Search

We propose a new method to detect sub-GeV dark matter, through their scatterings from free leptons and the resulting kinematic shifts. Especially, such an experiment can detect dark matter interacting solely with muons. The experiment proposed here is for directly probing the muonphilic dark matter in a model-independent way. Its complementarity with the muon on the target proposal is similar to e.g. XENON/PandaX and ATLAS/CMS on the dark matter searches. Moreover, our proposal can work better for relatively heavy dark matter such as those in the sub-GeV region. We start with a small device of a size around 0.1–1 m, using atmospheric muons to set up a prototype. Within only one year of operation, the sensitivity on the cross-section of dark matter scattering with muons can already reach σ D ∼ 1 0 − 1 9 (− 2 0 , − 1 8) cm 2 for the dark matter mass M D = 1 0 0 (10, 1000) MeV. We can then interface the device with a high-intensity muon beam of 1 0 1 2 /bunch. Within one year, the sensitivity can reach σ D ∼ 1 0 − 2 7 (− 2 8 , − 2 6) cm 2 for M D = 1 0 0 (10, 1000) MeV. [ABSTRACT FROM AUTHOR]

Research on aging processes of Gas Electron Multipliers (GEMs) is important to obtain insights on how to increase the detector's longevity, stability, and performance, as highlighted in the latest developments roadmap by the European Council of Future Accelerators (ECFA). One key aspect of the aging process is the deposit formation on the electrodes surfaces. In this work, through the analysis of the molecular content on the surface of a used GEM, we provide evidence for polyimide redeposition as a source of organic material contributing to the formation of insulating layers on the electrodes, which eventually lead to sparks and detector failure. Furthermore, we show that chromium, used to promote adhesion between copper and polyimide, in the device undergoes a diffusion process, effectively blurring the layered structure. We demonstrate the significance of surface-sensitive chemical analysis to investigate the surface deposits on electrodes of gaseous detectors and our results reveal the necessity of standardization and more stringent study protocols. [ABSTRACT FROM AUTHOR]

The purpose of this research is to design and construct a plasma radiation imaging system for fusion devices which is focused on soft X-ray region from about 2 to 15 keV photon energy. The proposed 2D diagnostic system, as opposed to conventional 1D systems, is expected to benefit from tangential field of view and to deliver new data for toroidal phenomena observations. This contribution relates to the introductory development of such 2D system laying out details on the overall design of the detecting unit (based on GEM technology) as well as on its acquisition module. The results cover also the expected photon flux and spectra foreseen for COMPASS-U device, as a first choice for testing and verification. Considerations on working medium and internal structure of the detecting sensor are presented including electrodes configurations and collecting electrode pattern. The preliminary establishments for data acquisition system are presented as well.

In this work a set of simulations that aim at the optimization of Micropattern Gaseous Detectors (MPGD) for applications in X-ray fluorescence imaging in the energy range of 3 – 30 keV is presented. By studying the statistical distribution of electrons from interactions of X-rays with gases, the energy resolution limits after charge multiplication for 6 keV X-ray photons in Ar/CO 2 (70/30) and Kr/CO 2 (90/10) were calculated, resulting in energy resolutions of 15.4(4)% and 14.6(2)% respectively. These two mixtures were studied in simulations to evaluate the advantages of using krypton-based mixtures to reduce the presence of escape peaks in fluorescence spectra. A model to evaluate the X-ray fluorescence from the conductive materials inside the detectors was implemented, serving as a tool to estimate the extent of contamination of fluorescence spectra when using copper or aluminum layers in the material composition of MPGDs. • Optimization studies of large gaseous imaging X-ray fluorescence detectors. • Simulations evaluating the best energy resolutions possible to achieve. • Assessment of spectra contamination by copper fluorescence from detector materials. • Evaluation of the capability to identify different elements by X-ray fluorescence. [ABSTRACT FROM AUTHOR]

