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20”
(50cms) long including radiator, 4”(10cms) bulb, dating probably to the mid
or late Twenties.
The “Line Focus” tube is basically a Coolidge tube
with the following modifications:
- The flat helical filament in a focusing cup is
replaced by a “line filament” backed by a cylindrical focusing reflector;
- The anode and target angle is reduced from 45
degrees to some 12-15 degrees.
- The source of radiation is no more a central
“spot” on the target, but a linear source which, seen from the patient side
of the tube, looks like a small spot source, about a 3mm square, resulting
in sharper x-ray images with an improved heat loadability of the target.
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The
principle of the line focus tube was patented in 1918 by Dr. Otto Goetze, practicing in Erlangen. “…..The first
practical electron x-ray tube with a line focus was introduced by C.H.F.Müller in 1922 under the name ‘Media’……While tube
loads in excess of 1 kW were hardly possible with the ion tube, the Media
tube enabled loads in excess of 10 kW. In practical operation, tube
voltages of up to 80kV were used with tube currents of up to 100 mA”.
(H. Bergmuller
– Medica Mundi – 1990 – Vol.35, p.19).
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The advertisements above, reproduced from
old Catalogs of C.H.F. Müller, show Media tubes with a water-cooling device, while
the tube in this collection is cooled by a multi-layer metal radiator, and is
rated 6 kW.
Media tubes, and later Metalix Tubes (Müller-Philips) were advertised as
containing traces of helium in order to go around the Coolidge patent held by
General Electric.
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