Multi-gap Resistive Plate Chamber Detectors Research Articles

A very thin MRPC developed for TOF-PET

PET (Positron Emission Tomography) is a medical molecular imaging modality employed in cancer diagnosis and monitoring. Multi-gap Resistive Plate Chambers (MRPCs) are utilized in Time of Flight (TOF)-PET due to their superior time resolution. Our research group has successfully developed a 4-chamber 32-gap MRPC prototype with 0.128 mm gap thickness. The measured time resolution for cosmic rays is 20 ps, while the time resolution for the time difference between 0.511 MeV photon pairs is 193 ps Full Width at Half Maximum (FWHM). The 23.6 mm thickness of the MRPC prototype will affect the time resolution. To investigate the influence of the number and total thickness of gas gaps on the time resolution, Geant4 software is used to simulate the interaction between particles (such as cosmic rays and photons) and MRPC detectors. Most of the gamma photons interact with the resistive plates in MRPCs. It is ejected mostly a Compton electron into one gas gap, causing the gas ionization. In this paper, two 8-gap MRPC prototypes with 0.128 mm gap thickness and 4.2 mm total thickness are fabricated and tested. The time resolution of 39 ps for cosmic rays and 166 ps FWHM for 0.511 MeV photons is obtained using the fast front-end amplifier and waveform acquisition system. So, a real time PET image can be obtained with a pair of MRPCs, and the detection efficiency for gamma can be improved by increasing the number of thin MRPCs.

Glass multi-gap RPCs for photon-transmission imaging

In the present R&D, multi-gap resistive plate chambers (MRPCs) are studied for photon non-destructive inspection of small airport baggages and cargos. Six-gap RPCs for line-scan operations are constructed with soda-lime glass with a thicknesses of 0.53 mm. The typical detector characteristics such as the operation high voltage (HV), the efficiency, and the strip multiplicity are measured by using 661.7 keV photons emitted from a 137Cs source with a current activity of 4.74 GBq. The efficiency for the 661.7 keV photons measured by the MRPC detector at the HV applied to obtain the photon-transmission images is 5.5%, which is about 84% of that predicted by a GEANT simulation. To demonstrate the quality operation of the MRPC detectors, we conduct line-scan operations for various objects and produce the photon-transmission images that barely identify 2 mm-thick stainless steel objects when measured with a color depth (contrast) of the image pixels of about 100.

The FAIR Phase 0 program of the CBM TOF

In order to provide particle identification (PID) of charged hadrons at the future high-rate Compressed Baryonic Matter (CBM) experiment, the TOF group has developed a large-area Time-of-Flight (ToF) wall equipped with Multi-gap Resistive Plate Chambers (MRPC) capable to operate at incident particle fluxes of up to 30 kHz/cm2. Prior to its destined operation at the Facility for Antiproton and Ion Research (FAIR)—starting in 2025—this high-rate timing MRPC technology will be used for physics research at two scientific pillars of the FAIR Phase-0 program: the end-cap TOF upgrade of the STAR experiment at RHIC and the mini-TOF (mTOF) wall of the mini-CBM (mCBM) experiment at Schwerionensynchrotron18 (SIS18). At STAR, the fixed-target program of the Beam Energy Scan II (BES-II) will rely on 108 CBM MRPC detectors for forward PID at trigger rates of up to 2 kHz. At mCBM, high-performance benchmark runs of Lambda-baryon production at top SIS18 energies and CBM design interaction rates of 10 MHz will become feasible with a PID backbone consisting of 25 CBM MRPC detectors. Apart from the physics perspective, these pre-FAIR involvements will help gathering experience in operating the final CBM TOF wall comprising about 1500 MRPC detectors and 110,000 readout channels. The status of the FAIR phase 0 program will be discussed.

