Performance of high rate MRPC with different gas mixtures

Abstract

A: A Time Of Flight system (TOF) based on MRPC technology is widely used and plays an important role in modern high energy and nuclear physics experiments. With the increase of the energy and luminosity of the accelerators, many experiments have higher demand for a better resolution TOF detectors working in an high data rate environment, which undoubtedly represents a big challenge for this technology. FAIR-CBM is a typical high rate experiment and the particle rate of its TOF can reach 30 kHz/cm 2 . A new type of MRPC, built with low resistive glass with bulk resistivity of about 10 10 Ohm cm, has been developed. The rate capability of this high rate MRPC can reach 70 kHz/cm 2 . The standard gas mixture for the high rate MRPC used for the FAIR-CBM-TOF is 90% C 2 H 2 F 4 , 5% i-C 4 H 10 and 5% SF 6 . For the high rate MRPC used for the STAR-eTOF the gas mixture contains only two components, namely 95% C 2 H 2 F 4 and 5% i-C 4 H 10 . In order to ensure the long time stability of the high rate MRPC and its use with different gas mixtures, we have studied the performance with different gas mixtures. The first measurements were performed with the standard gas mixture and different gas mixtures were tested by reducing the content of SF 6 . Three high rate MRPCs were tested at the same time for a cross-check, using a cosmic ray test-stand. The result of the test shows that the working point of the high rate MRPC moves toward a lower value of the high voltage by reducing the SF 6 content in the gas mixture. The working point for a chamber efficiency of 95% without SF 6 is about 800 V lower than the one with the standard gas mixture. Other properties such as time resolution, noise rate, dark current and cluster size have also been measured with different gas mixtures. K: Instrumentation and methods for time-of-flight (TOF) spectroscopy; Timing detectors 1Corresponding author.

Multigap Resistive Plate Chambers for Time of Flight Applications

“…The working point varies for MRPCs with different structures and working conditions. For example, the widegap (~0.25 mm) MRPC in avalanche mode usually operates at the electric field of around 110 kV/cm, while the very thin-gap (~0.1 mm) MRPC can work well at 150 kV/cm to achieve a good resolution; the working point will shift significantly for different gas mixtures [101][102][103][104][105]; MRPCs built with different resistive materials may have different working voltage and efficiency plateau: we can see from ref. [102] that the 6-gap MRPC with lowresistivity glass reaches the plateau at the electric field of around 110 kV/cm and the normal 6-gap MRPC reaches its plateau at a higher electric field of 120 kV/cm.…”

mTOF performance during the first main commissioning beam time at mCBM

“…According to the "Static" Model, the high rate capability of MRPC can be achieved either by reducing the resistivity of resistive plates or/and reducing the thickness of resistive plates [5]. In CBM-TOF project, the developments of two kinds of MRPC are close to be finished: a low resistive glass MRPC [6] called MRPC2 which is required to have a rate capability of 5 kHz/cm 2 and an ultra-thin float glass MRPC called MRPC3 which is required to have a rate capability of 1 kHz/cm 2 [7]. The structure of MRPC2 is shown by the schematic of the cross section in Figure 2.…”

“…The MRPCs used for mTOF are called MRPC2, which is one kind of high-rate MRPCs developed at Tsinghua University, Beijing [6][7][8][9]. The high rate capability of MRPC2 is achieved by using low resistive glass sheets as resistive plates.…”

Development and Production of High Rate MRPC for CBM TOF

“…The gas mixture in the eTOF is 95% C2H2F4 and 5% SF6. During the cosmic test, MRPC3a can work in both gas mixtures of eTOF and CBM [10].…”