Forward RPC upgrade at PHENIXChong Kim
Korea UniversityNew Frontiers in QCD - Oct. 27, Yonsei University
for the PHENIX collaboration
Contents
1. Introductiona. Spin physics at PHENIXb. Forward muon trigger upgrade
2. Station 3a. Geometrical structureb. Module assemblyc. Module QAd. Half Octants assembly and QAe. Efficiency measurement
3. Station 1a. Geometrical structureb. Module assembly, QA, and installation
4. Summary and Perspectives
2/30
1. Introduction - a. Spin physics at PHENIX3/30
PHENIXSTAR
PHOBOS BRAHMS
• RHIC (Relativistic Heavy-Ion Collider) at BNL, NY, US:• Max. √sNN : 500 GeV (pp) / 200 GeV (AA)• Max. luminosity: 1.5 × 1032 cm−2 s−1 (pp) / 2 × 1026 cm−2 s−1 (AA)• The only machine capable of colliding high-energy polarized proton beams
• PHENIX (Pioneering High-Energy Nuclear Interactions
eXperiment):• One of the two ongoing physics experiments at RHIC• Goal: Discover and examine the QGP & Analyze the proton spin
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1. Introduction - a. Spin physics at PHENIX4/30
• Spin crisis:• DIS result at 1980s: proton spin is not a simple sum of its constituent quarks• Component-by-component approach:
quarks/antiquarks, gluons, and their angular momenta
→ ½ = ½ΔΣ + ΔG + Lz
• W measurement at PHENIX:• Full flavor separation of quarks/antiquarks• Measure the polarization of the quark by leptons decayed from W boson
)()(
)()(1
WNWN
WNWN
pA
RL
RLWL
ALW: single spin asymmetry
p: beam polarization (Max. 70 % for 500 GeV pp)NL(R)(W) : # of events contains the muons from W
with corresponding helicity (L or R)
)(
)(
)(
)(
)()()()(
)()()()(
1
1
1
1
2121
2121
xd
xdor
xu
xu
xuxdxdxu
xuxdxdxuAW
L
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2.
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ΔΣ = 0.33 ± 0.025 (exp) ± 0.030 (th)
1. Introduction - a. Spin physics at PHENIX5/30
PHENIX detector
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1. Introduction - b. Forward muon trigger upgrade6/30
Muon
Hadron
Muon Tracker(MuTr)
Muon ID(MuID)
PHENIX muon arms (before up-
grade)
• Acceptance- 1.2 < |η| < 2.2- Δφ = 2π
• Muon Tracker (MuTR)- 3 stations of CSCs
• Muon ID (MuID)- 5 gaps of larocci tube in x & y directions- Total 80 cm thick steel absorber (plates)
• Muon tracking and triggering- Tracking by hit positions from each station- Most hadrons are absorbed before
reaching last gap of the MuID- Current 1st level rejection factor (RF):
~ 100 (MuID based 1st level trigger)
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1. Introduction - b. Forward muon trigger upgrade7/30
Simulated muons into Muon Arms(2000 pb-1, with PYTHIA 5.7)
Current Muon trigger at PHENIX
W measurement at PHENIX muon arms• √s = 500 GeV
• σ = 60 mb
• L = 1.5 x 1032 cm-2s-1
→ 3.0 x 1032 cm-2s-1 (after luminosity upgrade)
• Total interaction rate: 9 MHz
• DAQ limit: 2 kHz
• Required 1st level rejection factor (RF): 4500
• Dedicated trigger system is required:
→ Forward muon trigger upgrade
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After triggerupgrade
1. Introduction - b. Forward muon trigger upgrade8/30
RPC 3 RPC 3
MuTRG
RPC 1
35 cm thick Fe absorber
• PHENIX forward muon trigger upgrade• Iron (Fe) absorber: reduce hadron background• MuTRG: fast determination of high momentum tracks (tracking)• RPC: provide timing information and rough position information (timing + tracking)
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1. Introduction - b. Forward muon trigger upgrade9/30
• Momentum selectivity through online sagitta measurement• Uses MuTr station 1, 2, 3 and RPC station 1, 3• Implement trigger using fast, parallel logic on FPGA’s• Beam related background rejected by RPC’s timing information
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RPC 1
RPC 3
1. Introduction - b. Forward muon trigger upgrade10/30
• PHENIX muon trigger RPC• Bakelite double gap RPC• Based on CMS endcap RPC technology and expertise• Fast time response: 1 ~ 2 ns for MIP• Gas mixture:
