JP3517036B2 - Isotope separation device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an isotope separation device by an atomic laser method for selectively separating only a specific isotope from a metal containing a plurality of isotopes.

[0002]

2. Description of the Related Art A conventional isotope separation apparatus using an atomic laser method will be described with reference to FIG. That is, in FIG. 6, reference numeral 1 is a vapor sealed container, in which a raw material metal 2 containing a target isotope for the purpose of separation is housed in a crucible 3 and an electron beam 5 emitted from an electron gun 4 is applied by a magnetic field to the raw metal The raw material metal 2 is made to hit the surface of 2 by heat radiation from an electric heating element or heat conduction from a heating wire heater to generate metal vapor, that is, vapor atoms 6.

Only the isotope of interest is selectively excited by irradiating a laser beam tuned to the resonance excitation wavelength of the isotope of interest for the purpose of separation contained in the vapor atoms 6.
The target isotope atom is ionized by the first-stage excitation or the multi-stage excitation.

In FIG. 6, reference numeral 8 is a first-stage excitation laser irradiation region, 9 is a second-stage excitation laser irradiation region, and 10
Is a recovery electrode plate, 11 is a waste product recovery plate, and the isotope of interest is recovered by the recovery electrode plate 10.

Generally, in the case of multi-stage excitation, laser light having different wavelengths by the number of excitation stages is used. The wavelength at this time uses laser light tuned to each resonance line (resonance wavelength) that continuously transits from the first-stage excited state of the isotope atom of interest to the higher excited state.

Doppler broadening due to the distribution of the movement direction of the isotope of interest of this resonance line, and due to the fact that the isotope of interest has a non-zero nuclear spin, it is split and distributed into a plurality of hyperfine structure spectra. If the spread is wider than the spectral line width of the pump laser, sweep the oscillation wavelength of the laser (chirping) or make the pump laser multimode oscillate to increase the effective laser spectral line width and increase the pumping efficiency. You have to raise it.

Further, since the lasers of the respective excitation stages must be simultaneously irradiated to the vapor atoms, they must overlap each other both temporally and spatially. The ionized isotope atom is separated from the neutral atom by being induced by a potential gradient and attached by an electrode plate to which a voltage is applied.

The output of the laser beam for excitation required for efficiently and selectively exciting the isotope of interest needs to be considerably larger than the saturation output calculated from the resonance excitation cross section of the isotope of interest. Typically, laser light is oscillated by a pulse amplifier because it is necessary to simultaneously irradiate a plurality of laser lights of several [mJ / cm ² ] per one excitation stage in multistage excitation.

The fact that the output of the laser light for excitation has to be much higher than the net energy required to excite the isotope of interest means that the energy utilization of the laser light is well below 100%. To do. This means that the energy utilization rate of the isotope separation system, that is, the isotope separation efficiency is small.

[0010]

The first problem to be solved by the present invention is that the resonance excitation spectrum of the isotope of interest has a Doppler broadening or a hyperfine structure spectral distribution larger than the oscillation spectrum line width of the excitation laser. In some cases, the excitation efficiency becomes poor.

The second problem is as follows. Pulse amplifier lasers usually use continuous wave laser light as a pilot fire,
This is performed simultaneously with output amplification and pulsing by a multi-stage laser light amplifier. Therefore, the device configuration is complicated and expensive as compared with the continuous wave laser device.

Further, it is technically very difficult to stabilize the oscillation wavelength and output of each pulse. If the oscillation wavelength of each pulse fluctuates, the wavelength of the excitation laser light will deviate from the resonance excitation wavelength of the isotope of interest, thus lowering the excitation efficiency.
In the case of multi-stage excitation, the wavelength of the laser light at each excitation stage randomly deviates from the individual resonance wavelength, and the overall excitation efficiency further decreases.

In terms of energy efficiency, it is desirable to set the laser output to the minimum level necessary for the separation system, but if the output changes from pulse to pulse, the lower limit of the fluctuation range must be adjusted to the required output of the separation system. There is. Therefore, the required laser output becomes large.

Further, in the case of multi-stage pumping, the output balance between pumping stages also affects the pumping efficiency. Therefore, when the laser output of each pumping stage varies randomly for each pulse, the pumping efficiency for each pulse is It will be lower than the value achieved from the ideal output balance. That is, fluctuations in wavelength and output for each pulse cause a decrease in separation efficiency in isotope separation.

