US2840744A

US2840744A - Thyratron

Info

Publication number: US2840744A
Application number: US641508A
Authority: US
Inventors: Katzberg Jesse
Original assignee: Tung Sol Electric Inc
Current assignee: Tung Sol Electric Inc
Priority date: 1957-02-21
Filing date: 1957-02-21
Publication date: 1958-06-24
Anticipated expiration: 1975-06-24

Description

June 24, 1958 KATZBERG 2,840,744

THYRATRON Filed Feb. 21, 1957 FIG. I

FIG. 4

CURRENT I TIME M4 t t;

JESSE KATZBERG INVENTOR.

ATTORNEY United States Patent THYRATRON Jesse Katzberg, Tenafly, N. J., assiguor, by mesne assignments, to Tung-Sol Electric Inc., Newark, N. 1., a corporation of Delaware Application February 21, 1957, Serial No. 641,508 5 Claims. Cl. 313-493 This invention relates to a gaseous discharge device of the type which is triggered by a control electrode to convert it from a non-conducting condition to a conducting condition. The invention has particular reference to a shield arrangement which encloses a cathode and a control electrode and is designed to produce a discharge characteristic which is unvarying in the elapsed time between the application of a triggering potential and full conductive current between the anode and cathode.

Many types of thyratrons have been designed and used for many types of service. When used in radar circuits it is very important that the elapsed time between the application of a firing potential to the control electrode and the time of full conduction be kept as constant as possible. In ordinary types of thyratrons conduction may start between any part of the cathode emitting surface and the nearest point on the anode. Variations of temperature, ionization within the gas, and condition of the emitting surface make this time interval variable and consequently the accuracy of the radar system is reduced. The present invention employs a shield which encloses the cathode and permits conduction only through a narrow slot which is in alignment between the cathode and anode. At one end of the slot the geometry is altered so that a substantially wider portion exists, this wider portion always providing passage for the initial discharge between the cathode and anode. Since the discharge always starts at this portion, the triggering action is uniform in time duration and the entire radar system is made more accurate.

One of the objects of this invention is to provide an improved gaseous discharge device which avoids one or more of the disadvantages and limitations of prior art arrangements.

Another object of the invention is to provide a gaseous discharge device which has uniform firing characteristics.

Another object of the invention is to provide an improved gaseous discharge device which may be used in accurate radar systems or in any other timing arrangement where time delay characteristics are of prime importance.

Another object of the invention is to insure accuracy of timing characteristics in a gaseous discharge device by employing structural components which may be easily assembled in an accurate manner.

The invention comprises a gaseous discharge device which includes an envelope containing gas at a reduced pressure and includes a cathode, a control electrode, an anode, and a shield. The shield is constructed so as to enclose the cathode and the control electrode and has a slot opening adjacent to the anode, this slot having a substantially uniform width for the major portion of its length and a substantially greater width for the remainder of its length. I

For a better understanding of the present invention, together with other and further objects thereof, reference 2,840,744 Patented June 24, 1958 r is made to the following description taken in connection with the accompanying drawings. a

Fig. l is aside view of the discharge device with parts of the envelope broken away to show the internal construction.

Fig. 2 is a cross sectional view of the device shown in generally an elongated cylindrical electrode parallel to the sides of the envelope. The control electrode 12 may be in the form of a grid or a pluralityof closely spaced conductors, however, for the purposes of the present arrangement the control electrode comprises a single" cylindrical rod in alignment with the cathode and the anode. A shield 14 encloses the cathode and control electrode and is formed as shown with a slot 15 in alignment between the control electrode and the anode. The above mentioned components are held in place within the envelope by

insulating spacers

16 and 17 which are generally made of mica. The electrodes, including the shield, are connected to conductors which are sealed in a portion of the envelope and are connected to conducting pins 18 which are employed for connection with an external circuit.

