US3789214A

US3789214A - Irradiation apparatus

Info

Publication number: US3789214A
Application number: US00655231A
Authority: US
Inventors: C Goldie; R Fernald
Original assignee: US Atomic Energy Commission (AEC)
Current assignee: US Atomic Energy Commission (AEC)
Priority date: 1967-07-21
Filing date: 1967-07-21
Publication date: 1974-01-29
Anticipated expiration: 1991-01-29

Abstract

An apparatus for introducing ionizing radiation into compressed gas insulation systems, such as high voltage generators or transmission lines to smooth out electrical discontinuities, particularly those caused by foreign particulates, that produce high gradients and to increase the voltage holding capability of the system. The apparatus of the invention may also be used to regulate and stabilize the voltage of the system by varying the amount of applied load. A corona discharge device may also be used in conjunction with the invention.

Description

United States Patent [191 Goldie et a1.

[ Jan. 29, 1974 1 IRRADIATION APPARATUS [75] Inventors: Charles H. Goldie, Bedford; Robert A. Fernald, Carlisle, both of Mass.

[73] Assignee: The United States of America as represented by the United States Atomic Energy Commission, Washington, DC.

[22] Filed: July 21, 1967 21 Appl. No.: 655,231

[52] U.S. Cl. ..250/354, 174/28, 250/106, 333/96 [51] Int. Cl. .7 Holj 37/00 [58] Field of Search... 250/43, 106; 324/54; 333/96; 174/28 [56] References Cited UNITED STATES PATENTS 3,417,318 12/1968 Farmer ..250/43 2,756,840 7/1956 Maas 250/106 3,123,511 3/1964 Coleman 250/106 3,361,866 l/l968 Babigan 250/106 Primary ExaminerJames W. Lawrence Assistant Examiner-C. E. Church Attorney, Agent, or FirmJohn A. Horan [5 7] ABSTRACT An apparatus for introducing ionizing radiation into compressed gas insulation systems, such as high voltage generators or transmission lines to smooth out electrical discontinuities, particularly those caused by foreign particulates, that produce high gradients and to increase the voltage holding capability of the system. The apparatus of the invention may also be used to regulate and stabilize the voltage of the system by varying the amount of applied load. A corona discharge device may also be used in conjunction with the invention.

11 Claims, 7 Drawing Figures IRRADIATION APPARATUS BACKGROUND OF THE INVENTION Compressed gas insulated transmission lines such as particle accelerators which produce energetic charge particle beams have long been used for studying the atomic nucleus. All such accelerations generally involved the generating of electrostatic fields to acceler ate the particles and magnetic fields to constrain the accelerated particles in a selected trajectory.

Tandem accelerators such as disclosed in U.S. Pat. No. 2,206,558 to Bennett operate on the voltage doubling principle which depends on the controlled reversal of particle polarity. This principle uses a single DC. potential to twice accelerate the charged particle and can produce well directed homogeneous geams of charged particles having energies up to 30 MeV for simple ions.

However, such machines have failed to realize their full potential. One difficulty that has arisen with such machines is associated with foreign particulates such as dust within the machine which causes a breakdown in the insulating gas thereby resulting in electrical discharges between the terminal and the tank walls. These discharges cause instability in the voltage impressed on the terminal and prevent the terminal from maintaining its full rated voltage.

SUMMARY OF THE INVENTION Broadly speaking the present invention comprises an apparatus which produces ionizing radiation in the insulating gas used in compressed gas insulation systems to modify the breakdown potential of the gas gap and permit controlled leakage of charge from dust particulates in the system thereby immobilizing them and preventing catastrophic discharges from occurring in the system.

More specifically the apparatus of the present invention can be either a radioactive source or X-ray generator. Feedback information from a voltage measuring unit can be used to control the intensity of the radiation and thus control the voltage level and stability of the system.