Improving the time resolution of the MRPC detector using deep-learning algorithms

The multi-gap resistive plate chambers (MRPCs) will be used as the Time-of-Flight (ToF) system in the Solenoidal Large Intensity Device (SoLID). The time resolution required by the experiment for the MRPC system is 20 ps in order to make a 3 σ separation of the π/K created in the collisions. To achieve this goal, the whole system including the MRPC detector, the front-end electronics and the readout system will be upgraded. Based on the new system, a time reconstruction algorithm using a combined LSTM (ComLSTM) neural network is proposed. The best time resolution achieved with this algorithm in a cosmic ray test is 16.8 ps, which largely improves the timing ability of the MRPC detector and well satisfies the requirement of the SoLID.

Investigation of a prototype double-stack MRPC detector with 20 gas gaps for Time-Of-Flight measurement in PET imaging systems

Resistive Plate Chambers (RPC) are cost-effective gaseous detectors with a very good time and spatial resolution which are extensively used in High Energy Physics and Astroparticle experiments. RPCs have also proposed for Time-Of-Flight (TOF) measurements in Positron Emission Tomography (PET) imaging systems. However, the major limitation of common RPC detectors for PET imaging systems is their low detection efficiency for 511 keV gammas. This paper is focused on the development and investigation of a new RPC detector with improved detection efficiency and time resolution for TOF measurement of 511 keV gamma pairs from electron-positron annihilation. The proposed double-stack Multi-gap RPC (MRPC) detector which is optimized for TOF-PET, consists of 20 gas gaps (with 150 μm width) with 180 μm glass slides (with 24% PbO) as resistive plates in optimum thickness to act as the gamma to electron converter. The proposed detector can work at lower applied voltage with higher count rate capability thanks to the double-stack design and smaller gas gaps width in comparison to common RPCs which were used for TOF-PET applications. The experimental detection efficiency of the proposed MRPC detector for single 511 keV gammas is around 8.3%. At higher applied voltages although the electron multiplication of detector increases, but the detection efficiency saturates, which is related to saturation of dark count rate noise. By using the experimental TOF measurement for electron-positron annihilation gammas, the calculated timing standard deviation of each MRPC detector is 194±40 ps. Moreover, in previous work with the proposed detector it was proved that by using a suitable arrangement of vertical and horizontal readout strips, the pixelated detector can be formed to extract the spatial information of the interaction. According to these results, the proposed prototype detector (which is the first double-stack mode MRPC with 20 gas gaps for TOF-PET application) could be a candidate for TOF measurement system thanks to its suitable time and spatial resolution and also reasonable rate capability. Therefore, it could be an inexpensive alternative for commercial TOF-PET detectors.

Design of an optimised preamplifier for the MRPC detector

Multi-gap Resistive Plate Chamber (MRPC) is widely used in many major international projects as an important element of the Time-of-flight (TOF) system because of its high time resolution. The typical time resolution of a MRPC system is about 60 ps, while the intrinsic time resolution of the MRPC detector can be smaller than 20 ps. This paper aims to improve the time resolution preformance of a 32-gap, 104 μm-thick MRPC system by optimising the readout electronics, which consists of a current mirror (CM) and a modified transimpedance amplifier (TIA). A nominal time resolution of 11.37 ps can be achieved for a MRPC detector with a delta current signal input and a charge of around 34 fC according to a MATLAB simulation. The MRPC system using this preamplifier can achieve a time resolution of 27 ps combining with high-speed waveform sampling method.

Novel low resistivity glass: MRPC detectors for ultra high rate applications

Multigap Resistive Plate Chambers (MRPCs) are often used as time-of-flight (TOF) detectors for high-energy physics and nuclear experiments thanks to their excellent time accuracy. For the Compressed Baryonic Matter (CBM) TOF system, MRPCs are required to work at particle fluxes on the order of 1–10kHz/cm2 for the outer region and 10–25kHz/cm2 for the central region. Better time resolution will allow particle identification with TOF techniques to be performed at higher momenta. From our previous studies, a time resolution of 25ps has been obtained with a 20-gap MRPC of 140μm gap size with enhanced rate capability. By using a new type of commercially available thin low-resistivity glass, further improvement MRPC rate capability is possible. In order to study the rate capability of the 10-gap MRPC built with this new low-resistivity glass, we have performed tests using the continuous electron beam at ELBE. This 10-gap MRPC, with 160μm gaps, reaches 97% efficiency at 19.2kV and a time resolution of 36ps at particle fluxes near 2kHz/cm2. At a flux of 100kHz/cm2, the efficiency is still above 95% and a time resolution of 50ps is obtained, which would fulfil the requirement of CBM TOF system.

