High effi ciency Transition Radiation Detectors for high rate environments

M. Petrovici, V. Simion, M. Petriş, D. Moisă, A. Radu, D. Bartoş, I. Berceanu, V. Cătănescu, A. Herghelegiu, C. Măgureanu, NIPNE-Bucharest M. Hoppe, A. Wilk, J.P. Wessels, University of Münster The Transition Radiation Detector considered to be implemented in the CBM experiment at the future FAIR facility at GSI Darmstadt will be used for particle tracking and identifi cation of high energy electrons and positrons for J/Ψ meson reconstruction [1]. The specifi c challenge for such a detector in the CBM experiment is the high granularity and a good performance in a high counting rate environment. Based on the experience of the TRD for ALICE [2] and of the TRT for ATLAS [2], various prototypes of fast Multiwire Proportional Chambers (MWPC) [4] -[7] were designed, built and tested. Up to intensities of 100 kHz/cm, no major deterioration of the performance has been observed. However, this performance of the prototypes was reached decreasing drastically the conversion effi ciency of the transition radiation in a single layer of such a MWPC based TRD. In order to circumvent this aspect, we designed and built a few prototypes of TRD based on double sided pad read-out electrode. The main idea is to increase by a factor of ∼2 the conversion effi ciency obtaining the same performance and number of read-out channels of the protypes mentioned above. This can be reached by symmetrizing the counter structure relative to the readout electrode using a double sided pad-plane electrode. A sketch of the counter structure and a photo of the prototype is shown in Fig.1. The anode-cathode gap and the anode wire pitch