Moreover a corona discharge machine can be coupled with the apparatus of the invention to supply power to the X-ray generator and to further establish the desired voltage level of the system.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates one type of tandem generator that may advantageously use the present invention;

FIG. 2 is a cross sectional view of an apparatus for introducing a radioactive source into the accelerator of FIG. 1;

FIG. 3 illustrates schematically an X-ray generator for producing the desired radiation;

FIG. 4 illustrates schematically an X-ray generator modified with a corona apparatus;

FIG. 5 illustrates schematically a feedback network for control of the radiation level of the embodiments described in FIGS. 2, 3 and 4;

FIG. 6 illustrates schematically still another X-ray generator for producing the desired radiation;

FIG. 7 illustrates a co-axial gas insulated transmission line having an ionizing radiation source disposed on the inner wall of its outer shell.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a compressed gas insulated tandem accelerator of the MP type sold by High Voltage Engineering Corporation. This accelerator comprises an electrically grounded outer container such as a pressure tank 10 supported off the floor 11 by a plurality of legs 12. The tank is approximately 8| feet in length and varies in diameter from 18 feet at its mid point where it encloses the coaxial high voltage line such as terminal 14 to about I 1 feet at either end. The tank is filled with a compressed insulating gas, such as sulphur hexafloride, and contains an insulating column 15 which supports the terminal 14 and the necessary associated equipment not shown such as the charging belt drive motor, acceleration tubes, etc. Around the column are fitted a plurality of equipotential rings 16 having voltage divider resistors (not shown) which establish along the enclosed column a controlled potential gradient and form an electrically smooth envelope around the column which decreases in potential between the terminal and the ends of the tank.

The terminal 14 is raised to a high potential in a conventional manner by an endless traveling belt (not shown) which transports electrostatic charge between the high voltage terminal and ground. If the charge impressed on the terminal is assumed to be positive then negative ions produced in a negative ion source such as ion source 17 are injected into an acceleration tube (not shown) contained in the column. The negative ions in the tube are pulled toward the terminal by the positive charge existing thereon. Within the terminal the negative ions pass through a stripper (not shown) which converts them to positive ions. These positive ions then emerge from the terminal into a second tube and there are again accelerated by the repulsive force existing between the now positively charged ions and the positive charge on the terminal. The doublyaccelerated beam of now positive ions emerges from the machine and passes through a beam tube 18 where it is focused by a quadrupole magnet 19, analyzed by an analyzing magnet 20, and used.

In extended tests on various machines using this tandem acceleration principle it was often found that they failed to hold their full rated voltage because of random catastrophic discharges that occurred between the bottom of the terminal or immediately adjacent equipotential rings and the bottom of the tank. Evidence indicated that these discharges or sparks were associated with foreign particulates such as dust in the machine. Repeated cleanings and installation of mechanical dust suppression equipment reduced the problem and raised the attained voltages but only to a degree.

The introduction of the present invention was, however, an instant success and the results achieved spectacular. In one machine the random sparking occurred beginning at 8 million volts but after introduction of the present invention the machine operated quietly up to about 11 million volts, thus the use of the present invention greatly increased the voltage holding capabilities of the machine.

One embodiment of the present invention is shown in FIG. 2. Preferably two such devices 31 would be used in the accelerator shown in FIG. 1 and would be located at suitable entrance ports 21 at each end of the terminal 14. By thus locating the invention the radiation emitted will cover the entire field of interest which includes not only the region immediately under the terminal but also under the immediately adjacent equipotential rings 16.

In detail the devices 31 incorporating the invention are identical and each, as shown in FIG. 2 in cross section, comprise a steel housing 23 secured over the port 21 by a flange 24 carrying a lead shielded valve adapter 30. The housing 23 contains a radiation capsule 25, preferably of irridium 192 having a four curie intensity, centrally located within a lead shield 27. The capsule 25 is situated on the end of a slidable shaft 26 which is of a length sufficient to pass the capsule 25 out of the shield 27 through a first rotatable valve 32, a second rotatable valve 33 contained in the valve adapter 30, the flange 24 and port 21 into the tank where it is covered with a source shroud 36 which protects the capsule from direct contact by dust or other particles and provides a smooth equipotential surface. This source shroud must be sufficiently high enough above the tank walls so that the radiation capsule when inserted in the tank will clear the tank walls and exert its full share of influence.

