1914, Reiniger Gebbert & Schall type Apex X-ray unit. Dr. Alexander Timofeef in the Obstetric Clinic in Kazan, Russia.
The Netherlands Cancer Institute (NKI) provides the radiation therapy machine that Dr. Gaarenstroom uses in 1914 to treat patients in the Binnen Gasthuis. It is supplied by the German company Reiniger Gebbert & Schall, which will later become part of the Siemens concern. The trade name of the machine is "Apex-Spezial-Röntgenapparat für Intensiv-Tiefenbestrahlungen" .The tube voltage is 80-100 kV. By the end of 1914 this treatment unit is moved to the new Netherlands Cancer Institute - Antoni van Leeuwenhoekhuis at Keizersgracht 706 in Amsterdam.
The photo above shows an identical machine in the Women's Clinic in Kazan, Russia in 1915. (Source http://mfvt.ru/istoki-ucheniya-o-rake-matki-v-kazani/). In his right hand, the physician holds an insulating rod with an electrode which is used to connect high voltage to a gas-containing element which is melted onto the x-ray tube. This is to regulate the gas pressure in the ion tube, keeping the current and beam hardness as stable as possible. From the notes of Philips' researcher Gillis Holst taken during his visit to the AVL in December 1917, it appears that Dr. Gaarenstroom used an alternative method. He heated the palladium element with a gas flame. This method is described in the item 1896 "First applications of X-ray irradiations"
The physician observes the level of tube current and beam hardness, keeping the left arm scrupulously away from the unprotected wires which apply the 100 kV to the X-ray tube. He must bring the x-ray tube into a state in which the high voltage reaches the value which produces a spark between two electrodes mounted on the cabinet behind him. Then the voltage has the right value and the gas in the tube glows green, while the hot anode makes the cooling water bubble through the tubes in front of him.
In the factory catalogue of 1914, the price of the X-ray unit is 2350 German Goldmarks. Calculated to 2012 purchasing power, this is approximately €13,808, excluding the x-ray tube, treatment table and other auxiliary equipment. The unit is connected to a power source of 220 V, 8 A and 50 Hz. For the voltage rectification, no vacuum tubes or diodes yet exist. Instead, a synchronous rotating mercury switch is used, the Apex-interrupter, which switches the 50 Hz alternating current of the electricity grid every half period and connects to the primary coils of the high voltage inductor
Example from the catalogue of Reiniger Gebbert & Schall in 1914 : ´´ Apex-Spezial-Röntgenapparat für Intensiv-Tiefenbestrahlungen" for 2 X-ray tubes.
This machine is of the same type as that used in the NKI, but in dual version, so that two X-ray tubes can be used simultaneously. The Apex gas interrupter is located in the bottom of the cabinet. The interrupter has a rotating current distributor with a mercury jet which switches the alternating voltage from the electricity net to a pulsating DC voltage on the primary coils of the two high voltage inductors.
The unit used by Dr. Gaarenstroom has a single inductor and is designed for one X-ray tube.