US1962158A - Gaseous discharge device - Google Patents

Description

June 12, 19,34. l Q Q sMlTH 1,962,158

. GASEOUS DISCHARGE DEVICE original Filed Aug. 25, 1930 2 sheds-sheet 1 Jne 12, 1934. C, G SMITH 1,962,158

GASEOUS DISCHARGE DEVICE original Filed Aug. A25, 1930 2 sheets-sheet 2 con //v6 FL Ul D INVENTOR cgswuh. BY S MFM Wg ATTORNEY Patented June 12, 1934 v UNITED STATES PATENT OFFICE by mesne assignments,

to Raytheon Manufacturing Company, Newton, Mass., incorporation o! Delaware Application August 25, 1930s Serial Renewed May 6, 1933 13 Claims.

My invention relates to gaseous discharge devices. An object of the invention is the provision of such device in which the current flow is capable of being controlled by means of a grid or a magnetic field in a manner analogous to the control of the electron ow in high vacuum discharge devices.

For many years efforts have been made to provide gas-filled tubes in which a space current discharge produced by ionizing the gas in the tube may be controlled like in high vacuum tubes. In most of the tubes built heretofore for this purpose, no control action comparable to that in high vacuum tubes could be obtained because the positive ions filling the space within the tube would neutralize the control action and render it substantially ineffective.

In accordance with my invention a gaseous discharge device with full control of the current :dow by the action of a space charge grid or a magnetic eld may be obtained by a very simple arrangement of the electrodes of the device and suitable correlation of the several elements of the discharge path. In the device of my invention I arrange the two electrodes, namely the cathode and anode, between which the discharge that is to be controlled is maintained, in such manner that the cooperating electrode surfaces are separated by a path so short that no sub-- stantial ionization is produced by electrons traveling along said path under the influence of the electrostatic field produced by the application of a. relatively high potential to the anode.

The cathode is made in the form of a perforated body and on the side of said cathode opposite the anode the gas in the enclosing vessel is maintained in a highly ionized condition, by providing on said side an additional auxiliary electrode, for instance in the form of an incandescent thermionic member and connecting the perforated cathode v/ith the thermionic member in an auxiliary circuit ln which theperforated cathode acts as an anode and the therrnionic member acts as a cathode, maintaining a gaseous discharge in the space therebetween. 'Ihe configuration of the perforated cathode and its-arrangement with relation to the anode is such as tc substantially prevent positive ions in the space between the auxiliary thermionic cathode and the perforated cathode from entering the space between the perforated cathode and the anode. Electrons, however, enter freely through the openings in the perforated cathode and under the action of the high anode potential maintain a substantially pure electron discharge in the short gap between the perforated cathode and the anode. lBy providing a control grid extending transversely across the short gap between the perforated cathode and the anode, the electronic discharge can be readily controlled through variation of the potential applied to the control grid, as in high vacuum tubes.

ly across the lower end of the sheet-metal mein:a

ber 3 and forming a honeycomb structure hav-z ing vertically directed channels or perforations i. 'thev perforated cathode 2 is held in place by means of two supporting wires l which are mounted on a press t extending from a reenu trant stem 9 on the bottom side of the tube, one of the supporting wires being sealed through the press and forming a terminal conductor lo.

Mounted at a distance below the perforated cathode 2 is a thermionic electrode member lll forming an auxiliary cathode. This aurdliarfgr cathode may be made in the form ci a suitably coated larnent held on two lead-in wires l2 sealed through the press d.

'The tube has a gas iilling either in the torni. of a quantity oi gas-r such as helium, or in the form oi a vapor, such as mercury vapor or caesium vapor, the presence oi the gas filling being indicated by a drop oi' readily vaporizable metal 15 at the bottom of the tube.