Referring now to Fig. 3 it will be noted that the slot 15 which extends for a major portion of the length of the shield is terminated at the upper end by a much wider slot 20, this portion of the opening between the cathode and anode being arranged for the start of the conduction current. Because this opening 20 is about three times the width of slot 15, the initial conduction always occurs through this opening and is always initiated at the upper end of cathode 11. As long as the initial discharge is confined to this path the firing conditions will be more uniform than if the entire cathode surface were available.

The graph in Fig. 4 illustrates the operation of the device. The graph is plotted between current and time, the firing voltage being applied to the control electrode at time t During the first time interval, conduction is established between the cathode and the control electrode, this increase in current indicated by line 21, and the end of this operation being denoted by t During the second time interval, conduction is established be-' tween the cathode and the anode and ending when full conduction is established at time 1 The shape of the characteristic during the second time interval is shown by line 22. The shape of the characteristic 22 varies with different gasses and depends upon the ease of ionization of the gas. The characteristic shown in Fig. 4 illustrates the action of Xenon at a reduced pressure. It has been found that the time T for one type of tube is equal to .3 microseconds and that this time varies only .05 microseconds, plus or minus, for a wide range of temperatures and operating conditions.

If a wide slot of the same width as opening 20 were used, the tube would fire with less voltage applied to the control electrode but the variation in firing time T would be considerably greater. If the entire slot were narrow, the same dimension as slot 15, the firing voltage required would be much greater but the same variation in firing time would obtain. The firing voltage for the structure shown in Fig. 3 is only slightly greater than the firing voltage for a wide slot and the variation in necessary to place the wide slot at the end of theshield.-

Any other position will produce the same stable characteristics.

The foregoing disclosure and drawings are merely illustrative of the principles of this invention and are not to be interpreted in a'limiting sense. The only limitations are mine determined from the'seo'pe ofthe appended claims.

I claim:

1. A gaseous discharge device comprising; an envelope containing gas ata reduced pressure and including ,a cathode, a control electrode, an anode, and a shield; said shield enclosing the cathode and the control electrode and having a slot opening adjacent to the anode; said slot having a substantially uniform width for at least sixty percent of its length and a substantially greater width for the remainder of its length.

2. A gaseous discharge device comprising; an envelope containing gas at a reduced pressure and including a cylindrical cathode, a cylindrical control electrode, an elongated anode' and a shield; said shield enclosing the cathode and the control electrode and having a slot opening adjacent to the anode; said slot having a substantially uniform width for a least sixty percent of its length and a substantially greater width for the remainder of its length.

'3. Agaseous discharge device comprising; an envelope containing gas at a reduced pressure and including a cylindrical cathode, a cylindrical control electrode, an,

elongated anode and a metallic shield, said components positioned in substantially parallel arrangement; said shield enclosing the cathode and the control electrode and having a slot opening adjacent to the anode; said slot having a substantially uniform width for at least sixty percent of its length and a substantially greater width for the remainder of its length.

4. A gaseous discharge device comprising, an elongated cathode, an [anode spaced from and parallel to said cathode, an elongated control electrode between said anode and cathode, and a metallic shield which encloses the cathode and control electrode and having a slot opening adjacent to the anode; said slot having a substantially uniform width for at least sixty percent of 'its length and a substantially greater width for the remainder of its length.

5. A gaseous discharge device comprising, an elongated cathode with an emitting surface, an anode spaced from and parallel to said cathode, an elongated control electrode between said anode and cathode, and a metal shield which encloses the cathode and control electrode, the emitting surface of the cathode being exposed to the anode only through an elongated opening in said shield, said opening being substantially co-extensive with the cathode and uniform in width for at least sixty percent of its length and having a substantially greater width for the remainder of its length.

References Cited in the file of this patent UNITED STATES PATENTS I 2,185,852 Klopprogge Jan. 2,1940 2,431,237 Freeman Nov. 18, 1947 2,770,751 Prager et al Nov'. 13, 1956