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Communication Dans Un Congrès Année : 2018

HARPO, prototype of a gamma-ray polarimeter: Results of a polarised photon beam test between 1.7 and 74 MeV

S. Amano
  • Fonction : Auteur
P. Bruel
S. Daté
  • Fonction : Auteur
H. Ohkuma
  • Fonction : Auteur
A. Takemoto
  • Fonction : Auteur
M. Yamaguchi
  • Fonction : Auteur

Résumé

Access to the photon polarisation in the 1-100 MeV energy range is a challenge for the next generation of space telescopes. The current telescopes in space are almost blind in this energy range, mainly due to the degradation of the angular resolution of e+e- pair and due to elastic scattering in the matter. Pair-conversion detector technologies as gaseous detectors are a promising alternative to the technologies based on tungsten-converter/thin-sensitive-layer stacks such as COS-B/EGRET/Fermi-LAT, firstly to improve the single-photon angular resolution and secondly for the polarisation information. The use of a time projection chamber (TPC) as a target and a tracking detector will improve by up to one order of magnitude the single-photon angular resolution (0.5° @ 100 MeV) with respect to the Fermi-LAT (5° @ 100 MeV), and by up to a factor of three with respect to what can be expected for silicon detectors (1.0-1.5° @ 100 MeV). With such a good angular resolution, a TPC can close the sensitivity gap at the level of 10^-6 MeV/cm².s) between 3 and 300 MeV despite having e lower sensitive mass. Furthermore, this good single-track angular resolution allows us to measure the linear polarisation fraction. The HARPO (Hermetic ARgon POlarimeter) detector prototype that we built is a high pressure (0.5-4 bar) low pile-up and low-diffusion gas detector. We will present the results of its high-statistics characterisation in the 1.7-74 MeV fully-polarised and non-polarised gamma-ray beam provided by the BL01 line at NewSUBARU. The excellent value of the polarisation asymmetry dilution factor that we measured opens the possibility of having a polarimeter in space working in the MeV-GeV energy range. In conclusion, we will present the design of a balloon-flight prototype ST3G (Self-Triggered Time projection chamber as a Gamma-ray Telescope) which is being developed. We will discuss its expected performance.

Dates et versions

hal-01890896 , version 1 (09-10-2018)

Identifiants

Citer

David Attié, S. Amano, P. Baron, D. Bauduin, D. Bernard, et al.. HARPO, prototype of a gamma-ray polarimeter: Results of a polarised photon beam test between 1.7 and 74 MeV. 35th International Cosmic Ray Conference, Jul 2017, Busan, South Korea. pp.818, ⟨10.22323/1.301.0818⟩. ⟨hal-01890896⟩
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