A short distance above the perforated cathode is mounted a main anode i6 which is oi cupn shaped form and has its ilat bottom side arranged parallel to the top surface of the periorated cathode 2. lIhe distance between the opposite parallel surfaces is made very small, of the order of the mean free path of the molecules of the gas in the tube andpreferably less. TheY side walls of the cup-shaped anode are shaped so as to lie closely to the upper end of the cylindrical member 3 of the perforated cathode 2, the upper ends of the side walls extending for a substantial distance closely parallel alongthe walls of the envelope 1. Because of this arrangement soV all long paths between the portions of the perforated cathode 2 and the anode 16 are blocked, and direct gaseous conduction between said two electrodes by reason of ionization by collision along long paths under inuence of high voltages applied to the electrodes is substantially excluded.v

Extending transversely across the gap-like space between the upper surface of the perforated cathode 2 and the anode 16 is a grid electrode 18 which serves to control the current flow between the cathode 2 and theanode 16. Connection with the anode 16 is effected by means of a lead-in wire 19 sealed through a press 20 extending from a reentrant stem 21 at the upper end of the tube. The grid electrode 18 is connected to a similar lead-in wire 22, the portion of the grid lead-in Wire extending in the interior of the tube being surrounded by a glass sleeve 23 so as to exclude direct discharges to the anode portions by reason of the presence of paths of sufficient length to initiate conduction through ionization by collision.

The cylindrical tube l is surrounded by a magnet coil 25 that is suitably energized, as from a source 26, to produce a magnetic field extending longitudinally through the tube in the direction of the discharge path between the auxiliary cathode 11 and the perforated cathode 2 and the perforations 4 in said cathode.

The auxiliary thermionic cathode 11 is connected to a heating source, for instance in the form of a battery 31. A source of excitation current, such as a battery 32 has its negative terminal connected to the auxiliary cathode 11 and its positive terminal to the perforated cathode 2 which acts as an anode with respect to the auxiliary cathode 11 so as to maintain between said electrodes a gaseous discharge that ionizesvthe gas between said electrodes and produces in the space below the perforated cathode an abundant supply of electrons. Between the perforated cathode 2 and the anode 16 there is connected an output circuit 33 including an output device 34, such as a transformer, and a serially connected source of plate potential such as a battery 35 applying a relatively high positive potential to the plate.

An input circuit 36 including a source of input energy, for instance a transformer 37 and a source of biasing voltage such as a battery 38 shunted by a variable tap resistor 39 is connected between the perforated cathode 2 and the grid 18. The biasing battery 38 is sc arranged as to permit application of a negative biasing potential to the grid and the input transformer 37 serves to impress variable potentials that are to be amplified between the perforated cathode 2 and the grid 18.

Under the action of the excitation source 32, an ionized gas discharge is maintained between the auxiliary cathode 1l and the perforated cathode 2. Electrons are produced in abundance in this space by the cumulative ionization by collision of the electrons fiowing toward the anode. The space below the perforated cathode is thus filled with electrons and positive ions. The electrons flow upwardly towards the perforated cathode 2 and, partially because of the acquired velocity, they will pass through the perforations 4 and enter into the space 6 between the perforated cathode and the anode 16. The entering electrons come in this space under the infiuence of the strong eld produced by the high positive potential on the anode and a current iiow between the perforated cathode 2 and the anode 16 'is thus produced, like in a high vacuum tube.

By reason of the relatively long and close perforations 4 in the perforated cathode 2 very few of the positive ions from the space below get into the main discharge path between the cathode and the anode, so that the main discharge space contains only few positive ions and the discharge is substantially purely electronic.

'Ihis substantially pure electron current is readily controlled by varying the potential of the grid 18, there being insufficient positive ions in the space 6 to neutralize the charge on the control grid and render it inelfective, as in prior art constructions.

A limited amount of positive ions are present in Ithe main discharge space 6, either having gotten by the perforations in the cathode 2 cr having been produced by an isolated collision of an electron with a molecule. Such positive ions are only few in number and insuicient to neutralize or detrimentally affect the control action of the grid 18, the limited number of positive ions in the space 16 being beneficial in that they neutralize the space charge and reduce the impedance of the main discharge path.

The biasing battery in the input circuit connected to the grid 18 is so arranged as to apply a sufiiciently negative biasing potential to the grid so as to reduce the electron current tending to collecton the grid..

Tubes of the foregoing construction will operate'with very effective control of the current in the main discharge path by the grid action, with relatively large currents in the main discharge path and up to relatively high voltages in the output circuit. vIt is accordingly possible to control very large amounts of power in the output circuit by the application of very little input energy in the input circuit.