On the other hand, if the spatial output distribution in the beam of the pumping laser is not flattened, the spatial distribution of the separation efficiency in the beam occurs, which also lowers the separation efficiency as a whole. That is, in the case of performing multi-stage excitation, the laser beams of the respective excitation stages do not overlap with each other both temporally and spatially, so that the separation efficiency decreases.

However, when the pulse laser propagates in the metal vapor, there is a possibility that the propagation delay, pulse splitting, and further spatial convergence and divergence of the laser beam may occur, and the laser irradiation is performed over the entire area. It is technically very difficult to satisfy the conditions of output flattening and simultaneous irradiation.

The present invention has been made in order to solve the above-mentioned problems. It uses continuous wave laser light to enhance the excitation efficiency, and the target isotope can be efficiently inversely excited and separated and recovered.
An object of the present invention is to provide an isotope separation device that can measure the velocity distribution of metal vapor, can be used for optimization of heating energy, and does not require flattening of beam cross-section output.

[0018]

According to the present invention, a raw metal containing a plurality of isotopes is heated to vaporize a metal vapor, and the metal vapor is irradiated with a laser beam to select only the isotope of interest for separation. In an isotope separation device that is electrically excited and ionized, and is separated and recovered by a recovery electrode plate, a magnetic field whose magnetic field strength changes along the metal vapor flow direction is arranged in combination in the irradiation region of the laser light.

By utilizing the fact that the resonance excitation line (resonance excitation wavelength) of the isotope of interest changes due to the Zeeman effect, the resonance excitation line of the isotope of interest is caused by the Doppler effect resulting from the distribution of the isotope atom movement direction. Due to this, the oscillation wavelength is larger than the spectral line width of the excitation laser, or because the nuclear spin of the isotope of interest is not 0, the resonance excitation line is split into multiple lines and is larger than the spectral line width of the excitation laser. When the excitation efficiency is low in this excitation laser, by changing the magnetic field strength, polarity, etc., and shifting the resonance line while the isotope of interest passes through the laser irradiation region, which part of the resonance line spread Is also efficiently excited near the oscillation wavelength of the excitation laser and separated and collected as ions by the electric field of the recovery electrode plate. To.

[0020]

[0021]

According to the means for solving the first problem, the resonance excitation line of the isotope of interest is shifted by the Zeeman effect due to the magnetic field to cause resonance without changing the oscillation wavelength or spectrum line width of the excitation laser. The entire line distribution can be close to the laser oscillation wavelength to enhance pumping efficiency. Specifically, a magnetic field is set in the irradiation region of the excitation laser, and the magnetic field is not made constant in the laser irradiation region but the intensity or polarity is changed continuously or intermittently.

The shift amount of the resonance excitation line due to the Zeeman effect differs depending on the atom and the strength of the magnetic field.
The width of the change in the magnetic field strength here is set so that the entire distribution of the resonance excitation line of the isotope of interest overlaps with the oscillation wavelength of the excitation laser continuously or intermittently at a plurality of points.

In the means for solving the second problem, the isotope separation is performed by using a continuous wave laser beam which has a simpler apparatus configuration than the pulse amplifier laser and is excellent in output and wavelength stability. Since it is continuous oscillation, it is possible to avoid the problem of irradiation timing in which the isotope of interest has to be simultaneously irradiated with the laser light of each excitation stage in the case of multi-stage excitation with pulsed laser light.

The spatial output distribution within the laser beam does not have to be uniform in the beam cross-sectional direction, but rather the separation efficiency is high with a natural output distribution decreasing from the center to the periphery. Therefore, the isotope of interest is efficiently excited by the adiabatic inversion excitation process, and the required laser output is also reduced.

Adiabatic inversion excitation occurs when the resonance excitation line of the target isotope adiabatically passes through the oscillation wavelength of the laser. The specific means is as follows. Since the excitation energy level of the atom shifts to a value different from that in the absence of the magnetic field due to the Zeeman effect in the magnetic field, the magnetic field is changed so that the resonance excitation line passes the oscillation wavelength of the laser.

By the way, the metal vapor of the raw material containing the isotope of interest is heated and vaporized by the crucible and reaches the laser light irradiation region. Therefore, a magnetic field that continuously changes spatially is installed on this flight line. As the flying isotope of interest changes its position, the magnetic field intensity sensed by it also changes continuously, so that its resonance excitation line also continuously shifts due to the Zeeman effect.

