Glass RPC Research Articles

Test-beam and simulation studies towards RPWELL-based DHCAL

Digital Hadronic Calorimeters (DHCAL) were suggested for future Colliders as part of the particle-flow concept. Though studied mainly with RPC, studies focusing on sampling elements based on Micro-Pattern Gaseous Detector have shown the potential advantages; they can be operated with environment-friendly gases and reach similar detection efficiency at lower average pad multiplicity. We summarize here the experimental test-beam results of a small-size DHCAL prototype, incorporating six Micromegas and two RPWELL sampling elements, interlaced with steel-absorber plates. It was investigated with 2–6 GeV pion beams at the CERN/PS beam facility. The data permitted validating a GEANT4 simulation framework of a DHCAL, and evaluating the expected pion energy resolution of a full-scale RPWELL-based calorimeter. The pion energy resolution derived for the RPWELL concept is competitive to that of glass RPC and Micromegas sampling techniques.

Uniformity study of large size glass RPC detector using an alternative front-end electronics for INO-ICAL experiment

The proposed INO-ICAL experiment is planning to use large size RPC chambers as active detector element. Besides handling and operating issues for such large size detectors, uniformity of their response is going to be another challenge. Only a few works were dedicated to study this feature. We report on the study conducted to analyse the response uniformity of a large size 1 m × 1 m RPC prototype detector working in avalanche mode with a gas mixture of 94.5% R134a, 5% iso-butane and 0.5% sulphur hexafluoride. The cluster size, efficiency and count rate have been studied on the whole RPC chamber using cosmic rays for assessing the uniformity of the chamber and to spot any edge effects eventually. To perform this study we use a readout system based on the HARDROC ASIC. The latter with its 64 channels each equipped with a circuit made of preamplifier, fast shapers and discriminators to read out the RPC fast signal.

High Rate RPC detector for LHC

The High Luminosity LHC (HL-LHC) phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. The foreseen gradual increase of the instantaneous luminosity of up to more than twice its nominal value of 10×1034cm-1s-2 during Phase I and Phase II of the LHC running, presents special challenges for the experiments. The region with high pseudo rapidity (η) region of the forward muon spectrometer (2.4 >|η| > 1.9) is not equipped with RPC stations. The increase of the expected particles rate up to 2 kHz cm-2 (including a safety factor 3) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The current CMS RPC technology cannot sustain the expected background level. A new generation of Glass-RPC (GRPC) using low-resistivity glass was proposed to equip the two most far away of the four high η muon stations of CMS. In their single-gap version they can stand rates of few kHz cm-2. Their time precision of about 1 ns can allow to reduce the noise contribution leading to an improvement of the trigger rate. The proposed design for large size chambers is examined and some preliminary results obtained during beam tests at Gamma Irradiation Facility (GIF++) and Super Proton Synchrotron (SPS) at CERN are shown. They were performed to validate the capability of such detectors to support high irradiation environment with limited consequence on their efficiency.

Measurements of beam-induced photons for particle therapy

Resistive plate chambers are studied for in-vivo beam verification in particle therapy. A four-gap glass RPC is constructed with 1.1-mm-thick floating glass and tested with 662-keV gamma rays emitted from a 5-GBq 137Cs source, as well as high-energy photons induced by 140-MeV raster-scan-mode proton beams provided by the Samsung Proton Therapy Center. The desired 3 mm resolution of the RPC detector is confirmed by reconstructing gamma transmission images for the cesium gammas gathered from the data. Using the described RPC detector and a 10-cm-thick lead collimator, we obtain two-dimensional gamma-ray images for 140-MeV proton beams and confirm the detector technology proposed in the present research.

