1. RPC Production for Fast Muon Trigger System for
Byungsik Hong
Korea University
for the PHENIX Collaboration
February 13, 2008
RPC2007-Mumbai

2. Contents Motivation Characteristics for PHENIX RPCs
Quality assurance plan
Schedule
Gap production and installation
Summary
February 13, 2008
RPC2007-Mumbai

3. Motivation The origin of the proton spin u u d
Spin ½ quarks
Spin ½ q-bars
Spin 1 gluons
The origin of the proton spin u u d
Quark Spin ΔΣ = 0.25 ∓ 0.10
→ known as Spin Crisis
Ref.) EMC, Phys.Lett.B206, 364 (1988);
Nucl.Phys.B328, 1 (1989)
February 13, 2008
RPC2007-Mumbai

4. Present Understanding
(Ref.) M. Hirai, S. Kumano, N. Saito, Phys. Rev. D 74, (2006)
Spin dependent quark distribution functions by the QCD analysis of DIS data
Δq(x) : well known, Δq(x) : not well known x
Spin dependent gluon distribution functions by the QCD analysis of DIS data
ΔG = 0.47 ∓ 1.08 (largely unknown)
February 13, 2008
RPC2007-Mumbai

5. Detailed Quark and Antiquark Spins
Main motivation of the PHENIX RPC upgrade
W-boson production
The sea quark polarizations of the proton can be probed by
The single spin asymmetry, AL, of W+ and W-. R L
February 13, 2008
RPC2007-Mumbai

6. Analysis Method
The quark and antiquark polarizations of the proton can be estimated through AL, at Q 2 = MW2,
x1>>x2
x2>>x1
February 13, 2008
RPC2007-Mumbai

7. Experimental Requirement
Design Luminosity of RHIC
L = 2x1032/cm2/s for √s = 500 GeV
σtot = 60 mb
Raw rate at PHENIX = 12 MHz
PHENIX DAQ limit ≈ 2 kHz for muon arms
Required RF ~ 6,000
Cf.) Current RF by MuID trigger ~ 500
We need to introduce the muon trigger, based on the momentum measurement.
→ RPC based muon trigger upgrade
February 13, 2008
RPC2007-Mumbai

8. PHENIX RPC Locations We need total 256 RPC modules.
(For the detailed plan, see Rusty Towell’s talk in PL-8 on Friday.)
PHENIX RPC Locations
RPC1(a,b)
RPC2
RPC3
February 13, 2008
RPC2007-Mumbai

9. Why do we employ RPC? General characteristics of RPC Fast response
Suitable for the trigger device
Good timing resolution: 1~2 ns
Good spatial resolution
Typically a few cm
Determined by the strip width
and the cluster size
Low production cost
High-rate capability
in avalanche mode
February 13, 2008
RPC2007-Mumbai

10. Specific Characteristics of Trigger RPC
Characteristics of double gap RPC in avalanche mode as a muon trigger detector
Time resolution
1 ~ 2 ns for M.I.P.
Efficiency
> 95 % for M.I.P.
Rate capability
1 ~ 2 kHz/cm2
Noise rate for plain RPCs
10 ~ 50 Hz/cm2 for ~ 1010Ohm∙cm
Noise rate for oiled RPCs
0.5 ~ 5 Hz/cm2 for ~ 1010Ohm∙cm
Resistivity of resistive plates
1010 ~ 1011 Ohm∙cm
Typical strip multiplicity
1.5 ~ 3.0
February 13, 2008
RPC2007-Mumbai

11. Efficiency Typical shape of the efficiency Efficiencies for
curve for various thresholds
Efficiencies for
double- and single gap
(Ref.) S. H. Ahn et al., Nucl. Instrum. Methods A 508, 147 (2003)
February 13, 2008
RPC2007-Mumbai

12. Time Resolution Time spectrum at 9.0 kV with Th = 270 fC
Time resolutions as a function of HV
FWHM ~ 3 ns
No SF6
No SF6
February 13, 2008
RPC2007-Mumbai

13. Charge Our definition of the avalanche charge
<q> < 10 pC
Definition of the avalanche mode operation
P(streamers) < 10%
Large pulse
Large number of strips
Cause difficulty for the reconstruction of high momentum muons
No SF6
February 13, 2008
RPC2007-Mumbai

14. <q>~10 pC for the limit of avalanche
<q>~2.7 pC at ε~95%
For the specific R&D effort for the PHENIX RPC, see Beau Meredith’s talk
in PL-11 on Sat.
February 13, 2008
RPC2007-Mumbai

15. Korea Univ. & CMS
The Korea Detector Laboratory (KODEL) of Korea University has been an active member of the CMS (Compact Muon Solenoid)/LHC at CERN since 1997.
For more details,
see the following
two talks:
Sung Keun Park in PL-3 on Thursday
Kyong Sei Lee in PL-7 on Friday
February 13, 2008
RPC2007-Mumbai

