二甲醚气体像素探测器的光谱和偏振特性
Spectral and polarimetric characterization of the Gas Pixel Detector filled with dimethyl ether
摘要：
气体像素探测器属于非常有限的一类气体探测器，用于测量天体物理源发射中的X射线偏振。X射线光子被吸收和光电子传播的混合物的选择，深刻地影响了仪器的能量范围及其在增益，轨道尺寸和最终偏振灵敏度方面的性能。在这里，我们提出了表征的气体像素检测器与一个1厘米厚的细胞充满了二甲醚（DME）在0.79大气压，选择在其他混合物中的非常低的扩散系数。在INAF/IASF-Rome建立的校准设施利用布拉格衍射在近45度产生几乎完全偏振和单色的光子。有史以来第一次，我们测量了调制因子和仪器的光谱能力，能量低至2.0 keV，但也在2.6 keV，3.7 keV，4.0 keV，5.2 keV和7.8 keV。这些测量几乎完全覆盖了仪器的能量范围，并允许将所获得的灵敏度与由氦气和DME组成的标准混合物的灵敏度进行比较。
英文摘要：
The Gas Pixel Detector belongs to the very limited class of gas detectors optimized for the measurement of X-ray polarization in the emission of astrophysical sources. The choice of the mixture in which X-ray photons are absorbed and photoelectrons propagate, deeply affects both the energy range of the instrument and its performance in terms of gain, track dimension and ultimately, polarimetric sensitivity. Here we present the characterization of the Gas Pixel Detector with a 1 cm thick cell filled with dimethyl ether (DME) at 0.79 atm, selected among other mixtures for the very low diffusion coefficient. Almost completely polarized and monochromatic photons were produced at the calibration facility built at INAF/IASF-Rome exploiting Bragg diffraction at nearly 45 degrees. For the first time ever, we measured the modulation factor and the spectral capabilities of the instrument at energies as low as 2.0 keV, but also at 2.6 keV, 3.7 keV, 4.0 keV, 5.2 keV and 7.8 keV. These measurements cover almost completely the energy range of the instrument and allows to compare the sensitivity achieved with that of the standard mixture, composed of helium and DME.
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