MRPC Detectors Research Articles

Signal integrality analysis of sealed MRPC for muography

The signal quality is a crucial index to determine the performance of MRPC detector. This paper has analyzed the signal integrality of the sealed MRPC structure in detail with CST simulation. The simulation work includes the reflection of high frequency signal in readout line, the reflection of signal through via hole, the transmission of signals under multiplexing. The via hole will bring a reflection and overshoot to signal. The interconnection of the readout strips will lead to a reduction of the amplitude of the acquired signal and the jitter of the baseline is increased. A multiplexer will affect the quality of the signal to some extent, and this influence needs to be considered in the detector design.

Design, optimization and prototype testing of a double-stack MRPC detector for positron emission tomography (PET)

In this work, the performance of an RPC detector with a 70%Ar-30%CO2 gas mixture for a PET imaging system is investigated. A detailed GEANT4 simulation was performed to improve the detection efficiency by optimizing the thickness and material of the resistive components, the number of gas gaps and selecting an appropriate design and structure of the MRPC detectors. In previous studies, for the detection of gammas by MRPC detectors, a high atomic number (Z) converter such as Pb was suggested. However, in this study, by simulating some commercial glasses for MRPC detectors, it was found that, with a suitable design and using glasses with low-Z materials, without any separate converter, similar detection efficiencies and better spatial resolution are accessible. To achieve similar detection efficiency, the low-Z glasses, require a higher number of gas gaps. This complexity in fabrication of a real detector may be overcome in the future by using cost-effective 3D printing methods. With the proposed design, all double-stack structures have lower detection efficiency for low energy gammas, which is an advantage for rejecting Compton gammas. To verify the simulation results, a 5-layer double-stack MRPC detector was constructed and tested. The experimental detection efficiency of the proposed detector extracted by the coincidence method is 1.46%, which, with an error of less than 3.3%, is in good agreement with the simulation (1.51%). The measured count rate is around 17% larger than the ones estimated by the coincidence method, which is attributed to some spurious pulses generated in the RPC detector.

High time-resolution MRPC detector for TOF-PET

The traditional TOF-PET (Positron emission tomography) mainly uses the structure of a scintillator detector connected to a photomultiplier tube. The structure has the disadvantages that time resolution is not good enough (about 300 ps FWHM) for improving the signal-to-noise ratio of the acquisition system, which is not conducive to the detection of microtumors in the clinic and reduction in imaging time. The thickness of the scintillator is large (greater than 3 cm). Traditional PET has low geometric efficiency and sensitivity. It requires a long time to complete a full-body scan. However, the MRPC can be made into a 2.4-meter-long whole body PET. The high cost of traditional TOF-PET limits its widespread use in medical and other fields. The excellent time resolution of MRPC makes MRPC TOF-PET a good application prospect. This paper shows the time resolution of two 32-gap MRPCs with 128μm gap thickness on cosmic rays and 0.511 MeV photons. By using the fast front-end amplifier and waveform acquisition system, the time resolution for cosmic rays is 27 ps and the rms time accuracy per 0.511 MeV photon is 72 ps. The time resolution in terms of FWHM of the time difference between photon pairs is 239 ps FWHM. The reason why MRPC detectors have different time resolutions for cosmic rays and 0.511 MeV photons is related to the different ways different particles act and the thickness of the detector. We propose to use a Cerenkov radiator to convert gamma into ultraviolet photons and use a composite photocathode to detect, improving the detection efficiency to 6.4% for RPC.

The detection efficiency enhancement of MRPC detector with Pb converter for high energy gamma

A 20-layer MRPC with 20 layers of 160μm thickness of Pb converters is fabricated. The resistive plates of the MRPC are 145 ± 15μm borosilicate (D 263 M) glasses, which are separated by three layers of 50μm Kapton tape to create a 150μm gas gap. The experimental detection efficiency of fabricated 20-layer MRPC with 160μm thickness of Pb converter and Ar–CO2 (70:30) gas mixture, for 662 keV gammas at 1400 V applied voltage is around 6.07%. The experimental detection efficiency of the 20-layer MRPC with Pb converter (6.07%) with a relative error around 9.2% is in good agreement with the simulation result (∼6.63%). For the 20-layer MRPC with Pb converter, the experimental detection efficiency is around 17.3 times higher than the simulated results for a single RPC layer. The experimental results for 20-layer MRPC with Pb and Cu converters with reduced high voltage configuration show that the detection efficiency of MRPC with Pb converter is around 10% greater than the one with Cu converter.