Both

valves

32 and 33 prevent leakage of radiation from the unit when they are closed and the capsule is withdrawn within the shield 27. Each valve consists of a

rotatable ball

28 and 29 respectively which are provided with

axial openings

34 and 35 respectively and which line up with the capsule and shaft 26 when the

valves

32 and 33 are open.

The flange 24 bolted to the tank 10 by bolts 37, the adapter 30 and the steel housing 23 normally remain as a subassembly on the accelerator and only the inner core consisting of the lead shield 27 containing the capsule 25 is removed when it is necessary to replace the source.

In replacing the source the technique is to withdraw the shaft so that the capsule 25 passes through valve 32. Valves 32 and 33 are then closed. Valve 33 is used, in addition to sealing off the radiation, to seal off the tank insulating gas from the atmosphere. When both valves .are closed, the bolts 38 securing the shield 27 to housing 23 are removed and the entire radiation subassembly unit comprising shield 27, valve 32, capsule 25, and shaft 26 is withdrawn. Replacement of a new source is accomplished by reversing these steps.

The ionizing radiation emitted-by the capsule is effective in suppressing the dust only when the capsule is situated within the source shroud 36. This radiation prevents sparking in the machine until voltages higher than usual are reached.

The following explanation has been formulated to explain this resulting increase in voltage. An examination of accelerators, of the type shown in FIG. I, which randomnly sparked at voltages below the expected level, disclosed spark marks all over the lower surface of the terminal and the immediately adjacent equipotential rings at the terminal ends of the column. Few, if any spark marks, were found on the top surfaces of the hoops and terminal. This seemed to indicate that dust was a strong contributing factor. It is assumed that when a dust particulate falls to the bottom of the tank it, there, slowly charges up with the same charge polarity as the tank until the portion of the dust projecting furthest from the tank wall has a high gradient on it. When this gradient becomes sufficiently large the electrostatic forces acting between it and the terminal will become strong enough to overcome the forces of gravity causing the dust particulate to move to the terminal. Because of the high voltages involved in accelerators of this type, this movement of the dust particle from the tank wall to the terminal precipitates a spark discharge between the terminal and the tank wall.

The introduced radiation from capsule 25 creates leakage in the insulating gas filling the tank sufficient to prevent the dust particulate from becoming charged to a point where movement of the particulate will occur. Thus the ionizing radiation immobilizes the dust particulate on the tank wall and permits a high voltage to be impressed on the terminal without dust precipitated spark discharges occurring.

In the MP model accelerator shown in FIG. 1 it was found that the radiation sources should total at least 4 curies and should not be greater than 8 curies. These intensities will vary dependent upon the gas, its pressure, and the geometry of the tank.

Because the irradiator shown in FIG. 2 is a radioactive isotope, extreme precautions must be taken in its installation and handling. Moreover, since the isotope has a natural decay life time it is also necessary that it be periodically replaced. Thus it is desirable that an irradiation device be provided which will last long periods and which can be safely turned off or on at will and which will provide exact control of the radiation energy, intensity and geometrical distribution.

Such a device realizing all of these additional features is shown in FIG. 3. In this figure it is illustrated schematically an X-ray unit suitable for producing the desired radiation in the accelerator tank of FIG. 1. The unit comprises a pressure tank 40 containing a moving belt 41, a belt charging unit 42, a high voltage terminal 43, an accelerator tube 44, containing an electron emitter such as cathode 45, and an anode or target 46.

The described unit is bolted over port 21 such that the target 46 protrudes through the port into the source shroud 36. The belt made of insulating material runs between two pulleys, drive pulley 47 mounted on the generator and a terminal pulley 48 mounted on the high voltage terminal 43. The drive pulley is maintained positive with respect to the charging device 42. Negative charge from the charging device 42 is sprayed onto the moving belt which then carries the charge to the terminal 43. Here the charge is removed from the belt and deposited on the terminal itself. This charge is then used to maintain the terminal at a desired voltage level.

Simultaneously cathode 45 is biased to emit electrons into the accelerator tube and because of the voltage differential between the terminal 43 and the anode 46 which is at ground potential they are accelerated to an energy corresponding to the voltage on the terminal shell. Upon striking the anode 46 these highly energetic electrons cause X-rays to be produced. These X-rays pass through the anode shroud 36 which should be composed of a low, atomic number material, such as aluminum, to prevent the accumulation of charge on any dust particulates that may be present. Thus the X- rays prevent sparking in the same manner as did the radiation emitted by the irridium I92 capsule of FIG. 2.

