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Proceedings Paper

Peak Power Capability Of Small Focal Spots
Author(s): Martin Braun
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Paper Abstract

Conventionally, ratings of rotating x-ray tubes are calculated using the law: p oc w3/2, where P is peak power and w is the focal spot width. This formula is only true if the electron beam energy is deposited at the surface of the target ("surface mode of heating"), and is usually sufficient for focal spots larger than 0.5mm and tungsten as target material. For smaller focal spots, and/or target materials of lower atomic number, peak power capability is higher, especially at higher tube volt-age. The reason is the penetration of the electrons into the material ("Volume mode of heating"). A computer program was developed to calculate peak power versus maximum temperature and was applied to tungsten and various composites as target materials. For a 50μm focal spot, the power increase is 80% at 80kV (4" tungsten target, 10,000 rpm). This is verified by actual focal spot performance. Further, we compare power capability of rotating targets versus stationary targets, particularly with regard to micro focal spots. For a 100 μm focus, the difference is more than a factor of 20 in favor of the rotating anode.

Paper Details

Date Published: 25 March 1976
PDF: 9 pages
Proc. SPIE 0070, Application of Optical Instrumentation in Medicine IV, (25 March 1976); doi: 10.1117/12.954573
Show Author Affiliations
Martin Braun, The Machlett Laboratories, Inc. (United States)

Published in SPIE Proceedings Vol. 0070:
Application of Optical Instrumentation in Medicine IV
Joel E. Gray; William R. Hendee, Editor(s)

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