Low energy response of a prototype detector array for the PoGO astronomical hard X-ray polarimeter

J. Kataoka*, M. Kanal, T. Arimoto, T. Ikagawa, M. Saito, N. Ueno, R. Kawai, P. Blandford, T. Chen, G. Kamae, T. Madejski, J. Mizuno, H. Ng, T. Tajima, L. Thurston, A. Barbier, J. Harding, S. Krizmanic, J. Hunter, R. MitchellE. Streitmatter, R. Groth, D. Fernholtz, Y. Marlow, T. Saito, S. Takahashi, H. Gunji, Y. Sakurai, V. Fukazawa, P. Anderson, W. Carlson, M. Klamra, M. Pearce, S. Suhonen, F. Larsson, C. I. Ryde, G. Bjornsson, S. Bogaert, Kishimoto

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

3 Citations (Scopus)


The Polarized Gamma-ray Observer (PoGO) is a new balloon-borne instrument designed to measure polarization from astrophysical objects in the 30-200 keV range. It is under development for the first flight anticipated in 2008. PoGO is designed to minimize the background by an improved phoswich configuration, which enables a detection of 10 % polarization in a 100 mCrab source in a 6-8 hour observation. To achieve such high sensitivity, low energy response of the detector is important because the source count rate is generally dominated by the lowest energy photons. We have developed new PMT assemblies specifically designed for PoGO to read-out weak scintillation light of one photoelectron (1 p.e.) level. A beam test of a prototype detector array was conducted at the KEK Photon Factory, Tsukuba in Japan. The experimental data confirm that PoGO can detect polarization of 80-85 % polarized beam down to 30 keV with a modulation factor 0.25 ± 0.05.

Original languageEnglish
Article number58980J
Pages (from-to)1-11
Number of pages11
JournalProceedings of SPIE - The International Society for Optical Engineering
Publication statusPublished - 2005
Externally publishedYes
EventUV, X-Ray, and Gamma-Ray Space Instrumentation for Astronomy XIV - San Diego, CA, United States
Duration: 2005 Aug 12005 Aug 3


  • Balloon experiment
  • Polarimetry
  • Soft Gamma-rays

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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