Such an X-ray unit can be controlled to produce exact amounts of radiation and can be turned off or on at will thus reducing the hazards inherent in the handling of the isotope unit of FIG. 2. Preferably for the described tandem accelerator the X-ray machine should operate somewhere in the range between 400 and 1,000 kilovolts and be designed in such a way that the X-rays emitted at the anode would radiate the entire region of interest. Although this energy range is preferred higher or lower energies may be used with adequate results.

It should, of course, be obvious to those skilled in the art that the device described above as well as the device described in conjunction with FIG. 2 will operate with negative terminal machines as well as the positive terminal machine described previously in conjunction with FIG. 1. Thus the ionizing radiation producing device will operate to immobilize the dust regardless as to whether or not the machine were negative or positive. (Still further these ionizing producing devices concentrate in one device a single load having advantages both from a voltage point of view and a stabilizing point of view without having two load systems.)

It is also obvious that a valved adapter, similar to adapter 30 of FIG. 2, could be inserted between the X-ray tank 40 and the accelerator tank thereby providing a means of sealing off the interior of tank 40 from the interior of tank 10. When such an adapter is used then, of course, the anode 46 must be retractable through the valve in the adapter. This can be accomplished by either moving the tank 40 together with its contained equipment or by moving just the accelerator tube 44 to withdraw the anode from within the shroud 36.

If desired, the X-ray unit can be coupled with a corona discharge unit to precisely control and stabilize the terminal voltage as well as increase the terminal voltage to desired levels. In this case the corona unit can be used to provide the acceleration voltage required in the X-ray machine and thereby eliminate the charging belt and associated equipment as shown in FIG. 3.

A combined corona discharge X-ray unit which would satisfy this need is shown schematically in FIG. 4. The control circuit of this device is shown in FIG. 5. First considering FIG. 4, the X-ray machine comprises a tank 50 secured over port 21 by convenient means. Within the tank 50 there is provided only an accelerator tube 51 containing cathode 52, a cathode shield 53, and an anode 54. This tube is mounted in the tank through a slidable seal 58. Mounted on the accelerator tube 51 over the anode end of the tube is a corona discharge cap 55 bearing a plurality of corona points 56. This cap also serves as a source shroud to the anode 54.

The cathode 52 is serially connected with the secondary side ofa transformer 57 which is centrally tapped by a lead 59 which leads from a feedback circuit as shown in FIG. 5.

The intensity and level of the X-rays produced in this device is dependent on the discharge between the corona cap 55 and the terminal 14. The discharge between accelerator terminal 14 and corona cap 55 produces a current flow through voltage divider 13 and establishes the voltage of the anode at some level significantly above ground. The particular anode voltage, of course, depends on the voltage established by this discharge and the value of the voltage divider 13 while the corona voltage is dependent on the distance between the cap 55 and the terminal 14. Thus the corona voltage may be varied by moving the corona cap 55 closer to or farther from terminal 14. This movement is accomplished by sliding the entire device through the compression seal 58.

When the anode reaches its positive value, electrons emitted by the cathode will be accelerated by the voltage between the cathode and the anode and upon striking the anode produce X-rays to immobilize the dust particulates as previously discussed in conjunction with FIGS. 2 and 3.

In this particular embodiment, described in conjunction with this figure, the electron emission of the cathode 52 is controlled by its relative level with respect to the grounded cathode shield 53. This level is dependent upon the feedback signal received from the circuit of FIG. 5 through lead 59. The signal delivered through lead 59 varies the voltage received by the cathode and therefore determines its potential. If the cathode is biased properly with respect to the cathode shield 53 electrons are emitted which will upon striking the anode create X-rays. However, if the cathode is biased improperly with respect to the shield the emission ceases. This device is particularly safe since it automatically shuts off if the terminal voltage is turned down. Moreover, the device will last long periods of time without replacement and is simpler in operation and more easily controlled than the device shown in conjunction with FIG. 2.

