DE612213C - Discharge vessel, especially X-ray tubes, with pure electron discharge - Google Patents

Description

GERMAN EMPIRE

ISSUED ON April 16, 1935

REICH PATENT OFFICE

PATENT LETTERING

CLASS 21g GROUP 17 oi

C. H. F. Müller A.-G. in Hamburg-Fuhlsbüttel *)

Patented in the German Empire on July 26, 1931

In the case of discharge vessels, in particular X-ray tubes, those with pure electron discharge work, there is a risk that the vessel wall will be hit by electrons of primary and mainly secondary origin causing an uneven discharge and often destruction of the vessel wall entry. In order to remedy this problem, one has the potential gap

to such a discharge vessel is shielded from the vessel wall by a protective screen. Discharge tubes are used in particular in X-ray technology which the vessel wall itself consists of metal at the level of the discharge space. There for reasons of operational safety, this metal vessel wall against the As is known, it is also useful in the case of discharge vessels with a wall part made of metal, a metal screen surrounding the discharge space is arranged. This Metal screen, which is set up insulated in the tube, is charged by the impact of Electrons to a potential which is at least approximately equal to the potential of the Can be cathode. The full one then lies between the anode and the protective screen Electrode voltage and between the metal wall part and the protective screen half electrode voltage.

In order to ensure the most trouble-free operation of such a discharge tube, the electron shield must be arranged relative to the anode and the metal wall part that despite the high potential differences, no dangerous electrical stress from inside parts located in the discharge vessel. At the same time, you want the opportunity of flashovers between the anode and protective screen on the one hand or between the protective screen and the metal wall on the other can be prevented and for this purpose high field strengths are preferably excluded in the area of these metal parts.

The subject of the invention is a discharge tube with pure electron discharge, the one located at the level of the discharge space metal wall part, which is attached to a fixed potential in the middle between the electrodes, and one in the Contains protective screen arranged height of the discharge path. According to the invention, the arrangement of the inside the discharge vessel completely insulated attached protective screen at such a distance to the metal wall part on the one hand and to positive electrode on the other hand, that the existing between said parts electric field strengths are at least approximately the same. In an example

*) The inventor has been indicated by the patent seeker;

Josef AIf ter in Eindhoven, Holland.

wise cylindrical X-ray tubes, the geometrical relationships can be compared with those of a cylindrical capacitor. ' According to the well-known formula, the field strength for an arbitrary cylinder surface with a radius r is expressed by the following formula:

rlcr ^ ~

Taking into account the fact that the full electrode voltage lies between the anode and the protective screen and half the electrode voltage between the metal wall part and the protective screen, and if r _{x is} the radius of the anode, r _{2 is} the radius of the protective screen and r _s denotes the radius of the metal wall part, then the field strength which has a voltage difference B on the inner surface of a cylinder with a half diameter r _e and with respect to the inner cylinder with a half diameter r _{t is} thus

and on the outer surface of a cylinder with the half-diameter r ₂ , which is opposite to an outer cylinder with the half-diameter

F knife r _{3 has} a voltage difference - is

thus for Fi = F _a (condition which is set according to the invention)

= ^2l g -Γ ">

or

In the case of discharge vessels with a spherical wall, the same applies of a spherical capacitor in use.

In a discharge vessel with a protective hood attached according to the invention there is a completely even electrical field distribution, which means less interference The course of the discharge is guaranteed and the safe grounding of the metal wall part is made possible.

The device according to the invention will be explained in more detail below with reference to the figures be explained.

In Fig. 1 are in the X-ray tube 1 Fused in a vacuum-tight manner: the anode 2 and the hot cathode 3 and collecting device 4 existing cathode. At the level of the discharge space is also fused to the glass wall in a vacuum-tight manner metallic wall part 5 with a beam exit window 6 is provided. Between Electrodes and the wall part 5 is the metal protective cylinder 7 according to the invention at such a distance from the anode on the one hand and the wall part 5 on the other hand arranged that the electric field strengths prevailing in the interstices are at least approximately the same. To prevent the edge of the protective cylinder 7 Outgoing discharges, this edge is expediently with a melted glass bead 8 covered.

Fig. 2 shows a section along the line H-II. Between the anode 2 and the metal wall part 5 there is the electron protection cylinder 7, which has the distance α from the anode determined according to the invention and the distance b from the metal wall part. The spacing ratios a, b in this Fig. 2 are true to scale.

Claims (1)

Claim: Discharge vessel, especially X-ray tube, with pure electron discharge, a metal wall part located at the level of the discharge space, which is attached to a solid, in the middle between the electrodes lying potential, and one at the level of the discharge path completely insulated protective screen arranged within the discharge vessel, characterized in that the protective screen at such a distance to the metal wall part on the one hand and to On the other hand, positive electrode is arranged that the electric field strengths prevailing between said parts are at least approximately the same. 1 sheet of drawings