE1/1-III show an overall gain uniformity with variation less than 15% among different sectors. Rate capability tests have been performed with an Ag X-Ray source (peak energy 22 keV), whose data are reported in Fig. 3, and a high-intensity Cu X-Ray source (peak energies 8 and 8.9 keV): the gain is measured to be constant over four orders of magnitude of incident particle rate up to 100 MHz/cm2 [6].
3. Results from irradiation test 2. Results from test beams The performance of the various prototypes (named as GE1/1-I, GE1/1-II, etc.) has been measured in test beams at CERN and at Fermilab. At CERN the chambers were operated with Ar/CO2/CF4 45:15:40 gas mixture and read-out with binary-output VFAT2 front-end chips [2]; and at Fermilab, with Ar/CO2 70:30 gas mixture and read-out with analog APV25 front-end chips [3,4]. The n Correspondence address: Dipartimento di Fisica, Universitá degli Studi di Pavia, Pavia, Italy. E-mail address: [email protected]
http://dx.doi.org/10.1016/j.nima.2015.11.133 0168-9002/& 2015 Elsevier B.V. All rights reserved.
Aging tests were performed at the Gamma Irradiation Facility (GIF) at CERN, with a 137Cs source of 566 GBq (Gamma rays 662 keV). A GE1/1-IV prototype, operated at a gas gain of 2 104, was subjected to an incident gamma rate of the order of 100 kHz/ cm2. The mixture employed was the standard Ar/CO2/CF4 45:15:40 at 0.5 l/h. The system was also equipped with counters that monitor the cleanliness of the gas. Possible aging of the detector could be identified monitoring the readout current of the GE1/1-IV detector: a polymer deposit would indeed affect the gas gain. The normalized gain of the irradiated sectors of the GE1/1-IV prototype shows no drop after accumulating about 10 mC/cm2 of charge, corresponding to about two years of GE1/1 operation at
I. Vai / Nuclear Instruments and Methods in Physics Research A 824 (2016) 586–588
587
Fig. 2. GE1/1-IV spatial resolution, here defined as the sigma of the track-hit residuals (difference between the measured hit positions and the points where the fitted track impacts the chamber) distribution. Data obtained with a pion beam at CERN for the central sector of the detector, operated with Ar/CO2/CF4 45:15:40 and read-out with binary output VFAT2 chips [6].
14000
Ag Xray 22 keV GE1/1-IV Ar-CO2-CF4 45:15:40
Effective Gas Gain
12000 10000 8000 6000 4000 2000 0 1.0E-01
2
10 kHz/cm equivalent MIP 1.0E+00
1.0E+01
1.0E+02
1.0E+03
Rate (kHz/cm2) Fig. 3. Effective gas gain as a function of the incident photon rate measured in a GE1/1-IV detector operated with Ar/CO2/CF4 45:15:40 and irradiated with a 22 keV X-Ray source. The dashed line represents the expected rate in the CMS muon system [6].
Fig. 1. Measured detection efficiency for GE1/1 prototypes for charged particles. Top: Efficiency vs HV applied to the drift electrode for a GE1/1-IV operated with Ar/ CO2/CF4 45:15:40 and read out with VFAT2 chips, configured with a threshold of 0.8 – 1.2 fC charge per strip. Bottom: Efficiency vs HV applied to the drift electrode for the central sector of a GE1/1-III operated with Ar/CO2 70:30 and read out with APV25 chips. Three different cuts are applied offline to the strip charges to simulate VFAT2 threshold behavior. The resulting efficiency curves are fitted to sigmoid functions [6].
the HL-LHC (Fig. 4). The test setup has been moved to the new higher-intensity Gamma Irradiation Facility (GIF þ þ ) at CERN, where the aging test will continue with the aim of reaching an accumulated charge higher than 100 mC/cm2 [6].
4. Summary The results of several test beams and an irradiation test demonstrate that GEM technology is capable of sustaining the harsh conditions of HL-LHC and then it is a good candidate for the upgrade of the CMS muon system. For this reason, a first installation of a GEM demonstrator is foreseen for 2016–2017, while the installation of the full GE1/1 station is planned for 2018.
Fig. 4. Corrected and normalized gain in the sector of GE1/1-IV which was irradiated, as a function of the total charge accumulated in the detector during the GIF aging test: the flat curve takes into account the fluctuations due to temperature and pressure; the other one shows the gain only normalized to its initial measured value. No aging effects have been observed after a total accumulated charge of about 10 mC/cm2 [6].
Acknowledgments We gratefully acknowledge the support of FRS-FNRS (Belgium), FWO-Flanders (Belgium), BSF-MES (Bulgaria), BMBF (Germany),
588
I. Vai / Nuclear Instruments and Methods in Physics Research A 824 (2016) 586–588
DAE (India), DST (India), INFN (Italy), NRF (Korea), QNRF (Qatar), and DOE (USA).
References [1] The CMS Collaboration, Journal of Instrumentation 8 (2013) P11002. [2] P. Aspell, et al., VFAT2: a front-end system on chip providing fast trigger information, digitized data storage and formatting for the charge sensitive readout of multi-channel silicon and gas particle detectors, in: Proceedings of TWEPP-07, 2007, 〈http://cdsweb.cern.ch/record/1069906〉.
[3] M. Raymond, et al., The APV25 0.25 μm CMOS readout chip for the CMS tracker, in: Proceedings of the IEEE Nuclear Science Symposium Conference Record, vol. 2, 2000 pp. 9/113–9/118. [4] V. Bhopatkar, M. Hohlmann on behalf of the CMS GEM Collaboration, Performance of a large-area GEM detector prototype for the upgrade of the cms muon endcap system, in: 2014 IEEE Nuclear Science Symposium Conference Record (N50-5), 〈arXiv:1126499〉. [5] F. Sauli, Nuclear Instrumentation and Methods A386 (1997) 531. [6] CMS GEM Collaboration, CMS-TDR-013, CERN-LHCC-2015-012.