Gas Electron Multiplier (GEM) is one of the mostly used technologies in the High Energy Physics (HEP) experiments. GEMs are widely used as tracking devices due to their high-rate handling capability and good position resolution. An initiative is taken to study the stability in performance of the GEM chamber prototypes in the laboratory using external radiation for Argon/CO 2 gas mixture in 70/30 volume ratio. The effect of ambient parameters on the gain and energy resolution are studied. Very recently some behavioural changes in the performance of a single-mask GEM chamber is observed. The details of the experimental setup, methodology and results are reported here. [ABSTRACT FROM AUTHOR]

A novel ceramic Gas Electron Multiplier (GEM) has been developed to meet the demand of high counting rate for the neutron detection which is an alternative to 3He-based detector at China Spallation Neutron Source (CSNS). An experiment was performed to measure the neutron transmittance of ceramic-GEM and FR4-GEM at the small angle neutron scattering (SANS) instrument. The result showed the ceramic-GEM has higher transmittance and less self-scattering especially for cold neutrons. One single ceramic GEM could give a gain of 102-104 in the mixture gas of Ar and CO2 (90%:10%) and its energy resolution was about 27.7% by using 55Fe X ray of 5.9 keV. A prototype has been developed in order to investigate the performances of the ceramic GEM-based neutron detector. Several neutron beam tests, including detection efficiency, spatial resolution, two-dimensional imaging, and wavelength spectrum, were carried out at CSNS and China Mianyang Research Reactor (CMRR). The results show that the ceramic GEM-based neutron detector is a good candidate to measure the high intensity neutrons.

Introduced in the late 70s of the last century, a new generation of position-sensitive sensors named micro-pattern gaseous detectors (MPGDs) allows to detect and localize ionizing radiation with sub-mm accuracy and high-rate capability. Performing and reliable, MPGDs are gradually replacing detection systems based on multiwire proportional chambers, and find applications in particle physics, astrophysics, plasma diagnostics and other fields. [ABSTRACT FROM AUTHOR]

Purpose: A nanodosimeter is a type of detector which measures single ionizations in a small gaseous volume in order to obtain ionization cluster size probability distributions for characterization of radiation types. Working nanodosimeter detectors are usually bulky machines which require a lot of space. In this work, the authors present a compact ceramic nanodosimeter detector and report on first measurements of cluster size distributions of 5 MeV alpha particles. Methods: Single ionization measurements are achieved by applying a weak electric field to collect positive ions in a hole in a ceramic plate. Inside the ceramic plate, due to a strong electric field, the ions are accelerated and produce impact‐ionizations. The resulting electron avalanche is detected in a read‐out electrode. A Bayesian unfolding algorithm is then applied to the experimentally obtained cluster size distributions to reconstruct the true cluster size distributions. Results: Experimentally obtained cluster size distributions by the compact nanodosimeter detector are presented. The reconstructed cluster size distributions agreed well with Monte Carlo simulated cluster size distributions for small volumes (diameter = 2.5 nm). For larger volumes, discrepancies between the reconstructed cluster size distributions and cluster size distributions from Monte Carlo simulations were observed. Conclusions: For the first time, ionization cluster size probability distributions could be obtained by a small and compact nanodosimeter detector. This signifies the achievement of a critical step toward the wide application of nanodosimetric characterization of radiation types including in clinical environments. [ABSTRACT FROM AUTHOR]

This paper presents the performance of a 3GEM in terms of identification of high and low beta energy radiation sources through the energy distribution of the main beta radiation sources used for industrial application 90Sr and 204Tl. We compare the beta radiation theoretical energy loss into the drift zone with experimental energy distribution at different 3GEM voltages. The experimental results show that the Most Probable Value (MPV) of the fitted Landau distribution obtained from 90Sr and 204Tl obtained a degree of error lower than 14% in comparison to the theoretical calculation. Additionally, high energy beta radiation source (90Sr) is identified in comparison to low energy (204Tl) - taking into account the MPV and sigma values from the fitted Landau distribution. These results are essential to design and implement a new application that utilizes the performance and special characteristics of the 3GEM for beta radiation detection and identification.

