The
Focus Tube (1896)
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This type of tube, introduced in 1896,
a few months after Röntgen’s discovery of X-rays,
is commonly known as the JACKSON TUBE or Focus Tube. In the above pictures,
the tube is seen from different angles. The anti-cathode is a very thin square plate
of pure platinum. Etched on the back-side of the concave
aluminum
cathode are the maker’s name and address “
Hereafter is an early
description of this tube : …..The most important step in the
evolution of X-Ray tubes is marked by what is now commonly called the focus
tube. The credit of its inception is given to three different investigators,
namely, Prof. Röntgen himself, Prof. Elihu Thomson who is said to have worked with a focus
tube in January, 1896, and Mr. Herbert Jackson, of King’s College, London,
who, at any rate was the first to use
it publicly…….The design of the focus
tube obviates the defects of cathode tubes, in so far as the point which the
cathode rays strike is no longer the glass of the tube, but a suitable metal
(platinum) which may become white hot
without endangering the tube itself. Moreover, as the cathode is of
concave shape, the cathode rays converge to a focus, so that the source of
x-rays becomes limited in size and so permits of superior definition in the
resulting radiograms. ….. In later types, particularly of
continental origin, the tube is provided with a separate anode which may at
will be connected to the anticathode. Several forms of “multianodal”
tubes are illustrated: |
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Bulbar |
Cylindrical |
( A.W. Isenthal & H. Snowden Ward –“Practical
Radiography”, 1898, p.55)
Go
to: Bulbar
and Cylindrical focus tubes
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