Letter to the Editor

SPI instrumental background characteristics^*

¹ Centre d'Étude Spatiale des Rayonnements, CNRS/UPS, BP 4346, 31028 Toulouse Cedex 4, France
² Max Planck Institut fuer extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
³ Laboratory for High Energy Astrophysics, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁴ Universities Space Research Association, 7501 Forbes Blvd. Seabrook, MD 20706-2253
⁵ DSM/DAPNIA/Service dAstrophysique, CEA Saclay, 91191 Gif-sur-Yvette, France
⁶ Space Science Laboratory, University of California Berkeley, CA 94720, USA
⁷ Istituto di Fisica Cosmica del CNR “G. Occhialini”, via Bassini 15, 20133 Milan, Italy
⁸ Institut de Physique Nucleaire, Universite catholique de Louvain, 1348 Louvain-la-Neuve, Belgium
⁹ Centre de Spectrometrie Nucleaire et de Spectrometrie de Masse, IN2P3-CNRS, 91405 Orsay Campus, France

Corresponding author: P. Jean, jean@cesr.fr

Received: 15 July 2003
Accepted: 30 July 2003

Abstract

In its space environment the INTEGRAL observatory is subject to an intense irradiation by energetic cosmic-ray particles that leads, via nuclear interactions with the telescope and spacecraft materials, to an important background of false events. In this paper we present the characteristics of the instrumental background that is observed in the spectrometer SPI (SPectrometer of INTEGRAL). We explain the tuning that has been performed on the parameters of the anticoincidence system in order to optimise the telescope sensitivity over the full energy range. Temporal variations of the instrumental background are discussed and methods are proposed that allow for their modelling in first order.