By irradiating the region where the magnetic field is changed with the excitation laser beam and adjusting the oscillation wavelength of the laser beam and the intensity of the changing magnetic field, the resonance of the isotope of interest while passing through the region where the laser beam is irradiated. The excitation line could pass the oscillation wavelength of the laser light from the low wavelength side to the high wavelength side or from the high wavelength side to the low wavelength side.

During this time, the isotope of interest is adiabatically excited from the lower energy level to the upper energy level. In the case of causing such adiabatic inversion excitation, the laser intensity is the largest when the resonance excitation line of the isotope of interest crosses the oscillation wavelength of the laser light rather than being constant during the excitation reaction time. The reversal efficiency improves as the laser oscillation wavelength becomes smaller.

In the case of the present invention, the spatial output distribution of the laser beam is a natural output distribution form that would generally be the case of oscillating a laser beam, that is, the highest output at the center of the beam and the smaller it becomes at the periphery of the beam. As long as it has a shape, it is not necessary to carry out operations such as flattening the output distribution which is required for excitation by a pulse laser.

Here, when the isotope of interest moves to the position where the output is highest in the laser beam by adjusting the intensity distribution of the magnetic field or adjusting the laser oscillation wavelength, the resonance excitation line of the isotope of interest and the laser oscillation wavelength. Should cross each other.

Further, according to the present invention, the laser power density required for adiabatic inversion excitation on a time scale such that the isotope of interest passes through the laser beam cross section is equal to the average power density required for pulsed laser excitation. It is expected to be less than a few hundredths. Therefore, even a continuous wave laser can achieve a sufficient power density.

The adiabatic inversion excitation method using the continuously changing magnetic field described here is possible in principle not only with continuous wave lasers but also with pulsed lasers. It is applicable to the isotope separation device used.

[0033]

EXAMPLE A first example of the isotope separation apparatus according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 schematically shows the isotope separation device according to the present embodiment.
(A) to (f) are a conceptual diagram and a characteristic diagram for explaining an atomic excitation mechanism in this example.

In FIG. 1, reference numeral 1 is a vapor sealing container, and a main device for performing isotope separation is stored in the vapor sealing container 1. A crucible 3 accommodating a raw material metal 2 is arranged in the vapor sealing container 1, and an electron gun 4 is provided in the vicinity of the crucible 3.
Is provided.

Above the crucible 3, there are provided an electrode 7 having N and S poles facing each other, a recovery electrode plate 10 having an anode and a cathode facing each other, and a waste product recovery electrode 11. An ion current measuring device 12 is connected to the recovery electrode plate 10 on the cathode side, and the ion current measuring device 12, the S pole side electromagnet 7 and the electron gun 4 are connected to a vapor velocity detection system 13.

A first-stage excitation laser irradiation region 8 and a second-stage excitation laser irradiation region 9 are provided between the electromagnets 7, 7. Metal vapor evaporated from the crucible 3, that is, vapor atoms 6
Is irradiated by a first-stage excitation laser irradiation region 8 and a second-stage excitation laser irradiation region 9 between the electromagnets 7, 7.

The inside of the vapor sealing container 1 is depressurized by the vacuum pump. The raw material metal 2 containing a plurality of isotopes is heated in the crucible 3 by an electron beam 5 emitted from an electron gun 4 and evaporated. The vaporized metal vapor, that is, vapor atom 6, rises and jumps into the first-stage excitation laser irradiation region 8 between the electromagnets 7, 7.

The vapor atom 6 is generated in the laser irradiation area 8 by the electromagnet 7 by appropriately controlling the amount of change in the current flowing in the electromagnet 7 within the time from when the vapor atom 6 enters the laser irradiation area 8 until it exits upward. The magnetic field strength to be changed is changed so that the shift range of the first-stage resonance excitation line of the isotope vapor atom of interest due to the Zeeman effect intersects the oscillation wavelength of the first-stage excitation laser light 8.

As a result, the isotope of interest is adiabatically excited while passing through the laser irradiation region 7. Steam atom 6
After passing through the first-stage excitation laser irradiation region 8, it continues to enter the second-stage excitation laser irradiation region 9.

