RU149963U1 - ION TRIODE FOR NEUTRON GENERATION - Google Patents

Abstract

An ionic triode for neutron generation, containing a hollow cylindrical cathode and anode with an integrated source of heavy hydrogen nuclides, characterized in that the hollow cylindrical cathode is made in the form of a permanent magnet with longitudinal magnetization up to induction of 0.3 <B <0.5 T with the following dimensions: width H, internal and external radii R and R, the anode consists of two parts, coaxially and symmetrically located on both sides of the cathode at a distance L from each other, each part of the anode is in the form of a cylinder of radius R, the output nozzles of the sources ide heavy hydrogen on both parts of the anode face each other, all the foregoing dimensions satisfy the following relations:

Description

The utility model relates to the field of ion acceleration in electrostatic fields, in particular, to devices for generating neutrons in the nuclear interaction of heavy hydrogen nuclides for use in applied problems of science and technology, for example, for geophysical applications.

A known accelerator tube [1] containing a neutron-forming target, a storage of hydrogen isotopes, a cathode and anticathode of an ion source, a magnet, an anode of an ion source, an insulator, an anode and a cathode of an accelerating system.

This tube implements electrostatic locking of electrons in the region adjacent to the target by isolating the hollow cathode cylinder from the target. However, electrostatic systems for suppressing the electronic component become insufficiently effective when used in high-power tubes at high deuteron currents. The magnetic field is oriented along the electron flux and does not have the function of suppressing the electronic component of the current.

Known pulsed neutron tube [2], containing a vacuum housing, a system of cylindrical accelerating electrodes, an ion source located inside one of these electrodes, a neutron-forming target located on the inner surface of the other electrode, and in order to reduce the radial size of the tube, outside the housing and coaxially with it is a section of ring magnetic elements that completely cover the electrode system, while the electric and magnetic fields within the boundaries of the acceleration region make a right angle.

Focused laser radiation acts on the surface of the target ion source. The resulting laser plasma with deuterium ions fills the anode space. Simultaneously with the formation of plasma between the anode and cathode, an accelerating electric field is created. The magnetic field is created using permanent magnets or solenoids. This field focuses the plasma along the tube axis from the anode to the intra-cathode region, where ions are extracted and then accelerated from the side surface of the plasma to the cathode. The reverse electron current is suppressed by the magnetic field. Accelerated deuterons bombard the inner surface of the cathode, causing a flux of fast neutrons as a result of a nuclear reaction.

The advantages of the device include the possibility of a significant reduction in the radial dimensions of the neutron emitters while maintaining the neutron flux. Unlike the previous analogue, in this device the magnetic field suppresses the current of electrons moving across the lines of force of the magnetic field, which increases the energy efficiency of the tube. The disadvantage of this device is the use of solid-state neutron-forming targets.

Known ionic triode for neutron generation [3], selected as a prototype, containing a ring cathode, anode (laser target) with a conical cavity, a cylindrical magnet, solid-state neutron-forming target.

As a result of the action of laser radiation on a target located on the anode, deuterium plasma is formed. During its subsequent expansion, deuterons accelerate to the cathode, passing through the ring cathode. On a solid-state neutron-forming target containing heavy hydrogen isotopes, neutrons are formed under the action of accelerated deuterons.

The device uses a convenient coaxial design with a grounded neutron-forming target at the end of the device.

The disadvantage of the prototype is a decrease in the efficiency of neutron generation with increasing accelerating voltage, due to the lack of conditions for blocking the electron flow due to the magnetic isolation of the cathode and anode. In addition, the resource of a solid-state neutron-forming target has a short service life.

The technical result of the proposed utility model is to increase the upper limit of the accelerating voltage, the average current of accelerated deuterons and the efficiency of their acceleration compared to the prototype due to the organization of the device’s geometry, in which there is a magnetic field between the cathode and anode with lines of force perpendicular to the intensity vector of the accelerating electric field, as well as an increase in the resource of a neutron-forming target due to its replacement from a solid state to a plasma one.

This result is achieved by the fact that in the known ionic triode for generating neutrons containing a hollow cylindrical cathode and an anode with an integrated source of heavy hydrogen nuclides, the hollow cylindrical cathode is made in the form of a permanent magnet with longitudinal magnetization up to induction of 0.3 <B <0.5 T with the following dimensions: width H, inner and outer radii R _in and R _ex , the anode consists of two parts coaxially and symmetrically located on both sides of the cathode at a distance L from each other, each part of the anode has the shape of a cylinder of radius R _a , in the outlet pipes of the sources of heavy hydrogen nuclides on both parts of the anode are facing each other, while all of the above dimensions satisfy the following relationships:

;

;

; L≈H+2R_a.

;

;

; L≈H + 2R _a .

регулирует максимальный и минимальный пределы отношения внешнего и внутреннего радиусов катода, определяемые оптимальной массой и геометрией полого цилиндрического магнитного элемента при условии достижения требуемого диапазона величины индукции магнитного поля.First ratio

adjusts the maximum and minimum limits of the ratio of the external and internal radii of the cathode, determined by the optimal mass and geometry of the hollow cylindrical magnetic element, provided that the desired range of magnetic field induction is achieved.

