Effect of the drift field on avalanche gain and charge collection in microgap detectors at high pressure

Fraga, FAF Marques, RF Goncalves, J Goncalo, JR Policarpo, AJPL van Eijk, C Hollander, RW van den Berg, F

Faf. Fraga et al., Effect of the drift field on avalanche gain and charge collection in microgap detectors at high pressure, NUCL INST A, 419(2-3), 1998, pp. 460-463

5

INGLESE

Article

Spectroscopy /Instrumentation/Analytical Sciences","Instrumentation & Measurement

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT

0168-9002 → ACNP

419

2-3

1998

460 - 463

ISI

0168-9002(199812)419:2-3<460:EOTDFO>2.0.ZU;2-P

One of the main drawbacks of the use of microgap structures when used at hi gh pressure (6 bar) at high count rates ( similar to 10(6) s(-1) mm(-2)) is the limited maximum safe gain at which they can be operated. The use of a preamplification device such as the GEM (gas electron multiplier) can overc ome this limitation; however, secondary space charge effects due to charge accumulation at the non-metallic surfaces cannot be neglected and should be minimised. These positive charges are due to the intrinsic multiplication of the GEM device and also to the drift of ions from the anode of the main detector. In this study we present data on the variation of the positive io n collection by the drift electrode versus drift held at several pressures up to 6 bar using a Kr-CO2 mixture. Data were collected with microgaps havi ng several anode and insulator widths. The influence of the drift field in the pulse rise time is also considered. (C) 1998 Elsevier Science B.V. All rights reserved.