Flash X-Ray (FXR) Accelerator Optimization Electronic Time-Resolved Measurement of X-Ray Source Size

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Lawrence Livermore National Laboratory (LLNL) is currently investigating various approaches to minimize the x-ray source size on the Flash X-Ray (FXR) linear induction accelerator in order to improve x-ray flux and increase resolution for hydrodynamic radiography experiments. In order to effectively gauge improvements to final x-ray source size, a fast, robust, and accurate system for measuring the spot size is required. Timely feedback on x-ray source size allows new and improved accelerator tunes to be deployed and optimized within the limited run-time constraints of a production facility with a busy experimental schedule; in addition, time-resolved measurement capability allows the investigation ... continued below

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PDF-file: 9 pages; size: 0.7 Mbytes

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Jacob, J; Ong, M & Wargo, P July 21, 2005.

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Lawrence Livermore National Laboratory (LLNL) is currently investigating various approaches to minimize the x-ray source size on the Flash X-Ray (FXR) linear induction accelerator in order to improve x-ray flux and increase resolution for hydrodynamic radiography experiments. In order to effectively gauge improvements to final x-ray source size, a fast, robust, and accurate system for measuring the spot size is required. Timely feedback on x-ray source size allows new and improved accelerator tunes to be deployed and optimized within the limited run-time constraints of a production facility with a busy experimental schedule; in addition, time-resolved measurement capability allows the investigation of not only the time-averaged source size, but also the evolution of the source size, centroid position, and x-ray dose throughout the 70 ns beam pulse. Combined with time-resolved measurements of electron beam parameters such as emittance, energy, and current, key limiting factors can be identified, modeled, and optimized for the best possible spot size. Roll-bar techniques are a widely used method for x-ray source size measurement, and have been the method of choice at FXR for many years. A thick bar of tungsten or other dense metal with a sharp edge is inserted into the path of the x-ray beam so as to heavily attenuate the lower half of the beam, resulting in a half-light, half-dark image as seen downstream of the roll-bar; by measuring the width of the transition from light to dark across the edge of the roll-bar, the source size can be deduced. For many years, film has been the imaging medium of choice for roll-bar measurements thanks to its high resolution, linear response, and excellent contrast ratio. Film measurements, however, are fairly cumbersome and require considerable setup and analysis time; moreover, with the continuing trend towards all-electronic measurement systems, film is becoming increasingly difficult and expensive to procure. Here, we shall discuss an x-ray source size measurement system which utilizes a traditional roll-bar setup combined with a high resolution gated CCD camera, fast-response organic plastic scintillator, and image processing and analysis software, which is executable on a standard PC running which is executable on a standard PC running LabVIEW and Matlab. Analysis time is reduced from several hours to several minutes, while our experimental results demonstrate good agreement with both traditional film-based roll-bar measurements as well as the entirely unrelated technique of x-ray pinhole camera measurements; in addition, our time-resolved measurements show a significant variation in source size throughout the 70 ns beam pulse, a phenomenon which requires further investigation and indicates the possibility of greatly improving final spot size.

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PDF-file: 9 pages; size: 0.7 Mbytes

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  • Report No.: UCRL-TR-214040
  • Grant Number: W-7405-ENG-48
  • DOI: 10.2172/878193 | External Link
  • Office of Scientific & Technical Information Report Number: 878193
  • Archival Resource Key: ark:/67531/metadc880751

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • July 21, 2005

Added to The UNT Digital Library

  • Sept. 21, 2016, 2:29 a.m.

Description Last Updated

  • Dec. 5, 2016, 4:14 p.m.

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Jacob, J; Ong, M & Wargo, P. Flash X-Ray (FXR) Accelerator Optimization Electronic Time-Resolved Measurement of X-Ray Source Size, report, July 21, 2005; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc880751/: accessed December 14, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.