“MEDIA” Line Focus Tube by C.H.F.Müller

Ref. C9

This tube is 20” (50 cm) long including radiator with a 4”(10 cm) 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.

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).

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.