JPH04317722A - System for separating isotope - Google Patents

Abstract

PURPOSE:To obtain a high ionization efficiency with a small laser output, lower the density of the produced ions and reduce the loss of charge exchange. CONSTITUTION:A metal material 3 is placed into an evaporating crucible 2 and irradiated with an electron beam 5 from an electron gun 4. The metal material 3 is heated and melted by the irradiation of the electron beam 5. The metal vapor stream 7 of the metal material 3 being evaporated flows through recovery electrode plates 8 toward a collecting recovery plate 10. Laser beam irradiation areas 9 are provided between the recovery electrode plates 8 in the same number as super-fine structure lines, becoming larger in the direction of the metal vapor stream 7. In each of the irradiation areas 9, the metal vapor stream 7 is irradiated with selective excitation laser beam to excite the metal atom of a specific isotope selectively by an optical resonance reaction.

Description

[Detailed description of the invention]

[Object of the invention]

0002

[Field of Industrial Application] The present invention relates to an isotope separation device that separates and recovers isotope atoms having a hyperfine structure by selective ionization using pulsed laser light, and particularly relates to an isotope separation device that separates and recovers isotope atoms having a hyperfine structure by selective ionization using pulsed laser light. The present invention relates to an isotope separation device that can efficiently tune a laser beam to a resonant absorption line, regardless of size, and can improve ion recovery efficiency.

0003

2. Description of the Related Art In the field of isotope separation, a metal isotope separation method using an atomic laser method has a very high isotope separation efficiency and is superior to methods such as a gas diffusion method or a centrifugal separation method. For this reason, the atomic laser isotope separation method concentrates a specific isotope to a predetermined concentration level.
It is attracting attention because it eliminates the need to repeat the same separation operation many times in a cascade manner.

[0004] The isotope separation process using the atomic laser method includes a metal raw material supply step for supplying a metal raw material for isotope separation, a metal vapor generation step in which the supplied metal raw material is heated and melted to generate metal vapor, and A selective excitation step of selectively exciting a specific isotope from this metal vapor, and photoionization (ionization) of the selectively excited metal atoms of the specific isotope.
It is broadly divided into a separation and recovery process that collects ionized isotopes.

On the other hand, when a metal atom to be subjected to isotope separation is excited by a laser, an isotope shift is observed in this excitation. For this reason, in the isotope separation process, selective excitation laser light is irradiated to match the energy level of a specific isotope to excite only the specific isotope, and in the case of multi-step excitation, additional ionization The energy level of the excited specific isotope is further raised by irradiation with laser light, and only the specific isotope is ionized.

[0006] Furthermore, isotopes include even number nuclear isotopes and odd number nuclear isotopes.While the even number nuclear isotopes have a nuclear spin of zero, the odd number nuclear isotopes have a nuclear spin. The light absorption spectral line of the transition is split into multiple lines, and some have a hyperfine structure. If a specific isotope has a hyperfine structure and the excitation spectrum width due to its main transition is wide, in order to selectively excite all of the specific isotope by laser beam irradiation, the laser beam should be applied so as to cover the wide excitation spectrum width. It is necessary to widen the line width (wavelength width) or use multimode laser light.

[0007]

[Problems to be Solved by the Invention] In order to use a wide linewidth laser beam or a multimode laser beam to excite metal atoms with an ultrafine structure, a predetermined power is required in each wavelength range. It has been difficult to utilize laser light energetically effectively.

[0008] Furthermore, in order to excite metal atoms having a hyperfine structure, the method of excitation by sweeping the frequency of a single mode or several modes of laser light inevitably has a large frequency sweep range when the width of the hyperfine structure is large. This not only makes it technically difficult, but also reduces excitation efficiency if the sweep speed becomes too large.

Furthermore, in order to improve the separation performance of the device, it is necessary to increase the vapor density of the metal and ionize the isotope metal of interest without omission, but the higher the vapor density, the more
The effect of increasing the frequency of charge exchange between the ionized isotope of interest and other unnecessary isotopes that have not been ionized, and the effect that the higher the ion density, the longer the recovery time by the electric field, are combined.
Separation performance does not improve.