This paper presents the performance of a 3GEM in terms of identification of high and low beta energy radiation sources through the energy distribution of the main beta radiation sources used for industrial application 90Sr and 204Tl. We compare the beta radiation theoretical energy loss into the drift zone with ex perimental energy distribution at different 3GEM voltages. The ex perimental results show that the Most Probable Value (MPV) of the fitted Landau distribution obtained from 90Sr and 204Tl obtained a degree of error lower than 14% in comparison to the theoretical calculation. Additionally, high energy beta radiation source (90Sr) is identified in comparison to low energy (204Tl) - taking into account the MPV and sigma values from the fitted Landau distribution. These results are essential to design and implement a new application that utilizes the performance and special characteristics of the 3GEM for beta radiation detection and identification. [ABSTRACT FROM AUTHOR]

The quality control of thin film thickness measurements through the transmission and counting of beta and X-ray radiation has achieved very competitive precision with values to 0.2%. However, when the attenuated intensities by the thin film under measurement is above 90%, the method of counting beta or X-ray radiation generates a dramatic degradation in the precision to 30%. This work presents a new method to obtain and analyze thicknesses of aluminum and copper thin films using energy distribution information provided by a triple gas electron multiplier detector (3GEM). The method is based on the ratio of the peak of the Landau distribution generated by the background detection and the peak of the Gaussian distribution of soft X-ray photons generated by the radiation transmission through the thin films emitted by a 55Fe radiation source. The results improve the thickness measurement precision with respect to the radiation counting method when the intensity attenuated by the thin film is greater than 95% compared to precision values less than or equal to 30% obtained with the counting method to values below 10% achieved with the newly reported energy distribution method. [ABSTRACT FROM AUTHOR]

The study of resistive electrode thick gas electron multipliers (RETGEMs) of various designs is described. Four types of RETGEMs were tested. One was made of a substrate of a flame-retardant glass epoxy FR4 board coated with graphite as a resistive layer. The second was made of an FR4 board laminated with Kapton as a resistive layer. The third was made of a polyvinyl chloride (PVC) board coated with graphite as a resistive layer. Finally, a RETGEM with a diamond-like carbon coating produced by CERN was also tested. Multiple characteristics of the single RETGEM detector, such as absolute gas gains and maximum applicable voltages, were measured for all four types of RETGEMs at various voltages applied to the RETGEMs and various sizes of induction gaps, using Cm-244 alpha and F-55 X-ray sources. The results have shown that the highest absolute gas gain is achieved with the FR4 board laminated with Kapton. On the other hand, the PVC board coated with graphite gives the minimum voltage at which the signal can still be observed. [ABSTRACT FROM AUTHOR]

We have developed a gas electron multiplier (GEM)-based time projection chamber (TPC) for the H-dibaryon search experiment at J-PARC. High-rate K − beam particles enter a TPC gas volume of approximately 0.2 m3, in a direction perpendicular to the electric field. A long-rectangular hollow section is located inside the TPC volume to accommodate a diamond target. We commissioned the TPC using 230-MeV protons with beam rates of up to 1 MHz. The TPC data acquisition system collected 5768 pad signals in full readout mode, with almost 100% efficiency, at a preset trigger rate of 230 Hz. We operated the TPC in an Ar/CH 4 gas mixture (90/10) without a magnetic field. The spatial resolutions on the pad plane are measured to be 400– 700 μ m , which correspond to 230– 300 μ m in a magnetic field of 1 T. We confirmed high tracking capability at beam rates of up to 1 MHz. [ABSTRACT FROM AUTHOR]