Design validation and performance of closed loop gas recirculation system

A pilot experimental set up of the India Based Neutrino Observatory's ICAL detector has been operational for the last 4 years at TIFR, Mumbai. Twelve glass RPC detectors of size 2 × 2 m2, with a gas gap of 2 mm are under test in a closed loop gas recirculation system. These RPCs are continuously purged individually, with a gas mixture of R134a (C2H2F4), isobutane (iC4H10) and sulphur hexafluoride (SF6) at a steady rate of 360 ml/h to maintain about one volume change a day. To economize gas mixture consumption and to reduce the effluents from being released into the atmosphere, a closed loop system has been designed, fabricated and installed at TIFR. The pressure and flow rate in the loop is controlled by mass flow controllers and pressure transmitters. The performance and integrity of RPCs in the pilot experimental set up is being monitored to assess the effect of periodic fluctuation and transients in atmospheric pressure and temperature, room pressure variation, flow pulsations, uniformity of gas distribution and power failures. The capability of closed loop gas recirculation system to respond to these changes is also studied. The conclusions from the above experiment are presented. The validations of the first design considerations and subsequent modifications have provided improved guidelines for the future design of the engineering module gas system.

High rate, fast timing Glass RPC for the high η CMS muon detectors

The HL-LHC phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. To achieve this goal in a reasonable time scale the instantaneous luminosity would also increase by an order of magnitude up to 6 · 1034 cm−2s−1. The region of the forward muon spectrometer (|η| > 1.6) is not equipped with RPC stations. The increase of the expected particles flux up to 2 kHz/cm2 (including a safety factor 3) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The current CMS RPC technology cannot sustain the expected background level. The new technology that will be chosen should have a high rate capability and provide a good spatial and timing resolution. A new generation of Glass-RPC (GRPC) using low-resistivity glass is proposed to equip at least the two most far away of the four high η muon stations of CMS. First the design of small size prototypes and studies of their performance in high-rate particles flux are presented. Then the proposed designs for large size chambers and their fast-timing electronic readout are examined and preliminary results are provided.

High rate, fast timing Glass RPC for the high η CMS muon detectors

The HL-LHC phase is designed to increase by an order of magnitude the amount of data to be collected by the LHC experiments. To achieve this goal in a reasonable time scale the instantaneous luminosity would also increase by an order of magnitude up to 6·1034cm−2s−1. The region of the forward muon spectrometer (|η|>1.6) is not equipped with RPC stations. The increase of the expected particles rate up to 2kHz/cm2 (including a safety factor 3 ) motivates the installation of RPC chambers to guarantee redundancy with the CSC chambers already present. The actual RPC technology of CMS cannot sustain the expected background level. A new generation Glass-RPC (GRPC) using low resistivity glass (LR) is proposed to equip at least the two most far away of the four high eta muon stations of CMS Butler et al. (2015). The design of small size prototypes and the studies of their performances under high rate particles flux is presented.

A hadronic calorimeter with Glass RPC as sensitive medium

The SDHCAL technological prototype is a 1 × 1 × 1.3 m3 high-granularity Semi-Digital HadronicCALorimeter using Glass Resistive Plate Chambers as sensitive medium.It is one of the two HCAL options considered by the ILD Collaborationto be proposed for the detector of the future International LinearCollider project. The prototype is made of up to 50 GRPC detectors of1 m2 size and 3 mm thickness each with an embedded semi-digitalelectronics readout that is autotriggering and power-pulsed. The GRPCreadout is finely segmented into pads of 1 cm2. Measuredperformances of the GRPC and the full SDHCAL prototype in terms ofhomogeneity, low noise and energy resolution are presented in thisproceeding.

Induced charge signal of a glass RPC detector

A gas detector glass resistivity plate chamber (GRPC) is proposed for use in the hadron calorimeter (HCAL). The read-out system is based on a semi-digital system and, therefore, the charge information from GRPC is needed. To better understand the charge that comes out from the GRPC, we started from a cosmic ray test to get the charge distribution. We then studied the induced charge distribution on the collection pad. After successfully comparing it with the prototype beam test data at CERN (European Council for Nuclear Research), the process was finally implanted into the Geant4 based simulation for future study.

