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

Abstract

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-raymore » 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.« less

Authors:
; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
878193
Report Number(s):
UCRL-TR-214040
TRN: US0602282
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; CAMERAS; ELECTRON BEAMS; FEEDBACK; HYDRODYNAMICS; IMAGE PROCESSING; INDUCTION; LAWRENCE LIVERMORE NATIONAL LABORATORY; OPTIMIZATION; PLASTIC SCINTILLATORS; PRODUCTION; RESOLUTION; TUNGSTEN; X-RAY SOURCES

Citation Formats

Jacob, J, Ong, M, and Wargo, P. Flash X-Ray (FXR) Accelerator Optimization Electronic Time-Resolved Measurement of X-Ray Source Size. United States: N. p., 2005. Web. doi:10.2172/878193.
Jacob, J, Ong, M, & Wargo, P. Flash X-Ray (FXR) Accelerator Optimization Electronic Time-Resolved Measurement of X-Ray Source Size. United States. doi:10.2172/878193.
Jacob, J, Ong, M, and Wargo, P. Thu . "Flash X-Ray (FXR) Accelerator Optimization Electronic Time-Resolved Measurement of X-Ray Source Size". United States. doi:10.2172/878193. https://www.osti.gov/servlets/purl/878193.
@article{osti_878193,
title = {Flash X-Ray (FXR) Accelerator Optimization Electronic Time-Resolved Measurement of X-Ray Source Size},
author = {Jacob, J and Ong, M and Wargo, P},
abstractNote = {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.},
doi = {10.2172/878193},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2005},
month = {7}
}

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