Recent in-orbit measurements by high resolution soft X-ray telescopes have revealed low-level fin... more Recent in-orbit measurements by high resolution soft X-ray telescopes have revealed low-level fine structure in target spectra that cannot be attributed to a celestial source. Ultimately, this can be traced to the ability of the new high spectral resolution silicon detectors to resolve X-ray absorption fine structure (XAFS) produced in the various detection subsystems. Based on measurements taken at the
We discuss the effects of an apparent molecular surface contamination on the reflectance of the A... more We discuss the effects of an apparent molecular surface contamination on the reflectance of the Advanced X-ray Astrophysics Facility (AXAF) High Resolution Mirror Assembly (HRMA) witness flats. These flats are used to monitor the iridium coated surfaces of the HRMA and allow us to derive iridium optical constants for each of the HRMA mirror surfaces. Reflectance measurements of representative witness flats have been made at the Advanced Light Source (ALS) synchrotron facility over an energy range of 60 - 940 eV and we have observed a reduction in expected reflectance in the vicinity of 270 - 330 eV. This energy range includes the Carbon k absorption edge as well as the iridium N-IV and N-V absorption edges. The energy range is also an important region since it includes a number of spectral lines of astrophysical importance such as the C-V line. The observed decrease in mirror reflectance is believed to be the combined result of the presence of an organic thin film, on the mirror sur...
Detailed statistical properties of internal magnetic turbulence, and internal disruptions in magn... more Detailed statistical properties of internal magnetic turbulence, and internal disruptions in magnetically- and materially-limited discharges, are studied in the Tokapole II poloidal divertor tokamak over the safety factor range 0.6 less than q(sub a) less than 3. A nonlinear MHD code treats tearing modes in the divertor geometry.
Recent in-orbit measurements by high resolution soft X-ray telescopes have revealed low-level fin... more Recent in-orbit measurements by high resolution soft X-ray telescopes have revealed low-level fine structure in target spectra that cannot be attributed to a celestial source. Ultimately, this can be traced to the ability of the new high spectral resolution silicon detectors to resolve X-ray absorption fine structure (XAFS) produced in the various detection subsystems. Based on measurements taken at the
We discuss the effects of an apparent molecular surface contamination on the reflectance of the A... more We discuss the effects of an apparent molecular surface contamination on the reflectance of the Advanced X-ray Astrophysics Facility (AXAF) High Resolution Mirror Assembly (HRMA) witness flats. These flats are used to monitor the iridium coated surfaces of the HRMA and allow us to derive iridium optical constants for each of the HRMA mirror surfaces. Reflectance measurements of representative witness flats have been made at the Advanced Light Source (ALS) synchrotron facility over an energy range of 60 - 940 eV and we have observed a reduction in expected reflectance in the vicinity of 270 - 330 eV. This energy range includes the Carbon k absorption edge as well as the iridium N-IV and N-V absorption edges. The energy range is also an important region since it includes a number of spectral lines of astrophysical importance such as the C-V line. The observed decrease in mirror reflectance is believed to be the combined result of the presence of an organic thin film, on the mirror sur...
Detailed statistical properties of internal magnetic turbulence, and internal disruptions in magn... more Detailed statistical properties of internal magnetic turbulence, and internal disruptions in magnetically- and materially-limited discharges, are studied in the Tokapole II poloidal divertor tokamak over the safety factor range 0.6 less than q(sub a) less than 3. A nonlinear MHD code treats tearing modes in the divertor geometry.
Uploads
Papers by Dale Graessle