The “Anode Only” Tube

This enigmatic object practically corresponds to the anode section of a rotating anode tube that has been built (or may be rebuilt) without the cathode elements, solely for demonstration or experimental or teaching purposes.

The 4” (10cms) anode disc rotates very freely, and is perfectly balanced with presence of selective balancing abrasion zones on the back of the disc, and of drill marks on the cylindrical part of the anodic structure. Half of the anterior face of the disc, and the whole surface of its back, are black-coated.

I am thankful to James Burke (Varian X-Ray) who, “to the best of his recollection”, provided the following information:

- The tube dates probably to the Sixties or early Seventies.

- The rotating anode is probably not solid Tungsten but a Molybdenum or Molybdenum alloy (2%Tungsten), with a thin Tungsten (10%) Rhenium track.

- The black coating is an emissive ceramic coating (about 80% aluminium oxide co-sintered with titanium dioxide) allowing the anode to relatively cool.

- This “tube” may have been used in life testing the metal lubricants used in the bearings. Lead and silver are common.

- Possible manufacturers: Dunlee or Eureka.

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