Department of Engineering Physics, Tsinghua University, Beijing, China Progress on the real-size high-rate MRPC modules & Conceptual design of the CBM-TOF wall Jingbo Wang Department of Engineering Physics, Tsinghua University, Beijing, China wjb04@mails.tsinghua.edu.cn RPC 2012- XI workshop

Talk Layout CBM-TOF Low resistive glass Rate capability: proton beam test Real-size modules: Electron beam test Real-size modules Electron beam test @ELBE Flux estimate Performance Conceptual design of CBM-TOF Summary

CBM experiment @ FAIR FAIR = Facility for Antiproton and Ion Research CBM = Compressed Baryonic Matter The CBM experiment will be operational in year 2017 at FAIR accelerator facility in Darmstadt, Germany. CBM is designed to explore the QCD phase diagram under extremely high net-baryon densities and moderate temperatures. The hadron identification is considered to use a time-of-flight (TOF) system based on MRPCs. Rate capability: >20kHz/cm2

Low resistive glass White Light Interferometer: MicroXAM-30 50cm * 50cm Thickness distribution (Evaluation scale= 30cm) micrometer caliper Uniformity: <20 μm Typical: 5 μm Evaluation scale= 857μm Surface roughness: <10 nm (peak-to-valley)

Specifications of the glass plate Bulk resistivity at various positions Long term stability test Variation: <30% Bulk resistivity VS HV

Proton beam test, GSI@April2009 PMRPC#0: First high rate module for CBM-TOF 2.5GeV MRPC Geometry: Double-stack Pad size: 3.15cm * 3cm Gas gap: 0.22 mm Proton beam: 2.5 GeV, Pulsed Rate capability: 25 kHz/cm2. Time resolution: < 90 ps J. Wang, et al., Nucl. Instr. and Meth. A 621 (2010) 151.

Two real-size modules Rate region: Region2-4 PMRPC#1 SMRPC#2 Rate region: Region2-4 Glass type: Low-resistive glass Read out: 3 strips Strip size: 24cm * 2.2cm Strip pitch: 2.5cm Gas gap: 0.25 mm Active area: 24cm * 7.2cm Rate region: Region1 Glass type: Low-resistive glass Readout: 12 pads Pad size: 2cm * 2cm Pad pitch: 2.2cm Gas gap: 0.22 mm Active area: 13cm * 4.2cm J. Wang, et al., Nucl. Instr. and Meth. A 661 (2012) 125.

Electron beam test HZDR/Dresten@April2011 ELBE (Electron Linac for beams with high Brilliance and low Emittance) S1 S2 S3 S4 S9 S10 RPC S6 S5 e- beam Electron beam: 30MeV Pulse production rate: 6.5 MHz Trigger: S1^S2^S3^S4^S6^RF Typical beam size scanned by S5 Reference time from ELBE linac: σRF = 35 ps CAEN TDC 1290 N: 24.5 ps/bin QDC: V965: 25 fc/bin Beam profile scanned with S5 σ = 1.1cm σ = 1.5cm

Non-uniform Beam profile: Spatial resolution: 5mm – 10mm σx = 1.1 cm From Scintillator5 Assumption1. Identical multiple scattering Extrapolated by assuming identical multiple scattering in x and y directions. σx = 1.4 cm σy = 1.5 cm From the strip time difference σx = 2.15 cm σy = 2.38 cm S1 S2 S3 S4 S9 S10 e- beam S6 S5 Along the strip Across the strip We could believe that the multiple scattering is the main reason for the broader profile on the RPC plane. In this report, we use the profile from the time difference between both ends of the strip.