Study of high time resolution MRPC with the waveform digitizer system

A high time resolution Multi-gap Resistive Plate Chamber (MRPC) is proposed for the TOF system of SoLID experiment at Jefferson Lab. Efforts have being devoted to the research of a new MRPC structure, aiming at a time resolution of 20 ps. Two 32-gap MRPCs with 104 μ m gap thickness have been developed for the initial test. By using the fast amplifier and waveform digitizer system, the performace of these MRPC detectors is studied using the cosmic rays. Time resolution of the order of 20 ps and efficiency around 95% are obtained. Detector simulations are simultaneously carried out for MRPCs with different structures. Meaningful results and future plans are discussed in detail.

Study of transmission-line impedance of strip lines in an MRPC detector

Characteristic impedance study of differential transmission lines based on Digital Sampling Oscilloscope is carried out, and more than 72 multi-gap resistive plate chambers (MRPC) with different structures have been developed and tested. The results show that the impedance is related to the overall electromagnetic field structure, which is determined by the number and width of gas gaps and glass, the number of stacks, and the width of signal strips. The equivalent dielectric constant of the dielectrics between the paired readout strips has been introduced and applied into Wheeler’s equations. After that, the outcome of the equations corresponds with the test results. In addition, a new approximate formula for calculating the transmission-line impedance of multi-stack MRPC detectors is proposed. The values computed from the formula show a good agreement with the experimental data, thus demonstrating its validity.

A detailed study on the intrinsic time resolution of the future MRPC detector

A challenging goal of 20 ps for the total time resolution of the Multi-gap Resistive Plate Chambers (MRPCs) system has been recently addressed by high energy physics experiments. In order to meet this requirement, one should have a deeper understanding of the detector physics and the factors that contribute to the intrinsic time resolution of the MRPC, which are studied in this paper. The sources of the timing uncertainties, their influences and the relationship with the detector geometry are analyzed. A comparison between the time resolutions obtained using two different simulation algorithms is presented. The obtained results are useful for the design of the timing MRPCs with an improved performance, and meanwhile offer guidance for the R&D activities in the field.

Quality Evaluation Electronics for CBM-TOF Super Module

The time-of-flight (TOF) system in the compressed Baryonic matter (CBM) experiment is comprised of super modules and used for charged hadron identification. Each super module contains several multigap resistive plate chambers (MRPCs) for high-precision time measurements. The quality of each super module should be evaluated to ensure that the detectors achieve the targeted performance. In this paper, the quality evaluation electronics for super modules based on the peripheral component interconnect eXtensions for instrumentation platform is proposed. The discriminated MRPC signals are digitized by the time-to-digital converter (TDC). Then, the digitized time data from a super module are aggregated at the TDC readout motherboard and are transmitted to the data readout modules (DRMs) via optical links. Finally, the DRMs relay the digitized data to the data acquisition system through the Gigabit Ethernet ports in parallel. The laboratory test results indicate that the quality evaluation electronics achieve a time resolution better than 20 ps. The initial cosmic ray tests with the MRPC detectors have also been conducted to confirm the performance of the quality evaluation system. Based on the results, the evaluation system can subsequently be used for quality evaluation of the CBM-TOF super module.

The simulation and application of three-dimensional electrostatic weighting field in MRPC detector

This paper presents a simulation method with ANSYS Maxwell suited to study three-dimensional electrostatic weighting field in a Multi-gap Resistive Plate Chamber (MRPC). The variation of the three-dimensional weighting field with the change in the MRPC design parameters has been studied in detail, which will help us better understand the chamber response. Finally, we shall achieve more real simulation of the chamber signal by introducing the 3D weighting field results into our standalone simulation framework. Signals induced on strip electrodes and simulation results of time resolution and position resolution have been discussed and compared with experimental test.