In this work we show the operation and results of an X-ray fluorescence imaging system using a cascade of three gas electron multipliers (GEM) and a pinhole assembly. The detector operates in Ar/CO 2 (90/10) at atmospheric pressure, with resistive chains applied to the strip readout, which allow to use only five electronic channels: two for each dimension and a fifth for energy and trigger. The corrections applied to the energy spectra to compensate for small changes in the signal amplitude and also differences in gain throughout the sensitive area are described and the clear improvement of the energy resolution is shown. To take advantage of the simultaneous sensitivity to the energy and to the position of interaction, a color scale matching the energy spectrum to the RGB range was applied, resulting in images where the color has a direct correspondence to the energy in each pixel and the intensity is reflected by the brightness of the image. The results obtained with four different color pigments are shown. [ABSTRACT FROM AUTHOR]

This work presents recent efforts in optimization of Gas Electron Multiplier (GEM) detector simulations developed so far. The mentioned triple-GEM based measurement systems were already tested at the WEST project and other devices recording soft X-ray (SXR) plasma radiation in the target range of 2-15 keV. Long term plans may envisage usage of gaseous detector based SXR diagnostics in DEMO reactor for real time plasma monitoring and control, as high neutron fluxes preclude application of semiconductor-based technologies. Conditions in fusion reactors as well as in currently operating devices necessitate simulating the interactions of high-energy photons and neutrons with the detector parts, including proper handling of primary ionization electrons paths, gas mixture fluorescence and collisions with detector materials. For this use case a full-detector simulation software was created based on the already existing interface and previous results obtained so far within the group. It combines Geant4 package for interactions with solid parts of the detector, Garfield++ for electron avalanching, Heed for X-ray interaction with gas, Gmsh and Elmer for meshing and electrostatics and introduces hybrid approach to the simulation of electron drift in different manner depending on the electron position with respect to multiplication stage. To optimize the computation time software employs precomputation algorithms in later stages of the electron cascades. The expected response profiles of the triple-GEM detector, exposed to 55Fe calibration source radiation, were simulated and verified by comparing them with experimental data. • Extreme conditions in fusion reactors encourage application of GEM detectors for tokamak X-ray diagnostics. • Hybrid simulation software combines several numerical methods in different regimes. • New method uses precomputed distributions to speedup the avalanches. • Simulation results were tested against experimental data. [ABSTRACT FROM AUTHOR]

Abstract The synergic interplay between nuclear physics, detector technology and solid state and surface sciences is a fundamental aspect of the development of new neutron detection devices. The synthesis technique and the physical–chemical properties of the B 4 C films used as a neutron-to-charged particle converter are described in relation to the GEM side-on thermal neutron detector. Neutron detection is performed allowing scattered neutrons to be converted into charged particles by means of a series of sheets covered by 10B-enriched boron carbide (B 4 C) layers placed along their flight path inside the detector. The extremely interesting performance shown by the detector in neutron diffraction measurements at the ISIS spallation neutron sources are discussed and related to the chemical–physical properties of the converting layers. [ABSTRACT FROM AUTHOR]

Abstract A large Time Projection Chamber is the main device for tracking and charged-particle identification in the ALICE experiment at the CERN LHC. After the second long shutdown in 2019/20, the LHC will deliver Pb beams colliding at an interaction rate of about 50 kHz, which is about a factor of 50 above the present readout rate of the TPC. This will result in a significant improvement on the sensitivity to rare probes that are considered key observables to characterize the QCD matter created in such collisions. In order to make full use of this luminosity, the currently used gated Multi-Wire Proportional Chambers will be replaced. The upgrade relies on continuously operated readout detectors employing Gas Electron Multiplier technology to retain the performance in terms of particle identification via the measurement of the specific energy loss by ionization d E /d x. A full-size readout chamber prototype was assembled in 2014 featuring a stack of four GEM foils as an amplification stage. The performance of the prototype was evaluated in a test beam campaign at the CERN PS. The d E /d x resolution complies with both the performance of the currently operated MWPC-based readout chambers and the challenging requirements of the ALICE TPC upgrade program. Detailed simulations of the readout system are able to reproduce the data. [ABSTRACT FROM AUTHOR]

