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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 R&D of Gap production - Since 1997 2) Gap production
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Gap Production for Upscope of the Endcap RPCs Sung Keun Park Korea Detector Laboratory Korea University February5, 2010 Workshop on the Forward CMS RPC Upscope
1. Contributions to Forward RPC • 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 • Installation of 4 prototypes of RE1/1 • R&D of HPLs • R&D for Upgrade
Silk screen method for graphite coating (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
2. R&D activities 1) R&D of RE1/1 RPCs at CMS nose cones Low-η Forward RPCs 4-th station (Plan) Barrel RPCs High-η Forward RPCs (Plan) RE1/1
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 trapezoidal 36 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 ~ 10ⅹ1010cm. - Maximum size of HPLs : 2450 mm ⅹ 1245 mm 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 sheetsBatch1 : 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 3 Batch 2 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 (withoutgamma 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)andqe = 0.61 pC → At 12.7 kV, ε = 0.98 (by TDC)andqe = 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 % - Current activity of the source ~ 156 mCi = 5.77 GBq Distances Nγ (kHz/cm2) Nγ (signal) (kHz/cm2) -------------------------------------------------------------------------- 35 cm375.0 3.38 (estimation) 45 cm226.9 2.02 (measured at 13.97 kV) 55 cm 151.9 1.37 (estimation) 55 cm S 45 cm 35cm
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)ⅹ1010Ωcm (at H = 75%) in Jul. 15, 2009 (right after the production) ρ20 = (3.3 ± 0.8)ⅹ1011Ωcm (at H = 47%) in Jan. 6, 2010 (final measurement) - Resistivity of HPL should be ≤ 1011Ωcm after fully polymerized . Future R&Ds - QC for HPL - Test of prototype 6-gap RPCs for RE1/1 - Aging study with high gamma backgrounds Efficiencies & mean charges Efficiencies & cluster sizes Mean charges
3. Summary and Conclusion Gap production - KODEL is ready for production and QC of the gaps for upscope - Gap production facility is well maintained 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)