2-D beam profile Assumption2. The beam profiles in horizontal(x) and vertical(y) directions are independent X [cm] Y [cm] Φ[kHz/cm2] Flux over the central strip Profile from RPC: X [cm] Φ[kHz/cm2] Y [cm] X [cm] Φ[kHz/cm2] Flux vs x-Position

Description by DC model: Conversion from Qfast to Qtot The fast charge (Qfast) is recorded by the QDC. The total charge (Qtot ) is defined by Qtot=I/r. I is the current pushed by the HV supply and r is the particle rate. At low fluxes (HV scan), the experimental correlation between Qtot and Qfast can be descriped by a polynomial function. At high fluxes, Qtot can be obtained from Qfast with a simple conversion. Qfast vs x-Position Qtot vs Qfastc Qtot vs x-Position

Description by DC model: Qtot vs ϕRPC Qtot vs x-Position Qtot [pC] Qtot vs ϕRPC X [cm] Qtot [pC] X [cm] Φ[kHz/cm2] Flux vs x-Position Description by DC model Φ[kHz/cm2] The behavior of the RPC just depends on the localized flux

Average flux under non-uniform irradiation Option1: FWHM Option2: Mathematical expectation Under non-uniform irradiation, the flux calculation is sensitive to the effective irradiation area (A*). Mathematical expectation is an appropriate estimate for our test condition. For a finite detector, one should set integration boundaries and normalize the probability density function. X [cm] Φ[kHz/cm2] Y [cm] a factor of >2

All performances vs Average flux Under non-uniform irradiation, the average flux is defined as the mathematical expectation. The results from the two beam tests are consistent. The working HV of the strip counter is not optimized and the performance could be improved. Rate capability: 25-35 kHz/cm2 CBM requirement

Rate capability VS Bulk resistivity

Current conceptual design of CBM-TOF Timing RPC with: wall area: A = 150 m2 intrinsic time resolution: sT ~ 50 ps rate capability: R ~ 0.5 – 25 kHz/cm2 granularity: DA ~ 4 – 30 cm2 operation mode: free running 4 3 2 1 Rate profile (Au-Au(minimum bias) at E=25 GeV/A) Rate profile (Au-Au(minimum bias) at E=25 GeV/A) 1 8.0-25 kHz/cm2, #SM: 8 (low resistive glass/ceramic) 2 3.8-8.0 kHz/cm2, #SM: 12 (low resistive glass) A. Kiseleva, P.-A. Loizeau 3 1.5-3.5 kHz/cm2, #SM: 16 (low resistive glass) 4 0.5-1.5 kHz/cm2, #SM: 44 (float glass, warming up) Low resistive glass I. Deppner, et al., Nucl. Instr. and Meth. A (2010), doi:10.1016/j.nima.2010.09.165

Detector family for the CBM-TOF Its very inspiring that the appropriate MRPC prototypes have been already tested with high intensity beam and the performance can fulfill the CBM requirements. Based on the small structure modification, we design a high rate detector family and propose to construct the whole TOF wall with this type of counters. modules for Region3 and Region4 module for Region1 modules for Region2

Assembly design of the Super Module Rate profile (Au-Au(minimum bias) at E=25 GeV/A) Rate profile (Au-Au(minimum bias) at E=25 GeV/A) 4 3 2 1 SM for Region1 SM for Region2 SM for Region3 and Region4

Summary Low-resistive glass: ~1010 Ωcm Proton beam test, GSI@April2009 Performance of High rate MRPC Low-resistive glass: ~1010 Ωcm Proton beam test, GSI@April2009 Rate capability: 25 kHz/cm2 Electron beam test, HZDR@April2011 Rate capability: 25-30 kHz/cm2 Fullfill the CBM requirement(20 kHz/cm2) Flux estimate Beam profile obtained from RPC time difference under self-trigger Average flux estimated with mathematical expectation Conceptual design of CBM-TOF Based on low-resistive glass MRPCs Small structure modification

Thanks for your attention Contributing institutions: Tsinghua Beijing, NIPNE Bucharest, LIP Coimbra, GSI Darmstadt, USTC Hefei, PI Heidelberg, KIP Heidelberg, INR Moscow, ITEP Moscow, IHEP Protvino, FZD Rossendorf, KU Seoul, RBI Zagreb.