In the same manner as in the case of the first-stage excitation, the vapor atoms 6
The current of the electromagnet 7 is changed within a period of passing through the laser irradiation area to continuously change the second-stage resonance excitation line of the isotope of interest, and adiabatic inversion excitation is further performed to the upper level.
In the case of multi-step excitation of two or more steps, the excitation laser irradiation area and the magnetic field area are further continuous to repeat adiabatic inversion excitation.

The focused isotope is ionized when it passes through this multi-stage excitation laser irradiation region, and is further collected on the electrode plate by the potential gradient between the ion collection electrode plates 10 above. Non-target isotope atoms not intended for separation pass between the recovery electrode plates 10 and are vapor-deposited and recovered on the waste product recovery plate 11.

Information on the current flowing through the electromagnet 7 and its rate of change is sent to the vapor velocity detection system 13 together with the signal amount from the ion current measuring device 12 installed in a part of the recovery electrode plate 10. The excitation efficiency of the isotope of interest is high when the vapor atom 6 passes through each excitation stage laser irradiation region and the current change time of the electromagnet 7 coincides with each other. Therefore, the ion signal from the ion current measuring device 12 is The steam velocity can be estimated from the electromagnet current control pattern that maximizes the steam velocity.

On the other hand, since the velocity of the vapor atoms 6 is correlated with the temperature of the vaporizing portion, the output of the electron gun 4 is controlled based on the information of the vapor velocity detection system 13 to control the vapor velocity so as to enhance the excitation efficiency. Will also be possible.

Next, referring to FIG. 2, the excitation mechanism while the isotope of interest passes through the irradiation region 8 of the first-stage excitation laser will be described. In FIG. 2A, the position coordinates of the vapor atom 6 containing the target isotope are indicated by z (reference numeral 14). The position where the vapor atom 6 enters the laser irradiation area 8 is z1 (reference numeral 15),
The exit position is z2 (reference numeral 16). Further, the time at this time is indicated by t (reference numeral 17), and the vapor atom 6 is z1.
T1 (reference numeral 18) when in, and t2 when in z2
(Reference numeral 19).

The power density of the beam cross section of the first-stage excitation laser is shown by the electric field intensity E (reference numeral 20), which has a natural intensity distribution in which it is small at both ends of z1 and z2 and is maximum in the middle (FIG. 2 ( See b)). When the magnetic field intensity induced by the electromagnet is indicated by B (reference numeral 21), it continuously changes from time t1 to t2 (see FIG. 2C).

Due to the Zeeman effect due to this magnetic field, the resonance excitation wavelength λ (reference numeral 22) of the target isotope continuously changes from λ1 (reference numeral 23) to λ2 (reference numeral 24) from time t1 to t2 (FIG. 2 (d)). reference). When the resonance spectrum 25 at this time is shown by the relative relationship of the oscillation wavelength λ3 (reference numeral 26) of the excitation laser, the resonance excitation spectrum of the isotope of interest passes through the oscillation wavelength of the excitation laser (FIG. 2 (e )reference).

As a result, the isotope of interest is adiabatically inverted-excited, and the level density P (reference numeral 27) of the first excitation level of the isotope of interest changes from almost 0 to almost 1 from time t1 to t2 (FIG. 2 ( See f)).

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, instead of the magnet 7 in the first embodiment shown in FIG. 1, a continuously changing magnet 28 is provided as shown in FIG. 3, and the other points are the same as those in the first embodiment. Is.

According to the present embodiment, by disposing a plurality of permanent magnets or electromagnets 28 whose intensity continuously changes for each of the first and second stage excitation laser irradiation areas 8 and 9, the laser irradiation area is changed. A continuously changing magnetic field can be generated.

That is, one set of a combination of a magnetic field and laser light is provided, and a plurality of sets corresponding to the number of excitation steps required until the target isotope is ionized are continuously arranged in parallel with the vapor flow direction. To do. The continuously changing magnetic field can be created by continuously arranging a plurality of permanent magnets or electromagnets having different magnetic field strengths or polarities.

Next, a third embodiment of the present invention will be described with reference to FIG. In this embodiment, a rotating body 29 is provided as shown in FIG. 4 instead of the magnet 7 in the first embodiment. The rotor 29 has magnets having different strengths arranged in the circumferential direction, and is rotated with the rotation axis parallel to the flight direction of the vapor atoms 6. At this time, the rotating body 29 arranged on the opposite side across the first-stage excitation laser irradiation area 8 has the same strength of the magnet in the circumferential direction as the other rotating body 29, but the portions of opposite polarities are opposite to each other. Rotate synchronously to face each other.

