CXO Project Science: X-ray opacity probabilities from HRC-S +Y,-Z vertex

Figures show probability distributions of 60-keV absorption depth, as viewed from the HRC-S +Y,-Z vertex (worst-case location), for 3 locations of the detector. Solid line denotes HRC-S on the HRMA axis; dashed, ACIS-I; and dotted, ACIS-S. Note that x-ray absorption is roughly inversely proportional to the cube of the photon energy; thus, an absorption depth 0.04 at 60 keV corresponds to about 1 at 20 keV.

Of the 2 HRC Next-in-Line (NiL) locations, the more benign x-ray environment is with ACIS-S on the HRMA axis. However, low-opacity lines of sight are much more probable while in NiL position than during HRC-S pointed observations. Furthermore, this is true whether or not the tantalum shielding is on the focus structure.

HRC-S +Y,-Z vertex, with full focus-structure shielding

With full focus-structure shielding and the HRC-S on the HRMA axis, the HRC-S worst-case vertex is shielded in essentially all directions up to about 45 keV. However, even in the more benign HRC Next-in-Line (NiL) position, about 1.3% of the sky (0.15 sr) is transparent down to about 20 keV.

HRC-S +Y,-Z vertex, with no focus-structure shielding

With no focus-structure shielding and the HRC-S on the HRMA axis, only about 0.5% of the sky (0.06 sr) is transparent down to about 20 keV at the HRC-S worst-case vertex. However, even in the more benign HRC Next-in-Line (NiL) position, about 1.8% of the sky (0.2 sr) is transparent down to about 20 keV.

Back to top of page.

Back to HRC-S opacity maps

Back to AXAF x-ray shielding page

Editor: Dr. Douglas Swartz System Administrator: Mr. Bob Dean Privacy Policy and Important Notices Accessibility Statement