PoGOLite - A High Sensitivity Balloon-Borne Soft Gamma-ray Polarimeter
Abstract
We describe a new balloon-borne instrument (PoGOLite) capable of detecting 10% polarisation from 200mCrab point-like sources between 25 and 80keV in one 6 hour flight. Polarisation measurements in the soft gamma-ray band are expected to provide a powerful probe into high-energy emission mechanisms as well as the distribution of magnetic fields, radiation fields and interstellar matter. At present, only exploratory polarisation measurements have been carried out in the soft gamma-ray band. Reduction of the large background produced by cosmic-ray particles has been the biggest challenge. PoGOLite uses Compton scattering and photo-absorption in an array of 217 well-type phoswich detector cells made of plastic and BGO scintillators surrounded by a BGO anticoincidence shield and a thick polyethylene neutron shield. The narrow FOV (1.25msr) obtained with well-type phoswich detector technology and the use of thick background shields enhance the detected S/N ratio. Event selections based on recorded phototube waveforms and Compton kinematics reduce the background to that expected for a 40-100mCrab source between 25 and 50keV. A 6 hour observation on the Crab will differentiate between the Polar Cap/Slot Gap, Outer Gap, and Caustic models with greater than 5 sigma; and also cleanly identify the Compton reflection component in the Cygnus X-1 hard state. The first flight is planned for 2010 and long-duration flights from Sweden to Northern Canada are foreseen thereafter.
Cite
@article{arxiv.0709.1278,
title = {PoGOLite - A High Sensitivity Balloon-Borne Soft Gamma-ray Polarimeter},
author = {Tuneyoshi Kamae and Viktor Andersson and Makoto Arimoto and Magnus Axelsson and Cecilia Marini Bettolo and Claes-Ingvar Björnsson and Gilles Bogaert and Per Carlson and William Craig and Tomas Ekeberg and Olle Engdegård and Yasushi Fukazawa and Shuichi Gunji and Linnea Hjalmarsdotter and Bianca Iwan and Yoshikazu Kanai and Jun Kataoka and Nobuyuki Kawai and Jaroslav Kazejev and Mózsi Kiss and Wlodzimierz Klamra and Stefan Larsson and Grzegorz Madejski and Tsunefumi Mizuno and Johnny Ng and Mark Pearce and Felix Ryde and Markus Suhonen and Hiroyasu Tajima and Hiromitsu Takahashi and Tadayuki Takahashi and Takuya Tanaka and Timothy Thurston and Masaru Ueno and Gary Varner and Kazuhide Yamamoto and Yuichiro Yamashita and Tomi Ylinen and Hiroaki Yoshida},
journal= {arXiv preprint arXiv:0709.1278},
year = {2009}
}
Comments
11 pages, 11 figures, 2 tables