SU528834A1 - Pulsed neutron tube - Google Patents

Description

(54) PULSE NEUTRON PIPE

one

The invention relates to devices for producing pulsed neutron fields, in particular neutron generators, which are used in nuclear geophysics for pulsed neutron logging of cased and uncased wells, activation analysis of the environment in a transportable field laboratory, for studying the characteristics of nuclear reactors, as well as for radiation therapy.

Small-sized nuclear geophysical neutron generators are known on the basis of uncoupled neutron tubes, in which neutrons are formed by the interaction of accelerated deuterons with a solid target containing tritium or deuterium in the occluded state 1. Accelerated deuterium ions are pulled from the ion source, where they are formed by Pening, arc or high-frequency de. The increased neutron yield in such devices is achieved due to the high accelerating voltage and, as a consequence, the large dimensions of the ion source, which ensures the necessary current of deuterium ions.

Also known is the neutron generator with

a tube in which deuterium ions are formed using a laser ionization mechanism that allows large ion ion fluxes to be produced

2. However, the design of the instrument makes it impossible to significantly increase the neutron yield due to the incomplete use of the deuterons of the laser plasma. An increase in the neutron yield in such a device is achieved by increasing the laser power and the magnitude of the accelerating voltage.

The closest technical solution is a neutron tube of a neutron laser generator, comprising a vacuum case with electrical inputs and windows for introducing laser radiation, a laser and an ion field, a system of accelerating and shielding electrodes, gas absorbers, in which increased neutron output is achieved by using cylindrical, coaxialio located grid electrodes and ionic targets 3. The selection of deuterium ions for acceleration in such a neutron tube is carried out with the side surface of the plasma small clot.

However, the design of this device makes it difficult to effectively use it for activation analysis and pulsed neutron logging of cased wells due to insufficient neutron output, which is determined by the same incomplete use of the deuterium component of the scattering plasma. In addition, due to the cylindrical design of the tube, an uneven distribution of the plasma bunch ions over the surface of the accelerating cylindrical electrode is created, which leads to an uneven use of the working surface of the ionic target and creates conditions for the occurrence of breakdowns.

To increase the neutron output, the case of the proposed neutron tube is made in the form of a metal sphere, on the inner surface of which an ion target is located, a system of mesh electrodes is concentrically located inside the sphere, and in the center is a two-sided flat laser target, with two optical windows located on the spherical tube body.

Using a spherical system of electrodes in conjunction with Bilateral use of a laser target will allow the plasma bunch to expand into a solid angle of about 4p cf, while in a coaxial version, scattering occurs into a solid angle of no more than 2 liters. Such a tube design will almost completely avoid the loss of a deutropic current, create a more uniform distribution of the plasma cloud on the surface of the grid accelerating electrode, and reduce the likelihood of breakdowns.

In a neutron tube of this design, it is possible to carry out multilateral irradiation of a laser target, making the latter in the form of a gash placed in the center of the spherical tube body. Laser radiation in this case is introduced through several special windows in the tube body. This will, in principle, further increase the neutron yield.

The drawing schematically shows a neutron tube of a pulsed laser neutron generator. The design consists of a spherical body 1 of a neutron tube, an ionic target 2, saturated with tritium, optical windows 3, an accelerating mesh electrode 4, a shielding mesh electrode 5, a laser target 6, a focusing lens 7, a laser 8, a laser radiation divider 9, mirrors 10, a source 11 of a pulsed accelerating voltage, a dielectric cylinder 12, a getter 13, a high-voltage vacuum input 5 14, an insulator of a low-voltage input 15, a metal screen 16.

Pulsed neutron tube works as follows. Focused laser radiation 8

Q is introduced through the optical windows 3 and acts on the opposite surfaces of the laser target 6. The resulting plasma, containing deuterium ions, expands to evenly fill the space inside the mesh electrode 4. At the moment the plasma approaches the accelerating electrode 4 it is given a pulse from a high voltage source. Through the mesh surface

Q electrode 4 causes the deuterons to be pulled out of the plasma and accelerated to target 2, where a stream of fast neutrons is created. A high vacuum in the tube is maintained by gas getters 13.

Thus, the described neutron tube will make it possible to obtain a neutron yield of an order of magnitude or more exceeding the yield in known designs.

Claims (3)

1. Kiryov G.N. Sat. “Nuclear-physical methods for analyzing substances. M., Atomizdat, 1971, p. 279-287. 2.Iateit France № 1516920, cl. H 05h 5/00, 1968. 3. USSR author's certificate number 457406, cl. H 05h 7/00, 1972. ten yy .13