An evaluation of a bake-out of the ACIS instrument on the Chandra X-Ray Observatory

Paul P. Plucinsky; Stephen L. O'Dell; Neil W. Tice; Douglas A. Swartz; Marshall W. Bautz; Joseph M. DePasquale; Richard J. Edgar; Gordon P. Garmire; Rino Giordano; Catherine E. Grant; Perry Knollenberg; Steve Kissel; Beverly LaMarr; Richard Logan; Martin Mach; Herman L. Marshall; Leon McKendrick; Gregory Y. Prigozhin; Dan Schwartz; Norbert S. Schulz; Dan Shropshire; Tan Trinh; Alexey A. Vikhlinin; Shanil N. Virani

doi:10.1117/12.552029

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11 October 2004 An evaluation of a bake-out of the ACIS instrument on the Chandra X-Ray Observatory

Paul P. Plucinsky, Stephen L. O'Dell, Neil W. Tice, Douglas A. Swartz, Marshall W. Bautz, Joseph M. DePasquale, Richard J. Edgar, Gordon P. Garmire, Rino Giordano, Catherine E. Grant, Perry Knollenberg, Steve Kissel, Beverly LaMarr, Richard Logan, Martin Mach, Herman L. Marshall, Leon McKendrick, Gregory Y. Prigozhin, Dan Schwartz, Norbert S. Schulz, Dan Shropshire, Tan Trinh, Alexey A. Vikhlinin, Shanil N. Virani

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Proceedings Volume 5488, UV and Gamma-Ray Space Telescope Systems; (2004) https://doi.org/10.1117/12.552029
Event: SPIE Astronomical Telescopes + Instrumentation, 2004, Glasgow, United Kingdom

Abstract

The sensitivity of the Advanced CCD Imaging Spectrometer (ACIS) instrument on the Chandra X-ray Observatory (CXO) to low-energy X-rays (0.3 - 2.0 keV) has been declining throughout the mission. The most likely cause of this degradation is the growth of a contamination layer on the cold (-60 C) filter which attenuates visible and near-visible light incident on the CCDs. The contamination layer is still increasing 4 years after launch, but at a significantly lower rate than initially. We have determined that the contaminant is composed mostly of C with small amounts of O and F. We have conducted ground experiments to determine the thermal desorption properties of candidate materials for the contaminant. We have conducted experiments to determine the robustness of the thin filter to the thermal cycling necessary to remove the contaminant. We have modeled the migration of the contaminant during this bake-out process to ensure that the end result will be a reduction in the thickness of the contamination layer. We have considered various profiles for the bake-out consisting of different temperatures for the ACIS focal plane and detector housing and different dwell times at these temperatures. The largest uncertainty which affects our conclusions is the volatility of the unknown contaminants. We conclude that bakeout scenarios in which the focal plane temperature and the detector housing temperature are raised to +20~C are the most likely to produce a positive outcome.

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Paul P. Plucinsky, Stephen L. O'Dell, Neil W. Tice, Douglas A. Swartz, Marshall W. Bautz, Joseph M. DePasquale, Richard J. Edgar, Gordon P. Garmire, Rino Giordano, Catherine E. Grant, Perry Knollenberg, Steve Kissel, Beverly LaMarr, Richard Logan, Martin Mach, Herman L. Marshall, Leon McKendrick, Gregory Y. Prigozhin, Dan Schwartz, Norbert S. Schulz, Dan Shropshire, Tan Trinh, Alexey A. Vikhlinin, and Shanil N. Virani "An evaluation of a bake-out of the ACIS instrument on the Chandra X-Ray Observatory", Proc. SPIE 5488, UV and Gamma-Ray Space Telescope Systems, (11 October 2004); https://doi.org/10.1117/12.552029

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