Imad Laktineh IPN-Lyon On behalf of the CMS muon group New generation of high-rate fast timing RPC for the high eta CMS muon detector Imad Laktineh IPN-Lyon On behalf of the CMS muon group IPRD2016-Siena

Outline CMS RPC upgrade project High-rate RPC Fast timing RPC Conclusions IPRD2016-Siena

RE3/1-RE4/1: 72 chambers in all CMS RPC upgrade project To equip the RE3/1 and RE4/1 CMS muon stations with improved RPC chambers covering 1.8<|η|<2.4; each chamber spans 20° in φ; 1 layer per station RE3/1 RE4/1 RE3/1-RE4/1: 72 chambers in all Two scenarios are under investigation : -Double-gap RPC -Multi-gap RPC Using either doped glass or HPL/Bakelite as electrodes with strips-based readout Surface of each chamber ≈ 1.4 m2 Present RPC system: 1056 chambers (double-gap HPL/Bakelite RPC) covering 0 < |η| < 1.6 IPRD2016-Siena

Improve muon reconstruction efficiency in offline data CMS RPC upgrade is a part of the CMS muon upgrade project that proposes to equip the high η muon stations ahead of the HL-LHC with a new generation of detectors (iRPC, GEM, FTM,..) in addition to the present CSC detectors in order to : Increase muon system redundancy for |η|>1.6, where background rates are the largest Improve muon reconstruction efficiency in offline data Recover CSC inefficiencies in local reconstruction (stubs) in muon trigger CERN-LHCC-2015-010 phase2 CERN-LHCC-2015-010 CERN-LHCC-2015-010 IPRD2016-Siena

Requirements We expect 700 Hz/cm2 in hottest points of RE3/1 and RE4/1(based on Fluka simulation)  iRPC should stand a particle rate up to ≈ 2 kHz/cm2 (including a safety factor) with an accumulated charge of ≈ 1 C RMS displacement @ pT = 200 GeV gives ~2-3 mm for RE3/1 & RE4/1  Readout granularity of few mm with digital mode IPRD2016-Siena

iRPC high rate detection capability Present CMS RPC chambers were certified to be efficient up to 300Hz/cm2 irradiated with photons up to an integrated charge of 0.05 C/cm2, and a neutron fluence of 1012 n/cm2 and equivalent dose of about 45 Gy was reached. Rate capability of the RPC is related to the voltage drop in the resistive plate: ΔV = I R = q ρ d Φ To have RPC with increased rate capability one should reduce: electrode resistivity ρ: as low as the RPC principle still stands (> 109 Ωcm)  low-resistivity HPL or doped glass (Tsinghua glass) electrode thickness d: depends on electrode material easy for glass, possible for HPL produced charge q : depends on gas mixture and number of gaps The less the charge produced, faster the eviction : beneficial also for chamber aging but this necessitates to increase FE electronics sensitivity IPRD2016-Siena

Electrode Resistivity and thickness HPL/bakelite: Supplier :Puricelli Present system 1-5x1010Ωcm, but ~0.5-1x1010Ωcm may be achievable; thickness down to 1 mm, typical CMS sizes are no problem Low-resistivity glass: Developer: Tsinghua. Supplier: Chinese company tunable resistivity (1010Ωcm or lower) achieved; no oiling procedure needed; no humidification of gas mixture; limited sizes only Pressing units @ Puricelli Glass Specifications: Present max. dimension: 32cm×30cm Bulk resistivity: ≈1010.cm Standard thickness: 0.5mm--2mm Thickness uniformity: 0.02mm Dielectric constant: ≈7.5-9.5 Surface roughness: < 10 nm DC measurement: Ohmic behavior, stable up to 1 C/cm2 1kV applied on a glass plate 32days; integrated charge: 1 C/cm2 IPRD2016-Siena

HPL-based RPC max. γ rate ~1.4 kHz/cm2 Double-gap: gas gap = 1.6mm, HPL thickness = 2mm performance studied with cosmic rays in presence of Cs source performance studied with muon beam in presence of Cs source at GIF++ Plastic Cs-137 source RPC max. γ rate ~1.4 kHz/cm2 Shift @ ε=0.95 in HV due to γ backgr. ~ 70V Th = 110 fC IPRD2016-Siena

Glass-based RPC Small chamber : 30x30cm2; 1x1cm2 readout pads single-gap RPC: gas gap = 1.2mm, glass thickness = 1mm Small chamber : 30x30cm2; 1x1cm2 readout pads 150 GeV π,μ beam @ SPS, H2 (Jun. 2015) μ beam @ GIF++ H2 (Jul. 2015) 70% single-gap efficiency for low resist. GRPC @ > 2kHz/cm2 (i.e. >90% double-gap efficiency) Beam seen by one detector IPRD2016-Siena

Towards Full-Size GRPC Gluing method: Half size of RE4/1 Gluing small pieces of glass Gluing zone <100μm Mechanical fixation method: Half size of RE4/1 Mechanical fixation small pieces of glass Separation distance of few mm; top and bottom gaps staggered Gas tightness ensured by cassette Mechanical fixation method is more robust; issues regarding glue radiation hardness are absent ; less leakage current is observed IPRD2016-Siena

