1. Using Multi-gap Resistive Plate Chamber as TOF
WU, Jian
Department of Modern Physics University of Science & Technology of China
2018/9/22
Talk for EM group 伍健

2. Outline Introduction MRPC as TOF Results & Conclusions Why TOF
Options of TOF
MRPC as TOF
Working mechanism
Simulation & design
Major parameters
MRPC based TOF tray
Results & Conclusions
2018/9/22
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3. Heavy Ion Collisions to Go Back in Time
In the Big-Bang theory, our universe is in expansion since 15 billions of years.
Only ultra-relativistic heavy ion collisions
could allow to recreate a small volume of nuclear matter such as the one having existed in the first micro seconds of our universe, the Quark Gluon Plasma (QGP) , making then possible the study and the evolution of this phase of matter.
QGP – Brisure de la symetrie chirale – hadronisation - Evolution vers notre monde
Besoin de tres hautes energies, comme au LHC, pour remonter loin dans le temps.
Mais il y a aussi besoin de comprendre les phenomenes a plus basse energie avant !
2018/9/22
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4. Relativistic Heavy-Ion Collider at BNL
2018/9/22
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5. Solenoidal Tracker At RHIC
Great interest in large acceptance PID over an extended pT range
full TOF replaces the existing Central Trigger Barrel.
covers the TPC tracking detector
Based on Multi-gap Resistive Plate Chambers (MRPC)
prototype detector: TOFr
2018/9/22
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6. Time-Of-Flight Detector in Heavy-Ion Exp.
STAR at RHIC
ALICE at LHC
High multiplicity : 103 – 104 particles produced Large coverage : ~102 m Strong magnetic field : 0.5 – 2 T High event rate: 102 – 103 Hz/cm2
2018/9/22
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7. p/ Separation Momentum: 3GeV/c Flight path length: 277cm
t=432ps（prediction）
t=441ps（experiment）
2018/9/22
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8. Options of TOF
To reduce occupancy ~10%, need small size strip  channels
“Standard” TOF system built of fast scintillators plus phototubes would cost too much ! ( ~ 80 MCHF for ALICE)
Gaseous detectors route to large area detectors at affordable price
2018/9/22
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9. Gaseous Detector Advantages Important detector Application fields
Can be made at almost any shape and size
Low noise
Excellent dynamics range
Can make simultaneous measurements of energy and position
Important detector
Charged particles
X- and - ray
Visible light
Application fields
particle & nuclear physics
space-borne astro-particle physics
medical imaging
x-ray crystallography
environmental monitoring
2018/9/22
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10. Passage of Particles through Matter
Photon cross section
charged particles (other than electrons) energy lose
electrons energy lose
2018/9/22
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11. Gas Gain vs. High Voltage
Geiger Counter
MWPC
MRPC
2018/9/22
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12. Multi-Wire Proportional Chamber (MWPC)
G .Charpak, 1992 Nobel Prize for invention and application of MWPC in 1968
2018/9/22
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13. Resistive Plate Chamber
Fast trigger, good time resolution (<100ps for 300m gap in streamer mode, ~1ns for 2mm gap in avalanche mode), high rate capacity (>104s-1cm-2)
2018/9/22
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14. Simulation Procedure - step by step
Set time step dt, and position step dx = dt·vdrift
Get primary cluster position (exponential distribution) according to cluster density
Get primary cluster size following the size distribution
For each electron in each cluster, multiplies following Townsend’s law and the avalanche fluctuation distribution (include space charge effect)
Calculate the signal induced by using Ramo’s theorem
Induced current is convolved with FEE response, then passes to discrimination to provide TDC timing, ADC is also calculated
2018/9/22
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15. RPC Application – ATLAS Muon Trigger SystemHV
Bakelite Plates
Foam
X readout strips
Gas
Graphite electrodes
PET spacers
Y readout strips
Grounded plane
Gas mixture: C2H2F4 94.7% - C4H10 5% - SF6 0.3% Avalanche regime
2018/9/22
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16. MRPC Principle – from RPC to MRPC
Work in avalanche mode for high rate capacity
Thin gas gap to improve time resolution
Quench avalanche process to avoid streamer
Idea comes true in M.C.S. Williams et al., Nucl. Instr. and Meth. A 374 (1996) 132
2018/9/22
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17. MRPC Basic Structure
2018/9/22
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18.   Feedback Effect Normal Operation
Abnormal Operation: Feedback effect recovers the right electric potential
2018/9/22
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19. Gas Parameters for MRPC Operation
Gas Mixture: 90%C2F4H2 + 5%iso-Butane + 5%SF6
Operation E-field : ~ 110 kV/cm
Effective Townsend Coefficient :  ~ 1400 /cm Electron drift velocity ~ 200 microns/ns (2105m/s)
2018/9/22
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20. A MRPC Prototype Strip size：3.0cm×3.1cm gap：6×0.25mm 2018/9/22
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21. Beam Test at CERN PS-T10 facility
2018/9/22
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22. Test Setup MRPC prototype
Incident particle: 7GeV/c (~80%) and p(~20%) Tracking resolution: <0.5mm Timing resolution: 30ps(trigger), 25ps(system)
2018/9/22
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23. Signal Readout
2018/9/22
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24. Charge (ADC) and Timing (TDC) Spectra
2018/9/22
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25. Detection Efficiency ~97%
HV Plateau
Detection Efficiency ~97%
Time resolution ~60ps
Plateau range ~1KV
2018/9/22
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26. Time Walk
Time walk : timing change due to gas gain / drift velocity variation at different E-field
2018/9/22
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27. Position Effect
2018/9/22
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28. Speed of signal propagation on MRPC strip：40-45ps/cm
2018/9/22
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29. p/ Separation Momentum: 3GeV/c Flight path length: 277cm
t=432ps（prediction）
t=441ps（experiment）
2018/9/22
Talk for EM group 伍健

