Early Müller-Philips “Metalix” Tube (Type D)

Ref. D1

Designed in the mid-twenties by Pr. Albert Bouwers of the Philips Company, in Holland, this tube was built in the CHF Müller factory in Hamburg later in the decade (The CHF Müller being totally owned since 1927 by Philips).

This tube of the “Coolidge Type” built on the Media Line Focus principle was initially sold under the brand name of “Müller Media-Metalix” and later as “Philips Metalix”. Its cylindrical central part (the canister) was made of chrome-steel alloy, fused on either side to the glass tubing forming the rest of the body of the tube. The canister is surrounded by a protective layer of lead covered by the exterior visible metal parts.

X-rays come out of the tube through a round glass window fused to the center of the canister, and then through an aluminium filter. A thick cylindrical housing, of what is described as “special bakelite” protects the rest of the tube.

Unfortunately this tube was received broken. But looking inside, the glass seemed too fragile for the disproportionately heavy anode. The tungsten target embedded in copper is at a low angle, and the focal spot is a virtual 3mm square. This particular tube is water-cooled, but similar tubes were also sold with metal radiators.  Some tubes were even jet-air cooled (Go to“Philips Metalix Tube”).

This “Type D” tube boasted 100 mA at up to 70 kVp and 40 mA up to 100 kVp (for short exposures only), or 6 mA at 125 kVp continuously. Later models of the “Metalix” were better protected, larger in size and with an improved output, and were even manufactured in different parts of the world.

To the left are two old advertisements of the Metalix tube, one under the name of “Müller-Media-Metalix”, water-cooled, and the other under the name of “Philips-Metalix”, with a metal radiator.

In order to go around the G.E. Coolidge patent covering hot cathode tubes in vacuum, the Metalix tube had a Helium filling at a pressure of at least 1/1000 mm of Mercury. This Helium inclusion had practically no effect on the efficiency of the tube and  soon diffused out of its glass wall.