The GEM-TPC described herein will be part of the standard beam-diagnostics equipment of the Super-FRS. This chamber will provide tracking information for particle identification at rates up to 1 MHz on an event-by-event basis. The key requirements of operation for these chambers are: close to 100% tracking efficiency under conditions of high counting rate, spatial resolution below 1 mm and a superb large dynamic range covering projectiles from Z = 1 up to Z = 92 . The current prototype consists of two GEM-TPCs inside a single vessel, which are operating independently and have electrical drift fields in opposite directions. The twin configuration is done by flipping one of the GEM-TPCs on the middle plane with respect to the second one. In order to put this development in context, the evolution of previous prototypes will be described and its performances discussed. Finally, this chamber was tested at the University of Jyväskylä accelerator with proton projectiles and at GSI with Uranium, Xenon, fragments and Carbon beams. The results obtained have shown a position resolution between 120 to 300 μ m at moderate counting rate under conditions of full tracking efficiency. [ABSTRACT FROM AUTHOR]

Gain prediction theory of single foil Gas Electron Multiplier detector was developed. Gas electron multiplier (GEM) detector with single foil was developed. Soft X-ray spectra with an energy of 5.9 keV emitted by the isotope Fe-55 were measured. On this basis, the dependence of gain and energy resolution from the detector voltage was determined. The simple theory of gain dependence on various detector parameters was developed. Preliminary results of the study confirmed the potential usefulness of the GEM detector as a substitute for the multiwire proportional chamber.

We report on discharge probability studies with a single Gas Electron Multiplier (GEM) under irradiation with alpha particles in Ar- and Ne-based gas mixtures. The discharge probability as a function of the GEM absolute gain is measured for various distances between an alpha source and the GEM. We observe that the discharge probability is the highest when the charge deposit occurs in the closest vicinity of the GEM holes, and that the breakdown limit is lower for argon mixtures than for neon mixtures. Our experimental findings are in line with the well-grounded hypothesis of the charge density being the limiting factor of GEM stability against discharges. A detailed comparison of the measurements with GEANT4 simulations allowed us to extract the critical charge density leading to the formation of a spark in a GEM hole. This number is found to be within the range of ( 5 − 9 ) × 1 0 6 electrons after amplification, and it depends on the gas mixture. [ABSTRACT FROM AUTHOR]

Time Projection Chamber (TPC) has been chosen as the main tracking system in several high-flux and high repetition rate experiments. These include on-going experiments such as ALICE and future experiments such as PANDA at FAIR and ILC. Different R&D activities were carried out on the adoption of Gas Electron Multiplier (GEM) as the gas amplification stage of the ALICE-TPC upgrade version. The requirement of low ion feedback has been established through these activities. Low ion feedback minimizes distortions due to space charge and maintains the necessary values of detector gain and energy resolution. In the present work, Garfield simulation framework has been used to study the related physical processes occurring within single, triple and quadruple GEM detectors. Ion backflow and electron transmission of quadruple GEMs, made up of foils with different hole pitch under different electromagnetic field configurations (the projected solutions for the ALICE TPC) have been studied. Finally a new triple GEM detector configuration with low ion backflow fraction and good electron transmission properties has been proposed as a simpler GEM-based alternative suitable for TPCs for future collider experiments. [ABSTRACT FROM AUTHOR]

In CBM Experiment at FAIR, dimuons will be detected by a Muon Chamber (MUCH) consisting of segmented absorbers of varying widths and tracking chambers sandwiched between the absorber-pairs. In this fixed target heavy-ion collision experiment, operating at highest interaction rate of 10 MHz for Au+Au collision, the inner region of the 1st detector will face a particle rate of 1 MHz/cm 2 . To operate at such a high particle density, GEM technology based detectors have been selected for the first two stations of MUCH. We have reported earlier the performance of several small-size GEM detector prototypes built at VECC for use in MUCH. In this work, we report on a large GEM prototype tested with proton beam of momentum 2.36 GeV/c at COSY-Jülich Germany. The detector was read out using nXYTER operated in self-triggering mode. An efficiency higher than 96% at Δ V GEM = 375.2 V was achieved. The variation of efficiency with the rate of incoming protons has been found to vary within 2% when tested up to a maximum rate of 2.8 MHz/cm 2 . The gain was found to be stable at high particle rate with a maximum variation of ∼9%. [ABSTRACT FROM AUTHOR]