30. Excellent performance to ~300Hz/cm2 Expected rate at STAR ~100Hz/cm2
Rate Capacity
Excellent performance to ~300Hz/cm2
Expected rate at STAR ~100Hz/cm2
2018/9/22
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31. Operation in Different Gas Mixtures
3 kinds of gas mixtures are investigated : %C2F4H2 + 5%iso-Butane +5%SF6,
94.7%C2F4H %iso-Butane and 100%C2F4H2
2018/9/22
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32. Double-layer MRPC
2018/9/22
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33. An Example Cross section of double-stack MRPC for the ALICE TOF
130 mm
active area 70 mm
honeycomb panel
Flat cable connector
Differential signal sent from strip to interface card
(10 mm thick)
PCB with cathode pickup pads
external glass plates
0.55 mm thick
internal glass plates
(0.4 mm thick)
PCB with
anode pickup pads
Mylar film
(250 micron thick)
5 gas gaps
of 250 micron
PCB with cathode pickup pads
M5 nylon screw to hold
fishing-line spacer
Honeycomb panel (10 mm thick)
connection to bring cathode signal
Silicon sealing compound
to central read-out PCB
2018/9/22
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34. Performance of Double-layer MRPC
Better Efficiency ! Better time resolution !
ALICE’s final design, but not STAR’s – lack of structural space
2018/9/22
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35. PID at STAR by dE/dx
2018/9/22
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36. Achievement
2018/9/22
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37. MRPC Design for STAR TOF
Strip size：
3.15cm×6.3cm
Gas gap：
6×0.22mm
2018/9/22
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38. Position in a Tray Cover 6 in azimuth and 1 in pseudo-rapidity
at radius ~ 2.2m
2018/9/22
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39. Photographs
2018/9/22
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40. Results & conclusions
Proton/Kaon separation is extended from 1.1GeV/c to 3GeV/c Kaon/Pion from 0.6GeV/c to more than 1.6GeV/c with TOFr
2018/9/22
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41. More on Electron Identification
Use velocity cut (from TOF) to select fast particle – electrons are ALWAYS fast !!
2018/9/22
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42. Compton or photoelectric interaction
A Small Animal PET with (M)RPCs
The scanner
The detection
Compton or photoelectric interaction 
.... e-
Modules of n-stacked timing RPCs.
High acceptance geometry > 90%.
Fully 3D measurement of the interaction point of the photon. No parallax error.
Very high spatial resolution < 0.5 mm (FWHM).
High timing resolution < 1 ns, improve the random events rejection.
Efficiency  10% (sensitivity  6 cps/KBq).
Low cost vs. scintillator based implementations.
Compatible with Magnetic Resonance Imaging.
Incident photon
Gas gap
Alberto Blanco
2018/9/22
Talk for EM group 伍健 4

43. High voltage distribution
Prototype
Charge-sensitive electronics allow inter-strip positioning interpolation
32 strips
16 plates
16 stacked (M)RPCs. Z
X, Z
Sensitivity
High voltage distribution X
2018/9/22
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44. Thank you !
2018/9/22
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45. Backup Slides
2018/9/22
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46. Drift Chamber
2018/9/22
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47. Signal Induction
2018/9/22
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48. Time Projection Chamber
2018/9/22
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49. MicroStrip Gas Chamber
2018/9/22
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50. MSGC Advantage
2018/9/22
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51. Gas Electron Multiplier
2018/9/22
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52. GEM E-Field
2018/9/22
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53. 2018/9/22
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54. Time-Over-Threshold
2018/9/22
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55. MAXIM 3760 Bandwidth : 560MHz Max gain : ~6500 2018/9/22
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56. ALICE at LHC – the Muon spectrometer
HMPID
TRD
TPC
ITS
TOF
PHOS
MUON SPECTROMETER
MUON TRIGGER
MUON TRIGGER
Search for (muon) tracks
Compute their deviation
Pt cut for background subtraction
Detector :
72 RPC in streamer mode
120 m², 2 stations, 4 planes
Response time : 700 ns
(ALICE L0 trigger)
The muons spectrometer hosts a muons trigger system.
The electronics associated searches for muons tracks and compute their deviation.
A cut on the deviation then allows us to perform a Pt cut on each track
The detector is formed by 2 stations. Each of them contains 2 planes of RPC functioning in streamer mode.
The response time of the trigger is 700 ns.
2018/9/22
Talk for EM group 伍健