RU2802737C1 - Ion source for electromagnetic mass separator of transuranian element isotopes - Google Patents

Abstract

FIELD: ion sources.

SUBSTANCE: invention can be used in the technology of electromagnetic isotope separation. The ion source includes a compact block of a gas discharge chamber, a hot cathode with a filament, a removable flat crucible with a working substance, one of the walls of which is a gas discharge chamber wall, a flat rectangular ceramic heating element located under the bottom of the crucible.

EFFECT: simplification of the design of the ion source, increase in the reliability of its operation and increase in the efficiency of the use of the working substance supplied to the discharge chamber of the ion source.

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Description

The invention relates to ion sources and can be used in the technology of electromagnetic separation of isotopes of transuranic elements.

The urgency of the problem is based on the need to use devices with increased resolution in traditional ion sources for industrial electromagnetic isotope separation to achieve high process efficiency. This was dictated by the fact that such ion sources were, as a rule, based on the calutron design (J. Koch. Electromagnetic isotope separators and applications of electromagnetically enriched isotopes. North-Holland. Amsterdam. 1958), which is a mass spectrometer previously used for separating or enriching uranium isotopes in microgram measurements, consuming a lot of energy and characterized by low productivity. The main limitation in their use was the tendency to produce a “noisy” discharge, which leads to a decrease in the degree of neutralization of the space charge of the beam and requires careful optimization of the discharge parameters to achieve the existence of a quiet plasma. If it is necessary to achieve efficient isotope separation, high resolution is required.

From the prior art, a device for an ion source related to accelerator technology is known (RF patent No. 2716823, IPC H01J 27/22, published March 17, 2020), including an emitter unit, which contains a cathode electrode made of a high-conductivity metal, on which are applied successively layers of the working substance (alkaline earth or rare earth metal) and a solid electrolyte based on ceramics, and a layer of carbon as the anode material. As a result of the operation of the device, the efficiency of the process increases due to the formation of ion flows of high intensity and ion current density with a given charge (double-charged metal ions are formed), thereby increasing the efficiency of using the working substance.

An ion source is known (RF patent No. 2034336, IPC H01J 37/08, published April 30, 1995), containing a discharge chamber, a cathode, an anode and a reflector electrode when using an oscillating arc discharge mode.

Known as a prototype of the proposed device is a Freeman ion source used to separate isotopes in a 180° electromagnetic mass separator, in which a discharge chamber, a crucible with a working substance and heaters are combined into a single unit mounted on a unified basic structure (A.I. Kolosov, et al. Ions sources of solids tor the mass-separator "KINRIS". "Problems of atomic science and technology". 2008. No. 5. p. 81-84). To create the required vapor pressure of the working substance and stable combustion of the discharge, the gas-discharge chamber and the crucible with the working substance are heated by thermal radiation from two cylindrical active resistance heaters with a spiral of nickel chrome-plated wire (NiCr 20/80) with a heating power of up to 1250 W. The gas discharge chamber and the crucible with the working substance are connected by a steam line. In this source, the rate of supply of working substance vapor is regulated only by the heating power of the heaters, which allows for more significant losses of the working substance during the transition period. There are also significant difficulties when replacing the working substance, in the ion source and its repair with copying manipulators.

The disadvantages of the known analogues include the rather high complexity of the devices and, as a consequence, insufficiently high operational reliability.

The technical result is the use of an ion source for separating isotopes of transuranium elements (including californium), simplifying the design of the ion source, increasing the reliability of its operation and increasing the efficiency of using the working substance supplied to the discharge chamber of the ion source.

This technical result is ensured by the fact that, unlike the known ion source containing a gas-discharge chamber, a hot cathode with a filament, a crucible with a working substance and a heater, according to the invention the heater is made in the form of a flat rectangular ceramic element located behind a removable flat crucible with a working substance , one of the walls of which is the wall of the gas-discharge chamber.

In the proposed ion source, the technical result is realized through the use of a flat ceramic heater and a removable flat crucible with a working substance, one of the walls of which is the wall of the gas-discharge chamber, which allows optimizing the supply of the working substance into the discharge of the gas-discharge chamber, simplifies the design and increases the reliability of the ion source.

