Charge amplification and transfer processes in the gas electron multiplier

Citation
S. Bachmann et al., Charge amplification and transfer processes in the gas electron multiplier, NUCL INST A, 438(2-3), 1999, pp. 376-408
Citations number
20
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Spectroscopy /Instrumentation/Analytical Sciences","Instrumentation & Measurement
Journal title
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT
ISSN journal
0168-9002 → ACNP
Volume
438
Issue
2-3
Year of publication
1999
Pages
376 - 408
Database
ISI
SICI code
0168-9002(199912)438:2-3<376:CAATPI>2.0.ZU;2-Y
Abstract
We report the results of systematic investigations on the operating propert ies of detectors based on the gas electron multiplier (CEM). The dependence of gain and charge collection efficiency on the external fields has been s tudied in a range of values for the hole diameter and pitch. The collection efficiency of ionization electrons into the multiplier, after an initial i ncrease, reaches a plateau extending to higher values of drift field the la rger the GEM voltage and its optical transparency. The effective gain, frac tion of electrons collected by an electrode following the multiplier, incre ases almost linearly with the collection held, until entering a steeper par allel plate multiplication regime. The maximum effective gain attainable in creases with the reduction in the hole diameter, stabilizing to a constant value at a diameter approximately corresponding to the foil thickness. Char ge transfer properties appear to depend only on ratios of fields outside an d within the channels, with no interaction between the external fields. Wit h proper design, GEM detectors can be optimized to satisfy a wide range of experimental requirements: tracking of minimum ionizing particles, good ele ctron collection with small distortions in high magnetic fields, improved m ulti-track resolution and strong ion feedback suppression in large volume a nd time-projection chambers. (C) 1999 Elsevier Science B.V. All rights rese rved.