That is, the continuously changing magnetic field has a plurality of electromagnets or permanent magnets having different magnetic field strengths or polarities arranged continuously or a rotating body arranged in the circumferential direction thereof.
29 is rotated in synchronization with the steam flow rate. As a result, when the vapor atoms 6 pass near the rotating body 29, they can be created by acting as a relatively continuously changing magnetic field.

Next, a fourth embodiment of the present invention will be described with reference to FIG. The present embodiment is an improvement of the excitation laser irradiation unit and the magnetic field generation device unit in the case where the isotope of interest has a large Doppler spread in the first embodiment. First
The step excitation laser irradiation region 8 also overlaps with the second step excitation laser irradiation region 9 and the excitation step laser irradiation regions higher than that.

The electromagnet 7 is arranged so as to sandwich the laser irradiation region, and the magnetic field strength is changed continuously or intermittently during the time when the vapor atoms 6 pass through the laser irradiation region 8. The range of the magnetic field change is set so that the shift width of the resonance excitation line of the isotope of interest due to the Zeeman effect is about the Doppler distribution width.

The present invention is not limited to the above-mentioned embodiments, but may have the following constructions. (1) In the apparatus of the third embodiment, the velocity distribution of the vapor flow velocity is measured from the correlation between the rotational velocity of the rotor in which the magnet is arranged, the vapor flow velocity, and the excited fluorescence amount or ionization amount from the isotope of interest. It can be used for controlling the heating temperature of the crucible containing the metal raw material.

(2) For the magnetic field in the first embodiment and the continuously changing magnetic field in the second to fourth embodiments, one electromagnet is arranged, and the current flowing through it is changed in synchronization with the vapor flow velocity. Let

(3) The velocity distribution of the vapor flow velocity is measured from the correlation between the rate of current change of the electromagnet for changing the magnetic field strength, the vapor velocity, and the amount of excited fluorescence from the isotope of interest or the amount of ionization. The heating temperature of the crucible containing the metal raw material can be controlled using this.

(4) When the final excited state for ionizing the isotope of interest is the automatic ionization state, only the laser beam having a wide line width is provided only in this excitation stage without providing a continuously changing magnetic field. (5) By using a continuous wave laser beam as the excitation laser beam, it is possible to avoid the problem of deviation of the irradiation time timing when the target isotope is ionized by multistage excitation.

[0059]

According to the present invention, the Doppler broadening and the hyperfine structure spectrum in which the resonance excitation line of the isotope of interest is larger than the oscillation spectrum line width of the excitation laser by setting the changing magnetic field in the excitation laser irradiation region. The excitation efficiency can be increased even when the distribution is provided, and the isotope of interest can be efficiently and adiabatically inverted excited by setting a continuously changing magnetic field.

Further, by using a continuous wave laser device having a simpler device structure than the pulse amplifier laser device, it is possible to carry out multi-stage excitation of simultaneous irradiation without performing beam shaping such as output flattening of the beam cross section. In this case, the isotope of interest can be efficiently separated and recovered without the problem of the irradiation time timing shift between the excitation lasers.

Furthermore, since the velocity distribution of the metal vapor can be measured by combining the local magnetic field intensity with the separated and collected ion signal, it can be utilized for optimization of heating energy by feeding back to the evaporation heating control of the raw material metal. .

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of an isotope separation device according to the present invention.

2A and 2B are diagrams for explaining the excitation mechanism of atoms in FIG. 1, and FIG. 2A is a schematic diagram showing time coordinates during which vapor atoms pass through a first-stage excitation laser irradiation region;
(B) is an intensity distribution diagram showing the relationship between the laser irradiation area and the laser electric field intensity, (c) is a graph showing the relationship between the time coordinates and the magnetic field strength, and (d) is the time coordinates and the resonance excitation wavelength. The graph diagram which shows a relationship, (e) is a waveform diagram which shows the relationship between a resonance spectrum and a resonance excitation wavelength, (f) is a curve figure which shows the level density of a 1st excitation level, and a time coordinate.

FIG. 3 is a magnet layout diagram showing a main part of a second embodiment of the isotope separation device according to the present invention.

FIG. 4 is a magnet layout diagram showing a main part of a third embodiment of the isotope separation device according to the present invention.

