RU2703518C1 - Pulsed neutron generator - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to pulsed neutron generator. Pulsed neutron generator contains a vacuum neutron tube in a sealed metal housing with a three-electrode ion source with an anode, a cathode and an ignition, as well as a circuit for its supply and formation of a pulse of accelerating voltage. Circuit includes a high-voltage transformer, a storage capacitor, a bias resistance, a throttle, a spiral spring with a rectangular cross-section profile of the coil is inserted into the gap between the housing and the grid electrode of the neutron tube, and elements of power supply circuit and formation of accelerating voltage and electrodes of three-electrode ion source are connected to each other by means of floating contacts "rod-socket".

EFFECT: improving reliability, repairability, service life of neutron generator, reducing labor intensity of manufacturing of neutron generator.

1 cl, 1 dwg

Description

The invention relates to the field of physical instrumentation, in particular to sources of neutron radiation, and is intended for use in the development of neutron and x-ray generators.

Known pulsed neutron generator on a vacuum neutron tube, containing in a metal casing, filled with a liquid dielectric, a neutron tube with power elements of its source and a pulse accelerator voltage generator, including a high voltage transformer, a storage capacitor commutator. USSR copyright certificate No. 497932, IPC H05H 1/00, 08/27/1974.

The disadvantage of this generator is the rigid fastening of the neutron tube by the end of the anode electrode to the body with a metal sleeve and screws. The cantilever, rigid fastening of the neutron tube behind the end of the anode electrode leads to a large radial displacement of the target electrode, the asymmetry of the target relative to the body. The presence of clamping screws requires uniform tightening, which complicates the assembly. In addition, under mechanical loads, this can lead to depressurization of the neutron tube and the failure of the generator.

Known borehole pulsed neutron generator containing a vacuum neutron tube and a power circuit of a vacuum neutron tube, consisting of two high-voltage transformers, a storage capacitor, an accelerating pulse formation circuit, a capacitor of a neutron tube power source and a charging choke, placed in a sealed enclosure in which all elements The power circuit of the vacuum neutron tube is made in the form of bodies of revolution with central holes, interconnected th mechanically and electrically by means of electrical contacts with the threaded central holes, and the vacuum neutron tube - through the threaded cup-like sleeve with central and lateral holes are installed on the target and the anode by vacuum neutron tube. Patent of the Russian Federation No. 2368024, IPC G21G 4/02, 09/20/2009.

The disadvantage of this generator is the limited life of the tube due to the lack of anti-neutron mesh, i.e. systems for suppressing secondary electron emission resulting from bombardment of a tube target with deuterium ions. The consequence of this is the rapid failure of the ion source of the tube and the short life of the tube.

In addition, a disadvantage of the known generator is the rigid fastening of the neutron tube using threaded sleeves welded to the target and anode electrodes of the neutron tube. The connection of all elements of the power circuit of the neutron tube using threaded electrical contacts requires additional time in the assembly and disassembly of the neutron generator.

Known pulsed neutron generator containing placed in a sealed metal casing filled with a liquid dielectric vacuum neutron tube with a circuit for its power supply and an accelerating pulse formation circuit consisting of two high-voltage transformers made on closed cores of electrical steel, the outputs of the high-voltage transformers are connected by cup-shaped screens and located in them a vacuum neutron tube containing placed in a sealed sealed glass casing trolled 3-electrode spark source that consists of an annular anode, a cathode and an ignitor. Patent of the Russian Federation No. 165286, IPC G21G 4/00, 10/10/2016. This technical solution was made as a prototype.

The neutron tube is rigidly attached to the casing of the bowl-shaped screen using screws located at the end of the anode electrode. Rigid cantilever fastening of the neutron tube to the casing can lead to destruction of the flask of the neutron tube during mechanical stress in operation.

In addition, the bias resistance located around the grid electrode of the neutron tube affects the heat transfer from the target electrode. The assembly and disassembly of the generator is also difficult. If it is necessary to replace the neutron tube, the entire generator must be completely disassembled. Due to the large distance of the target from the side surface of the body and the presence of a slowing medium, the neutron yield decreases.

The objective of the invention is to increase reliability, maintainability, reduce the complexity of manufacturing, increase the yield of the neutron generator.

The technical result of the invention is to increase the reliability, maintainability, service life of the neutron generator, reducing the complexity of manufacturing a neutron generator.

The technical result is achieved by the fact that in a pulsed neutron generator containing in a sealed metal case a vacuum neutron tube with a three-electrode ion source with an anode, cathode and ignition, as well as a circuit for its power supply and acceleration voltage pulse formation, including a high-voltage transformer, storage capacitor, bias resistance , throttle, a spiral spring with a rectangular cross-sectional profile vit is inserted into the gap between the casing and the grid electrode of the neutron tube ka, and the elements of the power supply circuit and the formation of accelerating voltage and the electrodes of the three-electrode ion source are interconnected using floating pin-to-socket contacts.

