No abstract

No abstract

No abstract

The Advanced X-ray Astrophysics Facility (AXAF) contains two focal-plane science instrumentsthe microchannel-plate High-Resolution Camera (H1tC) and the AXAF CC1D Imaging Spectrometer (ACTS). Each of these instruments provides two low-internal-background detectors, one for imaging and the other for reading out AXAF's ol)jective transmission gratings. Taking maximum advantage of the low internal background of these instruments requires shielding against external electromagnetic and particle radiation. To optimize tlie shielding itlfii weight constraints, we peiformeci extensive numerical simulations of the photon transport and of the partidc tl'ansl)ort ail activation within the AXAF. \Ve discuss the simulations and report the results of the shielding study.With the adopted shielding design, the paiticle-iiiducecl background and the x-ray-induced background are each comparable to or less than the anticipated internal background of AXAF's imaging detectors (HRC and ACTS). Thus, the predicted total non-imaged background is very low -less than 0.2 counts arcsec2 day1 for the HII.C and even lower for the ACTS! In view of AXAF's half-aicsec angular resolution, this low background has negligible effect upon point-source detection, for reasonable observation durations. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx SPIE Vol. 2518 /109 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx SPIE Vol. 2518 / 115 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/24/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx

No abstract