Available on CMS information server CMS CR -2016/080

The Compact Muon Solenoid Experiment

Mailing address: CMS CERN, CH-1211 GENEVA 23, Switzerland

Conference Report08 May 2016 (v2, 14 May 2016)

R and D on a New Technology of Micro-patternGaseous Detectors Fast Timing Micro-pattern

Detector

Sinem Salva for the CMS Collaboration

Abstract

After the upgrades of the Large Hadron Collider (LHC) planned for the second and the third LongShutdown (LS), the LHC luminosity will approach very high values. Such conditions will affect theperformance of the CMS muon system, especially in the very forward region, due to the harsh expectedbackground environment and high pile-up conditions. The CMS collaboration considers upgrading themuon forward region to take advantage of the pixel tracking coverage extension a new detector, ME0station, possibly behind the new forward calorimeter. New resistive micro-pattern gaseous detectorsthat are able to handle the very demanding spatial, time resolution and rate capability, are being consid-ered. In this contribution we introduce a new type of MPGD technology the Fast Timing Micro-pattern(FTM) detector, utilizing a fully resistive WELL structure. It consists of a stack of several coupledlayers where drift and WELL multiplication stages alternate in the structure, yielding a significantimprovement in timing properties due to competing ionization processes in the different drift regions.Two FTM prototypes have been developed so far. The first one is micro-WELL-like, where multi-plication takes place in the holes of a kapton foil covered on both sides with resistive material. Thesecond one has a resistive structure with multiplication developing in a region delimited by a resistivemesh. The structure of these prototypes will be described in detail and the results of the characteriza-tion study performed with an X-Ray generator will be presented. The first results on rate capabilityand time resolution based on data collected with cosmic rays and beam tests will also be presented.

Presented at RPC2016 The XIII workshop on Resistive Plate Chambers and Related Detectors

R and D on a New Technology of Micro-pattern Gaseous Detectors: Fast Timing Micro-pattern Detector

D. Abbaneoo, M. Abbaso, M. Abbresciab, A.A. Abdelalimg, M. Abi Aklm,W. Ahmedg, W. Ahmedq, P. Altierib, R. Alyg, C. Armaingauda, C. Asawatangtrakuldeec, A. Ashfaqq, P. Aspello, Y. Assranh, I. Awanq, S. Ballyo, Y. Banc, S. Banerjees, P. Barriae, L. Benussin, V. Bhopatkarv, S. Biancon, J. Boso, O. Bouhalim, S. Braibantd, S. Buontempox, J. Caie, C. Calabriab, M. Caponeron, C. Caputob, F.Cassesex, A. Castanedam, S. Cauwenberghp, F.R. Cavallod, A. Celiki, M. Choi5, K. Choi5, S. Choi3, J. Christianseno, A. Cimminop, S. Colafranceschio, A. Colaleob, A. Conde Garciao, M.M. Dabrowskio, G. De Lentdeckere, R. De Oliveirao, G. De Robertisb, S. Dildicki, S. Dildickp, B. Dorneyo, W. Elmetenaweeg, G. Fabrice1, M. Ferrinin, S. Ferryo, W. Flanaganj, P. Giacomellid, J. Gilmorej, L. Guiduccid, A. Gutierrezl, R.M. Hadjiiska2, A. Hassang, J. Hauseru, K. Hoepfnera, M. Hohlmannv, H. Hooraniq, Y.G. Jengr, T. Kamoni, P.E. Karchinl, H.S. Kimr, V. Khotilovichj, S. Krutelyovi, A. Kumark, J. Lee5, T. Lenzie, L. Litov2, F. Loddob, T. Maerschalke, G. Magazzuz, M. Maggib, Y. Maghrbim, A. Magnaniy, N. Majumdars, P.K. Malf, K. Mandalf, A. Marchioroo, A. Marinovo, J.A. Merlino, N. Mohammedk, A.K. Mohantyw, A. Mohapatrav, S. Muhammadq, S. Mukhopadhyays, M. Naimuddink, S. Nuzzob, E. Oliverio, L.M. Pantw, P. Paoluccix, I. Park5, G. Passeggiox, B. Pavlov2, B. Philippsa, M. Phippsv, D.Piccolon, H. Postemao, G. Puglieseb, A. Puig Baranaco, A. Radih, R. Radognab, G. Raffonen, S. Ramkrishnak, A. Ranierib, C. Riccardiy, A. Rodrigueso, L.Ropelewskio, S. RoyChowdhurys, M.S. Ryur, G. Ryu5, A. Safonovi, A. Sakharovj, S. Salvap*, G. Savianon, A. Sharmao, S.K.Swainf, J.P. Talvitieo, J.P. Talvitiet, C. Tammab, A. Tatarinovi, H. Tenge, N. Turiniz, T. Tuuvat, J. Twiggerv, M. Tytgatp, I. Vaiy, M. Van Steniso, R. Venditib, E. Verhagene, P. Verwilligenb, P. Vituloy, D. Wangc, M. Wangc, U. Yang4, Y. Yange, R. Yonaminee, N. Zaganidisp, F. Zenonie, A. Zhangv

