Abstract
The atomic scattering factor in the energy range of 11.2-15.4 keV for the ASTRO-H Soft X-ray Telescope (SXT) is reported. The large effective area of the SXT makes use of photon spectra above 10 keV viable, unlike most other X-ray satellites with total-reflection mirror optics. Presence of gold's L-edges in the energy band is a major issue, as it complicates the function of the effective area. In order to model the area, the reflectivity measurements in the 11.2-15.4 keV band with the energy pitch of 0.4 - 0.7 eV were made in the synchrotron beam-line Spring-8 BL01B1. We obtained atomic scattering factors f1 and f2 by the curve fitting to the reflectivities of our witness sample. The edges associated with the L-I, II, and III transitions are identified, of which the depths are found to be roughly 60% shallower than those expected from the Henke's atomic scattering factor.
Highlights
The international X-ray observatory ASTRO-H [1], later renamed HITOMI, was launched on February 17, 2016(JST)
One of the hurdles in constructing the Soft X-ray Telescope (SXT) response is to obtain the accurate reflectivity around the complex gold L edges, which appear in the 11–15 keV band
In order to model the effective-area curve in the edge bands, the reflectivity of the SXT’s gold surface with a precise energy pitch should be measured, on which we focus in this paper
Summary
The international X-ray observatory ASTRO-H [1], later renamed HITOMI, was launched on February 17, 2016(JST). The ASTRO-H SXS has in principle a much higher potential to detect the line than any of the past X-ray instruments, due to its superior energy-resolution. Very fine calibration of the effective area of the telescope SXT, at around the gold edges, is essential to exploit fully the high resolution of the SXS. One of the hurdles in constructing the SXT response is to obtain the accurate reflectivity around the complex gold L edges, which appear in the 11–15 keV band. One of the issues of the SXTs response construction is to know the reflectivity around the gold L edges that appears in the 11-15 keV band. In order to model the effective-area curve in the edge bands, the reflectivity of the SXT’s gold surface with a precise energy pitch should be measured, on which we focus in this paper. We here present the result of our experiment, in which we have accomplished the finest energy-pitch measurements of 0.4–0.7 eV, ever reported at this energy range for the SXT reflector
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