The ATLAS RPC system upgrade for the High

The ATLAS RPC system upgrade for the High Luminosity LHC Yongjie Sun, on behalf of the ATLAS Muon Collaboration XV Workshop on Resistive Plate Chambers and Related Detectors, 10 -14 February 2020, Rome, Italy

Outline ØIntroduction ØThe upgrade of the ATLAS RPC trigger system ØThe pilot BIS 78 in Phase-I upgrade ØThe new considerations for Phase-II BI RPC upgrade ØSummary and outlook Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 2

The High Luminosity LHC • Luminosity upgrade to 7× 1034 cm-2 s-1 @ 14 Te. V p-p collisions • ATLAS Detectors need a major upgrade: • Phase-I (LS 2, 2019 -2021) • Phase-II (LS 3, 2025 -2027) Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 3

The current ATLAS RPC system • Trigger detector in the barrel region (|η|<1. 05) • Designed for 1034 cm-2 s-1 and 300 fb-1 • About 1000 RPC doublet UNITS • Outer layer for high p. T trigger (1/2 + low p. T) • Middle layer for low p. T trigger (3/4) • No RPC in the Inner layer (MDT only) • 6 independent layers measuring η or φ • Total surface 7000 m 2 • 370000 FE channels • Excellent detector and trigger performance during RUN-1&2 Heng Li, Performance of the ATLAS RPC detector and L 1 Muon Barrel trigger at $sqrt{s} = 13; $Te. V Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 4

Why we need the upgrade? • The Rate capability • Extrapolated from 2012 data, Max rate of ~ 350 Hz/cm 2 expected @ HL-LHC • Upgrade: ~ 100 Hz/cm 2 >k. Hz/cm 2 • The longevity • Current RPC designed for 300 fb-1, 10 yrs operation @ LHC • 0. 3 C/cm 2 4 C/cm 2 (4000 fb-1 @ HL-LHC, till 2040) • The acceptance • Due to ATLAS support structures (toroid and feet), barrel trigger acceptance just above 70%. • The trigger logic/electronics upgrade • 1 MHz rate capability • 2 μs Lvl. 0 trigger seed • the present trigger and readout electronics is not able to fulfill the rate and latency requirements of the ATLAS Phase II trigger scheme Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 5

Is the current RPCs still usable? • ATLAS RPC have shown a very stable and effective running throughout Run - 1 and Run – 2 • The HL-LHC rate is a litter higher than the design limit at high-η region (100 vs 340 Hz/cm 2) • The longevity is dominated by integrated charge limitation of 0. 3 C/cm 2. • The charge estimation for 10 years of LHC operation: 30 p. C/count× 20 Hz/cm 2× 107 s/yr × 10 yr = 60 m. C/cm 2 • At HL-LHC luminosity, a factor of 8 applies • If we apply on the BM station a 2/4 majority instead of the 3/4, it allows a consistent reduction of gap efficiency without affecting the trigger efficiency To operate this majority an increase of redundancy is needed From “TDR for the Phase-II Upgrade of the ATLAS Muon Spectrometer”, CERN -LHCC-2017 -017 2/4 vs. 3/4 majority Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 6

The upgrade plan: new layer of BI • Keeping the current RPCs (with lowered HV, charge and efficiency), adding 3 BI layers will increase the redundancy. • 96 BIS + 176 BIL triplet • 1400 m 2, 115000 FE channels. • The BI layers will also patch the holes and recover the acceptance. • Replace “ 3 -out-of-3 chambers” requirement with “ 3 -out-of-4 chambers”: Acceptance 78% → 92% • Adding BI-BO two-chambers coincidences: Acceptance → 96% • Additional overall lever arm will be benefitted from this layer. • 9 layers instead of 6 • 4 chambers instead of 3 Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 7

New generation of RPC for BI Ø Ø The challenge is to build a new generation of RPCs with higher rate capability and longevity. Higher rate capability: k. Hz/cm 2 Longer longevity: >10 years @ HL-LHC Higher spatial resolution: <1 cm Higher time resolution: ~ 0. 5 ns Gap size: 2 mm 1 mm Bakelite: 1. 8 mm 1. 2 mm Ø Reduced bakelite thickness: • Less voltage loss in bakelite improve the rate capability, larger induced signals Ø Reduced gap size: • Less charge produced per event improve longevity, rate capability • Less high voltage applied but higher field better time resolution Ø New generation FE electronic: • Higher amplification factor and high S/N ratio to compensate the lost gas amplification. Ø Improved readout panel and method • Better mechanics structure, better signal transmission and better spatial resolution. Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 8

The pilot in Phase-I upgrade: BIS 7/8 • 16 + 16 BIS 7/8 RPC is installing in Phase-I upgrade. (~ 150 m 2, 10% of the BI) • This will suppress the large fraction of fake muons in the 1<|η|<1. 3 region, the transition between barrel and endcap. • Main parameters are the same as BI RPCs • Good performance demonstrated the strategy The BIS 7 triplet Standard RPC BIS 78 RPC BI RPC 1 m. V 0. 5 m. V 0. 3 m. V 30 m. W 6 m. W 10 m. W Ga. As BJT Si + Si. Ge Bi-CMOS Si. Ge Embedded Separated Embedded No No Yes 2 mm 1 mm Operating voltage 9600 V 5800 V 5400 V Electrode thickness 1. 8 mm 1. 2 mm 1 ns 0. 4 ns FEE Effective threshold Power consumption Technology Discriminator TDC embedded Detector Gap Width Time resolution Lorenzo, The BIS 78 Resistive Plate Chambers upgrade of the ATLAS Muon Spectrometer for the LHC Run-3 Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 9