The circuit shown in FIG. 5 is typical ofa control circuit and operates by sensing small deviations in the beam path and using the resulting signals to control the cathode emission of the X-ray machine shown in FIG. 4 to thereby hold the terminal voltage at a set value by increasing or decreasing the X-ray flux which increases or decreases the ionization in the insulating gas between the terminal and tank. Moreover, this circuit can be used to vary the corona beam load by varying the position of the corona cap further establishing the desired value of the terminal voltage.

Basically the device works as follows. Accelerated ion beam 60 passes through the beam tube 18 towards an analyzing magnet 20 which deflects the particles comprising the beam through an angle from their original path. The lower the energy content of a particle of a given mass the greater its deflection for a given magnetic flux density. Contrarywise the higher the energy the same particle, the smaller its deflection for the same flux density.

Since the equipment maintaining the magnetic flux is extremely stable and since only those particles having the same mass and energy are deflected equally, the an alyzing magnet produces a homogeneous beam 60a of particles which pass down the beam tube extension 18a. The remaining variable, i.e., energy of the particles, depends then upon the terminal voltage and fluctuations in the energy of the particles above or below a set value.

The analyzed beam 60a passes a pair of slit edges 63 and 64 which are located in the beam tube extension 18a. When these slit edges are adjusted to define a beam axis for a particular beam energy, the beam passes centrally through the slit edges and is in contact with both. The beam current intercepted by these edges is of course kept at a minimum value. When terminal voltage fluctuations above or below the desired value occur they introduce an undesired beam deflection towards one slit edge and away from the other which varies the amount of current intercepted by each edge. The resultant signal shift is interpreted by the respective signal sources 61 and 62 which provide error signals to matched

D.C. preamplifiers

65 and 67. These

preamplifiers

65 and 67 are powered by suitable

D.C. power sources

66 and 68 respectively.

The now amplified error signals are fed to a differential amplifier 69 powered by source 70 and designed to combine and analyze the signals received from the matched pair of

preamplifiers

65 and 67. This differential amplifier now supplies an error correction signal via line 59 to the X-ray corona unit shown in FIG. 4. This signal is not only fed into the transformer 57 which controls the cathode bias of the X-ray tube of FIG. 4 but also may be used to drive a motor control which varies the distance of the corona cap from the terminal. This variation in distance between the cap and the terminal increases or decreases the corona load on the terminal and simultaneously increases or decreases the flux of X-rays emitted by the X-ray machine.

The signal derived from the circuit of FIG. 5 may also be used with the X-ray unit as shown in FIG. 4 to vary the intensities of the X-rays alone without changing the value of the corona load. Other control circuits can be used such as signals from GVM, capacitor pickups, nuclear instrumentation, etc.

This signal may also be used to vary the X-ray flux emitted by the X-ray device of FIG. 3 by varying the 'charge sprayed onto the belt. However, this application is not preferred because of the time delay involved in the belt of this machine. It can also be used to vary the emission of the cathode via coupling to the high voltage terminal by such devices as an insulating light pipe or by an RF carrier wave.

The signal fed along line 59 may also be used to drive a mechanical shield across the anode thereby suppressing the X-rays. Proper shaped shields can also be used to vary the distribution of the X-rays. This mechanical shield could also of course be used with the irradiation source of FIG. 2.

FIG. 6 illustrates still another embodiment of an X-ray generator suitable for producing the desired radiation. This device contains features of the machine of FIG. 3 with features of the machine of FIG. 4 and comprises a pressure tank 40a containing a moving belt Ma, a belt charging unit 42a, a high voltage terminal 43a, an accelerator tube 44a containing an electron emitter such as cathode 45a and an anode 46a. This device, however, differs from that of FIG. 3 in that the charging unit 42a and the terminal shell 43a are reversed and is similar to that of FIG. 4 in that the grounded cathode 45a is controlled by signals from the control circuit of FIG. 5 received along lead 59.

These charges and combination of features provide certain distinct advantages not obtainable in the separate devices of FIGS. 3 and 4. Reversal of the terminal from the cathode end to the anode end permits grounding of the cathode, establishes a better irradiation field in the tank without undesirable field distortion in the tank and eliminates the need of a source shroud. Grounding of the cathode and utilization of the signals from the circuit of FIG. 5 along lead 59 provides closer control of the electron emission and hence closer control of the X-ray emission. Thus this feature provides easier stabilization of the machine.

