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Description: | LMP 201 h (spurious Nat. Phil. departmental MADE BY NEWTON & WRIGHT LTD.,Electro-Medical Instrument Makers, 72, WIGMORE STREET, LONDON, W.( on a printed paper label originally stuck to the cathode limb of the glass envelope). MANU Newton and Wright Ltd. circa 1911 72, Wigmore St, London, England. DES after RONTGEN,Wilhelm,Conrad,von. 1895 Wurzburg, Germany. DES after CROOKES,William,Sir. 1870 London, England. DES after HITTORF,Johann,Wilhelm,Professor. 1869 Munster University This is a gas filled or cold cathode medical X-ray tube . The anticathode is constructed from a block of copper with a 2mm thick inset disc of tungsten. This assembly is angled at 45 degrees to the axis of the tube and hence to the flow of electrons from the cathode. It is attached to a copper tube which is clinched into the glass envelope and connected to the lead in wire by a? steel or tungsten rod. The cathode is a dished tungsten disc supported by a tungsten rod clinched to a glass stem in a limb of the tube. It is welded to the platinum lead in wire. The anticathode is a nickel rod welded to its platinum lead in wire.
As the vacuum hardened with use a spark would pass from the anode to the side arm liberating sufficient gas to regenerate the soft vaccum. This is the Glew automatic acclusion process. All the end caps are nickel with loop connectors except the the side arm which has a screw clamp to connect to earth. The anode and anticathode are not connected by the usual coiled nickel wire which is presumably lost.
In this type of tube the electrons from the cathode were reflected from the anticathode and generated X-rays by collision with residual gas in the tube. They were operated initially by Whimshurst machines and by spark gap induction coils or later by closed core transformers. Typical ratings for tis class of tube were 100KV. The main disadvantage was that there was no current control which meant that greater penetrating power could only be achieved by increasing the potential which decreased the wavelength.
The three electrode x-ray gas tube appears to have been developed in Germany. It has been said that no one was quite sure why the anode was added and several theories have been put forward. In 1904 Pusey and Caldwell postulated that the third electrode gave some advantage in regulation of the resistance of the tube. In 1956 Albert Linberg thought that the Germans used the third electrode in the manufacturing process to control the gassing process. However, in 1957 Hans Vatter demonstrated the third electrode simply increased the life of the tube by preventing damage to the platinum anticathode. However, It should be pointed out that the three electrode tube was a standard pattern for all cold cathode tubes until production of this type of tube finally ended in about 1928. | License: | http://www.hmag.gla.ac.uk/spirit/rights/ | Publisher: | Hunterian Museum and Art Gallery, University of Glasgow | Rights holder: | Hunterian Museum and Art Gallery, University of Glasgow | Subjects: | SCIENTIFIC COLLECTION : | Source: | Hunterian Museum | Creator: | Hunterian Museum and Art Gallery, University of Glasgow | Identifier: | http://www.huntsearch.gla.ac.uk/cgi-bin/... | Language: | en-GB | Go to resource |
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