Hole-Type Gaseous Electron Multipliers (GEM)

2014 ◽  
pp. 76-102
Keyword(s):  
Electric Field ◽  
Strong Electric Field ◽  
Drift Region ◽  
Avalanche Multiplication ◽  
Electron Multiplier ◽  
Gas Electron Multiplier ◽  
Gaseous Electron ◽  
Robust Version ◽  
The Family ◽  
Primary Electrons

This chapter describes another popular micropattern detector, the Gas Electron Multiplier (GEM). The GEM belongs to the family of hole-type detectors made of a dielectric sheet metalized on both sides with a matrix of holes through it. When a voltage is applied between the metalized electrodes, a strong electric field is created inside the holes. The electric field is sufficiently strong for avalanche multiplication of primary electrons produced by radiation in a drift region adjacent to the plate. In contrast to other hole-type detectors, GEM is manufactured by a photolithographic technology from thin metalized Kapton sheets. This detector has several unique features (e.g. the possibility to operate in cascade mode to increase the maximum achievable gain or to combine a GEM with other gaseous detectors, MSGC, MICROMEGAS, etc.). Cascaded GEMs are used today in several experiments at CERN and elsewhere. A modified robust version of the GEM, called a “thick GEM,” can operate at gas gains higher than ordinary GEMs and is used in various designs of photodetectors.

The Physics of Operation of Gaseous Detectors and their Main Designs

2014 ◽  
pp. 1-30 ◽  
Keyword(s):  
Electric Field ◽  
Parallel Plate ◽  
Strong Electric Field ◽  
Charged Particles ◽  
High Energy ◽  
Electrical Charge ◽  
Avalanche Multiplication ◽  
Multiplication Process ◽  
Gas Volume ◽  
Primary Electrons

This chapter reviews the principle of operation of gaseous detectors and their main designs. Historically, avalanche gaseous detectors were the first devices allowing one to detect a few, and even single, primary electrons created by ionization of a gas volume. In all existing designs of gaseous detectors, these primary electrons trigger an avalanche of secondary electrons, ions, and photons in the detector region powered by a sufficiently strong electric field. In this way, a low number of initial electrons produce a large electrical charge, which is collected on an anode. In this chapter, the various processes involved in the operation of the gaseous detectors are described step by step. Initially, it describes the interactions of radiation (charged particles and high-energy photons) with gases leading to the creation of primary electrons, as well as electron diffusion and the avalanche multiplication process. Later, the design of classical gaseous detectors developed before the invention of micropattern detectors are reviewed. These include single-wire counters, parallel-plate chambers (including spark and streamer detectors), multi-wire proportional chambers, and resistive plate chambers. Finally, the physics behind the main breakdown mechanisms in gaseous detectors in general are discussed. The material presented in this chapter give the background necessary for a better understanding of the following chapters.

scholarly journals Numerical Investigation on Electron and Ion Transmission of GEM-based Detectors

2018 ◽  
Vol 174 ◽  
pp. 06001
Author(s):  
Purba Bhattacharya ◽  
Sumanya Sekhar Sahoo ◽  
Saikat Biswas ◽  
Bedangadas Mohanty ◽  
Nayana Majumdar ◽  
...  
Keyword(s):  
Field Configuration ◽  
Generation Process ◽  
Simulation Framework ◽  
Physical Processes ◽  
Electron Multiplier ◽  
Gas Electron Multiplier ◽  
Detector Geometry ◽  
Gem Detectors ◽  
Primary Electrons ◽  
Good Percentage

ALICE at the LHC is planning a major upgrade of its detector systems, including the TPC, to cope with an increase of the LHC luminosity after 2018. Different R&D activities are currently concentrated on the adoption of the Gas Electron Multiplier (GEM) as the gas amplification stage of the ALICE-TPC upgrade version. The major challenge is to have low ion feedback in the drift volume as well as to ensure a collection of good percentage of primary electrons in the signal generation process. In the present work, Garfield simulation framework has been adopted to numerically estimate the electron transparency and ion backflow fraction of GEM-based detectors. In this process, extensive simulations have been carried out to enrich our understanding of the complex physical processes occurring within single, triple and quadruple GEM detectors. A detailed study has been performed to observe the effect of detector geometry, field configuration and magnetic field on the above mentioned characteristics.

scholarly journals Development of Gating Foils To Inhibit Ion Feedback Using FPC Production Techniques

2018 ◽  
Vol 174 ◽  
pp. 02007 ◽  
Author(s):  
D. Arai ◽  
K. Ikematsu ◽  
A. Sugiyama ◽  
M. Iwamura ◽  
A. Koto ◽  
...  
Keyword(s):  
Drift Region ◽  
Electron Multiplier ◽  
Gas Electron Multiplier ◽  
Position Resolution ◽  
Electron Transmission ◽  
Printed Circuit ◽  
Flexible Printed Circuit ◽  
Production Techniques ◽  
Time Projection ◽  
Positive Ion

Positive ion feedback from a gas amplification device to the drift region of the Time Projection Chamber for the ILC can deteriorate the position resolution. In order to inhibit the feedback ions, MPGD-based gating foils having good electron transmission have been developed to be used instead of the conventional wire gate. The gating foil needs to control the electric field locally in opening or closing the gate. The gating foil with a GEM (gas electron multiplier)-like structure has larger holes and smaller thickness than standard GEMs for gas amplification. It is known that the foil transmits over 80 % of electrons and blocks ions almost completely. We have developed the gating foils using flexible printed circuit (FPC) production techniques including an improved single-mask process. In this paper, we report on the production technique of 335 μm pitch, 12.5 μm thick gating foil with 80 % transmittance of electrons in ILC conditions.

scholarly journals Axion assisted Schwinger effect

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Valerie Domcke ◽  
Yohei Ema ◽  
Kyohei Mukaida
Keyword(s):  
Electric Field ◽  
Production Rate ◽  
Strong Electric Field ◽  
Background Field ◽  
Chiral Anomaly ◽  
Fermion Mass ◽  
Anomaly Equation ◽  
Electric And Magnetic Fields ◽  
Schwinger Effect ◽  
Momentum Transverse

Abstract We point out an enhancement of the pair production rate of charged fermions in a strong electric field in the presence of time dependent classical axion-like background field, which we call axion assisted Schwinger effect. While the standard Schwinger production rate is proportional to $$ \exp \left(-\pi \left({m}^2+{p}_T^2\right)/E\right) $$ exp − π m 2 + p T 2 / E , with m and pT denoting the fermion mass and its momentum transverse to the electric field E, the axion assisted Schwinger effect can be enhanced at large momenta to exp(−πm2/E). The origin of this enhancement is a coupling between the fermion spin and its momentum, induced by the axion velocity. As a non-trivial validation of our result, we show its invariance under field redefinitions associated with a chiral rotation and successfully reproduce the chiral anomaly equation in the presence of helical electric and magnetic fields. We comment on implications of this result for axion cosmology, focussing on axion inflation and axion dark matter detection.

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