- 95 % C2H2F4 (R134A, base gas for avalanche mode RPC)
- 4.5 % i-C4H10 (isobutane, photon quencher)
- 0.5 % SF6 (electron quencher)
- ~ 40 % relative humidity
Cu foil (2 mm)Mylar sheet
Module frame (Al) PHENIX RPC requirements• Most conditions are same as
those for the CMS endcap RPCs
Time resolution ≤ 3 ns
Average cluster size ≤ 2 strips
Efficiency > 95 %
Rate capability 0.5 kHz/cm2
Average noise rate < 10 Hz/cm2
# of streamer mode < 10 %
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Station 3 (16 half oc-tants) A half octant (3 RPC modules)
RPC3
Module C
Module B
Module A
1.96 m
3.59 m
0.56 m
2. Station 3 - a. Geometrical structure11/30
• RPC station 3• One side (N or S) of RPC station 3 is composed of 16 half octants• A half octant is composed of 3 RPC modules (type A, B, and C)• Each module is a double-gap RPC which satisfies PHENIX requirements
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RPC 3 RPC 3
2. Station 3 - b. Module assembly12/30
Module assembly flow
Lay down a Mylar sheet & Cu foilon the bottom module frame
Put lower gap &Attach service lines (H.V, gas)
Prepare readout strips &Place it on the lower gap
Put upper gap on the strip &Attach service lines
Put a Mylar sheet on upper gap &Wrap the cu foil
Close module frame
• Modules for the station 3: ALL (total 96) modules were produced
Fully assembled RPC detector moduleBefore wrap the Cu foilConnect CPE cable to the H.V cable (upper gap)Connect gas tubes to the upper gapPut upper gap on the readout stripPut readout strip on the lower gapPreparing readout strip (attach signal cables)Connect CPE cable to H.V cable on the bottom RPC gapConnected gas tubePlace lower gap into Cu foil & Connect Polyethylene gas tubesLay down Cu foil on the Mylar sheet (+ frame)
Assembly of module C
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2. Station 3 - c. Module QA13/30
Module QABefore assembly
(Gap QA)
• Spacer pop check• Gas leakage check
• HV hold• Dark current
After assembly(module QA)
• Noise rate check• Cosmic ray test
• QA(Quality Assurance) for a detector module:• Before assembly: spacer condition, gas leakage, HV hold and dark current• After assembly (test by cosmic muons):
noise rate, total & strip efficiencie, time resolution & cluster size
RPC cosmic ray test stand - event display
cosmic raytrigger scintillators
RPC readout stripplanes
cosmic ray trajectory
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2. Station 3 - c. Module QA14/30
Noise rate:RPC HV = 9.5 kV, PHENIX RPC FEE threshold = 160 mV
Noise rate (Hz/cm2)Raw TDC :1 unit = 100 ns/44 = 2.41 ns
Time resolution vs. HV
Efficiency of a module (%) vs. HVwith different threshold
Cluster size of a module vs. HVwith different threshold
Operation voltage
Operation voltage
PHENIX require-ments
PHENIX require-ments
Module QA results
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2. Station 3 - d. Half octants assembly and QA15/30
Half octant assembly
Route service lines of the modulefor the assembly
Insert prepared modulesto the HO frame
Connect & Re-route service linesto the patch pannel View from inside of patch pannel
Insert prepared modulesto the HO frame (2)
Insert prepared modulesto the HO frame (3)
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2. Station 3 - d. Half octants assembly and QA16/30
Integrated result of half-octants QA AT FACTORY
Average noise rate: 0.37 Hz/cm2
↔ PHENIX requirement: < 10 Hz/cm2
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2. Station 3 - d. Half octants assembly and QA17/30
Integrated result of half-octants QA AT FACTORY
RPC3S
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Average noise rate: 0.25 Hz/cm2
↔ PHENIX requirement: < 10 Hz/cm2
2. Station 3 - d. Half octants assembly and QA18/30
RPC3N - installation (Nov. 11th, 2009) RPC3S - installation (Sep. 22nd , 2010)
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2. Station 3 - e. Efficiency measurement19/30
3D Event display
