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Register a new userStudies on ion back-flow of Time Projection Chamber based on GEM and anode wire grid
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Gated wires are widely used in Time Projection Chamber (TPC) to avoid ion back-flow (IBF) in the drift volume. The anode wires can provide stable gain at high voltage with a long lifetime. However, switching on and off the gated grid (GG) leads to a dead time and also limit the readout efficiency of the TPC. Gas Electron Multiplier (GEM) foil provides a possibility of continuous readout for TPC, which can suppress IBF efficiently while keeping stable gain. A prototype chamber including two layers of GEM foils and anode wires has been built to combine both advantages from GEM and anode wire. Using Garfield++ and the finite element analysis (FEA) method, simulations of the transmission processes of electrons and ions are performed and results on absorption ratio of ions, gain and IBF ratio are obtained. The optimized parameters from simulation are then applied to the prototype chamber to test the IBF and other performances. Both GEM foils are run at low voltage (255V), while most of the gain is provided by the anode wire. The measurement shows that the IBF ratio can be suppressed to ~0.58% with double-layer GEM foils (staggered) at an effective gain about 2500 with an energy resolution about 10%.
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The IBF and the transparent rate of electrons are two essential indicators of TPC, which affect the energy resolution and counting rate respectively. In this paper, we propose several novel strategies of staggered multi-THGEM to suppress IBF, where the geometry of the first layer THGEM will be optimized to increase the electron transparent rate. By Garfield++ simulation, the electron transparency rate can be more than 90% of single THGEM with a optimized large hole. By simulating these configurations of triple and quadruple THGEM structures, we conclude that the IBF can be reduced to 0.2% level in an optimized configuration denoted as ACBA. This strategy for staggered THGEM could have potential applications in future TPC projects.
For the International Large Detector concept at the planned International Linear Collider, the use of time projection chambers (TPC) with micro-pattern gas detector readout as the main tracking detector is investigated. In this paper, results from a prototype TPC, placed in a 1 T solenoidal field and read out with three independent GEM-based readout modules, are reported. The TPC was exposed to a 6 GeV electron beam at the DESY II synchrotron. The efficiency for reconstructing hits, the measurement of the drift velocity, the space point resolution and the control of field inhomogeneities are presented.
In this paper we present the R&D activity on a new GEM-based TPC prototype for AMADEUS, a new experimental proposal at the DA{Phi}NE {Phi}-factory at the Laboratori Nazionali di Frascati (INFN), aiming to perform measurements of the low-energy negative kaons interactions in nuclei. Such innovative detector will equip the inner part of the experiment in order to perfom a better reconstruction of the primary vertex and the secondary particles tracking. A 10x10 cm2 prototype with a drift gap up to 15 cm was realized and succesfully tested at the {pi} M1 beam facility of the Paul Scherrer Institut (PSI) with low momentum hadrons. The measurements of the detector efficiency and spatial resolution have been performed. The results as a function of the gas gain, drift field, front-end electronic threshold and particle momentum are reported and discussed.
A large number of high-energy and heavy-ion experiments successfully used Time Projection Chamber (TPC) as central tracker and particle identification detector. However, the performance requirements on TPC for new high-rate particle experiments greatly exceed the abilities of traditional TPC read out by multi-wire proportional chamber (MWPC). Gas Electron Multiplier (GEM) detector has great potential to improve TPC performances when used as amplification device. In this paper we present the R&D activity on a new GEM-based TPC detector built as a prototype for the inner part for AMADEUS, a new experimental proposal at the DAFNE collider at Laboratori Nazionali di Frascati (INFN), aiming to perform measurements of the low-energy negative kaons interactions in nuclei. In order to evaluate the GEM-TPC performances, a 10x10 cm2 prototype with a drift gap up to 15 cm has been realized. The detector was tested at the pM1 beam facility of the Paul Scherrer Institut (PSI) with low momentum pions and protons, without magnetic field. Drift properties of argonisobutane gas mixtures are measured and compared withMagboltz prediction. Detection efficiency and spatial resolution as a function of a large number of parameters, such as the gas gain, the drift field, the front-end electronic threshold and particle momentum, are illustrated and discussed. Particle identification capability and the measurement of the energy resolution in isobutane-based gas mixture are also reported.
We report on the successful operation of a double phase Liquid Argon Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC) equipped with two dimensional projective anodes with dimensions 10$times$10 cm$^2$, and with a maximum drift length of 21 cm. The anodes were manufactured for the first time from a single multilayer printed circuit board (PCB). Various layouts of the readout views have been tested and optimised. In addition, the ionisation charge was efficiently extracted from the liquid to the gas phase with a single grid instead of two previously. We studied the response and the gain of the detector to cosmic muon tracks. To study long-term stability over several weeks, we continuously operated the chamber at fixed electric field settings. We reproducibly observe that after an initial decrease with a characteristic time of $tauapprox 1.6$ days, the observed gain is stable. In 46 days of operation, a total of 14.6 million triggers have been collected at a stable effective gain of $G_inftysim 15$ corresponding to a signal-to-noise ratio $(S/N)gtrsim 60$ for minimum ionising tracks. During the full period, eight discharges across the LEM were observed. A maximum effective gain of 90 was also observed, corresponding to a signal-to-noise ratio $(S/N)gtrsim 400$ for minimum ionising tracks, or $S/Napprox10$ for an energy deposition of 15 keV on a single readout channel.
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