Research On Long-strip Multi-gap Resistive Plate Chamber

Prototypes of Long-strip Multi-gap Resistive Plate Chamber (LMRPC) have beendeveloped for STAR-MTD. For the6-gap LMRPC prototype, the efficiency is able toreach round100%, and the time resolution is around75ps in the cosmic-ray tests.During the beam-test in IHEP, the efficiency is able to reach100%and time resolutionis around70ps. The module has a good uniformity among strips and along the strip. Thenoise level of the module is very low.In order to reduce the working HV of STAR-MTD, a new prototype ofSTAR-MTD LMRPC module with1-gas-gap less has been developed and tested. It isthe final prototype for STAR-MTD. The efficiency of the module is around98%duringthe cosmic-ray test and the time resolution is around the range of90ps to110ps. It alsohas a good uniformity among strips and low noise rate.The influence of the double coated tapes and silicones used during the assemblageto the performance of the modules is investigated. It is observed that the module withoutany tape and silicone has lower noise rate, which is more preferable for STAR-MTD.We decide to build LMRPC module without any tape and silicone for STAR-MTD. Theperformance comparison of the moudules with0.246mm-gas-gap and0.258mm-gas-gapis also performed to investigate the influence of the width of gas gap. The module with0.256mm-gas-gap has much lower streamer ratio at the same or comparable electricfield in the gas gap. We decide to build0.256mm-gas-gap LMRPC modules forSTAR-MTD.A new cosmic-ray test system with long scintillators has been developed toaccelerate the Quality Control process during the mass production of STAR-MTD. Aselection of perpendicular cosmic-ray events for more accurate evaluation of the timeresolution is achieved.We introduce an “induction+transmission” framework for the simulation ofLMRPC. In this model, the single shapes are directly simulated in order to get theperformance of LMRPC. The transmission part is performed with “Transmission LineTheory”. The exact solution of the2-strip loss-less transmission line problem is derivedin detail and the losses can be introduced with a convolution at a later stage. Ameasurement to the2-strip structure in both the time-domain and the frequency-domain was done to demonstrate the precision of the simulation. The loss-less solution is able todescribe the measured waveforms quite well but has some discrepancy when lookinginto the rise time of the signals. The discrepancy disappears when the losses isconvoluted to the solution. A simplified solution for5-strip case is also introduced.The concept of “electrostatic compensation” is introduced to demonstrate the wayof suppressing cross-talk level and enhancing transmission by remove the modaldispersion away, who plays an important role in introducing cross-talk and signalshaping in the counters. We observed the “electrostatic compensation” during the testand from the simulation result. The electrosatic compensated system shows maximaltransmission (or highest bandwidth for the transmission) and minimal cross-talk level.The measurement and simulation is also performed to the real-size counter. For the6-gap6-strip STAR-MTD LMRPC module, the simulation is able to describe themeasurement quite well within the bandwidth of the Front-End Electronics. Bandwidthreduction is also observed in the measurement, probably due to the non-perfectconnection and the mutual conductances which are not included in the simulation. Forthe5-gap STAR-MTD module, we are not able to get a nice data set due to the badconnection between the module and the Network Analyzer.