The performance study of MRPCs used for muon tomography

Muon tomography system built by 2-D readout high spatial resolution Multi-gap Resistive Plate Chamber (MRPC) detector is a project in Tsinghua University. In 2013, we had developed a prototype of muon tomography system named TUMUTY, now we try to develop larger sensitive area and smarter structure MRPC detector to upgrade the system to a car detection system, which is used to detect high Z metal hidden in cars or other objects. For the system, 2 layers × 3 detectors are needed to get the incident particle's track, and the setting is the same for the outgoing track. Therefore, there will four layers containing twelve detectors in total, and its detection area will reach 1× 3 m2. An encoding readout method is suggested to minimize the number of the readout electronics, which reduces the complexity and the cost of the system. In this paper, we measured the performance of 12 MRPCs used for the system.

Design of a prototype readout electronics with a few picosecond time resolution for MRPC detectors

Multi-gap Resistive Plate Chamber (MRPC) is widely used as a Time-of-Flight (ToF) detector in physics experiments, featuring a high time precision requirement both on the detector and readout electronics. Efforts are being devoted to the research of a new MRPC structure, aiming at a much higher resolution, which demands an enhancement of the readout electronics performance. In this paper, a 10-ps prototype readout electronics for the MRPCs is presented. By using the cascaded high performance preamplifiers, gain between 20 dB and 40 dB is achieved for an 8-channel Analog Frontend Electronics (AFE) prototype module. The output signals of the AFE are digitized by a 16-channel high-speed Waveform Digitization Module (WDM), integrating the waveform correction and filtering, digital discrimination, linear interpolation, and other control logics within one Field Programmable Gate Array (FPGA) device. To evaluate the performance of the proposed design, a series of tests were conducted with synthesized signals from a pulse generator. These signals have the same rise time and width with that of real MPRC output signal, and cover the detector’s charge range. Test results indicate that the prototype readout electronics functions well, and its time resolution is better than 10 ps in the dynamic range of 50–500 fC.

Time of flight technology based on multi-gap resistive plate chamber

Particle identification is very important in nuclear and particle physics experiments. Time of flight system (TOF) plays an important role in particle identification such as the separation of pion, kaon and proton. Multi-gap resistive plate chamber (MRPC) is a new kind of avalanche gas detector and it has excellent time resolution power. The intrinsic time resolution of narrow gap MRPC is less than 10 ps. So the MRPC technology TOF system is widely used in modern physics experiments for particle identification. With the increase of accelerator energy and luminosity, the TOF system is required to indentify definite particles precisely under high rate environment. The MRPC technology TOF system can be defined as three generations according to the timing and rate requirement. The first-generation TOF is based on the float glass MRPC and its time resolution is around 80 ps, but the rate is relatively low (typically lower than 100 Hz/cm<sup>2</sup>). The typical systems are TOF of RHIC-STAR, LHC-ALICE and BES III endcap. For the second-generation TOF, its time resolution has the same order as that for the first generation, but the rate capability is much higher. Its rate capability can reach 30 kHz/cm<sup>2</sup>. The typical experiment with this high rate TOF is FAIR-CBM. The biggest challenge is in the third-generation TOF. For example, the momentum upper limit of <inline-formula><tex-math id="M1">\begin{document}$ {\rm{K}}/{\text{π}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20182192_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20182192_M1.png"/></alternatives></inline-formula> separation is around 7 GeV/c for JLab-SoLID TOF system under high particle rate as high as 20 kHz/cm<sup>2</sup>, and the time requirement is around 20 ps. The readout electronics of first two generations is based on time over threshold method, and pulse shape sampling technology will be used in the third-generation TOF. In the same time, the machine learning technology LSTM network is also used to analyze the time performance. As a very successful sample, MRPC barrel TOF has been used in RHIC-STAR for more than ten years and many important physics results have been obtained. A prominent result is the observation of antimatter helium-4 nucleus. This discovery proves the existence of antimatter in the early universe. In this paper, we will describe the evolution of MRPC TOF technology and key technology of each generation of TOFs including MRPC detector and related electronics. The industrial and medical usage of MRPC are also introduced in the work finally.