Induced Charge Profile in a Glass RPC Operated in Avalanche Mode

We measured the spatial distribution of induced charges in resistive plate chambers (RPCs) using thin readout wires. The RPC was operated in avalanche mode with gas mixtures containing SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> , C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> , and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> . We found that the maximum spread of 4-9 mm was dependent on the time window of the signal acquisition. The spatial distribution is defined mainly by the induced charge spread. It also has a time dependent component, which may result from the charge transmission effect on the carbon electrode.

Study of spatial resolution properties of a glass RPC

A prototyping glass RPC with excellent signal-to-noise ratio was constructed and tested. Detection efficiencies for cosmic rays of about 95% were obtained for both avalanche and streamer modes of operation. A simple method to measure the signal charge profile is developed, which is consistent with other methods such as direct optical observation. A narrow profile for avalanche signal mode is obtained, which may lead to an intrinsic spatial resolution less than 1.0 mm FWHM. If a delay-line or charge division technique is used to determine the centroid of the signal charge distribution, it is important to reduce the electronics noise and the fluctuations of the delay-line (or resistor) units in order to reach the ultimate intrinsic position resolution.

Glass resistive plate chambers for a semi-digital HCAL

The Particle Flow Algorithm (PFA) concept is one of the main features of the future ILC experiments. This implies a highly granular hadronic calorimeter. A 1cm2 segmentation can be obtained using semi-digital embedded electronics together with an efficient gas detector. The Glass RPC is an excellent candidate that was successfully used in the BELLE experiment. To apply the PFA efficiently it is necessary to reduce the detector dead zones while keeping it as thin as possible. We have designed and constructed very thin GRPCs for which the number and volume of spacers as well as the area of the gas-tight frame are minimized. New resistive coatings were used to reduce cross-talk. Attempts to improve on the high voltage connection were made and novel gas distribution schemes were tested.

A simulation study of the e+/e− sensitivity of a low resistive phosphate glass electrode in a RPC using GEANT MC

The resistivity of conventional glass is quite high and is unacceptable in a high rate environment. Low resistive glass-electrodes could be a solution for this problem. The present study reports the e+/e− simulation results of an RPC detector made from low resistive phosphate glass electrodes. The detailed geometrical configuration of the content materials which are the essential components of the glass of the RPC detector have been created with the GEANT4 simulation code. Two different types of particle sources, i.e. for e+/e−, have been located on the detectors surface to evaluate the performance of the phosphate glass RPC. Both of the particles have been simulated as a function of their respective energies in the range of 0.1 MeV − 1.0 GeV. The present simulation work has shown that the resistive electrode plays an important role for the particle production in the RPC configuration.

Study of neutron response for two hybrid RPC setups using the GEANT4 MC simulation approach

The present article describes a detailed neutron simulation study in the energy range 10−10 MeV to 1.0 GeV for two different RPC configurations. The simulation studies were taken by using the GEANT4 MC code. Aluminum was utilized on the GND and readout strips for the (a) Bakelite-based and (b) glass-based RPCs. For the former type of RPC setup the neutron sensitivity for the isotropic source was Sn = 2.702 × 10−2 at En = 1.0 GeV, while for the latter type of RPC, the neutron sensitivity for the same source was evaluated as Sn = 4.049 × 10–2 at En = 1.0 GeV. These results were further compared with the previous RPC configuration in which copper was used for ground and pickup pads. Additionally Al was employed at (GND+strips) of the phosphate glass RPC setup and compared with the copper-based phosphate glass RPC. Good agreement with sensitivity values was obtained with the current and previous simulation results.

