DE1055134B - Cold cathode switch tubes with slit diaphragm system - Google Patents

Description

GERMAN

The invention relates to cold cathode interrupters. One limitation of their applicability is that that after deleting a previous discharge, a certain period of time must be waited for, until voltage can be applied to the tube again. This time is hereinafter referred to as the minimum deletion time designated. The minimum extinguishing time limits the maximum switching frequency, i. H. the number of controlled Ignitions that are permitted with such a tube in a certain unit of time. The maximal Switching frequency of cold cathode interrupters or current gates in the previously usual design for under normal operating conditions, the low-current technology averages around 1 ms.

It has already become known, the maximum switching frequency of gas-filled interrupters thereby to increase that the deionization time lowering additives are added to the filling gas of the tube. This z. B. from the Geiger-Müller counter tubes known additives such as hydrogen, alcohol or a ° other organic compounds, however, have the disadvantage that they are in the stronger discharges a switching tube lead to constant changes, because the additives are either absorbed or decomposed or even chemically change the cathode surface.

It is also known to reduce the erase time in that when a hollow cathode, for. B. in the manner of a hollow disk, formed cathode in which the discharge burns essentially inside, the inactive parts of the cathode and any additional surfaces galvanically connected to the cathode as capture or recombination surfaces for the residual charge carriers at least on the surface made of a material higher Work function can be established. By this known measure it is z. B. succeeded in shortening the extinction time of cold cathode interrupters on average to about 200 μδ.

The object of the invention is to shorten the extinguishing time even further by means that remain constant and that practically do not affect the functioning of the tube in the ignited state. This is achieved with a cold cathode interrupter for high switching frequency with a cathode, the surface of which in the area of the discharge path is more active than the parts outside the discharge path, and an electrode in the form of a diaphragm arranged between the cathode and anode and essentially perpendicular to the direction of discharge extensive area dividing the discharge space into two subspaces according to the invention in that the diaphragm for the formation of the main discharge has a central longitudinal slot (gap) of less than 1 mm, in particular 0.1 mm, width and that of the cold cathode parallel to the slot length Switch tube
with slit screen system

Applicant:
Siemens & Halske Aktiengesellschaft,
Berlin and Munich,
Munich 2, Wittelsbacherplatz 2

Dr. phil. Herbert Gawehn _r Munich, has been named as the inventor

elongated cathode all points of the effective part a smaller distance than 1 mm from the Have slot opening.

With this measure, the slit diaphragm has a double effect on the discharge mechanism the end. Once it acts in a known way as a recombination surface for the residual plasma during the Deionization process, so that thereby the deionization time and thus the minimum extinguishing time shortened will. So that as few secondary electrons as possible are released from it during this process, they are expediently produced at least on their surface from a material with a high work function. Second, when you reinstall the Anode voltage most of the residual charge carriers on the diaphragm wall, so that it is necessary for the reconstruction The dark current available for a new discharge is reduced the more the the aperture is smaller. This results in a correspondingly strong reduction in the minimum deletion time the end. The same effect can also be achieved with pinhole diaphragms with a correspondingly smaller size opening, from z. B. 0.1 mm in diameter. However, pinhole diaphragms have the disadvantage that they have the Hinder the main discharge current much more, which results in an increase in the operating voltage. the The shorter the discharge paths, the more effective the reduction of the extinguishing time by the diaphragm Have to put back load carriers. This is achieved according to the invention in an advantageous manner a narrow, band-shaped, effective cathode surface, which is arranged in such a way parallel to the diaphragm slot is that all points are less than 1 mm from this.

In the case of appropriate investigations, 60 to 120 gates were used in neon for a pinhole diaphragm with 0.1 mm diameter the same minimum extinguishing

80 »790/409

Claims (5)