A standalone simulation framework of the MRPC detector read out in waveforms

Dedicated detector simulations are very important for the success of high energy physics experiments. They not only bring benefits to the optimization of the detectors, but can also improve the precision of the physics results. To design a Multi-gap Resistive Plate Chamber (MRPC) with a very good time resolution, a detailed monte-carlo simulation of the detector is needed and described in this paper. The simulation can produce detector signal waveforms which contain a complete information about the events. The detector performance filled with different gas mixtures is studied, and comparisons between simulation and experimental results show a good agreement.

Design and experimental test of a novel double stack MRPC detector for medical imaging applications

The Resistive Plate Chambers (RPC) are parallel-plate gaseous detectors, thanks to their good spatial resolution and high time resolution in comparison to the scintillation detectors, have been recently used for time of flight measurements in PET imaging systems. In this work, design and testing of a new Multi-gap RPC (MRPC) with a suitable time and energy resolution for medical imaging applications is proposed. This MRPC detector, consists of glass plates with optimum thickness to achieve acceptable detection efficiency. In addition, the optimum thickness of gas gaps is estimated to improve the time response by reducing the space-charge effect. The electrodes which are used to apply the electric field are special graphite foils (0.07 mm thick, 0.7 g/cm3 density and 3kΩ/cm2 surface resistivity) with the purity of 99.95%. The arrangement of the vertical and horizontal readout strips are also optimized to achieve more uniformity of electric field in each pixel. The Monte Carlo simulation and experimental results show that this low-cost detector has a suitable ability to be used in PET imaging applications.

The Extreme Energy Events experiment: an overview of the telescopes performance.

The muon telescopes of the Extreme Energy Events (EEE) experiment are based on Multigap Resistive Plate Chambers (MRPC). The EEE network is composed, so far, of 53 telescopes, each made of three MRPC detectors; it is organized in clusters and single telescope stations distributed all over the Italian territory and installed in High Schools, covering an area larger than 3×105 km2. The study of Extensive Air Showers (EAS), that is one of the goal of the project, requires excellent performance in terms of time and spatial resolution, efficiency, tracking capability and long term stability. The data from two recent coordinated data taking periods, named Run 2 and Run 3, have been used to measure these quantities and the results are here reported, together with a comparison with expectations and with the results from a beam test performed in 2006 at CERN.

Performance study of large area encoding readout MRPC

Muon tomography system built by the 2-D readout high spatial resolution Multi-gap Resistive Plate Chamber (MRPC) detector is a project of Tsinghua University. An encoding readout method based on the fine-fine configuration has been used to minimize the number of the readout electronic channels resulting in reducing the complexity and the cost of the system. In this paper, we provide a systematic comparison of the MRPC detector performance with and without fine-fine encoding readout. Our results suggest that the application of the fine-fine encoding readout leads us to achieve a detecting system with slightly worse spatial resolution but dramatically reduce the number of electronic channels.

Design, development and performance study of six-gap glass MRPC detectors

The Multigap Resistive Plate Chambers (MRPCs) are gas ionization detectors with multiple gas sub-gaps made of resistive electrodes. The high voltage (HV) is applied on the outer surfaces of outermost resistive plates only, while the interior plates are left electrically floating. The presence of multiple narrow sub--gaps with high electric field results in faster signals on the outer electrodes, thus improving the detector's time resolution. Due to their excellent performance and relatively low cost, the MRPC detector has found potential application in Time-of-Flight (TOF) systems. Here we present the design, fabrication, optimization of the operating parameters such as the HV, the gas mixture composition, and, performance of six--gap glass MRPC detectors of area 27cm $\times$ 27 cm, which are developed in order to find application as trigger detectors, in TOF measurement etc. The design has been optimized with unique spacers and blockers to ensure a proper gas flow through the narrow sub-gaps, which are 250 $\mu$m wide. The gas mixture consisting of R134A, Isobutane and SF$_{6}$, and the fraction of each constituting gases has been optimized after studying the MRPC performance for a set of different concentrations. The counting efficiency of the MRPC is about 95% at $17.9$ kV. At the same operating voltage, the time resolution, after correcting for the walk effect, is found to be about $219$ ps.