Relative efficiency calculation:# of hits on RPC / # of projected track on RPC= # of RPC TDC count / # of Muons
Raw RPC TDC distribution
Count
TDC (106 ns for 44 bins)
RPC coincidence timing hit
Projected hits on RPC3 * Muon tracks at boundaries cut out
Muon pT (GeV)
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2. Station 3 - e. Efficiency measurement20/30
Efficiency vs. runsRUN 11, pp 500 GeV
Before gas mixture optimization:High dark current
After gas mixture optimization:Dark current problem resolved
Blue: south Red: north
Black: top sideRed: bottom side
Black: module ARed: module BGreen: module C
Effici
ency
(%)
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Module A
Module B
Module C
2. Station 3 - e. Efficiency measurement21/30
Efficiency of modules
Average cluster size ( < 2 )
Efficiency vs. Height of HO
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2. Station 3 - e. Efficiency measurement22/30
• Temperature: almost constant at tunnels• Relative humidity correlated with pressure• Pressure affects RPC efficiency:
ADC gain changed in the chamber
• ΔEfficiency / ΔPressure: ~ - 0.219(* 30 mbar ~ 12 inches of water)
Slope: - 0.219
Good runs selectedEfficiency vs. environment
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2. Station 3 - e. Efficiency measurement23/30
Efficiency vs. BBC rate
RPC3 North & South
BBC rate (MHz)
Effici
ency
(%)
Effici
ency
(%)
BBC rate (MHz)
RPC3 North & South,module A, B, and C
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2. Station 3 - e. Efficiency measurement24/30
Absolute efficiency measurement
RPC3 MuID MuTR
Hodoscope
Hodoscope design
Location of hodoscope
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RPC1
90 cm
67 cmOctant
34 cm
3. Station 1 - a. Geometrical structure25/30
• Structure - RPC station 1• Composed of 16 octants for both sides (8 octants for one side)• Each octant is a double-gap RPC• Two types of octants (A1, A2) for one side: geometrical condition was consid-
ered
RPC 1
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3. Station 1 - b. Module assembly, QA, and installation26/30
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3. Station 1 - b. Module assembly, QA, and installation27/30
RIGHTLEFT
Trigger scintillator
Trigger scintillator
123456789
10
• QA by using cosmic ray• Same QA process to the station 3 case• Average noise rate, Efficiency, Cluster size, etc…
Intermediate QA result (efficiency)for the south side octants
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3. Station 1 - b. Module assembly, QA, and installation28/30
RPC1N - installation (Sep. 22nd , 2011)
• Station 1 status• All octants (total 26, 10 as spares) were assembled• North side installed in Sep. 22nd • QA is underway for the south side octants• South side installation is expected in the end of October• Preparing for the integration
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4. Summary and Perspectives29/30
• PHENIX RPCs for the forward muon trigger system:- Provide timing and additional position information- Triggers muons with pT 20 ≥ GeV from W decay
• Station 3:- Installation, integration, and commission was completed by early 2011- Relative efficiency was measured for various conditions:
trigger works fine, but still requires stability test- Absoulte efficiency measurement by using hodoscopes is underway
• Station 1:- All 26 octants production completed- North side installed at late Septetmber- South side QA is underway- Installation of south side expected at the end of October- Preparing for the integration
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30/30 Thanks!
Backup slides31
MuTRGADTX
MuTRGMRG
Level 1TriggerBoard
MuTrFEE
Resistive Plate Chamber(RPC) (Φ segmented)
B
2 planes
5%
95%
Trigger
Trigger
Trigger
Interaction Region Rack Room
Optical
1.2Gbps
Amp/Discri.Transmit
DataMerge
MuTRG
RPCFEE
Trigger events with straight track(i.e. Δstrip ≤ 1)
RPC / MuTRG data arealso recorded on disk
Backup slides32
Backup slides33
Backup slides34
Backup slides35