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Issue A&A
Volume 411, Number 1, November III 2003
Special letters issue on: first science with integral
Page(s) L173 - L177
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20031208



A&A 411, L173-L177 (2003)
DOI: 10.1051/0004-6361:20031208

Letter

In-flight calibrations of IBIS/PICsIT

G. Malaguti1, A. Bazzano2, A. J. Bird3, G. Di Cocco1, L. Foschini1, P. Laurent4, A. Segreto5, J. B. Stephen1 and  P. Ubertini2

1  Istituto di Astrofisica Spaziale e Fisica Cosmica, IASF/CNR, Sezione di Bologna, Italy
2  Istituto di Astrofisica Spaziale e Fisica Cosmica, IASF/CNR, Roma, Italy
3  School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK
4  CEA, Saclay, France
5  Istituto di Astrofisica Spaziale e Fisica Cosmica, IASF/CNR, Sezione di Palermo, Italy

(Received 11 July 2003 / Accepted 1 August 2003)

Abstract
PICsIT (Pixellated Imaging CaeSium Iodide Telescope) is the high energy detector of the IBIS telescope on-board the INTEGRAL satellite. It consists of 4096 independent detection units, ~0.7 cm 2 in cross-section, operating in the energy range between 175 keV and 10 MeV. The intrinsically low signal to noise ratio in the gamma-ray astronomy domain implies very long observations, lasting 105- 106 s. Moreover, the image formation principle on which PICsIT works is that of coded imaging in which the entire detection plane contributes to each decoded sky pixel. For these two main reasons, the monitoring, and possible correction, of the spatial and temporal non-uniformity of pixel performances, expecially in terms of gain and energy resolution, is of paramount importance. The IBIS on-board 22Na calibration source allows the calibration of each pixel at an accuracy of <0.5% by integrating the data from a few revolutions at constant temperature. The two calibration lines, at 511 and 1275 keV, allow also the measurement and monitoring of the PICsIT energy resolution which proves to be very stable at ~19% and ~9% (FWHM) respectively, and consistent with the values expected analytical predictions checked against pre-launch tests.


Key words: gamma-ray telescopes -- imaging detectors -- gamma-ray astronomy

Offprint request: G. Malaguti, malaguti@bo.iasf.cnr.it




© ESO 2003


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