The fundamental difference of the proposed design of the Freeman ion source is the use of a heater made in the form of a flat rectangular ceramic element located behind a removable flat crucible with a working substance, one of the walls of which is the wall of the gas-discharge chamber.

The proposed design of the ion source is shown in Fig. 1. The design of the ion source includes: a compact block of gas-discharge chamber 8; removable crucible with working substance 1; flat ceramic heating element 3; a wire thermal cathode made of tantalum wire with a diameter of 1.5 mm 9, located parallel to the emission slit 10 at a distance of 4 mm; electron reflectors made of tantalum 5; magnet 6, creating a magnetic field with a strength of up to 0.02 Tesla parallel to the emission slit; rectangular tantalum cover 11 with emission slot. The thermal cathode is isolated from the gas-discharge chamber by two insulators 7 made of boron nitride. To reduce heat losses due to radiation, a heat-reflecting screen is placed around the discharge chamber. The temperature in the gas discharge chamber is controlled by a thermocouple. The gas discharge chamber is supported by current leads. To start the ion source, argon gas is supplied through a tantalum tube into a gas distribution chamber 4 with many holes for uniform gas flow into the gas discharge chamber.

After the gas discharge is ignited, the body of the gas-discharge chamber heats up and vapors of the working substance chloride from the cavity through hole 2 will begin to enter the discharge. The main source of heating is the radiation from the thermionic cathode. Fine adjustment of the temperature of the discharge chamber and the flow of working substance vapor into the discharge is carried out by a flat heating element.

It is known that the cost of transuranium elements (such as californium) is very high, which suggests the use of design solutions in ion sources aimed at more efficient use of the working substance and minimizing losses. The efficiency of using a substance is determined by the operating modes of the source, including the reduction of losses of the working substance during the so-called “transition” mode from the start of operation to reaching the operating mode. In this ion source, minimizing losses during the “transition” mode time is carried out by changing the power of a flat ceramic heater 3 located behind the crucible 1. The low power of such a heater is an advantage, since with standard power sources it allows more accurately and smoothly regulating the temperature of the heater and gas-discharge chamber, which makes it possible to speed up the time it takes for the ion source to reach operating mode and reduce losses of the working substance during the “transition” mode.

The possibility of industrial implementation of the proposed ion source is confirmed by the following example.

Example 1. Experimental studies were carried out in laboratory conditions on the use of the proposed ion source device, designed as shown in Fig. 1.

Initially, the ion source was started by supplying argon to the gas distribution chamber 4, from where the gas flow enters the gas discharge chamber 8. Then, ignition was carried out by the heat flow coming from the ceramic heating element 3, heated by heat from the radiation of the thermal cathode 9. The temperature in the gas discharge chamber is controlled by a thermocouple.

After ignition of the gas discharge, the body of the gas-discharge chamber 8 with the working substance placed in it heats up and vapors of the metal chloride of the working substance from the cavity of the crucible 1 through hole 2 enter the discharge chamber 8. By adjusting the heating power of the ceramic heater 3, which ensures heating of the crucible 1, acceleration of the source output is achieved ions to the operating mode, thereby minimizing the loss of the working substance during the “transition mode”.

For this ion source design, numerical thermophysical calculations were carried out, which showed that for the proposed ion source design, the maximum achievable crucible heating temperature is 1070 K, which is sufficient, in particular, for using californium chloride with a melting point of 818 K as a starting material and desorption California from the surface of the walls of the gas-discharge chamber.

Simplifying the design of the ion source and increasing the reliability of its operation is achieved by the fact that the gas-discharge chamber, crucible with the working substance, and flat ceramic heater are combined into a compact unit mounted on cylindrical current leads. Each of these elements is structurally made separately removable, which allows for complete disassembly of the block and/or quick replacement of any element using copying manipulators. This also simplifies the replacement of a crucible with a spent working substance with a new one with a full load without removing all other elements.

Claims (1)

An ion source for an electromagnetic mass separator of isotopes of transuranium elements, containing a gas-discharge chamber, a thermionic cathode with a filament, a crucible with a working substance and a heater, characterized in that the heater is made in the form of a flat rectangular ceramic element located under the bottom of a removable flat crucible with a working substance , one of the walls of which is the wall of the gas-discharge chamber, and each of these elements is made removable, with the possibility of independently replacing the elements with copying manipulators.

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