a RWTH Aachen University, III Physikalisches Institut A, Aachen, Germany b Politecnico di Bari, Universite di Bari and INFN Sezione di Bari, Bari, Italy c Peking University, Beijing, China d University and INFN Bologna, Bologna, Italy e Universite Libre de Bruxelles, Brussels, Belgium f National Institute of Science Education and Research, Bhubaneswar g Helwan University & CTP, Cairo, Egypt h Academy of Scientific Research and Technology, ENHEP, Cairo, Egypt i Texas A&M University, College Station, USA j Kyungpook National University, Daegu, Korea k University of Delhi, Delhi, India l Wayne State University, Detroit, USA

m Texas A&M University at Qatar, Doha, Qatar n Laboratori Nazionali di Frascati - INFN, Frascati, Italy o CERN, Geneva, Switzerland p Ghent University, Dept. of Physics and Astronomy, Ghent, Belgium q National Center for Physics, Quaid-i-Azam University Campus, Islamabad, Pakistan r National University, Jeonju, Korea s Saha Institute of Nuclear Physics, Kolkata, India t Lappeenranta University of Technology, Lappeenranta, Finland u University of California, Los Angeles, USA v Florida Institute of Technology, Melbourne, USA w Bhabha Atomic Research Centre, Mumbai, India x INFN Napoli, Napoli, Italy y INFN Pavia and University of Pavia, Pavia, Italy z INFN Sezione di Pisa, Pisa, Italy 1 IRFU CEA-Saclay, Saclay, France 2 Sofia University, Sofia, Bulgaria 3 Korea University, Seoul, Korea 4 Seoul National University, Seoul, Korea 5 University of Seoul, Seoul, Korea_________________________ *Corresponding author. E-mail: Sinem.Salva@ugent.be

ABSTRACT: After the upgrades of the Large Hadron Collider (LHC) planned for the second andthe third Long Shutdown (LS), the LHC luminosity will approach very high values. Suchconditions will affect the performance of the CMS muon system, especially in the very forwardregion, due to the harsh expected background environment and high pile-up conditions. TheCMS collaboration considers upgrading the muon forward region to take advantage of the pixeltracking coverage extension a new detector, ME0 station, possibly behind the new forwardcalorimeter. New resistive micro-pattern gaseous detectors that are able to handle the verydemanding spatial, time resolution and rate capability, are being considered.

