In 1924 Philips publishes the invention of the Metalix X-ray tube. In 1925, Dr. Daniel den Hoed tests the Metalix tube before it is released for sale by the Philips company . Image: Philips Technical Journal
The Metalix tube is an invention of the development group of Dr. Albert Bouwers at the Philips NatLab. In 1920 Bouwers is given the task of developing X-ray tubes and equipment. In the new X-ray tube, the glass envelope around the anode is replaced by a metal housing with a window for the X-ray beam. The metal housing absorbs the radiation outside the useful beam and is less likely to break on impact. Working with this type of tube is therefore safer.
Metalix therapy tube as used in the Netherlands Cancer Institute from 1929. Depot Philips Museum Eindhoven 2008. Photo: H. van der Gugten
The Metalix tube is a further development of the Coolidge tube. In the new tube the vulnerable glass sphere has been replaced by a metal cylinder with an exit window for the X-ray beam. This resulted in integrated radiation protection and a sturdy construction. It was an important step in the further development of the X-ray tube technology. Like the Coolidge tube the cathode is heated by an electrical filament. To avoid the patent on the Coolidge tube the early Metalix tubes contained a small quantity of helium gas instead of being under vacuum. After this, other manufacturers came onto the market with similar constructions.