DE551178C - Process for creating a high vacuum in x-ray tubes - Google Patents

Description

ISSUED ON May 30, 1932

REICH PATENT OFFICE

PATENT LETTERING

CLASS 21 g GROUP

C. H.F. Müller Akt.-Ges. in Hamburg-Fuhlsbüttel *)

Process for generating a high vacuum in X-ray tubes

Patented in the German Empire on May 29, 1929

Hot cathode x-ray tubes and similar discharge vessels for high voltages must be largely emptied of base gases to prevent impact ionization. As is known, this is achieved in that the electrodes put into high embers and the gases escaping from them by pumping for several hours be discharged by means of a high vacuum pump.

Attempts have been made to shorten the pumping process in the radio tubes and Incandescent lamp technology common methods of chemical or mechanical vacuum generation by a metal that absorbs gas at high temperature or by a so-called getter also on X-ray tubes to be used, but practical successes have not been achieved because of the high vapor pressure of the usual getter substances. The use of earth metals, such as. B. Zircon, which has a lower vapor pressure have already been proposed for high-voltage discharge vessels. Included the zircon is, as suggested, at the hottest point of the anode, for example attached to a transmitter tube. With X-ray tubes, however, the situation is different, because the anodes of the transmitter tubes do not reach the temperatures necessary for complete evaporation. .,.,

The getter was also often placed directly in the glass bulb by heating the glass wall or another method by heating a glass auxiliary container that contained the getter substance, evaporated. There naturally the heating temperature of the getter due to the melting point of the Glass was limited, evaporation was imperfect because of the evaporation temperature must be chosen expediently as high as possible. Furthermore, condensation of the getter can continue after evaporation take place at every point of the glass wall, so that a considerable electrical stress the glass wall occurs when the thin metal coating is caused by scattered electrons charges. Furthermore, the inner metal coating of the glass bulb resulted in a shortening the isolation path along the tube surface, which increases the voltage safety of the X-ray tube.

According to the invention, the getter is in any form, directly on the focal point, so on the most of the electron impact and thus the greatest warming exposed point of the anode applied. The getter material chosen is a substance that is only just below the normal operating temperature in the focal spot for evaporation. One will therefore Select a different getter material for material test tubes with copper anodes than in a therapy tube with a tungsten anode that works at voltages of around 200 KV.

*) The patent seeker stated as the inventor:

Dr. Paul Vierkötter in Hamburg.

Claims (1)

The method according to the invention is particularly important because one with his Help simplify the fabrication of the X-ray tubes and reduce the time required can shorten significantly. While you previously needed a high voltage source to degas the anode 'and the Exposed the anode to the electron impact of the cathode for heating purposes, it is now sufficient to when using the method according to the invention, the anode by eddy current heating Pre-degassed in a magnetic alternating field or by directly acting heat sources without the use of high voltage will. The use of such means, which without heating the cathode to a sufficient Lead pre-degassing of the anode has the significant advantage that it is unnecessary Loading of the hot cathode is avoided. In order to degas these yourself, only a short annealing process is required. In this pre-degassed state, ■ in which the getter has naturally not yet evaporated, the tube is melted by the pump. The tube is now connected to high voltage placed and bombarded the anode with electrons by heating the hot cathode, so takes place as soon as the anode front surface 'a certain, not in the previous pumping process reached temperature, the evaporation of the getter. The occurring here Binding of the base gases creates a vacuum of a quality as it is after the customary pumping process achieved only after several hours of careful pumping will. The getter can be in any form, for example as a sheet metal body or as a paste, which consists of the powdery getter and a binder, e.g. B. alcohol, is to be brought directly into the focal point on the anode. As already mentioned, depending on the different properties of the anodes in the different tube constructions, a whole number of metals can be used as ¹ getter, if only their evaporation temperature is above the heating of the tube parts during normal operation and just below the operating temperature of the focal spot its surroundings. So come z. B. in question metals such as nickel, iron, molybdenum and others The accompanying drawing shows two X-ray tubes from which the Operation of the invention can be seen. Fig. Ι shows an X-ray tube with a metallic Middle part and Fig. 2 a normal glass X-ray tube, in which by arrangement a precipitation of the thin metallic or glass screen surfaces Getters on the glass wall is prevented. The metallic wall part 1 is used in Fig the X-ray tube, which for example has glass necks 2 and 3 on both sides, which in turn the anode 4 and the cathode 5 wear, as a condensation surface for the on the suitably consisting of tungsten Anode front surface 6 evaporating getter 7. The getter 7 can, for example, as Pieces of sheet metal arranged on the anode or in finely divided form with alcohol or mixed with another useful binder onto the anode front surface 6 be glued on. The metal parts of the X-ray tube, i.e. the middle part 1, the metal parts the hot cathode 5 and the anode 4 are expediently without the use of high voltage pre-degassed. After the pump has melted, high voltage is applied between the hot cathode 5 and the anode 4 of the hot cathode 8 emitted electrons at high speed onto the anode front surface 6 or getter substance 7 flings. Due to the local warming that occurs there the getter material evaporates and condenses due to the linear expansion of the molecular radiation preferably on an annular surface 9 in the interior of the metallic Wall part 1. In Fig. 2 are within the glass, Tubular body 10, the anode 4 and the cathode 5 arranged. The cathode 5 carries a screen 11, while an annular body 12 is expediently connected to the anode 4. This arrangement prevents precipitation of the tanner on the glass tube wall, because the precipitation takes place on the screen surfaces, so that the voltage security the X-ray tube is preserved. .PATKNTANSJeRUCU: Process for generating a high vacuum in X-ray tubes, characterized in that that the metal parts of the tube are pre-degassed by means known per se without the application of high voltage and that a getter is then evaporated by electron bombardment from the cathode, which is attached to the • Operation is attached to the hottest point of the anode and its vapor pressure is selected is that it only evaporates just below the normal operating temperature in the focal point. 1 sheet of drawings