Gap Production for Upscope of the Endcap RPCs

Sung Keun Park

Korea Detector Laboratory Korea University

February 5, 2010

Workshop on the Forward CMS RPC Upscope

1. Contributions to Forward RPC

1) R&D of Gap production - Since 1997

2) Gap production KODEL in charge of production and QC for gaps for all the RE RPCs. - Low eta : RE 1/2, 1/3, 2/2, 2/3, 3/2, 3/3 (432 RPCs, 1548 gaps produced) - Upscope Low eta : RE2bis (288 RPCs) - High eta : RE1/1, RE2/1, RE3/1

3) Installation of 4 prototypes of RE1/1

4) R&D of HPLs

5) R&D for Upgrade

Silk screen method for graphitecoating (100 ~ 200 k/square)

PET film coating

Gap assembly Linseed oil coating

200 mCi 137Cs gamma irradiation facility & DAQ + electronics 200 mCi 137Cs gamma irradiation facility & DAQ + electronics

Barrel RPCs Low-η

Forward RPCs

High-η Forward RPCs (Plan)

4-th station (Plan)

RE1/1

1) R&D of RE1/1 RPCs at CMS nose cones

2. R&D activities

RE1/1 Design for RE1/1 in 1.6<<2.1

- 6 RE1/1 RPC modules tested for cosmic rays

- 4 RE1/1 RPCs installed

RE1/1 RPCs : 10 degree trapezoidal36 RPC modules on each wing

2) R&D of HPLs

Feasibility study for HPLs - A local HPL factory in Korea (Meltech). - Thin melamine-paper cladding on both surfaces of bakelite - The range of resistivity : 2 ~ 10 10ⅹ 10 cm. - Maximum size of HPLs : 2450 mm 1245 mm ⅹ

Quality Assurance for the HPL - KODEL built tools for resistivity measurement

Recent procurement of HPLs for multigap RPCs - Thickness : 0.5 - 1 mm for the multigap structure - The test results of the small prototype to be presented in RPC2010 workshop

Resistivity tests for HPLs consisting of Melamine + Phenol sheets

Batch1 : 20 samples of 0.5 mm melamine-phenol-melamine Batch2 : 20 samples of 0.5 mm melamine-phenol-melamine Batch3 : 15 samples of 1.0 mm melamine-phenol-melamine

Batch 1

Batch 2 Batch 3

)Tá(T

Tb eññ 020 −=

α = 0.12/°C

Mean humidity ~ 75 %

3) R&D of multigap RPCs

R&D for high-rate triggers at RE1/1 for future CMS Higher rate capability ← lower avalanche charge - Rate capability ~ 1 /<qe> - Rate capability ~ 1/ ρ

Then, what if multigap RPCs with HPLs ? - <Qe> ~ 10 times smaller than CMS RPCs - HPL : Melamine+Phenol → ρ < 1011 - Oiling required to reduce noises

0.6 ~1.1 pC

80 ~150 fC

For 6-gap RPCs (without gamma rays) TDC threshold = 1 mV ADC thresholds = 80 ~ 150 fC (in offline analysis)

Mean qe at the efficiency plateau region → At 11.8 kV, ε = 0.97 (by TDC) and qe = 0.61 pC → At 12.7 kV, ε = 0.98 (by TDC) and qe = 1.12 pC

ε = 0.96 ε = 0.96

Tests with gamma rays

A 6-gap RPC installed at a 200 mCi 137Cs gamma source (0.662 MeV) for high-rate background test - Accidental coincidences (geometrical) ~ 10 %

45 cmS

- Current activity of the source ~ 156 mCi = 5.77 GBq Distances Nγ (kHz/cm2) Nγ (signal) (kHz/cm2) -------------------------------------------------------------------------- 35 cm 375.0 3.38 (estimation) 45 cm 226.9 2.02 (measured at 13.97 kV) 55 cm 151.9 1.37 (estimation)

Muon data with gamma background

- Shifts in HV ~ 1.5 kV at 2.02 kHz/cm2 - Caused by increase in resistivity of HPL ρ20 = (6.9 ± 3.5) 10ⅹ 10 Ωcm (at H = 75%) in Jul. 15, 2009 (right after the production) ρ20 = (3.3 ± 0.8) 10ⅹ 11 Ωcm (at H = 47%) in Jan. 6, 2010 (final measurement)- Resistivity of HPL should be ≤ 1011 Ωcm after fully polymerized .

Mean charges

Efficiencies & mean charges Efficiencies & cluster sizes

Future R&Ds

- QC for HPL - Test of prototype 6-gap RPCs for RE1/1 - Aging study with high gamma backgrounds

3. Summary and Conclusion

1) Gap production - KODEL is ready for production and QC of the gaps for upscope - Gap production facility is well maintained

2) Other areas to contribute- Assembly of chambers- Electronics- High eta : RE1/1 (72 RPCs), RE2/1 (36 RPCs), and RE3/1 (36 RPCs)

3) R&Ds - HPL- RE1/1 (Multigap RPC, GEM)