For the operativeness of the device it is absolutely essential that the several elements of the tube be so arranged with respect to each other as to prevent the formation of an ionized gas discharge in the main discharge path between the perforated cathode 2 and the anode 1 6. This is secured by the special construction which blocks the entrance of excessively large numbers of positive ions into the short gap main discharge path, and the blocking of all long paths between the anode 16 and the perforated cathode 2 as Well as the grid 18.

The honeycomb construction of the perforated cathode is particularly effective in preventing entrance of the positive ions from the space below 138 the cathode into the main discharge space while at the saine time permitting relatively free flow of electrons through the perforations, especially in combination with the action of the longitudinal magnetic eld produced by the coil 25. The magnetic field keeps the electrons flowing upwardly in straight vertical direction and facilitates their passing through the perforations without going to the walls forming the honeycomb structure, and overcoming the attraction 140 exercised by the positively charged walls on the negative electron charges.

By reason of the relatively great length of these perforations 4 the likelihood of positive ions passing through the honeycomb structure is very M5 small, inasmuch as the positive charge of the walls of the perforations exercise a cumulative repelling action over a substantial length of the path of flow of such positive ions, which have only relatively small velocity, thereby assurlngl a strong blocking action against their entrance into the main discharge path.

The combined effects of the honeycomb structure and the magnetic field thus'enable the use of relatively wide perforations in the main cathode 2 and secure an abundant supply of electrons for maintaining the main discharge under control of the grid 18. The honeycomb cathode structure thus acts like a wide-mesh grid for electrons, but like a close-mesh grid .for positive ions.

The longitudinal magnetic field gives also other effects beneficial for the operation of the tube. Without the field many of the electrons in the discharge space below the perforated cathode 2 collide with the surrounding glass walls and get trapped there, attracting positive ions from the discharge, thus reducing the ionization and conductivity of the space. With the longitudinal field present, electrons either flow straight along the magnetic lines of force without reaching the glass walls, or move along small helices without reaching the wall. In the latter case, the paths of the electrons are lengthened, giving additional ionization while at the same time reducing the loss of ionization by preventing the trapping of electrons on the glass walls.

Because of the foregoing effect of the longitudinal magnetic field in preserving the ionization in the discharge path between the auxiliary cathod 11 and the perforated cathode 2, it is possible to maintain in the space between said electrodes an ionized gas discharge at low pressures which would otherwise be insufficient to secure such discharge. This enables the construction of tubes with relatively low pressures and yet maintaining the main discharge with, electrons supplied from an ionized gas body, the low pressure permitting farther spacing of the electrodes in the controlled discharge path and securing efranged that the vapor pressure in said arms is` relatively small compared to the pressure directly above the mercury 53. In each of the two arms 55 is mounted a perforated cathode 56, a main anode 57 and a control grid 58, these several parts Ibeing constructed and arranged in accordance with the principles described in connection with the arrangement of the corresponding parts in the tube of Fig. 1. An auxiliary exciting anode60\ is provided in a side pocket adjacent to the mercury cathode 53. By means of a switch 61 the exciting cathode may be connected to the positive pole of a source of exciting potential 62 having its negative pole connected to the cathode 53, so as to start an arc discharge at the surface of the mercury cathode.

'I'he two perforated cathodes 56 are likewise connected by means of switches 63 to the positive pole of the exciting source 62 so that once the discharge at the mercury cathode has been started, the-gaseous discharge may bey readily transferred to said perforated cathodes 56 which will then act asl anodes with respect to the mercury cathode 53. y

The anodes 57 are connected to the end terminals of a supply transformer winding 65 and an output device 66 isk connected between the midpoint of said transformer winding and the conducting connection between the two perforated cathodes 56 so that two partially common output circuits are provided, one for each of the main anodes 57. Between each of the grids 58 and the common conducting connection between the two cathodes 56, is connected an input circuit including an input source 67 and a source of biasing potential 68.

In operation, a gaseous discharge will be maintained between the perforated cathodes and the auxiliaryI mercury cathode 53 in the same Way as a discharge is normally maintained between the anodes and the mercury cathode of a mercury arc rectifier. By reason of the arrangement of the perforated cathodes 56 and the main anodes 57 with the grids 58 associated therewith, as explained in connectionl with Fig. 1, the space in the two side arms 55 above the perforated cathodes 56 will be substantially free from ionized gas and the discharge between the perforated cathodes and the anode 57 will be substantially purely electronic and under full control of the grids 58. By varying the voltage impressed upon the grids 58 as by means of the input devices 67, the current flow between the perforated cathodes 56 and the anodes 57 may be readily controlled as explained above, notwithstanding the high voltage applied between the anodes and the perforated cathodes, and the large current fiow secured by the abundant supply of electrons from the discharge space below the perforated cathode.