In this contribution we introduce a new type of MPGD technology: the Fast TimingMicro-pattern (FTM) detector, utilizing a fully resistive WELL structure. It consists of a stack ofseveral coupled layers where drift and WELL multiplication stages alternate in the structure,yielding a significant improvement in timing properties due to competing ionization processesin the different drift regions. Two FTM prototypes have been developed so far. The first one ismicro-WELL-like, where multiplication takes place in the holes of a kapton foil covered onboth sides with resistive material. The second one has a resistive structure with multiplicationdeveloping in a region delimited by a resistive mesh. The structure of these prototypes will bedescribed in detail and the results of the characterization study performed with an X-Raygenerator will be presented. The first results on rate capability and time resolution based on datacollected with cosmic rays and beam tests will also be presented.

KEYWORDS: CMS; GEM; Upgrade; Micropattern Gaseous Detectors; Muon Spectrometers.

Contents

1. Introduction 1

2. The Fast Timing Micro-pattern detector 2

3. Measurements of the detector with source 3

4. Test-beam and time resolution calculation 5

5. Conclusion 6

1. Introduction

The intensive environment of High-Luminosity LHC, also the flux of particles through the CMSdetector will greatly increase during Phase 2 and Phase 3 period. New detector requirementsinclude a high rate capability (~Mhz/cm²), and in addition, a new station must be able to survivethe high radiation background, where the charge expected to be integrated in 20 years ofoperation of the LHC is around 100 mC/cm². In particular, the high pseudorapidity (η) region ofthe muon system of the CMS experiment will have to handle big challenges as redundancy andlongevity.

The CMS muon system will be upgraded also with the introduction of new stationsinstrumented with Micro-pattern Gas Detectors (MPGD) to handle these hard conditions. As itis shown in figure 1, the GE1/1 (GEM Endcap 1/1) station will be instrumented with GEMdetectors and installed during Long Shutdown 2 (LS2) [1].

Figure 1: A quadrant of the CMS muon system with different subsystems. The stations ofthe forward detectors are shown in the red box with GE1/1, GE2/1 and ME0.

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For the other two stations proposed for LS3, GE2/1 (GEM Endcap 2/1) and ME0 (MuonEndcap 0), the baseline solution is again GEM detectors, but optional solutions foreseenμRWELL [2] technology for GE2/1 and the FTM technology for ME0.

One of the particular goals of the ME0 station is the increase in pseudorapiditycoverage and acceptance up to |η| < 3. In addition, in order to match with the new tracker thatwill provide triggering up to |η| < 2.4, the ME0 station should also provide a robust muontrigger with low pT threshold and muon tagging. These conditions in which the station wouldhave to be operated will be extremely harsh, with a pile-up in the order of 140-200 and a veryhigh background rate up to 100 kHz/cm². For these reasons the detectors to be installed in theproposed station will need to have high granularity and spatial segmentation to allow pTassignment and improve pile-up rejection. The new structure with multiple layers, as it is shownin figure 2, will allow an improvement of local muon track reconstruction and discriminationbetween muons by resulting in a segment, and neutrons by resulting in uncorrelated hits. On theother hand, good timing will allow object reconstruction, and help in vertex association. Also,neutron background mitigation will benefit from timing such that only small time windows arecompatible with genuine muon hits from the interaction point, if the detection location is knownprecisely.

Figure 2: Multi-layer structure of ME0 station for improvement of local muon trackreconstruction and discrimination between muons

2. The Fast Timing Micropattern detector

The first prototype of Fast Timing Micro-pattern (FTM) detector's structure is described in [3].The segmentation of the drift gap is used as a parameter that is worked on it to obtain animprovement in the time resolution to reach 1 ns scale.

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The principle is to divide a single thick drift region in many thinner drift regions, and then eachcoupled to its amplification stage. The number of stages is proportional to the reduction in timeresolution that can be obtained. The first prototype of the FTM detector exploits this principleusing two 250 μm-thick drift gaps, each coupled with an amplification region composed by afully resistive WELL. The construction of consecutive drift-amplification stages is allowed bythe use of resistive layers to polarize drift and multiplication volumes. The overall structure istransparent to the signal that can be extracted from every amplification stages, and it iscomposed by two independent drift-amplification stages as in the figure 3.