A large Time Projection Chamber (TPC) is the main device for tracking and charged-particle identification in the ALICE experiment at the CERN LHC. After the second long shutdown in 2019–2020, the LHC will deliver Pb beams colliding at an interaction rate up to 50 kHz, which is about a factor of 100 above the present read-out rate of the TPC. To fully exploit the LHC potential the TPC will be upgraded based on the Gas Electron Multiplier (GEM) technology. A prototype of an ALICE TPC Outer Read-Out Chamber (OROC) was equipped with twelve large-size GEM foils as amplification stage to demonstrate the feasibility of replacing the current Multi Wire Proportional Chambers with the new technology. With a total area of ∼0.76 m 2 it is the largest GEM-based detector built to date. The GEM OROC was installed within a test field cage and commissioned with radioactive sources. [ABSTRACT FROM AUTHOR]

The International Linear Collider (ILC) is a future electron–positron collider with centre of mass energy of 500–1000 GeV. The International Large Detector (ILD) is one of two detector concepts at the ILC. Its high precision tracking system consists of Silicon sub-detectors and a Time Projection Chamber (TPC) equipped with micro-pattern gas detectors (MPGDs). Within the framework of the LCTPC collaboration, a Large Prototype (LP) TPC has been built as a demonstrator. This prototype has been equipped with Gas Electron Multiplier (GEM) modules and studied with electron beams of energies 1–6 GeV at the DESY test beam facility. The performance of the prototype detector and the extrapolation to the ILD TPC is presented here. In addition, ongoing optimisation studies and R&D activities in order to prepare the next GEM module iteration are discussed. [ABSTRACT FROM AUTHOR]

Spatial resolution of GEM-based tracking detectors is determined in the simulation and measured in the experiments. The simulation includes GEANT4 implemented transport of high energy electrons with careful accounting of atomic relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing with accounting of diffusion, gas amplification fluctuations, distribution of signals on readout electrodes, electronics noise and particular algorithm of final coordinate calculation (center of gravity). The simulation demonstrates that the minimum of spatial resolution of about 10 μm can be achieved with a gas mixture of Ar − CO 2 (75–25 %) at a strips pitch from 250 μm to 300 μm. At a larger pitch the resolution quickly degrades reaching 80–100 μm at a pitch of 460–500 μm. Spatial resolution of low-material triple-GEM detectors for the DEUTERON facility at the VEPP-3 storage ring is measured at the extracted beam facility of the VEPP-4 M collider. One-coordinate resolution of the DEUTERON detector is measured with electron beam of 500 MeV, 1 GeV and 3.5 GeV energies. The determined value of spatial resolution varies in the range from approximately 35 μm to 50 μm for orthogonal tracks in the experiments. [ABSTRACT FROM AUTHOR]

In this work we describe the ongoing construction of a Time Projection Chamber-based (TPC) spectrometer for light charged particles utilising magnetic field as a means for energy measurement, combining Multi Wire Proportional Chambers (MWPC) with Timepix3 pixel detectors for improved spatial and angular resolution. The spectrometer will be operated at the Institute of Experimental and Applied Physics (IEAP) Van-de-Graaff facility with the goal of verifying the so-called ATOMKI anomaly (deviation in the distribution of the opening angle between electrons and positrons originating in internal pair creations – IPC – in the decay of 8Be and 4He excited nuclei). Description of the detectors is provided along with a few results. [ABSTRACT FROM AUTHOR]