An active collimator system for a high-energy photon beam

Citation
G. Zeitler et al., An active collimator system for a high-energy photon beam, NUCL INST A, 459(1-2), 2001, pp. 6-15
Citations number
5
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
459
Issue
1-2
Year of publication
2001
Pages
6 - 15
Database
ISI
SICI code
0168-9002(20010221)459:1-2<6:AACSFA>2.0.ZU;2-G
Abstract
Active collimators are designed to both collimate the tagged photon beam an d suppress the background of secondary photons. These secondary photons are generated by interaction processes in the collimator medium. They may reac h the hadron target with a lower energy compared to the energy determined b y the tagging system. Accordingly, those events are tagged with a wrong ene rgy and have to be rejected. By means of a Monte Carlo simulation we invest igated the effect and the performance of an active collimator system and de veloped an optimal design of the collimators to prepare a clean high-energy photon beam. The resulting set-up ensures a precise determination of the t agging efficiency and of the photon flux. The active collimators are a nece ssary tool to correctly determine photoproduction cross-sections. Results o f test measurements at ELSA in Bonn, and MAMI B in Mainz are discussed. Spe cial interest is given to the use of the active collimators in the experime nt to test the GDH sum rule at ELSA up to 3.2 GeV. (C) 2001 Elsevier Scienc e B.V. All rights reserved.