SU1737559A1 - Secondary emission type radioisotope current source - Google Patents

Abstract

Summary of the Invention: Each of the emitters of a current source is made in the form of alternating layers of two different metals electrically isolated by vacuum gaps, the secondary ion-electron emission coefficients that differ by more than the J / N value, where J1 is the average value of the secondary emission coefficient of the two metals N is the number of pairs of layers of metals of the emitter. 2 ill., 1 tab.

Description

The invention relates to devices using secondary electron emission induced by a stream of charged particles produced by a radioisotope, and can be used as an autonomous source of power for various electronic circuits.

Known thermionic Converter containing a cylindrical cathode and the surrounding collector. The cathode consists of end chambers with a substance, connected by gaskets with a cylindrical shell.

The disadvantage of this device is low energy efficiency, which can be quantitatively characterized by a coefficient of useful action (efficiency), defined as the ratio of the energy carried in the form of an electric current to the energy expended on heating a semiconductor crystal. In addition, the need to maintain the high temperatures necessary for the operation of the device inside creates additional difficulties in operating it under extreme conditions.

The closest in technical essence and the achieved result to the proposed is a radioisotope source, which consists of an isotope layer and an emitter, which is a metal layer no thicker than the length of the charged particle emitted by the isotope in the metal from which the emitter is made.

Secondary electrodes are formed along the entire path of a charged particle in a metal, and only a small part is emitted from a thin surface layer equal in thickness to the mean free path of electrons in the metal, which leads to low currents of secondary electrons.

(L

with

JV SL

WITH

317

The aim of the invention is to increase the energy efficiency of converting nuclear radiation energy into electrical energy by increasing the current of secondary electrons. FIG. 1 shows a diagram of a secondary emission radioisotope current source; in fig. 2 - binary cell current source.

The secondary emission radioisotope current source contains (Fig. 1) an evacuated body 1 in which a thin layer of isotope 2 is placed

thickness SC, not exceeding the path length of the charged particle in the isotope. Such an isotope layer thickness is selected to reduce the loss of particles emitted by dividing the isotopic material. On both sides of the isotope layer there is an emitter consisting of alternating layers of two metals 3 and k with different secondary emission factors y. The sum of the thicknesses of the metal layers on each side of the isotope must not exceed the mean free path of the charged particle emitted by the isotope in the metal Rsch. The layer is insulated from each other by vacuum gaps, the thickness of which should provide electrical insulation between the metal layers. In addition, the vacuum gap pe must exceed the mean free path of electrons in the residual gas in order to avoid loss of secondary electrons. The emitter layers made of metal with a large V3 are interconnected and form a positive terminal of the current source, and the emitter layers made of metal with a smaller) r ,, are interconnected by an isotope and form a negative terminal.

Consider the operation of a binary cell emitter (Fig. 2), consisting of one pair of thin layers of two different metals, irradiated by ions emitted by the isotope. With the passage of the ion

To create a secondary emission radioisotope source, it is necessary to know the required electrical power and the required service life. El

through both layers of secondary electronic power, the power is removed from the run. EMISSION IS HAPPENING FROM BOTH SURF-3U into such an opioi otpt .. PGG, Igm ™ of each layer. Consider the surface facing each other. For definiteness, we assume that layer 3 is made of metal with a thickness of 55

The water of such a radioisotope power source is proportional to the area of the isotope layer. To obtain the electric power P, the following area S of the radioactive isotope layer of thickness dR is required:

the secondary emission coefficient, and the layer k is of the metal with a smaller J. The secondary emission coefficient, defined as

Mr KVN;

five

five

0

five

S

where Ng is the number of secondary emission electrons knocked out of the metal by NJ ions, and measured in a number of experimental studies turned out to be significantly different for different metals. Then, when a charged particle passes through this binary cell, it will be knocked out of the layer of metal 3 from the electrons, and from the layer of G4 - electrons.

