1 / 11

Update on a Proposed Bakeout CXC SOT & FOT, ACIS Instrument Team and MSFC Project Science

Update on a Proposed Bakeout CXC SOT & FOT, ACIS Instrument Team and MSFC Project Science. Contributors to the Bakeout Effort.

amity
Télécharger la présentation

Update on a Proposed Bakeout CXC SOT & FOT, ACIS Instrument Team and MSFC Project Science

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Update on a Proposed Bakeout CXC SOT & FOT, ACIS Instrument Team and MSFC Project Science

  2. Contributors to the Bakeout Effort The``ACIS Contamination Working Group’’ has been studying the ACIS contamination issue for the last two years. This presentation is a summary of that work. Those contributing directly to this presentation: CXC: P. Plucinsky, A. Vikhilin, H. Marshall, N. Schulz, R. Edgar, D. Schwartz, S. Wolk, H. Tananbaum, J. DePasquale, S. Virani, D. Dewey, L. David MIT: M. Bautz,C. Grant, W. Mayer, R. Goeke, P. Ford, B. LaMarr, G Prigozhin, S. Kissel, E. Boughan PSU: G. Garmire, L. Townsley, G. Chartas, D. Sanwal, M. Teter, G. Pavlov MSFC: S. O’Dell, D. Swartz, M. Weisskopf, A. Tennant, R. Elsner NGST: M. Mach, P. Knollenberg, D. Shropshire, L. McKendrick, R. Logan, R. Giordano, T. Trinh, K. Chen, K. Henderson, F. Cottrell, J. Lamb, D. McGregor, H. Tran, D. Lindemann, L. Harper, L. Ryan, A. Tao LMA: N. Tice McMaster University: A. Hitchcock Many others have contributed directly or indirectly.

  3. New Items since Last CUC Briefing (June 2004) • Tests on spare OBFs at NGST are complete and the project is convinced that OBFs will not be damaged during the bakeout • Chandra FOT determined that it is not safe to use the additional heaters on the SIM to heat the ACIS collimator/SIM interface • Project decided to postpone bakeout decision until the impact of not using the heaters was understood • MSFC Project Science generated new simulations with these colder surfaces and not surprisingly, the contaminant does not vent as effectively. The recommendation is to keep the OBF warmer than any of the surrounding surfaces during the bakeout. • Calibration team continues to work on the characterization of the contaminant (see Herman Marshall’s talk) • ACIS team is planning new irradiation tests to better understand the mechanism for the CTI increase from the room temperature bakeout in Sep 1999

  4. Chandra X-Ray Observatory ACIS Location OBA Vent Locations Contaminate Migration Path Optical Bench Assembly (OBA) Integrated Science Instrument Module (ISIM)

  5. Geometric model OBA vent SIM focus structure SIM translation table Optical bench (OBA) ACIS collimator Snoot OBA stove pipe ACIS camera top ACIS OBF TRASYS model by NGST/ H. Tran et al.

  6. 1 mo 1 wk 1 dy 5 yr 1 yr 10.´DOP de-rated TOBF: Mass column O’Dell & Swartz (MSFC) 1: ACIS OBF 2: Camera top 3: ACIS snoot 4: ACIS collimator 5: SIM trans table 6: SIM focus struc 7: OBA stove pipe 8: Optical bench 9: OBA vent NOMINAL DE-RATED

  7. 1 mo 1 wk 1 dy 5 yr 1 yr 1.0´DOP de-rated TOBF: Mass column O’Dell & Swartz (MSFC) NOMINAL DE-RATED 1: ACIS OBF 2: Camera top 3: ACIS snoot 4: ACIS collimator 5: SIM trans table 6: SIM focus struc 7: OBA stove pipe 8: Optical bench 9: OBA vent

  8. Limits on vaporization rates O’Dell & Swartz (MSFC) Min to vent 0.2 g in 1 orb:510-3mg cm-2 s-1 @ Tcoldest Min to clean OBF in 1 orb:210-3mg cm-2 s-1 @ TOBF-bake Upper limit at OBF center:110-7mg cm-2 s-1 @ TOBF-ops

  9. Conclusions From New Simulations • If the contaminant has a volatility of less than 0.1 X DOP’s volatility, a one orbit +30 C bakeout will not move a significant amount of the contaminant • If the contaminant volatility is within an order of magnitude of DOP’s volatility, a significant amount of the contaminant will vaporize and migrate to the cold surfaces at the top of the ACIS collimator and the SIM. The contaminant will then migrate very slowly back to the OBF and it may be years before a significant amount re-accumulates on the OBF • If the contaminant volatility is an order of magnitude higher than that of DOP, a significant amount of the contaminant will vaporize and migrate to the cold ACIS collimator and SIM surfaces. The contaminant will then migrate back to the OBF such that after 1 year, the thickness will be 1/3 of the original thickness.

  10. Work Still to be Done (January 2004) • ACIS team will conduct irradiation tests, analyze the results, and refine the prediction for the effect of another room temperature bakeout on the CTI • The working group will prepare another briefing for the Chandra project and seek approval for the bakeout

More Related