The various details of construction, and arrangements referred to above in describingV the various modifications of my invention are intended for illustrative purposes only and I desire it to be distinctly understood that my invention is not limited thereto, as many modifications thereof will suggest themselves to those skilled in the art. I accordingly desire that the appended claims be given a broad construction in accordance with the scope of the invention,

1. A gaseous conduction device comprising a gas tight vessel containing a gas at a pressure suicient to secure its ionization and maintenance of a gaseous discharge therein, a relatively large area cathode having perforations over its surface, a relatively large area ano-de disposed adjacent one side of said cathode and spaced therefrom by a gap sufficiently short to prevent a gaseous discharge due to gas ionization between the opposed electrode surfaces under application of a high voltage therebetween, means for maintaining in the space on the side of the cathode opposite said Y anode a gaseous discharge ionizing the gas therein and generating electrons tending to enter through the cathode perforations the gap between the cathode and anode, and sustain an electron discharge to the anode therein upon application of a positive potential thereto, a control grid between said cathode and said anode arranged to control the discharge therebetween, and means associated with said cathode and anode for preventing entrance of electrons from the space of the gaseous discharge into spaces within the vessel through which continuous gaseous paths extend between any parts of the cathode and anode along which the gas would break down upon application of high voltages.

2. A gaseous conduction device comprising a gas tight vessel containing a gas at a pressure ysumcient to secure its ionization and maintelarge area cathode having perforations over its surface, a relatively large area anode disposed adjacent one side of said cathode and spaced therefrom by a gap of the order of the mean free path of a gas molecule or less, means for maintaining in the space on the side of the cathode opposite said anode a gaseous discharge ionizing the gas therein, a control grid between said cathode and said anode arranged to control the discharge therebetween, and means associated with said cathode and anode for preventing entrance of electrons from the space of the gaseous discharge into spaces within the vessel through which continuous gaseous paths substantially longer than the molecular mean free path extend between any parts of the cathode and anode.

3. A gaseous conduction device comprising a gas tight vessel containing a gas at a pressure sufficient to secure its ionization and maintenance of a gaseous discharge therein, a relatively large area cathode having perforations over its surface, a relatively large area anode disposed adjacent one side of said cathode and spaced therefrom by a gap suiciently short to prevent a gaseous discharge dueto gas ionization between the opposed electrode surfaces under application of a high voltage therebetween, means for maintaining in the space on the side of the cathode opposite said anode a gaseous discharge ionizing the gas therein and generating electrons tending to enter through the cathode perforations the gap between the cathode and anode, and sustain an electron discharge to the anode therein upon application of a positive potential thereto, and a control grid between said cathode and said anode arranged to control the discharge therebetween, said perforated cathode having associated therewith a body constituting conducting-wall channels extending from the space on theside opposite the gap toward the anode to permit entrance of elec- -trons from the gas discharge space into the gap While obstructing passage of positive ions into said gap. y

