Gas Electron Multiplier Readout Research Articles

New technique of ion identification in Accelerator Mass Spectrometry using low-pressure TPC with GEM readout

We have developed and successfully tested a low-pressure Time Projection Chamber (TPC) with Gas Electron Multiplier (GEM) readout for Accelerator Mass Spectrometry (AMS).AMS facility in Novosibirsk has a problem of separating isobar ions of different chemical elements that have the same atomic mass. The typical example is radioactive isotopes 10Be and 10B that are used to date geological objects at a time scale of ten million years. To solve this problem, a new ion identification technique, namely that based on measuring both ion track ranges and ion energies in low-pressure TPCs with GEM readout, has been developed. This technique is proposed to be applied in AMS for dating geological objects, namely for geochronology of Cenozoic era.In this work, we developed a new larger version of the TPC with a dedicated thin silicon nitride window for an efficient passage of ions. The TPC characteristics were studied in isobutane at low pressures using alpha particle sources. In addition, the use of GEM instead of THGEM has been shown to substantially improve the energy resolution at a nominal pressure (50 torr). Using these results and SRIM code simulations, it is shown that isobaric boron and beryllium ions can be effectively separated at AMS, providing efficient dating on a scale of ten million years. This technique will be applied in the AMS facility in Novosibirsk in the near future.

Double-hit separation and dE/dx resolution of a time projection chamber with GEM readout

A time projection chamber (TPC) with micropattern gaseous detector (MPGD) readout is investigated as main tracking device of the International Large Detector (ILD) concept at the planned International Linear Collider (ILC). A prototype TPC equipped with a triple gas electron multiplier (GEM) readout has been built and operated in an electron test beam. The TPC was placed in a 1 T solenoidal field at the DESY II Test Beam Facility, which provides an electron beam up to 6 GeV/c. The performance of the readout modules, in particular the spatial point resolution, is determined and compared to earlier tests. New studies are presented with first results on the separation of close-by tracks and the capability of the system to measure the specific energy loss dE/dx. This is complemented by a simulation study on the optimization of the readout granularity to improve particle identification by dE/dx.

Development of a Segmented GEM Readout detector

Micromegas (Micro-MEsh GAseous Structures) detectors are a type of micro-pattern gaseous detectors. The primary charges are amplified in electron avalanches between a planar anode and a mesh typically 120 μm above the anode. For resistive anode type Micromegas detectors the signal is read out via copper readout strip layers below the anode. A 2D particle position can be reconstructed using two perpendicular readout strip layers below the resistive anode structure.Using a standard 2D resistive anode Micromegas readout structure, a unique 2D particle position reconstruction is only possible if the detector is hit by only one particle at the same time. Ambiguities will occur if multiple particles arrive at the same time. A unique X–Y assignment is strongly complicated.This issue can be resolved by replacing the mesh with a GEM (Gas Electron Multiplier) foil, which is segmented into 0.5 mm wide strips on at least one of the two sides. The GEM strips need to be turned by 45∘ with respect to the Micromegas readout strips. Thus the detector with a GEM foil segmented on both sides has four readout strip directions (X, Y, U and V) and a detector with a GEM foil segmented on only one side has three readout strip directions (X, Y and V).A prototype of such a Segmented GEM Readout (SGR) detector is built with GEM strips and readout strips perpendicular to each other. Test beam measurements with this detector were performed using 120 GeV muons. Results of the test beam measurements are presented here.

Manufacturing of a 70 × 70 mm2 LTCC strip electrode readout for Gas Electron Multiplier detectors

Introduced by Fabio Sauli in 1997, the Gas Electron Multiplier (GEM) technology is commonly used in many high energy physics experiments. It has proven unique value in many scientific domains and adaptability to new research tasks. Typically, the GEM detectors are made with polyimide films (GEM foils and readout plate), halogen-free FR4 epoxy resins (supporting and stretching structures), conductive copper layers, etc. Because of outgassing and ageing, those components release in time residues of dust, moisture, and vapors. The residues pollute the gas mixture and consequently degrade the detector's working parameters. To avoid such a problem, devices can be constantly flushed by pure gas from an external source. This solution is not optimal for autonomous space detectors because of volume and weight limitations. The paper describes the successive work to develop an autonomous GEM detector without a gas mixture circulation system. As a solution, the use of Low-Temperature Cofired Ceramics (LTCC) materials was proposed and validated. The dedicated LTCC readout plates were manufactured and tested, and results are presented.

Leakage current-induced effects in the silicon microstrip and gas electron multiplier readout chain and their compensation method

Leakage current flowing into the charge sensitive amplifier (CSA) is a common issue in many radiation detection systems as it can increase overall system noise, shift a DC baseline or even lead a recording channel to instability. The commonly known leakage current contributor is a detector, however other system components like wires or an input protection circuit may become a serious problem. Compensation of the leakage current resulting from the electrostatic discharge (ESD) protection circuit by properly sizing its components is possible only for a narrow temperature range. Moreover, the leakage current from external sources can be significantly larger. Many applications, especially High Energy Physics (HEP) experiments, require a fast baseline restoration for high input hit rates by applying either a low-value feedback resistor or a high feedback resistance combined with a pulsed reset circuit. Leakage current flowing in the feedback in conjunction with a large feedback resistance supplied with a pulsed reset results in a significant voltage offset between the CSA input and output which can cause problems (e.g. fake hits or instability). This paper shows an issue referred to the leakage current of the ESD protection circuit flowing into the input amplifier. The following analysis and proposed solution is a result of the time and energy readout ASIC project realization for the Compressed Baryonic Matter (CBM) experiment at FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. This chip is purposed to work with microstrip and gaseous detectors, with high average input pulses frequencies (250 kHit/s per channel) and the possibility to process input charge of both polarities. We present measurements of the test structure fabricated in UMC 180 nm technology and propose a solution addressing leakage current related issues. This work combines the leakage current compensation capabilities at the CSA level with high, controllable value of the amplifier feedback resistor independent of the leakage current level and polarity. The simulation results of the double, switchable, Krummenacher circuit-based feedback application in the CSA with a pulsed reset functionality are presented.

A compact Time Projection Chamber for the Crystal Ball

We report on a development of a compact Time Projection Chamber with triple Gas Electron Multiplier readout to replace the current tracking detector in the Crystal Ball/TAPS Experiment at the A2 Tagged Photon Facility at MAMI in Mainz, Germany. Challenges are the limitations in size and the absence of a longitudinal magnetic flied.

A study with a small prototype TPC for the international linear collider experiment

A time projection chamber (TPC) is a strong candidate for the central tracker of the international linear collider (ILC) experiment and we have been conducting a series of cosmic ray experiments under a magnetic field up to 4T, using a small prototype TPC with a replaceable readout device: multi-wire proportional chamber (MWPC) or gas electron multiplier (GEM). We first confirmed that the MWPC readout could not be a fall-back option of the ILC-TPC under a strong axial magnetic field of 4T since its spatial resolution suffered severely from the so called E×B effect in the vicinity of the wire planes. The GEM readout, on the other hand, was found to be virtually free from the E×B effect and gave the resolution determined by the transverse diffusion of the drift electrons (diffusion limited). Furthermore, GEMs allow a wider choice of gas mixtures than MWPCs. Among the gases we tried so far a mixture of Ar–CF4-isobutane seems promising as the operating gas of the ILC-TPC because of its small diffusion constant especially under a strong magnetic field. We report the spatial resolution obtained with the GEM readout in this gas mixture. Also presented is the spatial resolution of a GEM-based ILC-TPC estimated from the measurement with the prototype.