X-ray CCD operated onboard satellite are contaminated by outgas from organic material used in satellites. This contamination causes a significant reduction in the detection sensitivity of X-ray detectors. In order to prevent such contamination to the Back-Illuminated CCD (BI-CCD) of the Soft X-ray Imager (SXI) onboard ASTRO-H, we have developed a Contamination Blocking Filter (CBF), which consists of ~30nm thick Aluminum and ~200nm thick Polyimide. The CBF is be placed on the top of the CCD camera hood and is required to have a high X-ray transmission in order to take advantage of the high detection efficiency of BI-CCD. We measured the X-ray transmission of three flight candidates of the CBF last October at the SPring-8 and obtained the X-ray transmission of three CBFs in the soft X-ray energy from 0.2 to 1.8 keV which covers the absorption edges around C-K, N-K, O-K, and Al-K including X-ray absorption fine structure (XAFS). In these measurements, we found three CBFs have high X-ray transmission below 2ke V, e.g. ~70% at around 0.5 keV, and determined the thickness of Al and Polyimide to be 220 nm and ~50 nm, respectively. We will calculate the response function of SXI including these results.

Date Published: 31 July 2014
PDF: 8 pages
Proc. SPIE 9144, Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray, 91445D (31 July 2014); doi: 10.1117/12.2056473

Published in SPIE Proceedings Vol. 9144:
Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ray
Tadayuki Takahashi; Jan-Willem A. den Herder; Mark Bautz, Editor(s)