4. A gaseous conduction device comprising a gas tight vessel containing a gas at a pressure sufficient to secure its ionization and maintenance of a gaseous discharge therein, a relatively large area cathode having perforations over its surface, a relatively large area anode disposed adjacent one side of said cathode and spaced therefrom by a gap sufficiently short to prevent a gaseous discharge due to gas ionization between the opposed electrode surfaces under application of a high voltage therebetween, means for maintaining in the space on the side of the cathode opposite said anode a gaseous discharge ionizing the gas therein Aand generating electrons tending to enter through the cathode perforations the gap between the lcathode and anode, and sustain an electron discharge to the anode therein upon application of a positive potential thereto, a control grid between said cathode and said anode arranged to control the discharge therebetween, said perforated cathode having associated therewith a body constituting conducting-wall channels extending from the space on the side opposite the gap toward the anode to permit entrance of electrons from the gas discharge space into the gap while obstructing passage of positive ions into said gap, and means -for producing a magnetic eld in the direction along said channels. 5. A gaseous conduction device comprising a gas tight vessel containing a gas at a pressure sufiicient to secure its ionization and maintenance of a gaseous discharge therein, a relatively large area cathode having perforatlons over its surface, a relatively large area anode disposed adjacent one side of said cathode and spaced therefrom by a gap sufliciently short to prevent a gaseous discharge due to gas ionization between the opposed electrode surfaces under application of a high voltage therebetween, an additional electrode on the side of said perforated cathode opposite said anode arranged to be operated as cathode with respect to said perforated cathode and maintain therewith a gaseous discharge ionizing the gas therebetween and generating electrons tending to enter through the cathode perforations the gap between the cathode and anode, and sustain an electron discharge to the anode upon application of a positive potential thereto, a control grid between said cathode and said anode arranged to control the discharge therebetween, and means associated with said cathode and anode for preventing entrance of electrons from the space of the gaseous discharge into spaces within the vessel through which continuous gaseous paths extend between any parts of the cathode and anode along which the gas would break down upon application of high voltages.

6. A gaseous conduction device .comprising a gas tight vessel containing a gas at a pressure suicient to secure its ionization and maintenance of a gaseous discharge therein, a relatively large area cathode having perforations over its surface, a relatively large area anode disposed .adjacent one side of said cathode and spaced therefrom by a gap of the order of the mean free path of a gas molecule or less, an additional thermionically emitting electrode on lthe side of said perforated cathode opposite said anode arranged to be operated as cathode with respect to said perforated cathode and maintain therewith a gaseous discharge ionizing the gas therebetween and generating electrons tending to enter through the cathode perforations the gap between the cathode and anode, and sustain an electron discharge to the anode upon application of a positive potential thereto, a control grid between said cathode and said anode arranged to control the discharge therebetween, and means associated with said cathode and anode for preventing entrance of electrons from the space of the gaseous discharge into spaces within the vessel through which continuous gaseous paths extend between any parts of the cathode and anode along which the gas would break down upon application of high voltages.

7. A gaseous conduction device comprising a gas tight vessel containing a gas at a pressure sufficient to secure its ionization and maintenance of a gaseous discharge therein, a relatively large area cathode having perforations over its surface, a relatively large area anode disposed adjacent one side of said cathode and spaced therefromby' a gap of the order of the mean free path of a gas molecule or less, an additional therrnionically emitting electrode on the side of said perforated cathode opposite said anode arranged to be operated as cathode with respect .to said perforated cathode and maintain therewith a gaseous discharge ionizing the gas therebetween and generating electrons tending to enter through the cathode perforations the gap between the cathode and anode, and sustain an electron discharge to the anode upon application of a positive potential thereto, a control grid between said cathode and said anode arranged to control the discharge therebetween,

and means associated with said cathode and anode for blocking ypaths between the cathode and anode within the vessel suiiiciently long to permit breakdown of the gas therebetween upon application of a high voltage.

8. A gaseous conduction device comprising a gas tight vessel containing a gas at a pressure sulcient to secure its ionization and maintenance of agaseous discharge therein, a relatively large area cathode having perforations over its surface, a relatively large area anode disposed adjacent one side of said cathode and spaced therefrom by a gap of the order of the mean free path of a gas molecule or less, an additional electrode on the side of said perforated cathode opposite said anode arranged to be operated as cathode with respect to said perforated cathode and maintain therewith a gaseous discharge ionizing the gas therebetween and generating electrons tending to enter through the cathode perforations the gap between the cathode and anode, and sustain an electron discharge to the anode upon application of a positive potential thereto, a control grid between said cathode and said anode arranged to control the discharge therebetween, and. means associated with said cathode and anode for preventing entrance of electrons from the space of the gaseous discharge into spaces within the vessel through which continuous gaseous paths substantially longer than the molecular mean free pathv extend between any parts of the cathode and anode, said perforated cathode having associated therewith a body constituting conducting-wall channels extending from the space on the side yopposite the gap toward the anode to permit entrance of electrons from the gas discharge space into the gap While obstructing passage of positive ions into said gap.

