Development and test of a real-size MRPC for CBM-TOF

Abstract

In the CBM (Compressed Baryonic Matter) experiment constructed at the Facility for Anti-proton and Ion Research (Fair) at GSI, Darmstadt, Germany, MRPC(Multi-gap Resistive Plate Chamber) is adopted to construct the large TOF (Time-of-Flight) system to achieve an unprecedented precision of hadron identification, benefiting from its good time resolution, relatively high efficiency and low building price. According to the particle flux rate distribution, the whole CBM-TOF wall is divided into four rate regions named Region D, C, B and A (from inner to outer). Aiming at the Region C and B where the rate ranges from 3.5 to 8.0 kHz/cm 2 , we've developed a kind of double-ended readout strip MRPC. It uses low resistive glass to keep good performance of time resolution under high-rate condition. The differential double stack structure of 2x4 gas gaps help to reduce the required high voltage to half. There are 24 strips on one counter, and each is 270mm long, 7mm wide and the interval is 3mm. Ground is placed onto the MRPC's electrode and feed through is carefully designed to match the 100Ω impedance of PADI electronics. The prototype of this strip MRPC has been tested with cosmic ray, a 98% efficiency and 60ps time resolution is gotten. In order to further examine the performance of the detector working under higher particle flux rate, the prototype has been tested in the 2014 October GSI beam time and 2015 February CERN beam time. In both beam times a relatively high rate of 1 kHz/cm 2 was obtained. The calibration is done with CBM ROOT. A couple of corrections has been considered in the calibration and analysis process (including time-walk correction, gain correction, strip alignment correction and velocity correction) to access actual counter performances such as efficiency and time resolution. An efficiency of 97% and time resolution of 48ps are obtained. All these results show that the realsize prototype is fully capable of the requirement of the CBM-TOF, and new designs such as self-sealing are modified into the strip counter prototype to obtain even better performance.

Multigap Resistive Plate Chambers for Time of Flight Applications

“…This MRPC (Figure 7a) has 2 × 4 gaps with 250 µm gap size and 32 readout strips, each of 1 × 27 cm 2 . The results of SPS beam time in 2015 for the prototypes were presented in [26]. The efficiency and time resolution curves correspond well to the changes of high voltage and PADI threshold.…”

“…3.2.2. High-Rate MRPC Towards the particle flux ranges from 1-5 kHz/cm 2 in the intermediate rate region [63], the double-stack MRPC prototype [26] developed at Tsinghua University has been considered. It is built The high-performance electronics for the whole CBM ToF wall is based on the PADI [69] and the GET4-ASIC chips [70].…”

“…Towards the particle flux ranges from 1-5 kHz/cm 2 in the intermediate rate region [63], the double-stack MRPC prototype [26] developed at Tsinghua University has been considered. It is built by the low resistive glass plates described above.…”

“…This detector is easy to build and possible to cover a large area. It has been extensively employed as a ToF system in many nuclear physics experiments, such as BESIII [21], ALICE [22][23][24], CBM [25,26], STAR [27][28][29] and PHENIX [30].…”

Performance studies of MRPC prototypes for CBM

“…The requirements of the full system is a time resolution better than 80 ps at an efficiency higher than 95 %. Since the charged particle flux drops exponentially from small angle (2.5 • ) to large angle (25 • ), ranging from 25 kHz/cm 2 to 1 kHz/cm 2 high rate capable MRPCs with low-resistive electrode material [4][5][6][7][8][9][10] but also with thin float glass [11,12] and with different granularities were developed. An overview of the conceptual design of the CBM ToF-wall is given in [13].…”