Development of conductive coated polyester film as RPC electrodes using screen printing

Each of the three 16 kton ICAL detector modules at the India-based Neutrino Observatory (INO) will use RPCs as the active element, sandwiched between 6 cm thick soft iron plates, for measurements on atmospheric neutrinos. The electrodes of the RPC are float glass sheets having a volume resistivity of about 10 12 –10 13 Ω cm (at room temperature) covered with carbon/graphite or a conductive paint with a surface resistivity of ∼800 kΩ/square to 1 MΩ/square to apply high voltage on the glass surface, so that this surface does not shield the discharge signal from the external pickup plates and is small compared to the resistivity of the glass to provide a uniform potential across the entire surface. We initially coated the surface with locally available graphite powder, mixed with lacquer and thinner, and were able to get a few hundred kΩ/square resistivity. However, we observed a drastic reduction in surface resistivity with time and it came unstuck from the glass. Subsequently a conductive paint developed by Kansai–Nerolac was used. This paint uses modified acrylic resin as binder, conductive black pigment and solvents, which include aromatic hydrocarbons and alcohols. At room temperature, the surface dries in 10 minutes, while complete drying takes ∼18 hours. The spraying is done at a pressure of 4 kg/cm 2 with the glass plate kept at a distance of 8–10 in. Using this paint, we are able to achieve the required resistance of ∼ few hundred kΩ/square. We still need to study the long term stability and best curing method. We need to automate the procedure to get a uniform coat and to coat a large number of glasses for the final detector. While robotic systems are available abroad costing about 5 000 000 rupees, we are exploring other alternatives. In particular, we are in the process of developing a polyester film, with a conductive coating on one side, which can be glued on to the glass. The coating was done using on a local commercial screen printing machine (Grafica Flextronica, Vasai, India) using the screen printing ink viz. CARBO PASTE DC-1000M and DC-20 (Dozen Tech, Korea). A surface resistivity of a few hundred kΩ/square was obtained on a 100 mm thick polyester sheet of dimension 0.7 M×1.2 M. Curing was done for ∼30 minutes at 150 °C. We are planning to test this film on a glass RPC very soon.

Simulation on the response of new phosphate glass RPC for γ-rays and e+/e− particles using GEANT3

Abstract The influence of phosphate glass electrode in the configuration of resistive plate chamber has been studied using GEANT3.21 Monte Carlo code. Bakelite electrodes were replaced by phosphate glass electrodes, as these glass materials have low bulk resistivity, are portable and easy to handle. These types of RPCs in their compact form of all materials are suitable for high rate background environment. We find that these new types of RPCs give little higher response to γ-rays and e+/e− particles, both for single-and double gap RPCs. The results of simulation are discussed.

Preliminary results from India-based Neutrino Observatory detector R&D programme

We are currently developing and studying the performance of glass RPC prototypes, under the INO detector R&D programme. While we were successful in building and characterising a large number of chambers using local glass, these have met with severe aging problems after a few months of continuous operation. We have then built a couple of RPCs using a Japanese glass. We report in this paper on our long term stability tests of these RPCs. We also present some of our recent results on tracking of cosmic ray muons in a stack of glass RPCs.

Performance of Glass RPC in Streamer Mode for Irradiation With Coherent Photons

We have tested the RPC operated in streamer mode irradiating the laser light, and investigated its properties. We found that the gas in the RPC can be ionized in two photon absorption process. The laser irradiation method is useful technique to investigate the characteristics of RPC systematically.

The Veto system of the OPERA experiment

OPERA is a neutrino oscillation experiment to search the ν τ appearance in the future CNGS beam from CERN to Gran Sasso. A large VETO system, consisting of two 9.6 × 9.2 m2 planes made of glass RPCs, is foreseen to flag the events due to the neutrino interactions with the rock surrounding the OPERA detector. We describe the VETO system, its monitoring system, the glass RPC developed.

Quenching properties of gas mixture in glass RPC operated with streamer mode

Quenching properties of gas mixture in a resistive plate chamber operated with streamer mode were investigated using optical image taken by the CCD camera and signal pulse waveform recorded by the digital oscilloscope. We have tested four quenching gases: C2H2F4, C2F6, CBrF3 and SF6. Streamer size, brightness and induced charge linearly depend on the ratio of Ar to quenching gas and their slopes are a function of electron affinity for each quenching gas.