9. A gaseous conduction device comprising a gas tight vessel containing a gas at a pressure sufficient to secure its ionization and maintenance of ar gaseous discharge therein, a relatively large area cathode having perforations over its surface, a relatively large area anode disposed adjacent one side of said cathode and spaced therefrom by a gap of the order of the inean free path of a gas molecule or less, an additional electrode on the side of said perforated cathode opposite said anode arranged to be operated as cathode with respect to said perforated cathode and maintain therewith a gaseous discharge ionizing the gas therebetween and generating electrons tending to enter through the cathode perforations the gap between the cathode and anode, and sustain an electron discharge t to the anode upon application of a positive potential thereto, a control grid between said cathode and said anode arranged to control the discharge therebetween, and means associated with said cathode and anode for preventing entrance of electrons from the space of the gaseous discharge into spaces within the vessel through which continuous gaseous paths substantially longer than the molecular mean free path extend between any parts of the cathode and anode, said perforated cathode having associated therewith a body constituting conducting-wall channels extending from the space on the side opposite the gap toward the anode to permit entrance of electrons from the gas discharge space into the gap while obstructing passage of positive ions into said gap, and means for producing a magnetic field in the direction along said channels.

10. A gaseous conduction device comprising a gas-tight vessel containing a gas at a pressure sufiicient to secure its ionization and maintenance of a gaseous discharge therein, a relatively large-area electrode having perforations over its surface, a relatively large-area anode disposed adjacent the perforated electrode and spaced therefrom by a. gap sufficiently short to prevent substantial gas ionization between the opposed electrode surfaces under application of -a high voltage applied therebetween, means for maintaining in the space on the side of the perforated electrode opposite said anode a gaseous discharge, ionizing the gas therein and generating electrons tending to enter, through the electrode perforations, the gap between the perforated electrode and the anode, and to sustain a discharge to the anode therein; means for controlling the discharge between said perforated electrode and said anode, and means associated with said perforated electrode and said anode for blocking and preventing gaseous discharges along paths suiiiciently long to permit ionizing gaseous discharges between said perforated electrode and anode. Y

11. A gaseous conduction device comprising a gas-tight vessel containing a gas at a pressure sufncient to secure its ionization and maintenance of a gaseous discharge therein, a relatively large-area electrode having perforations over its surface, a relatively large-area anode disposed adjacent the perforated electrode and spaced from by a gap suiciently short to prevent suhstantial gas ionization between the opposed electrode surfaces under application of a high voltage applied therebetween, means for maintaining, in the space on the side of the perforated electrode opposite said anode, a gaseous discharge, ionizing the gas therein and generating electrons tending to enter, through the electrode perforations, the gap between the perforated electrode and the anode, and to sustain a discharge to the anode therein, a control electrode between said anode andvsaid perforated lll@ electrode to control the discharge to said anode,

and means associated with said perforated electrode and said anode for blocking and preventing gaseous discharges along paths sufiiciently long to permit ionizing gaseous discharges between said perforated electrode and anode.

l2. A gaseous conduction device comprising a gas-tight vessel `containing a gas at a pressure sufcient to secure its ionization and maintenance of a gaseous discharge therein, a relatively large-area electrode having perforations over its surface, a relatively large-area anode disposed adjacent the perforated electrode, means for maintaining, in the space on the side of the perforated electrode opposite said anode, a gaseous discharge, ionizing the gas therein and generating electrons tending to enter the gap between the perforated electrode and the anode through the electrode perforations and to sustain a discharge to the anode therein, means for controlling the discharge between said perforated electrode and said anode,'ali surfaces of said perforated electrode and said anode along which substantial conduction may occur during operation under the potentials applied to said electrode being spacedv from each other a distance sufficiently short to prevent substantial gas' ionization between said electrode surfaces.

13. A gaseousfconduction device comprising a gas-tight vessel containing a gas at a pressure suiiicient to secure its ionization and `mainterated electrode and the anode, and to sustain a discharge to the anode therein, means for controlling the discharge between said perforated electrode and said anode; and means associated with said perforated electrode and said anode for preventing the entrance of electrons from said gaseous discharge into spaces within the vessel through which extended paths between parts of the anode and said perforated electrode sufficiently long to produce ionizing gaseous discharges upon the application of relatively high voltages to said anode.

' C. G. SMITH.

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