Diego Gonzalez Diaz University of Santiago de Compostela ITEP IHEP (Protvino), ITEP (Moscow), INR (Moscow), LIP(Coimbra), USC(Santiago de Compostela)

Diego Gonzalez Diaz University of Santiago de Compostela Diego González Díaz (Santiago de Compostela-Spain) A. Blanco, P. Fonte, L. Lopes, R. Ferreira-Marques (LIP-Coimbra)

Diego Gonzalez Diaz University of Santiago de Compostela Detector used for tests - Gas mixture: 80% C 2 H 2 F % SF 6. - 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).

Diego Gonzalez Diaz University of Santiago de Compostela Sources used for tests Na 22 (~ 0.1 mCi) (mainly used for calibration) Na 22 (~ 1 mCi) Co 60 (~ 1 mCi) 2 x MeV collinear (positron annihilation) MeV MeV, 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.

Diego Gonzalez Diaz University of Santiago de Compostela Trigger system used for testsEfficiency triggerTime resolution trigger source L RPC self-trigger mode source RPC Coincidence with a 110 ps scintillator scintillator Due to the high rate environment, coincidences by chance are dominant and must be suppressed with adecuate cuts.

Diego Gonzalez Diaz University of Santiago de Compostela ‘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. As a first approach, if the reduced high voltage V* is kept constant Temperature dependence

Diego Gonzalez Diaz University of Santiago de Compostela 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 [!]

Diego Gonzalez Diaz University of Santiago de Compostela Efficiency measurements Na 22 Na 22 + Co 60 (2.5 cm further)

Diego Gonzalez Diaz University of Santiago de Compostela Efficiency measurements X12 Increasing T 33 degrees

Diego Gonzalez Diaz University of Santiago de Compostela Geometric acceptance ≈ 87 % Results in Carbon 2GeV/A beam tests, for the same detector. April 2003 Conclusions (I) T~20 degrees

Diego Gonzalez Diaz University of Santiago de Compostela When the Temperature increases?? Rate capability measuredexpected Under study! Conclusions (II)

Diego Gonzalez Diaz University of Santiago de Compostela Geometric acceptance ≈ 87 % for κ(T) measured in 30 degrees increase Conclusions (III)

Diego Gonzalez Diaz University of Santiago de Compostela App1: Ageing T increase of 30 degrees