Towards Full-Size GRPC Gluing method: Half size of RE4/1 Gluing small pieces of glass Gluing zone <100μm Mechanical fixation method: Half size of RE4/1 Mechanical fixation small pieces of glass Separation distance of few mm; top and bottom gaps staggered Gas tightness ensured by cassette Large detector built with low-resitivity glass was built and successfully tested at H2 and will be soon exposed to GIF++ IPRD2016-Siena

FE Electronics HARDROC ASIC is proposed to read the 2-gap iRPC 64-ch, SiGe technology, gain correction, 10fC-15pC 3 thresh. levels, i.e. semi-analogue readout, will improve spatial resol. beyond digital readout ! ~10 000 ASICs were already tested with a dedicated test bench for the CALICE SDHCAL project Successfully tested on both HPL and glass RPC; two kinds of PCB used: Pickup pads of 1cmx1cm 4.7 mm 4.3mm HARDROC2 and 2B:160pins Strips of 2.5mm pitch . IPRD2016-Siena

Spatial resolution of ~1-2 mm achievable GRPC telescope consisting of several low resist. Chamber (gas mixture 93% TFE, 5% CO2, 2% SF6), was used to test a 2-gap GRPC with pickup strips @ PS, CERN, August 2014 HV = 7200V Spatial resolution of ~1-2 mm achievable IPRD2016-Siena

Fast timing Multi-gap RPC is an excellent fast timing detector (ALICE, STAR). For CMS it should help in several Fields among which: Background mitigation Long lived neutrons are captured by nuclei  γs : Photoelectric effect and Compton scattering few MeV electrons leaving hits in RPC. These hits could corrupt the muon track reconstruction and increase trigger rate. Looking for correlated hits in time in the different MRPC stations one could get rid of many noisy hits. HSCP searches will get benefit of precise time information by looking for particles reaching the muon chambers at delayed times with respect to BX. IPRD2016-Siena

Multi-gap HPL/Bakelite RPC Dual bi-gap RPC (eq. 4- gap RPC) Using HPL electrodes thickness of (1.5 mm) compared to the present CMS RPC (2 mm) and gap thicknesses (0.5, 0.8 mm) compared to the CMS RPC (2 mm) Operating HV = 6.5 ~ 7.0 kV for 0.5 mm and 9.1 ~ 9.8 kV for 0.8 mm dual bi-gap respectively Using lower threshold thanks to higher sensitive front end electronics (min. threshold ~ 70 fC) For 0.8 mm Dual bi-gap RPC <qe> ~ 0.6 pC @ HVε=0.95 = 9.1 kV Th = 0.60 mV 72 Hz cm-2 1055 Hz cm-2 Dual bi-gap RPC tested @ GIF++: Shift @ ε=0.95 in HV due to ~ 1.0 kHz cm-2 γ background ~ 100 V IPRD2016-Siena R&D is ongoing to achieve detection capabilities higher than 2kHz/cm2

Multi-gap GRPC 5-gap GRPC Prototype Mosaic GRPC MRPC Component Size (mm) PCB 320×540×0.7 Mylar 260×480×0.18 Mosaic Glass 250×330×0.7 & 250×200×0.7 Spacer 0.5 Gap 0.25×5 Total thickness ≈ 5.5 mm ELBE @ HZDR (September 2015) 30 MeV e-beam Gas: 90% TFE + 5% i-butane + 5% SF6 Few electronic channels Glue, brand? Performance to be validated soon in GIF++ IPRD2016-Siena

Electronic readout for Multi-gap CMS-RPC FE electronics PETIROC - 32-ch, SiGe, 0,16-400 pC -32 trigger output -NOR32_charge -NOR32_time -global&individual threshold adjustment 20 ps resolution for Qinj >.3 pC TDC on FPGA TDC -TDC on FPGA (25 ps time resolution) -TDC on ASIC (based on Vernier principle) is being developed, aiming at better resolution, lower power consumption and more robustness 1 2 3 4 5 -- Ns-1 Ns Nf-1 Nf Fast Slow Start Stop T Same phase IPRD2016-Siena

PCB pick-up strips read from both sides is being designed with the with the aim to achieve Absolute time measurement Y-position determination (η position) Y= L/2-v*(t2-t1)/2. No need of η segmentation. On-detector Strip Off-detector Strip Y Strip jitter rms (charges injected = 5pC) 16 0.0347 18 0.03162 20 0.03355 22 0.03445 24 0.03479 26 0.03567 28 0.03467 30 0.03443 32 strips of 3 mm width (4 mm pitch) Time difference of the two signals detected in channels 16 and 17 associated to two ends of the same strip. IPRD2016-Siena Time resolution/channel ≈ 25 ps

Conclusions and prospects New double-gap RPC detectors (glass and HPL) are able to stand the expected high rate fluences of the HL-LHC in the high η region of CMS muon stations (RE3/1, RE4/1). New low-noise Front End electronics to achieve such performance is available and is being adapted to CMS running conditions. Fast timing could be an asset. Multi-gap RPC are the best detectors to achieve this. Low-jitters Front-End electronics equipped with TDC providing excellent time resolution is being developed and preliminary results are very encouraging. Simulation studies on trigger and trigger performance will allow to assess the interest of fast timing MRPC. Additional tests at CERN and elsewhere are planned to confirm the performance of the new detectors and to study their robustness within the CMS conditions. IPRD2016-Siena