If desired a field shaping element 80 may be provided over the anode 46a to shape the irradiation field emitted by anode 46. Proper shaping of this element when made of a radiation absorbing material such as lead provides a selected geometrical distribution of the irradiation field thereby providing suitable dust suppression without causing undue loading of the terminal.

This field shaping element can also be used with any of the other devices previously described in FIGS. 2, 3 or 4. Moreover, it should now be obvious, to those skilled in the art, that other features of FIGS. 2, 3 and 4 could be incorporated in the device shown in FIG. 6. For example, two such features would be the sliding seal 58 of FIG. 4 and the valved adapter 30 of FIG. 2.

The invention may also be used with gas filled transmission lines. Such lines as shown in FIG. 7 generally comprise hollow cylindrical shells 81 and a central coaxial solid conductor 83. Between the central line 83 and the shell 81, the space 82 is usually filled with a compressed gas. In this view the ionizing radiation source is a radioactive material dispersed in a paint or plastic coating 84 which is disposed over the entire inner wall of the shell 81.

Having now described the invention and several embodiments thereof it is desired that the invention not be limited to the particular examples given herein but limited only by the following appended claims.

What is claimed is:

l. A compressed gas electrical system comprising an electrically grounded outer container, a line, means for maintaining said line at a high voltage within said outer container, a gas maintained at greater than atmospheric pressure between said outer container and said line, said gas being susceptible to the introduction therein of foreign particulates such as dust, and means for introducing ionizing radiation into said compressed gas to smooth out electrical discontinuities in said gas by preventing the movement of said particulates by electrostatic means between the line and the outer container, to increase the permissible level of voltage that may be applied to said line and to stabilize the voltage level that is applied to said line, wherein said introducing means comprises a port in the container, an apertured flange across said port, a valved adapter on said flange, a radiation shield on said adapter and a moveable radiation source in said shield aligned with said adapter and the aperture in said flange and means for passing said source out of said shield through said adapter and flange into said container.

2. A compressed gas electrical system comprising an electrically grounded outer container, a line, means for maintaining said line at a high voltage within said outer container, a gas maintained at greater than atmospheric pressure between said outer container and said line, said gas being susceptible to the introduction therein of foreign particulates such as dust, and means for introducing ionizing radiation into said compressed gas to smooth out electrical discontinuities in said gas by preventing the movement of said particulates by electrostatic means between the line and the outer container, to increase the permissible level of voltage that may be applied to said line and to stabilize the voltage level that is applied to saidline, wherein said outer container has a port and wherein said introducing means comprises a pressure tank mounted across said port in said container, said pressure tank containing a charging unit, a moving belt for transporting charge from said unit, a terminal for receiving the charge from said belt, and an acceleration tube having a cathode disposed on one end adjacent to said terminal and an anode disposed at the other end of said tube, said anode being disposed within said container beneath said line.

3. The device of claim 2 wherein there is further provided a radiation absorbing device between said anode and said line.

4. The device of claim 2 wherein said terminal is disposed over said anode between said anode on said line.

5. A compressed gas electrical system comprising an electrically grounded outer container, a line, means for maintaining said line at a high voltage within said outer container, a gas maintained at greater than atmospheric pressure between said outer container and said line, said gas being susceptible to the introduction therein of foreign particulates such as dust, and means for introducing ionizing radiation into said compressed gas to smooth out electrical discontinuities in said gas by preventing the movement of said particulates by electrostatic means between the line and the outer container, to increase the permissible level of voltage that may be applied to said line and to stabilize the voltage level that is applied to said line, wherein said system is an electrical transmission line.