регулирует в нижнем пределе исключение падения пучка дейтронов (ионов тяжелых изотопов водорода) на катод, а верхний предел соотношения обеспечивает максимальное заполнение области генерации нейтронов пучком дейтронов.Second ratio

in the lower limit, it regulates the exclusion of the deuteron beam (heavy hydrogen isotope ions) from falling onto the cathode, and the upper limit of the ratio ensures the maximum filling of the neutron generation region with the deuteron beam.

нижний предел Н определяется достаточной глубиной потенциальной ямы электрического поля, а верхний предел определяется экономией материала полого цилиндрического магнитного элемента.In the third ratio

the lower limit H is determined by the sufficient depth of the potential well of the electric field, and the upper limit is determined by the economy of the material of the hollow cylindrical magnetic element.

The fourth ratio (L≈H + 2R _a ) is a condition for sufficient electrical insulation of the vacuum gap between the anode and cathode in the presence of a magnetic field of a hollow cylindrical magnetic element.

In the ratio determining the magnitude of the magnetic field, the lower limit (B _min ) is determined by the value of the Larmor radius of accelerated electrons, which becomes less than the distance between the cathode and anode in the accelerating gap. The upper limit (B _max ) of the magnitude of the magnetic induction should not be more than 2-3 times greater than B _min based on the saving of magnetic material, and also so that the Larmor radius of accelerated ions is much larger than the accelerating gap.

, тем самым достигается высокий КПД использования энергии импульса высоковольтного источника исключительно на ускорение ионов.The magnetic field of the hollow cylindrical magnetic element prevents the movement of electrons that are possibly formed in the interelectrode space to the anode, since the Larmor radius of electrons in the selected magnetic field at the cathode is much smaller

Thus, a high efficiency of using the pulse energy of a high-voltage source exclusively for ion acceleration is achieved.

The proposed device is illustrated by figure 1, which shows the layout of the main elements of the ionic triode for neutron generation: 1 - cathode; 2 - anodes with counter sources of ions of heavy hydrogen isotopes; 3 - low voltage insulators; 4 - power sources of ion sources; 5 - pump; 6 - a vacuum chamber; 7 - a source of high voltage; 8 - high voltage insulator.

In a specific implementation, the device will be operable subject to the following dimensions: R _a = 1 ÷ 1.5 cm; R _in = 2 ÷ 3 cm; R _ex = 4.5 ÷ 5 cm; H = 3 ÷ 5 cm; L = 4 ÷ 6 cm. In this case, this device will be a small-sized device with a high neutron yield, reaching a ~ 10 ⁸ neutron / imp output in the D + D reaction. when an accelerating voltage of 200 ÷ 500 kV is applied to the cathode in pulses of ~ 1 μs duration.

Permanent magnets, for example, of NdFeB, which provide the indicated magnitude of the magnetic field induction in the proposed geometry, have now been developed.

The proposed ionic triode for generating neutrons works as follows. When sources of heavy hydrogen isotopes ions are turned on, deuterons exit the anode cavity. At this moment, the high voltage source is turned on. Deuterons are accelerated along the axis of the cathode and magnetic field toward the second anode. Approaching the second anode, accelerated deuterons slow down and begin to move in the opposite direction, moving again to the first anode. Such a deuteron motion is repeated many times, increasing the neutron yield of the nuclear reaction from colliding deuterons. The magnetic field of the magnetic elements impede the movement of electrons formed in the interelectrode gap to the anode.

The proposed technical solution allows to increase the productivity of studies of rocks containing productive hydrocarbons, uranium and precious metals, by the method of neutron elemental analysis, as well as works related to the search and identification of hidden dangerous objects by neutron methods.

Information sources

1. Kiryanov G.I. Fast neutron generators / Kiryanov G.I. - M .: Energoatomizdat. 1990 .-- 136-137 p.

2. Bespalov D.F., Kozlovsky K.I., Tsybin A.S., Shikanov A.E. Pulsed neutron tube, A.S. USSR, No. 766048, class G21G 4/02. - Bull. No. 35, 09/23/1980.

3. NEW APPROACHES IN PLASMA NEUTRON SOURCES / Tsubin A.S., Kuznetsov A.Y., Kozlovsky K.I., Shikanov A.E. // APPLIED PHYSICS A: MATERIALS SCIENCE & PROCESSING. - 2002. - A74. - S1. - s36-s39.

Claims (1)

An ionic triode for generating neutrons, containing a hollow cylindrical cathode and anode with an integrated source of heavy hydrogen nuclides, characterized in that the hollow cylindrical cathode is made in the form of a permanent magnet with longitudinal magnetization up to induction of 0.3 <B <0.5 T with the following dimensions: width H, the inner and outer radii of R _in and R _ex, the anode consists of two parts, coaxially and symmetrically arranged on both sides of the cathode at a distance L from each other, each of the anode has the shape of a cylinder of radius R _a, the output pipes source nuclides in heavy hydrogen on both parts of the anode face each other, all the foregoing dimensions satisfy the following relations:

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