The present invention has been made in consideration of the above-mentioned circumstances, and uses a plurality of laser beam resonances due to the ultrafine structure of the isotope atoms to be separated and recovered (hereinafter referred to as the isotope of interest). Absorption line (hereinafter referred to as ultrafine structure line)
An object of the present invention is to provide an isotope separation device that can efficiently tune a laser beam to a targeted resonant absorption line without depending on the size of the distribution spread of the isotope, and can improve ion efficiency between laser pulses. purpose. [Structure of the invention]

[0011]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the isotope separation device according to the present invention separates and recovers isotope atoms having an ultrafine structure by selective ionization using pulsed laser light. In an isotope separation device, the laser beam is irradiated in multiple locations at different positions in the direction of isotope atom propagation. Among a plurality of laser beam resonance absorption lines, the laser beam is tuned to each different absorption line to cause ionization.

0012

[Operation] In the isotope separation device according to the present invention, a plurality of regions are provided with laser light irradiated at positions shifted in the direction of movement of the isotope atoms, and in each region, the ultrafine structure line of the isotope of interest is Of these, the laser beam is tuned to each different absorption line to cause ionization. Therefore, it is possible to efficiently tune the laser beam to the targeted resonance absorption line, regardless of the size of the distribution spread of the hyperfine structure line, and the amount of ions of the isotope of interest can be distributed over multiple illumination areas. By doing so, the ion density is suppressed and the ion collection efficiency between laser pulses can be increased.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an isotope separation apparatus according to the present invention. In the figure, reference numeral 1 is a vacuum container, and an evaporation crucible 2 is installed at a lower position inside the vacuum container 1. The evaporation crucible 2 contains metal raw materials 3 such as gadolinium, zirconium, uranium, plutonium, etc. whose isotopes are to be separated. And this metal raw material 3
is irradiated with an electron beam 5 from an electron gun 4.

As shown in FIG. 1, this electron beam 5
For example, 1
The metal raw material 3 is irradiated with the beam deflected by 80 to 270 degrees, thereby heating and melting the metal raw material 3. Then, when the electron beam 5 irradiated to the metal raw material 3 hits the molten metal liquid surface,
The metal raw material 3 is evaporated, and the metal vapor flow 7 of the evaporated metal raw material 3 rises with a predetermined spread.

This rising metal vapor flow 7 flows between the collection electrode plates 8 as shown in FIG.
A plurality of irradiation regions 9 are set at positions shifted in the flow direction of the metal vapor flow 7, and the metal vapor flow 7 is exposed to selective excitation laser light and ionization laser light from a laser device (not shown) in each of these irradiation regions 9. It is designed to be irradiated with laser light. Figure 1 shows that the nuclear spin I of the isotope of interest is I
= 1/2, and the irradiation areas 9 are set at three locations, the same number as the ultrafine structure lines.

In each of these irradiation regions 9, by irradiation with selective excitation laser light, the metal atoms of a specific isotope in the metal vapor flow 7 are selectively excited by optical resonance reaction, and the excited By further irradiating metal atoms of a specific isotope with ionizing laser light, the energy level of the metal atoms is raised and ionized. The ionized specific isotope becomes a positively charged ionized isotope, and is recovered toward the negative electrode by an electric field formed between the recovery electrode plates 8.

The laser beam irradiation method in each of the irradiation regions 9 may be a method of simply tuning a single-mode laser beam to a predetermined ultrafine structure line, or by frequency sweeping within the same laser pulse, the same A method of multi-stage excitation while adiabatically inverting the energy level density distribution of the body may be used, or other methods may also be used.

[0019] Metal atoms that are not ionized are not affected by the electric field, so they pass through between the collection electrodes 8 and are collected and collected by the collection plate 10 disposed above. .

Next, the operation of this embodiment will be explained.

When the nuclear spin of the isotope of interest is I, this atom has (2I+1) major optical resonance absorption lines (hyperfine structure lines) due to its hyperfine structure. Therefore, in this embodiment, a separate laser beam irradiation area 9 is set for each ultrafine structure line by shifting the position in the vapor flow direction of the raw material atoms. In addition, the number of oscillations of the pulsed laser beam in each irradiation area 9 is determined according to the passing vapor velocity and the size of the irradiation area 9 so that all raw material atoms passing through the irradiation area 9 can be irradiated at least once without omission. It is set.

