[Artist's Concept of AXAF]

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

------------------------------------------------------------------

Images display 60-keV x-ray absorption depth (forward hemisphere directional cosine), as viewed from the HRC-S +Y,-Z vertex (worst-case location). The left panel includes attenuation by the existing focus-structure baffle; the right panel omits it. The color scale is logarithmic, ranging from a 60-keV absorption depth of 0.01 (red) to 10 (blue). Because x-ray absorption is roughly inversely proportional to the cube of the photon energy, an absorption depth 0.04 (red-orange) at 60 keV corresponds to about 1 at 20 keV.

Note that the focus-structure shielding fills gaps in coverage by the HRC snout. To evaluate more quantitatively the coverage afforded by this shielding, compare the opacity probability distributions as viewed from HRC-S +Y,-Z vertex.

HRC-S +Y,-Z vertex, during HRC-S observation

With the focus-structure tantalum, less than 0.01 steradian is transparent down to about 20 keV; without it, 0.06 steradian is. Thus the additional 20-keV coverage afforded by this shielding is only 0.5% of the sky.

[HRC-S +Y,-Z vertex, when observing]

HRC-S +Y,-Z vertex, during ACIS-S observation

With the focus-structure tantalum, 0.15 steradian is transparent down to about 20 keV; without it, 0.2 steradian is. Thus, with or without this shielding, the 20-keV coverage has a gap of about 1.5% of the sky.

[HRC-S +Y,-Z vertex, when next in line]
Back to top of page.
Back to AXAF x-ray shielding page

Go to AXAF Project Science Page or to X-ray Astronomy at MSFC
Editor: Dr. Douglas Swartz
System Administrator: Mr. Bob Dean
Privacy Policy and Important Notices
Accessibility Statement
CXO Project Science page Valid HTML 4.01!