6. A compressed gas electrical system comprising an electrically grounded outer container, a line, means for maintaining said line at a high voltage within said outer container, a gas maintained at greater than atmospheric pressure between said outer container and said line, said gas being susceptible to the introduction therein of foreign particulates such as dust, and means for introducing ionizing radiation into said compressed gas to smooth out electrical discontinuities in said gas by preventing the movement of said particulates by electrostatic means between the line and the outer container, to increase the permissible level of voltage that may be applied to said line and to stabilize the voltage level that is applied to said line, wherein said outer container has a port and wherein said introducing means comprises a pressure tank mounted across said port in said container, said pressure tank containing an acceleration tube having a cathode at one end and an anode at the opposing end, a corona cap disposed over the anode end of said tube, a resistor chain along said tube from said cap to said cathode end, and means coupled to said cathode for controlling the level of electron emission from said cathode.

7. The device of claim 6 wherein said controlling means comprises a circuit that detects the voltage level of said line and returns a signal to said cathode to control the emission of said cathode, said circuit comprising matched signal detectors feeding matched preamplifiers amplifying said signal and feeding a differential amplifier which transmits a signal to said cathode to control the electron emission thereof.

8. A compressed gas electrical system comprising an electrically grounded outer container, an inner electrode, means for delivering charging current to and thus maintaining said inner electrode at a high voltage within said outer container, a gas maintained at greater than atmospheric pressure between said outer container and said inner electrode, said grounded container having an opening for the purpose of permitting entrance from time to time into said container by persons for maintenance and other purposes, whereby dust and other foreign particulates are introduced into the space within said container, means for introducing ionizing radiation into said compressed gas to smooth out electrical discontinuities in said gas by preventing the movement of said particulates by electrostatic means between the electrode and the outer container, to increase the permissible level of voltage that may be applied to said electrode, said ionizing radiation causing a partial load current, and means other than said ionizing radiation to provide a controllable current (other than said partial load current) to said electrode for controlling the voltage thereof.

9. The method of increasing the permissible level of voltage that may be applied to a compressed gas insulating system which system includes an insulating gas maintained at greater than atmospheric pressure, an inner electrode, and an outer electrode substantially surrounding said inner electrode and insulated therefrom by said insulating gas, said system also including all necessary means for controlling the voltage of said inner electrode, which method comprises, apart from voltage-controlling or voltage-stabilizing steps, the additional step of introducing ionizing radiation into said system to prevent foreign particulates from becoming electrostatically charged to a level where movement of said particulates will occur.

10. A gas filled electrical transmission line comprising an outer hollow, cylindrical shell and an inner coaxial line, a compressed insulating gas between said shell and said line and means for introducing ionizing radiation into said gas.

11. The device of claim 10 wherein said means comprise a coating of radioactive material disposed along the inner surface of the shell.

Claims

1. A compressed gas electrical system comprising an electrically grounded outer container, a line, means for maintaining said line at a high voltage within said outer container, a gas maintained at greater than atmospheric pressure between said outer container and said line, said gas being susceptible to the introduction therein of foreign particulates such as dust, and means for introducing ionizing radiation into said compressed gas to smooth out electrical discontinuities in said gas by preventing the movement of said particulates by electrostatic means between the line and the outer container, to increase the permissible level of voltage that may be applied to said line and to stabilize the voltage level that is applied to said line, wherein said introducing means comprises a port in the container, an apertured flange across said port, a valved adapter on said flange, a radiation shield on said adapter and a moveable radiation source in said shield aligned with said adapter and the aperture in said flange and means for passing said source out of said shield through said adapter and flange into said container.

2. A compressed gas electrical system comprising an electrically grounded outer container, a line, means for maintaining said line at a high voltage within said outer container, a gas maintained at greater than atmospheric pressure between said outer container and said line, said gas being susceptible to the introduction therein of foreign particulates such as dust, and means for introducing ionizing radiation into said compressed gas to sMooth out electrical discontinuities in said gas by preventing the movement of said particulates by electrostatic means between the line and the outer container, to increase the permissible level of voltage that may be applied to said line and to stabilize the voltage level that is applied to said line, wherein said outer container has a port and wherein said introducing means comprises a pressure tank mounted across said port in said container, said pressure tank containing a charging unit, a moving belt for transporting charge from said unit, a terminal for receiving the charge from said belt, and an acceleration tube having a cathode disposed on one end adjacent to said terminal and an anode disposed at the other end of said tube, said anode being disposed within said container beneath said line.