FIG. 5 is a magnet layout diagram showing a main part of a fourth embodiment of the isotope separation device according to the present invention.

FIG. 6 is a schematic diagram showing a conventional isotope separation device.

[Explanation of Codes] 1 ... Steam Enclosure, 2 ... Raw Metal, 3 ... Crucible, 4 ... Electron Gun, 5 ... Electron Beam, 6 ... Steam Atom, 7 ... Electromagnet, 8
... 1st-stage excitation laser irradiation area, 9 ... 2nd-stage excitation laser irradiation area, 10 ... Collection electrode plate, 11 ... Waste collection plate, 12 ... Ion current measuring device, 13 ... Vapor velocity detection system, 14 ... Vapor atom position coordinates (Z), 15 ... laser irradiation-area-lower-end position (Z _1), 16 ... laser irradiation-area-upper-end position (Z _2), 17
... time coordinate (t), 18 ... vapor atom laser irradiation region entry time (t ₁ ), 19 ... vapor atom laser irradiation region passage time (t ₂ ), 20 ... laser electric field intensity (E), 21 ... magnetic field intensity (B), 22 ... resonant excitation wavelength (lambda), resonant excitation wavelength at 23 ... time t ₁ (λ _1), resonance excitation wavelength at 24 ... time _{t 2 (λ 2), 25} ... resonance spectrum (S) , 26 ... Oscillation spectrum of excitation laser (λ ₃ ), 27 ... Level density of the first excitation level (P).

Continuation of front page (56) Reference JP-A-6-154557 (JP, A) JP-A-50-96799 (JP, A) JP-A-1-249128 (JP, A) JP-A-5-212249 (JP , A) JP-A-6-47257 (JP, A) JP-A-63-42723 (JP, A) JP-A-1-310724 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) (Name) B01D 59/34

Claims (4)

(57) [Claims] 1. A raw material metal containing a plurality of isotopes is heated to vaporize a metal vapor, and the metal vapor is irradiated with a laser beam to selectively excite, ionize and recover only an isotope of interest for separation. In an isotope separation device that separates and collects as ions by an electric field of an electrode plate, a combination of a magnetic field whose magnetic field strength changes along the metal vapor flow direction is arranged in an irradiation region of the laser light, and the combination of the magnetic field and the laser light. As one set, and a plurality of sets of the combination regions of the magnetic field and the laser beam are continuously arranged along the vapor flow direction of the metal vapor by the number of excitation steps required to ionize the isotope of interest. Body separation device. 2. A raw material metal containing a plurality of isotopes is heated to vaporize a metal vapor, and the metal vapor is irradiated with a laser beam to selectively excite, ionize, and recover only the isotope of interest for separation. In an isotope separation device that separates and collects as ions by an electric field of an electrode plate, a pair of rotating bodies in which magnets having different intensities are arranged in the circumferential direction so as to sandwich the irradiation region of the laser beam, the rotation axis of which is the metal vapor. An isotope separation device, which is arranged in parallel to a flow direction, and rotates each rotating body synchronously so that portions having the same magnet strength but opposite polarities face each other. 3. A calculated vapor velocity of the metal vapor from the correlation between the excitation fluorescence amount or ionizing amount from the rotator vapor velocity between the target isotopes rotational speed and the metal vapor of the gold
From the steam velocity of the metal vapor and the heating temperature of the crucible containing the metal raw material and the obtained steam velocity
Claim 2, characterized by controlling the heating temperature of the crucible
The isotope separation device described in. 4. A raw material metal containing a plurality of isotopes is heated to vaporize a metal vapor, and the metal vapor is irradiated with a laser beam to selectively excite, ionize and recover only the isotope of interest for separation. In the isotope separation device that separates and collects as ions by the electric field of the electrode plate, in order to change the magnetic field strength by arranging a combination of magnetic fields whose magnetic field strength changes along the metal vapor flow direction in the irradiation region of the laser light. and the current rate of change of the electromagnet, and the vapor rate of the metal vapor, calculated vapor velocity of the metal vapor from the correlation between the excitation fluorescence amount or ionizing amount from interest isotopes vapor velocity and a metal of the metal vapor An isotope separation device, characterized in that the heating temperature of the crucible is controlled from the interphase relationship with the heating temperature of the crucible containing the raw material and the obtained vapor velocity.