Letter to the Editor

Cosmic rays tracks on the PICsIT detector^*

¹ IASF/CNR, sezione di Palermo, via Ugo la Malfa 153, 90146 Palermo Italy
² IASF/CNR, sezione di Bologna, via P. Gobetti 101, 40129 Bologna Italy
³ IASF/ CNR sezione di Roma, via del Fosso del Cavaliere 100, 00133 Roma, Italy
⁴ School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK
⁵ Dipartimento di Fisica Universita' di Bologna, Viale B. Pichat 6/2, 40127 Bologna

Corresponding author: A. Segreto, segreto@pa.iasf.cnr.it

Received: 15 July 2003
Accepted: 16 September 2003

Abstract

Since the first in orbit activation of the PICsIT detector, frequent spikes have been noticed in its count rate. Tracks in the detector images, corresponding to the spikes, indicate that these events are generated by interaction of cosmic rays with the detector plane.
Since these events constitute a significant fraction of the instrument background, a dedicated study has been performed and it has been clarified that the mechanism that leads to spikes and track formation is related to the presence in the CsI crystals of phosphorescence states having decay times of the order of 100 ms. We have also shown that these events, thanks to their temporal characteristics, can be removed from the PICsIT data when the instrument is in Photon by Photon mode. 
Moreover, thanks to the pixellated structure of the PICsIT detector, we have also obtained evidence of the presence of numerous electromagnetic and hadronic showers generated by the primary cosmic rays.