16. Gap Production for CMS Endcap RPCs
Endcap Region of CMS
Phase I
Phase II
February 13, 2008
RPC2007-Mumbai

17. February 13, 2008
RPC2007-Mumbai

18. Flow of RPC Gaps and Parts for PHENIX
bakelite route
gas cell route
frames and parts
Korea
BNL
China
Italy
►Bakelites are produced and cut in Italy ►Gas gaps are produced at Korea University
►RPC frame & parts are procured in China (CIAE) ►Final assembly is done at BNL.
February 13, 2008
RPC2007-Mumbai

19. Quality Control of Gaps
Inspection of raw bakelite for the surface quality
Checking the graphite surface and the condition for PET coating
Test for gas leak and spacer bonding
Add 20 hPa to each gap (1 hPa=1 mbar)
No detached spacers
Pressure loss : < 0.2 hPa for 15 minutes
Test for high-voltage holding and current
1.5 days for flushing + 5 days for HV test
Current limit for each gas gap right after the production: < 3 μA/m2/gap at working HV (9.4 kV at 1013 hPa)
Assignment of the bar code only for the qualified gas gaps
February 13, 2008
RPC2007-Mumbai

20. Current Limits for PHENIX
PHENIX Region
Current limit for each gap
at 8.5 kV (μA)
at 9.4 kV (μA)
Current limit for RPC
RE3 Ring 1-2 (N+S) 1 2 10
RE3 Ring 3-4 (N+S) 4 15
RE3 Ring 5-6 (N+S) 3 5
RE2 Ring 1-2 (N+S)
RE2 Ring 3-4 (N+S)
RE2 Ring 5-6 (N+S)
RE2 Ring 7-8 (N+S)
February 13, 2008
RPC2007-Mumbai

21. Examples of CMS Endcap RPCs
9.4 kV (72 h)
8.5 kV (12 h)
Current (μA)
Individual Gap ID
Rejected Gaps
Blue: begin
Pink: end
February 13, 2008
RPC2007-Mumbai

22. PHENIX Schedule I 2008 January
Send 6 sets of prototype C (RPC3A) gaps to BNL
March
Send prototype D gaps to BNL
Complete RPC3 ‘half octant’
Install two ‘half octant’s in one arm
One in the RPC2 and another one in the RPC3 positions
Install one octant absorber made of ~30 cm (or 2 λI) thick Cu in one arm
~June
Start the mass production of RPC gaps for PHENIX
RPC 3A
RPC 3B
RPC 3C
February 13, 2008
RPC2007-Mumbai

23. PHENIX Schedule II 2009 2010 2011 Install absorber in the North arm
Install RPC2 and RPC3 in the North arm
2010
Install absorber in the South arm
Install RPC2 and RPC3 in the South arm
2011
Take out one nuclear interaction length absorber
Install RPC1 in both arms
Start to take the high statistics polarized p+p data
February 13, 2008
RPC2007-Mumbai

24. Current Production Plan
PHENIX Region
Number of
RPC Modules (Gaps)
Estimated months for production
Tentative Schedule
RPC3 (North)
48(96)
~ 2.5
Start ~June 2008
RPC2 (North)
64(128)
~ 3.0
Finish by the end of 2008
RPC3 (South)
RPC2 (South)
Finish by the end of 2009
RPC1a (both arms)
16(48) ~1
RPC1b (both arms)
16(64)
Finish by the end of 2010
Sum
256 (560)
~13
February 13, 2008
RPC2007-Mumbai

25. Summary
The origin of the proton spin is the fundamental question of nuclear physics.
The PHENIX is upgrading the muon trigger system by using the RPCs in order to filter out the small cross-section W-candidate events.
The flavor dependent quark and anti-quark spin distribution functions can be measured.
Korea University will produce all PHENIX RPC gas gaps.
The mass production and installation will be completed by 2011.
Additional potential application of the L1 muon trigger for heavy-ion collisions still need to be explored, for example,
Heavy-flavor trigger in combination with the forward vertex upgrade
Dimuon trigger for the vector mesons for RHIC II
February 13, 2008
RPC2007-Mumbai

26. Back-up Slides
February 13, 2008
RPC2007-Mumbai

27. CMS Endcap RPC 1. Function : L1 muon triggers 2 wings (RE+, RE-)
4 stations (RE1, RE2, RE3, RE4)
Pseudo rapidity coverage :
0.9 < η < 2.1 (1.6)
η segmentations : 10 (6)
2. Total # of RPCs : 756 (432)
Total # of FEBs : 2,268 (1,296)
Total # of channels : 85,248 (41,472)
3. By March 2007,
the gap production for phase I
(0.9 < η < 1.6) was completed for
the first operation of CMS in 2008.
February 13, 2008
RPC2007-Mumbai