The new FE electronics High gain low noise FE is essential for the low gain BI RPC operation. • Integrating all the functions: amplifier discriminator TDC and serializer • 100 ps resolution TDC • 100 ps resolution discriminator • Performance • 10 m. W per channel already matched • 1 -2 f. C threshold for BIS 78 FE, a 4 - BIS 78 FE board prototype channel chip with • No dead time Amp. & Disc. • Rad hard • Next generation with TDC embedded is under developing. • A very first prototype of the chip containing the complete chain of discriminator and TDC has been tested. • The new ASIC prototype is expected to be submitted in March. Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 10

Trigger electronics Level-0 trigger and readout scheme in the barrel for Phase II. • The on-detector DCT boards sample the RPC front-end data and send the digitized data on GBT optical fibres to the offdetector Sector Logic boards. • FPGA-based DCT boards • 1 (or 2) for BI RPC chambers • 2+2 for BM doublets • 2 for BO chambers • Sector Logic boards will perform the trigger algorithm and readout logic. Feb. 12, 2020 ATLAS- CAVERN The ATLAS RPC system upgrade for HL-LHC, RPC 2020 USA 15 COUNTING ROOM 11

The mechanics design • The space is limited in the BI region • The total thickness of the BI triplet < 60 mm • Many constrains and limits for the realization. Interface rails – environment: -Projective extension constraints -Rail installation constraints -Rail supports constraints -Rail profile BI DCT boxes: -Access constraints -BIS routing -Available space for all BIS services The detector requires a very smooth force distribution on the gas gap surface which is difficult to achieve. • Any surface interfacing the gas gap must not be locally deformed by more than 0. 1 mm to avoid to deform the gaps gap surface • The gas gap should be kept pressed by the mechanics as a redundancy safety factor, in case of the internal spacer gluing failure Oliver, Design and construction of the mechanical structure for thin-gap RPC triplets for the upgrade of the ATLAS muon spectrometer Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 12

New readout panel • Present ATLAS RPCs: milled PET film + Foam • BIS 7/8 RPCs: PCB strip panel + Forex • BI RPCs: PCB strip panel + paper honeycomb Keeping the low εr of the filling spacer for higher impedance, the mechanical characteristic is improving. PCB strip panel for BIS 78 Apply PCB to Forex Side view of honeycomb panel Rigid and light! Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 13

The eta-eta readout • Readout from two opposite ends on separated panels • Using the time difference to determine the incident position • Robust to the ghost events of eta-phi strips • Save electronics channels • Reduce the dead area on the long side (the bending direction of ATLAS magnet) Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 14

The two-end readout • Readout from two opposite ends on single panel • Keeping the advantages of the eta-eta readout, and reducing the thickness of the singlet. Test results from USTC Spatial resolution v = 19. 69 cm/ns Quanyin Li, R&D on double-end readout RPC for ATLAS Phase-II upgrade Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 15

Management: responsibilities by Institute Roma 2 Bakelite Bologna Cosenza Roma 1 China Cluster HK cluster Protvino MPI Dubna Turkey cluster production Gas gap Design & Production FE chip Design & Production drawings Design & production Strip panel Design & production FE board Production & test Singlet Design, BIL production triplet On chamber service Mechanics Power and gas Design & production BIS production 50% BIL production Layout simulation production Design & production Production Serial cables BM-BO Retrofitting Feb. 12, 2020 mechanics design, chamber integration Retrofitting The ATLAS RPC system upgrade for HL-LHC, RPC 2020 16

Status of the upgrade project • Most of the tasks are progressing well up to now. • To make the best use of the one-year delay from LHC, some details will be re-scheduled. 2018 Q 1 Q 2 2019 Q 3 Q 4 Q 1 Q 2 2020 Q 3 Q 4 Q 1 Q 2 2021 Q 3 Q 4 Q 1 Q 2 2022 Q 3 Q 4 Q 1 Q 2 2023 Q 4 Q 1 Q 2 2024 Q 3 Q 4 Q 1 Q 2 Q 3 Gas gap FE ASIC RPC singlet Mechanics RPC chamber Contingency Installation Feb. 12, 2020 Design Prototyping Pre-production Production The ATLAS RPC system upgrade for HL-LHC, RPC 2020 17 Q 4

Summary and outlook ü The tasks and methods for the ATLAS RPC upgrade towards the HL-LHC have been well defined. ü As a pilot project, the BIS 78 production in Phase-I progresses smoothly. Side A production will be completed by march 2019 ü Beyond BIS 78, new methods in developing show even more positive results. ü Benefit from the upgrade, the new generation of RPC indicates a wider use field in the future. Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 k n a h T 18

Backup Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 19

The status of BIS 78 upgrade BIS 78 production stages at BB 5 • Side A will be installed in March-May, 2020 • Side C will be installed in LS 3 The Side A production status • FE electronics fully delivered and tested yield >90% • Gas gap production quality hit the target yield > 90% • Read Out Panels: All assembled in CERN BB 5 • Mechanics all delivered at CERN. • Most of the singlets are ready Efficiency curve averaged all over the singlet surface • • • The FE threshold is set to the middle of its dynamic range W. P. HV =5600 Noise ~ 0. 1 Hz/cm 2 All items produced are identified via an MTF code and stored in a production database: http: //project-atlasmuon-bis 78. web. cern. ch/project-atlas-muon-bis 78/ HV applied (k. V) Feb. 12, 2020 The ATLAS RPC system upgrade for HL-LHC, RPC 2020 20