用HARPO TPC首次测量gamma-ray光束在1.74到74 MeV之间的偏振不对称性
First measurement of polarisation asymmetry of a gamma-ray beam between 1.74 to 74 MeV with the HARPO TPC
摘要：
目前的$γ$射线望远镜在100 keV和100 MeV之间的能量范围内存在灵敏度差距，并且没有对1 MeV以上的宇宙源进行过偏振测量。过去和现在的e $^+$ e $^-$对望远镜在较低能量时受到被动钨转换板中电子的多次散射的限制。这导致低的角分辨率，并且因此，对低于1GeV的点源的灵敏度下降。由于相同的原因，由转换平面的方位角携带的偏振信息丢失。HARPO（密封氩偏振计）是一个研究开发计划，以验证气体探测器（时间投影室或TPC）作为高角分辨率和灵敏度望远镜和偏振计的操作，用于宇宙源的$γ$射线。它是朝着未来MeV-GeV范围的空间仪器迈出的第一步。我们建造并表征了一个30厘米的立方演示器[SPIE 91441 M]，并将其放入日本新斯巴鲁加速器的极化$γ$射线束中。数据是在光子能量从1.74 MeV到74 MeV，并与不同的偏振配置。我们描述的实验装置在梁。然后，我们描述了我们开发的软件来重建光子转换事件，特别关注低能量。我们还描述了用于比较结果的检测器的彻底模拟。最后，我们将提出的性能检测器提取从这个分析和初步测量的偏振不对称性。这种气体TPC原型在$γ$射线束中的束测试资格可以在不久的将来为MeV-GeV能量范围内的高性能$γ$射线天文学和偏振测量开辟道路。
英文摘要：
Current $γ$-ray telescopes suffer from a gap in sensitivity in the energy range between 100keV and 100MeV, and no polarisation measurement has ever been done on cosmic sources above 1MeV. Past and present e$^+$e$^-$ pair telescopes are limited at lower energies by the multiple scattering of electrons in passive tungsten converter plates. This results in low angular resolution, and, consequently, a drop in sensitivity to point sources below 1GeV. The polarisation information, which is carried by the azimuthal angle of the conversion plane, is lost for the same reasons. HARPO (Hermetic ARgon POlarimeter) is an R\&D program to characterise the operation of a gaseous detector (a Time Projection Chamber or TPC) as a high angular-resolution and sensitivity telescope and polarimeter for $γ$ rays from cosmic sources. It represents a first step towards a future space instrument in the MeV-GeV range. We built and characterised a 30cm cubic demonstrator [SPIE 91441M], and put it in a polarised $γ$-ray beam at the NewSUBARU accelerator in Japan. Data were taken at photon energies from 1.74MeV to 74MeV, and with different polarisation configurations. We describe the experimental setup in beam. We then describe the software we developed to reconstruct the photon conversion events, with special focus on low energies. We also describe the thorough simulation of the detector used to compare results. Finally we will present the performance of the detector as extracted from this analysis and preliminary measurements of the polarisation asymmetry. This beam-test qualification of a gas TPC prototype in a $γ$-ray beam could open the way to high-performance $γ$-ray astronomy and polarimetry in the MeV-GeV energy range in the near future.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