Figure 3: Transversal view of the first prototype of FTM detector.

Each amplification region is based on a pair of polyimide foils, i.e. kapton, stacked dueto the electrostatic force induced by the polarization of the foils: the first foil, perforated withinverted truncated-cone-shaped holes (with top base 100 μm and bottom base 70 μm and pitch140 μm), is a 50 μm thick polyimide foil (Apical) from KANECA, coated with diamond-likecarbon (DLC) technique, to reach up to 800 MΩ/cm² ; the second foil is 25 μm thick XCDupont Kapton, with a resistivity of 2 MΩ/cm² . The drift volumes are 250 μm thick, withplanarity ensured by coverlay pillars, 400 μm diameter and pitch of 3.3 mm. The active area ofthe prototype is of the order of 20 cm². The induced signal can be picked up from the readoutelectrode, but also from the drift electrode, through a capacitive coupling.

3. Measurements of the detector with source

The first performance of the FTM prototype was performed with an Amptek mini X-ray sourcewith 22 keV X-Rays. The signals were collected from the drift and readout electrodes and theprototype was readout with an electronics chain composed by a preamplifier ORTEC 142PCand an amplifier ORTEC 474 as shown in figure 4.

Hit rate from both the readout and drift electrodes at different values of current from theX-ray source is shown in the figure 5. The response of the detector is linear for both electrodes.Furthermore, the two data sets are comparable, giving an indication of the electricaltransparency of the layers.

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Figure 4: Signals from the FTM detector after amplification and shaping. The blue signal isfrom the readout electrode, and the orange one is from the drift electrode.

Figure 5: Measured hit rate from both channels of the FTM detector as a function of the X-ray current. The increase of the rate measured is linear with the increase of the incident flux.

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4. Test-beam and time resolution calculation

The FTM prototype was performed with a test beam that was in fall 2015 at the SPS H4 beamline at CERN with muon and pion beams. The aim of this test beam was measuring the timeresolution of the detector. The setup is shown in figure 6 with instrumentation of three 10×10cm² Triple-GEM detectors (3:2:2:2 mm gap configuration) for alignment with the beam andfour scintillators, including one 2.5×3.5 cm² finger scintillator for triggering.

Figure 6: Test-beam setup of FTM with tracker GEMs and trigger scintillators

The time resolution was evaluated in different powering configuration of the detector.Figure 7 shows the time distribution of events induced by muons.

Figure 7: Time distribution of the events induced by muons. Time resolution is evaluated fromthe sigma of the Gaussian fit.

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The signal is taken from the drift electrode and readout by a fast electronic chaincomposed by a Cividec amplifier. The time resolution is the sigma of the Gaussian fit to thetime distribution and it is of the order of 2.5 ns with a green-house-gas-free gas mixture,composed by Ar/CO2 (70:30).

5. Conclusion

The first prototype of Fast Timing Micro-pattern detector was tested and showed to have alinear response to the rate, to be electrically transparent and its time resolution was measured asthe order of 2 ns with Ar/CO2 (70:30) gas mixture. The detector is being considered to cover theME0 station of the CMS Muon system. The R&D is ongoing with the design of a new prototypewith fully PCB-based and at least 4 independent stages.

Acknowledgments

We gratefully acknowledge the support of FRS-FNRS (Belgium), FWO-Flanders (Belgium),BSF-MES (Bulgaria), BMBF (Germany), DAE (India), DST (India), INFN (Italy), NRF(Korea), QNRF (Qatar), and DOE (USA).

References

[1] CMS GEM Collaboration, CERN-LHCC-2015-012.

[2] G.Becivenni et al., The micro-Resistive WELL detector: a compact spark protected singleamplification-stage MPGD, 2015 JINST 10 P02008.

[3] R. De Oliveira et al., A novel fast timing micropattern gaseous detector: FTM, arXiv:1503.05330.

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