Multigap Resistive Plate Chambers for Time of Flight Applications

With the advantages of high-performance, easy to build and relatively low cost, the multigap resistive plate chamber has been arousing broad interests over the last few decades. It has become a new standard technology for the time of flight system in high energy physics experiments. In this article, we will give a description of the structure and the operating principles of the MRPC detector and focus on reviewing the applications on the time of flight system in several famous experiments. The performances, including time resolution and particle identification, are discussed in detail. Some recent advances and points of view for the future development of the next generation MRPC are also outlined.

MRPC technology for muon tomography

Muon tomography is an innovative high-Z material detection technology developed in recent years. The most crucial part of this technology is the high position resolution detectors used for the muon track reconstruction. Multi-Gap Resistive Plate Chambers (MRPCs in the following) are gaseous detectors first developed at CERN in middle 1990s. Considering their characteristics in terms of high efficiency, low cost, robust structure, and excellent position resolution, MRPC became the detector of choice for the TUMUTY (Tsinghua University cosmic ray muon tomography facility) system built in 2012. This paper features a summary about the latest developments on MRPC technology for muon tomography. After the success of the TUMUTY prototype, researches were carried out on larger sensitive area position resolution MRPCs with 2-D readout, and on environment-friendly sealed MRPCs (SMRPC) for industrial applications and future muon tomography systems. It was studied how encoding readout methods and external environment influence the performance of MRPC detectors. Also, an MRPC simulation frame and new data processing methods were both developed, which have provided useful information on optimal design of the future position resolution MRPCs and muon tracking systems.

Simulation and measurement of the impedance of transmission lines in MRPC Detector

At high frequencies, the impedance matching along the transmission line such as between an integrated circuit and the Printed Circuit Board (PCB) is critical to maintain the signal quality and integrity. This paper focuses on studying the impedance of transmission lines in MRPC detectors. We present the 3D electromagnetic (EM) simulation for the real MRPC configurations to obtain the impedance results by using CST Microwave studio. The simulated results show a nice agreement with the results obtained by actual measurements. The strip impedance associated to different MRPC structure configurations has been has been analyzed and discussed in detail.

Readout Electronics for CBM-TOF Supermodule Quality Evaluation

Super module assembled with MRPC detectors is the component unit of TOF (Time of Flight) system for the Compressed Baryonic Matter (CBM) experiment. Quality of super modules needs to be evaluated before it is applied in CBM-TOF. Time signals exported from super module are digitalized at TDC (Time to Digital Converter) station. Data rate is up to 6 Gbps at each TDC station, which brings a tremendous pressure for data transmission in real time. In this paper, a real-time data flow control method is designed. In this control method, data flow is divided into 3 types: scientific data flow, status data flow and control data flow. In scientific data flow, data of each TDC station is divided into 4 sub-flows, and then is read out by a parallel and hierarchical network, which consists of multiple readout mother boards and daughter boards groups. In status data flow, status data is aggregated into a specific readout mother board. Then it is uploaded to DAQ via readout daughter board. In control data flow, control data is downloaded to all circuit modules in the opposite direction of status data flow. Preliminary test result indicated data of STS was correctly transmitted to DAQ with no error and three type data flows were control orderly in real time. This data flow control method can meet the quality evaluation requirement of supper module in CBM-TOF.

CAD-II: the second version current-mode readout ASIC for high-resolution timing measurements

This paper presents the second version of a fully current-mode front-end ASIC, CAD (Current Amplifier and Discriminator), for MRPC detectors for TOF applications. Several upgrades have been made in this new version, including: 1). Using differential input stages with input impedance down to 30 Ω and LVDS compatible outputs; 2). Much higher current gain and bandwidth of 4.5 A/A and 380 MHz; 3). Fabricated in 0.18 μ m CMOS process instead of 0.35 μ m CMOS technology used in CAD-I. The detailed design of the ASIC will be described as well as the measurement results. The single-ended input impedance could be as low as 32 Ω and the power consumption was measured to be 15 mW per channel. Input referred RMS noise current was about 0.56 μ A. The threshold could be set as low as 4.5 μ A referred to input, corresponding to 9 fC for the typical MRPC detector signal with 2 ns width. Sub-10 ps resolution has been measured for input signal above 200 μ A.

