GEM detectors for COMPASS

Citation
B. Ketzer et al., GEM detectors for COMPASS, IEEE NUCL S, 48(4), 2001, pp. 1065-1069
Citations number
7
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Nuclear Emgineering
Journal title
IEEE TRANSACTIONS ON NUCLEAR SCIENCE
ISSN journal
0018-9499 → ACNP
Volume
48
Issue
4
Year of publication
2001
Part
1
Pages
1065 - 1069
Database
ISI
SICI code
0018-9499(200108)48:4<1065:GDFC>2.0.ZU;2-U
Abstract
For the small-area tracking of particles within COMPASS (common muon and pr oton apparatus for structure and spectroscopy), a new fixed target experime nt at CERN/SPS, several large-size (31 x 31 cm(2)) detectors based on the g as electron multiplier (GEM), have been built. These new devices, consistin g of several GEM amplification stages with a two-coordinate readout, combin e good spatial resolution with high rate capability, which is required by t he large particle flux near the beam. At the same time, the material expose d to the beam is minimized in order not to spoil the mass resolution of the spectrometer. The first detectors out of a total of 20 were subject to ext ensive tests in the beam and in the laboratory, showing that full (i.e., > 98%) detection efficiency for minimum ionizing particles can be achieved at a total effective gain of 6000. Ongoing research work focuses on discharge s triggered by heavily ionizing particles entering the detectors. Systemati c studies of the energy released in discharges and their probability of occ uring at all as a function of a variety of parameters suggest several means to minimize their impact on detector performance. First results of the ope rational characteristics of these detectors in the real COMPASS beam are pr esented.