Varian Associates, Inc.

Machlett Labs. Inc.

Ming-Wei P Xu

Albert F Fengler

James R Caraher

Thomas J Koller

Steven Tavoletti

Raymond A Daly

An x-ray tube rotor structure wherein a target support stem has an externally threaded end portion engaged with an internally threaded surface of an encircling bushing and fixedly attached thereto by an interposed brazed joint. The stem is made of predominantly molybdenum material having a linear thermal expansion coefficient of 58.times.10.sup.-7 per degree Fahrenheit and is thermally matched with the bushing which is made of an iron cobalt nickel alloy material having a linear thermal expansion coefficient of 60.times.10.sup.-7 per degree Fahrenheit. The bushing has an outer surface fixedly attached through a welded joint with an inner surface of an annular plug which has an outer marginal portion fixedly attached to an adjacent end portion of a coaxial rotor skirt. The annular plug is made of an iron chrome nickel alloy material having a linear thermal expansion coefficient of 84.times.10.sup.-7 per degree Fahrenheit and is thermally compatible with the rotor skirt which is made of magnetic flux conductive steel having a linear thermal expansion coefficient of 75.times.10.sup.-7 per degree Fahrenheit. Thus, the largest thermal disparity and the maximum thermal stresses occur between the bushing and the plug at the interposed welded joint which is structurally stronger than the brazed joint between the bushing and the stem.

X-ray tube rotor structure

An x-ray rotor structure wherein a target support stem has an externally threaded end portion brazed to an internally threaded surface of an encircling bushing which is provided with a barrier layer of oxidation restricting material. The stem is made of predominantly molybdenum material and the bushing is made of iron cobalt nickel alloy material having therein a small percentage by weight of titanium. The barrier layer comprises a layer of substantially pure nickel material which coats the entire inner surface of the bushing including the internally threaded portion thereof. Thus, the titanium is restricted from leaching to the surface during brazing and forming oxides which prevent the surface from being completely wetted by the brazing material. As a result, during brazing, the liquified brazing material alloys with the nickel material of the barrier layer to wet the inner surface of the bushing completely. Consequently, upon cooling, the alloyed brazing material and the nickel material of the barrier layer constitute an interlocking layer forming a durable brazed joint for fixedly attaching the bushing to the stem.

Rotor structure brazed joint

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Stamford, CT, United States of America

Ming-Wei P Xu