The invention is illustrated in the drawing, where:

1 - metal block body;

2 - neutron tube;

3 - pulse high-voltage transformer;

4 - storage capacitor;

5 - source capacitor;

6 - throttle;

7 - bias resistance

8 - target electrode of a neutron tube;

9 - grid electrode of a neutron tube;

10 - anode electrode of a neutron tube;

11 - cathode electrode of a neutron tube;

12 - an igniting electrode of a neutron tube;

13 - spring contact;

14 - thermally conductive ceramic sleeve;

15 - floating pin-to-socket contacts;

16 - high-voltage bushing;

17 - liquid dielectric;

18 - electric screen;

19 - temperature compensator.

A pulsed neutron generator is made according to the scheme for switching on a neutron tube with a grounded target. A pulsed neutron generator includes a housing 1 made in the form of two cylinders of larger and smaller diameters and a truncated cone between them, a neutron tube 2, a high-voltage part of its power circuit providing accelerating voltage with a high-voltage transformer 3 on a closed metal core, a storage capacitor 4, a source capacitor ions 5, throttle 6.

Neutron tube 2 is a vacuum-sealed shell with elements placed in it: target electrode 8, grid electrode 9 and ion-optical system of a spark-arc type ion source containing coaxially located anode 10, cathode 11 and ignition 12. Bias resistance 7 is made in the form of a sleeve 14 of heat-conducting ceramic having thermal and electrical contact with the target electrode on the one hand, and on the other, good thermal contact with the housing 1. The resistance of the ceramic cylinder 14 is equal to the resistance cm scheniya between the grid 9 and the target 8 electrodes. The value of this resistance lies in the range from 800 Ohms to 2 kOhms.

Technologically, the resistance on ceramics can be performed in various ways: by winding the PEVNH wire, by performing volume resistance in ceramics, etc.

In order to "soft" fasten, center the neutron tube, ensure electrical contact and increase heat transfer, a spring contact 13 is inserted into the gap between the smaller cylinder of the housing 1 and the grid electrode 9 of the neutron tube 13 in the form of a spiral spring with a rectangular cross-sectional profile of a coil of rectangular cross-section. When installed in the housing on adjacent sides, the contact spring 13 is flattened. The springs are made of a material with high thermal conductivity and electrical conductivity, for example, bronze, the spring properties of which provide sufficient contact pressure on the walls in a gap of variable size, and therefore good electrical contact and good heat transfer.

To ensure maintainability, reduce the complexity of manufacturing, quickly replace a neutron tube, the elements of the power circuit and the formation of accelerating voltage and the electrodes of a three-electrode ion source are interconnected using floating contacts 15 "pin-socket".

To ensure electric strength and improve heat transfer from internal energy sources to the external environment, the block is filled with a liquid dielectric 17. To compensate for the temperature change in the volume of the liquid dielectric, a compensator 19 is installed. To align the electric fields on the target electrode and the anode of the ion source, screens 18 are installed.

As a liquid dielectric 17, transformer oil TKp having good dielectric properties is used in the block.

External power and trigger pulses are fed through ceramic bushing insulators 16.

The emitter unit operates as follows.

₁Н² + ₁Н³ → ₂Не⁴ + n образуются нейтроны с энергией 14 МэВ и вторичные электроны.When the switching element is activated (not shown in the drawing), the storage capacitor 5, charged to a voltage of 4.5 kV, is discharged through the primary windings of the transformer 3. A negative voltage pulse of 100-150 kV with a duration of 4 μs is generated on the secondary winding and fed through spring contacts 13 to the grid 9 of the neutron tube. With a delay of 0.8 μs, an ion source ignition pulse and a capacitor discharge 5 are formed through the anode 10 and cathode 11. The formed deuterium ions bombard target M of neutron tube 2. On the target as a result of the reaction

₁ H ² + ₁ H ³ → ₂ He ⁴ + n neutrons with an energy of 14 MeV and secondary electrons are formed.

When the current flows through the accelerating gap on the ceramic cylinder 14 as a result of the presence of an electric displacement resistance (from 800 Ohms to 2 kOhm), a potential difference arises that closes the secondary electrons formed during the bombardment of the neutron tube target by deuterium ions, which reduces the parasitic current tube and thereby increase its service life.

The proposed design of the "soft" fastening of the neutron tube in the neutron generator housing provides centering of the neutron tube, cushioning under mechanical stress, good thermal and electrical contact, ease of assembly and disassembly of the generator, the ability to quickly replace the tube after running out of life.

Improving heat transfer by increasing the heat flux from the target electrode, to which free access of the liquid dielectric is provided, leads to an increase in service life.

In addition, the proposed housing design, having a minimum diameter around the target and grid electrodes, can increase the neutron yield by reducing the oil gap.

Claims (1)

A pulsed neutron generator containing in a sealed metal case a vacuum neutron tube with a three-electrode ion source with an anode, cathode and ignition, as well as a circuit for its power supply and acceleration voltage pulse generation, including a high-voltage transformer, storage capacitor, bias resistance, inductor, characterized in that a spiral spring with a rectangular coil cross-sectional profile is inserted into the gap between the case and the grid electrode of the neutron tube, and the elements of the pit circuit Accelerating voltage and formation and the electrodes of a three-electrode ion source are interconnected using floating pin – socket contacts.

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