Radiation Measurement Accuracy of Z-Dynamic Hohlraums
Abstract
As calculational capabilities mature the data accuracy requirements become more stringent. Typical Z-pinch power measurements use multiple sets of filtered X-Ray Diodes (XRD) to provide temporally and spectrally resolved information on the pinch performance within a plus or minus 12% error bar. Integrated power measurements are provided by Ni-foil bolometers with plus or minus 10% accuracy Los Alamos has performed 75 experiments at the Sandia Z-machine in which both XRD's and bolometers viewed a Trad >150 eV radiation source. Comparison between the diagnostics revealed puzzling discrepancies of up to a factor of two. Closer examination of the XRD's and bolometers reveals fabrication, material properties, calibration, and analysis subtleties that may account for the differences. Assumptions of constant Cp and linear resistance changes are invalid if the bolometer heating is too great. Also if the element is heated to its Curie temperature nonlinear behavior occurs. Furthermore, the thin film properties of the nickel bolometer element can vary greatly from the bulk material properties. For the XRD's, the photoemissive surface properties of the cathodes can be altered as they are used in a high xray fluence and dirty vacuum environment. The x-ray filters can also be damaged from x-ray heating and blast debris. How filters are characterized and calibrated can also be an issue. We present the methods used to construct, calibrate the detectors, field the experiment, and analyze data in order to quantify the error bars on the measurements.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 2007
- Accession Number
- ADA635462
Entities
People
- G. C. Idzorek
- R. G. Watt
- T. E. Tierney
Organizations
- Los Alamos National Laboratory