Study of the counting rate capability of MRPC detectors built with soda lime glass

We report the results of three MRPC detectors built with soda lime glass and tested in the T10 beam line at CERN. The detectors consist of a stack of 280μm thick glass sheets with 6 gaps of 220μm. We built two identical MRPCs, except one had the edges of glass treated with resistive paint. A third detector was built with one HV electrode painted as strips. The detectors' efficiency and time resolution were studied at different particle flux in a pulsed beam environment. The results do not show any improvement with the painted edge technique at higher particle flux. We heated the MRPCs up to 40°C to evaluate the influence of temperature in the rate capability. Results from this warming has indicated an improvement on the rate capability. The dark count rates show a significant dependence with the temperature.

Online aging study of a high rate MRPC**Supported by National Natural Science Foundation of China (11420101004, 11461141011, 11275108), Ministry of Science and Technology (2015CB856905)

With the constant increase of accelerator luminosity, the rate requirements of MRPC detectors have become very important, and the aging characteristics of the detector have to be studied meticulously. An online aging test system has been set up in our lab, and in this paper the setup of the system is described and the performance stability of a high-rate MRPC studied over a long running time under a high luminosity environment. The high rate MRPC was irradiated by X-rays for 36 days and the accumulated charge density reached 0.1 C/cm2. No obvious performance degradation was observed for the detector.

Mathematical modelling and study of the encoding readout scheme for position sensitive detectors

Encoding readout methods based on different schemes have been successfully developed and tested with different types of position-sensitive detectors with strip-readout structures. However, how to construct an encoding scheme in a more general and systematic way is still under study. In this paper, we present a graph model for the encoding scheme. With this model, encoding schemes can be studied in a more systematic way. It is shown that by using an encoding readout method, a maximum of n(n−1)2+1 strips can be processed with n channels if n is odd, while a maximum of n(n−2)2+2 strips can be processed with n channels if n is even. Furthermore, based on the model, the encoding scheme construction problem can be translated into a problem in graph theory, the aim of which is to construct an Eulerian trail such that the length of the shortest subcycle is as long as possible. A more general approach to constructing the encoding scheme is found by solving the associated mathematical problem. In addition, an encoding scheme prototype has been constructed, and verified with MRPC detectors.

The cosmic ray muon tomography facility based on large scale MRPC detectors

Cosmic ray muon tomography is a novel technology to detect high-Z material. A prototype of TUMUTY with 73.6cm×73.6cm large scale position sensitive MRPC detectors has been developed and is introduced in this paper. Three test kits have been tested and image is reconstructed using MAP algorithm. The reconstruction results show that the prototype is working well and the objects with complex structure and small size (20mm) can be imaged on it, while the high-Z material is distinguishable from the low-Z one. This prototype provides a good platform for our further studies of the physical characteristics and the performances of cosmic ray muon tomography.

Development of a current-mode ASIC for MRPC detectors

A fully current-mode front-end ASIC, named CAD has been developed for MRPC detectors for TOF applications. It consists of a current mirror preamplifier and a current discriminator for each channel. Current mode circuits can easily achieve high bandwidth and are suitable for low power supply design. A simplified circuit model has been introduced to analyze the timing performance of the current discriminator. 20 ps time jitter can be achieved for 40 fC input signal by simulation. The time jitter dramatically decreases as signal amplitude increases. A 4-channel prototype ASIC has also been designed and fabricated in a 0.35 μm CMOS technology. The chip has been evaluated with MRPC detector. The total time jitter of 184 ps has been measured.

The MRPC detector for the ALICE Time Of Flight System: Final Design and Performances

The ALICE Time Of Flight (TOF) system will perform charged particle identification in the intermediate momentum range (from 0.5 to a few GeV/c) and in the central pseudorapidity region ( | η | 0.9 ). In particular the TOF has to cover an area of ∼ 160m2 and has to be highly segmented (∼ 160000 readout pads of 2.5 × 3.7 cm2 active area) in order to keep the occupancy in Pb-Pb collisions below the 15 % level. In order to satisfy these requirements, the double-stack MRPC detector has been chosen for the TOF system. The most relevant results on the performances of the final version of the MRPC and of the front-end/readout electronics will be presented. The device has a very good uniformity, a long streamer-free plateau, an efficiency higher than 99 % and an intrinsic time resolution below 50 ps.

Quality Assurance procedures for the construction of ALICE TOF detector

The goal of the MRPC–detector production for the ALICE TOF is to guarantee the same excellent performances obtained so far with all the prototypes. A set of quality assurance tests has been developed for this purpose; these tests are applied both to the single chamber components and to the assembled detectors. In this paper the results of these tests over a few hundreds MRPCs of the mass production will be presented.