Experimental and theoretical study of diffraction properties of various crystals for the realization of a soft gamma-ray Laue lens
Nicolas Barriere, Julien Rousselle, Peter von Ballmoos, Nikolai V. Abrosimov, Pierre Courtois, Pierre Bastie, Thierry Camus, Michael Jentschel, Vladimir N. Kurl… 展开作者
Nicolas Barriere, Julien Rousselle, Peter von Ballmoos, Nikolai V. Abrosimov, Pierre Courtois, Pierre Bastie, Thierry Camus, Michael Jentschel, Vladimir N. Kurlov, Lorenzo Natalucci, Gilles Roudil, Nicolai Frisch Brejnholt, Denis Serre
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12 pages. Accepted for publication in Journal of Applied Crystallography
Crystals are the elementary constituents of Laue lenses, an emerging technology which could allow the realization of a space borne telescope 10 to 100 times more sensitive than existing ones in the 100 keV - 1.5 MeV energy range. This study addresses the current endeavor to the development of efficient crystals for the realization of a Laue lens.
In the theoretical part 35 candidate-crystals both pure and two-components are considered. Their peak reflectivity at 100 keV, 500 keV and 1 MeV is calculated assuming they are mosaic crystals. It results that a careful selection of crystals can allow a reflectivity above 30% over the whole energy range, and even reaching 40% in its lower part. Experimentally, we concentrated on three different materials (Si_{1-x}Ge_x with gradient of composition, mosaic Cu and Au) that have been measured both at ESRF and ILL using highly-monochromatic beams ranging from 300 keV up to 816 keV. The aim was to check their homogeneity, quality and angular spread (mosaicity). These crystals have shown outstanding performance such as reflectivity up to 31% at ~600 keV (Au) or 60% at 300 keV (SiGe) and angular spread as low as 15 arcsec for Cu, fulfilling very well the requirements for a Laue lens application. Unexpectedly, we also noticed important discrepancies with Darwin's model when a crystal is measured using various energies.
CdTe Spectroscopic-Imager Measurements with Bent Crystals for Broad Band Laue Lenses
在天体物理学中，硬X软伽马射线范围（100 keV以上）的几个关键问题需要灵敏度和角分辨率，这是目前技术难以实现的。因此，一种能够聚焦硬X射线和伽马射线的新型仪器是必不可少的。宽带劳厄透镜似乎是满足这些要求的唯一解决方案，它显著提高了X射线和伽马射线望远镜的灵敏度和角分辨率。这种类型的高能光学器件将需要在检测效率、空间分辨率和光谱学方面具有高性能的焦平面检测器。本文介绍了在项目“劳厄透镜技术准备增加（TRILL）”框架中使用Caliste-HD探测器模块所获得的结果。该探测器是在CEA（Commissiona Energie Atomique，Saclay，France）开发的像素光谱仪。它用于在LARIX设施（意大利费拉拉大学）的硬X射线束下获取劳厄透镜弯曲晶体产生的焦斑的光谱图像。
我们介绍了LAUE的现状，该项目由意大利航天局（ASI）支持，致力于开发用于硬X射线/软伽马射线天文学（80-600 keV）的长焦距（可达100米）劳厄透镜。由于它们的聚焦能力，设计目标是将当前仪器在上述能带中的灵敏度提高2个数量级，低至$10^{-8}$光子/（cm $^2$ s keV）的几倍。
本文提出了一种在兆电子伏能区建造天文望远镜的新概念。该概念建立在晶体布拉格衍射的基础上，过去曾讨论过这一点，但到目前为止，在宽能量范围内具有良好灵敏度的设计似乎遥不可及。在本文中，我们指出，如果我们找到方法来调整，在轨道上，在透镜中的所有晶体的个人倾斜，这将允许一个单一的透镜，以良好的效率，覆盖从200千电子伏到2.5兆电子伏的全部范围内的能量在几个观察步骤。其次，我们注意到使用具有双晶体层的透镜将显著增加光子收集。在随附的论文中，我们更详细地描述了我们的整体镜头设计，并提出了我们的第一个原型倾斜调整基座与个别镜头面使用。Keyords：Gamma ray astronomy，Telescope technology，Laue lenses