Almost all secondary electrons knocked out by the ion will reach the opposite plate in the absence of electromagnetic fields in the space between the layers of the electromagnetic fields. As a result, on the metal layer 3, there is a lack of charge, and on the layer, their excess equal to jj1 K l. -electrons. When a binary cell is connected to a load, an electric current will flow in the circuit. The energy conversion coefficient of one pair of plates Ј can be written as

I - (JA XiiЈ °.

with & 0 (.

average electron emission energy;

 energy of the charged particle (ion). Typing N such binary cells,

where N Rnp / d, + v 2. (d, d2 are the thicknesses of the metal layers), we will increase the conversion factor by 2 N, increasing, therefore, the current of the secondary electrons. The 2N coefficient indicates that emission occurs from the Q of both surfaces of each metal layer. The efficiency of such a device can be written as

and 2 (i3) NЈo

i - --B; G -

To create a secondary emission radioisotope source, it is necessary to know the required electrical power and the required service life. Elekde

Т0tricheskoe power, removeable from vyvsyuv such oopioi otpt .. PGG, IgT ™

The water of such a radioisotope power source is proportional to the area of the isotope layer. To obtain electrical power P, the following area S of the radioactive isotope layer with a thickness of dR is required:

R

(jf9-) 3.7 10co

S

5 1

where 9Ј0 is the specific activity of 1 cm of the isotope in Ci / cm5.

The isotope selection is determined by the required lifetime. In addition, the isotope must emit p particles, the other types of radiation (And, V) should be negligible or completely absent. The following isotopes can be used, for example, to create a secondary emission radioisotope current source with a life span of about a year: Californium-2 8, Curie-2 2.

Beryllium and copper are most suitable as materials for the fabrication of layers with large and small J among the materials studied, having the following secondary emission factors when irradiated with Ј-particles:

Be 30; fcu 55- in these metals, the mean free path of oЈ-particles with an energy of 5-6 MeV is about 23 microns, and the average energy of the secondary emission electrons is about 15 V. To prevent electrons from being lost between the metal layers, the residual gas pressure should be no worse than 10 Torr. At this pressure, the thickness of the vacuum gap, which is of the order of the thickness of the metal layer, will be significantly less than the mean free path of electrons in the residual gas.

The technical characteristics of current sources with a radioactive isotope Curium-2 2 and with an emitter made of beryllium and copper are listed in the table.

During the operation of a secondary emission radioisotope current source, part of the radiation energy of a radioactive isotope is spent on heating the device. When heat is removed from the device only due to radiant heat transfer through the lateral surface, the stationary temperature is determined by

4 o

37559

where S Ј is the side surface area of the device;

FROM 5.6 KG erg / cm2 degree - constant Stefan-Boltzmann I

R is the coefficient of grayness, T0 is the temperature of the Rökelvin. If this source is combined into a cube with a side of 1 m, then due to only the loss of excess heat by radiation, the temperature of the current source will be no higher than 300 ° C, and when special measures are taken to increase 15 the radiating surface, it is much lower.

Thus, in comparison with the prototype, the proposed device allows to increase the energy efficiency of conversion by increasing the current of secondary electrons. The proposed radioisotope current sources eliminate the need to create a high operating temperature and 25 have high radiation resistance.

Claims (1)

Invention Formula JQ Secondary emission radioisotope current source, comprising a case in which an isotope layer is placed, on both sides of which metallic emitters are located with a thickness not exceeding the path length 35 in the emitter metal of a charged particle emitted by an isotope, characterized in that, in order to increase energy efficiency, each of the emitters is made in the form of electrically isolated vacuum gaps of successively alternating layers of two different metals, the coefficients of secondary ion emission of which differ more than the value (f / N, where # is the average value of the coefficient of secondary emission of two metals, and N is the number of pairs of layers of metals of the emitter. 45 0.1 n, 1 7.5-15 70-8P ten 1000 10,000 3.0-3.5 , x , / Y77 / 7 / y //// Y ////// y /, J HCH hh - # & / g / /