times as measured for a slit diaphragm with an opening width of 0.1 x 6 mm and found that the operating voltage in the case of the perforated diaphragm rises with increasing current strength at currents above 1 mA and at 5 mA discharge current is already about 130 V, while in contrast the Burning voltage when using a slit diaphragm maintains a constant value of around 106 V over the entire current range from 1 to 20 mA. In addition, the diaphragm must in any case have such a large surface area or extend so close to the vessel wall that ignition cannot take place outside around the diaphragm. The effect of the diaphragm on the minimum extinction time can be varied by the level of the voltage between the diaphragm and the cathode during the extinction time; it must always be below the operating voltage. The minimum quenching time is the shorter, the more this voltage is below the burning voltage between the diaphragm and the cathode. The ignition of the main discharge path takes place most advantageously by igniting an initial discharge between the diaphragm and the cathode, the diaphragm acting as a starter. The short discharge paths result in a low ignition voltage. For a high switching capacity that is desired in many cases, however, an ignition voltage that is as high as possible above the operating voltage is required. The arrangement according to the invention offers the advantage that, when using a bias voltage from the diaphragm to the cathode, the ignition voltage from the anode to the cathode increases by approximately the amount of this bias voltage. In contrast to the known starter arrangements, this effect arises from the fact that the large-area screen divides the discharge space between anode and cathode into two areas which are largely electrostatically shielded from one another. If the aperture is narrow, the anode-cathode penetration is therefore particularly small. It is therefore possible to use higher operating voltages for the main anode-cathode route if the slit diaphragm used as a starter is positively biased in relation to the cathode. Because of the very small penetration between the anode and the cathode, we recommend using neon, helium or a mixture of these gases as filling gas in order to achieve good control sensitivity (transfer). The invention is to be explained in more detail using the exemplary embodiments shown schematically in FIGS. In Fig. 1, the longitudinal cathode 1 is made of pure metal, such as. B. tantalum or molybdenum, designed trough or trough-shaped, so that a particularly activated and an outer, less active, in particular artificially deactivated part by a coating is created within the channel. The cross-section dimensions are less than 1 mm. In front of the open end of the cathode, the aperture 2 is arranged with an extensive surface with a very narrow slot 3, approximately cathode length, in such a way that it practically divides the actual discharge space. Immediately behind this, a rod-shaped anode4 is provided in the plane of the slot. A likewise rod-shaped auxiliary anode 5 is arranged on the end of the cathode facing away from the diaphragm, whose continuously burning discharge path to the cathode serves only for sufficient pre-ionization to generate scattering electrodes. FIG. 2 shows another technical embodiment in which the same reference numerals as in FIG. 1 are used for the corresponding parts. In this case, the cathode 1 consists of two approximately square metal sheets of the same size, each on one edge. bent at right angles and connected to these bent parts by interposing a web 6 in such a way that a metal trough of approximately rectangular cross-section is created in which the web itself forms the bottom and thus belongs to the active part of the cathode. In contrast to the inner surface of the cathode, the outer part is deactivated in a known manner. The selected cathode shape enables particularly good mechanical stability to be achieved with a relatively simple method of manufacture. In front of the cathode, in a manner analogous to that in FIG. 1, first the diaphragm 2 with a narrow slot 3 and a rod-shaped anode 4 are arranged in the plane of the slot. For the local fixation of an auxiliary discharge serving for pre-ionization, the cathode on the side facing away from the diaphragm opposite the auxiliary anode 5 likewise has a channel shape. The embodiment of the cathode is not limited to the two examples shown, but rather all other shapes can be used for the present purpose which have an active part delimited in the form of a band and which can be arranged in the immediate vicinity of the diaphragm slot. Patent claims: 1. Cold cathode interrupter for high switching frequency with a cathode whose in the area of the .The surface lying on the discharge path is more active than the surface lying outside the discharge path Parts, and an electrode arranged as a screen and arranged between the cathode and anode substantially perpendicular to the direction of discharge, the discharge space is expanded into two sub-spaces dividing surface, characterized in that the diaphragm for the formation of the main discharge centrally has a longitudinal slot gap of less than 1 mm, in particular 0.1 mm in width, and that of the cathode, which is elongated parallel to the length of the slot, all points of the effective Partly have a distance of less than 1 mm from the slot opening. 2. cold cathode interrupter according to claim 1, characterized in that the diaphragm at least consists of a material with a high work function on its surface. 3. cold cathode interrupter according to claim 1, characterized in that the ineffective Parts of the cathode are deactivated. 4. cold cathode interrupter according to claim 1 and 3, characterized in that the cathode Is shaped like a trough or trough and consists of pure metal. 5. cold cathode interrupter according to one or more of the preceding claims, characterized characterized in that an auxiliary anode, which is used only for pre-ionization, is placed on the . turned side of the cathode is arranged. Considered publications:
German Patent Nos. 963 010, 935 684;
U.S. Patent No. 2,373,175. 1 sheet of drawings © «09 790/409 4.59