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Development of high rate RPCs. IHEP (Protvino), ITEP (Moscow), INR (Moscow), LIP(Coimbra), USC(Santiago de Compostela). ITEP. I. High rate capability of ordinary glass RPCs. Diego González Díaz (Santiago de Compostela-Spain). A. Blanco, P. Fonte, L. Lopes, R. Ferreira-Marques
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Development of high rate RPCs IHEP (Protvino), ITEP (Moscow), INR (Moscow), LIP(Coimbra), USC(Santiago de Compostela) ITEP
I. High rate capability of ordinary glass RPCs Diego González Díaz (Santiago de Compostela-Spain) A. Blanco, P. Fonte, L. Lopes, R. Ferreira-Marques (LIP-Coimbra)
Detector used for tests • Gas mixture: 80% C2H2F4 + 20% SF6 . • Normal window glass, 2 mm thick. • 4-gaps, 0.3 mm thick. • Aluminum electrodes, 2 mm thick. • Shielding boxes. • BGA2712 amplifier. • - Reference BICRON scintillator (110 ps for gammas).
Sources used for tests Na22 (~ 0.1 mCi)(mainly used for calibration) Na22 (~ 1 mCi) Co60 (~ 1 mCi) 2 x 0.511 MeVcollinear (positron annihilation) 1.274 MeV 1.173 MeV, 1.332 MeV (opposite directions but not perfectly collinear) Interaction occurs through Compton scattering in the electrodes. The electron scattered ionizes the gas and is detected. Charge distribution is different than for MIPS.
Trigger system used for tests Efficiency trigger Time resolution trigger Coincidence with a 110 ps scintillator self-trigger mode scintillator RPC RPC source source L Due to the high rate environment, coincidences by chance are dominant and must be suppressed with adecuate cuts.
Temperature dependence As a first approach, if the reduced high voltage V* is kept constant ‘Rate capability’: If the rate capability κ(T) increases a factor n, the rate can be increased by the same factor and the performance of the detector remains unaltered.
Time resolution measurements Time resolution for gammas stands within 90 ps without significative dependence on primary rate. So it is hard to get the κ(T) factor from timing measurements. No significative dependence [!]
Efficiency measurements Na22 Na22 + Co60 (2.5 cm further) Na22 + Co60
Efficiency measurements Increasing T 33 degrees X12
Conclusions (I) Results in Carbon 2GeV/A beam tests, for the same detector. April 2003 Geometric acceptance ≈ 87 % T~20 degrees
Conclusions (II) When the Temperature increases?? Rate capability Under study! measured expected
Conclusions (III) Geometric acceptance ≈ 87 % for κ(T) measured in 30 degrees increase
App1: Ageing T increase of 30 degrees