Now, suppose that the nuclear spin I of the isotope of interest is I=
If it is 1/2, there are three ultrafine structure lines. For convenience of explanation, these lines are referred to as A, B, and C to distinguish them. In this case, the laser beam is tuned to line A from the upstream side to the downstream side of the metal vapor flow 7 of raw material atoms. A total of three irradiation areas 9: a region where the laser beam is tuned to the B line, and a region where the laser beam is tuned to the C line.
will be set continuously. In addition, the isotope of interest is 1
If ionization is not carried out using just a laser beam (single-stage excitation), but is ionized through multi-stage excitation using multiple laser beams, a predetermined number of laser beams are incident on each irradiation area 9. It turns out.

[0023] Since the laser beam is tuned to only one ultrafine structure line within one irradiation area 9, all the ultrafine structure lines within one irradiation area 9 have multi-mode or line width characteristics. Compared to the conventional method of applying a wide single mode laser beam, the energy density of the laser beam can be increased, and therefore the ionization efficiency of the isotope of interest can be improved.

[0024] Note that in the region where the laser beam is tuned to the A-line of the isotope of interest, the ionization efficiency here is determined as follows: If everything in the corresponding level state can be ionized, it can be said that the ionization efficiency is practically 100%, and if the same is true for other irradiation areas, then all three irradiation areas 9 from A line to C line have been passed. At that point, all isotopes of interest will be ionized.

Furthermore, since the isotope ions of interest generated by laser beam irradiation are dispersed in three irradiation regions 9,
The ion density is suppressed accordingly, the penetration of the recovery electric field is fast, and the recovery time to the recovery electrode plate 8 is shortened. Therefore, it is possible to suppress the problem that the vapor density of the raw material atoms increases and the frequency of charge exchange between the ionized isotope of interest and other unnecessary isotopes that are not ionized increases, resulting in a decrease in separation performance. Can be done.

In the above embodiment, the case where the irradiation areas 9 are provided in the same number as the number of ultrafine structure lines has been explained, but there are cases where the evaporation density of the metal raw material 3 is small, and each irradiation area 9 is
When loss of the isotope of interest due to charge exchange is not a problem, such as when the ion density of the isotope of interest generated is small and the ion recovery time is short enough, the irradiation area 9
The number of ultrafine structure lines may be reduced and one irradiation area 9 may be excited from a plurality of hyperfine structure lines. And vice versa,
The number of irradiation areas 9 may be further increased than the number of ultrafine structure lines, and a plurality of irradiation areas 9 using the same ultrafine structure line may be provided to reduce the density of generated ions.

[0027]

Effect of the Invention As explained above, the present invention provides a plurality of laser beam irradiation regions shifted in the direction of movement of isotope atoms, and in each region, the hyperfine structure line of the isotope of interest is Since the laser beam is tuned to each different absorption line to cause ionization, it is possible to efficiently tune the laser beam to the targeted resonant absorption line, regardless of the size of the distribution spread of the ultrafine structure line. Furthermore, by dispersing the amount of ions of the isotope of interest over a plurality of irradiation regions, the ion density can be suppressed and the ion recovery efficiency between laser pulses can be improved.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram showing an isotope separation apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1 Vacuum container 2　Evaporation crucible 3 Metal raw materials 4 Electron gun 5　Electron beam 7 Metal vapor flow 8 Recovery electrode plate 9 Irradiation area 10 Collection plate for collection

Claims (1)

[Claims] Claim 1: In an isotope separation device that separates and recovers isotope atoms having a hyperfine structure by selective ionization using pulsed laser light, a region to which the laser light is irradiated is located in the direction of travel of the isotope atoms. At the same time, in each of these regions, the laser beam is tuned to a different absorption line among the multiple laser beam resonance absorption lines due to the ultrafine structure of the isotope atoms to be separated and recovered. An isotope separation device characterized by ionizing.