Astronomy and Astrophysics – Astrophysics
Scientific paper
Oct 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992veta.nasa.....k&link_type=abstract
In its VETA-I X Ray Test Analysis 8 p (SEE N93-26183 09-74)
Astronomy and Astrophysics
Astrophysics
Calibrating, Grazing Incidence, High Resolution, Mirrors, Reflectance, X Ray Astrophysics Facility, X Ray Sources, X Ray Telescopes, Apertures, Bremsstrahlung, Electron Impact, Polishing, Proportional Counters, Surface Layers
Scientific paper
The x-ray reflectivity of the VETA-I optic, the outermost shell of the AXAF x-ray telescope, with a bare Zerodur surface, is measured and compared with theoretical predictions. Measurements made at energies of 0.28, 0.9, 1.5, 2.1, and 2.3 keV are compared with predictions based on ray trace calculations. The data were obtained at the x-ray calibrations facility at Marshall Space Flight Center with an electron impact x-ray source located 528 m from the grazing incidence mirror. The source used photoelectric absorption filters to eliminate bremsstrahlung continuum. The mirror has a diameter of 1.2 m and a focal length of 10 m. The incident and reflected x-ray flux are detected using two proportional counters, one located in the incident beam of x-rays at the entrance aperture of the VETA-I, and the other in the focal plane behind an aperture of variable size. Results on the variation of the reflectivity with energy as well as the absolute value of the reflectivity are presented. We also present a synchrotron reflectivity measurement with high energy resolution over the range 0.26 to 1.8 keV on a flat Zerodur sample, done at NSLS. We present evidence for contamination of the flat by a thin layer of carbon on the surface, and the possibility of alteration of the surface composition of the VETA-I mirror perhaps by the polishing technique. The overall agreement between the measured and calculated effective area of VETA-I is between 2.6 percent and 10 percent, depending on which model for the surface composition is adopted. Measurements at individual energies deviate from the best-fitting calculation to 0.3 to 0.8 percent, averaging 0.6 percent at energies below the high energy cutoff of the mirror reflectivity, and are as high as 20.7 percent at the cutoff. We also discuss the approach to the final preflight calibration of the full AXAF flight mirror.
Chartas George
Elsner Ronald F.
Graessle Dale
Hughes John Patrick
Kellogg Edwin M.
No associations
LandOfFree
The x ray reflectivity of the AXAF VETA-I optics does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The x ray reflectivity of the AXAF VETA-I optics, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The x ray reflectivity of the AXAF VETA-I optics will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1346496