JPH0679141A - Method for recovering ion by heating photoionized plasma using electromagnetic wave - Google Patents

Abstract

(57) [Summary] [Objective] To provide a method for efficiently collecting ions when the temperature of photoionization plasma is low and the recovery time is long. In a method of separating an atomized isotope of an atom using an electric field by irradiating a vapor atom having an isotope with a laser beam to generate a photoionization plasma, the plasma is irradiated with an electromagnetic wave to generate a plasma of the plasma. A method comprising raising the temperature to recover the isotope in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an isotope separation method by an atomic method using laser light.

[0002]

2. Description of the Related Art Up to now, in isotope separation such as uranium enrichment by an atomic method using laser light, the ions in the plasma generated by the laser light generate an electric field or a magnetic field in the plasma in a pulsed or stationary manner. It was applied onto the electrode by electromagnetic force. In laser concentration, ions that have been selectively photoionized by pulsed laser light are recovered from a high-speed vapor stream. In that case, if the recovery rate is slow, the recovery rate of ions decreases, or the concentration rate of ions decreases due to collision between ions and neutral atoms. Therefore, it is necessary to rapidly collect ions in order to increase the recovery rate of ions from the laser-induced plasma passing between the electrodes at high speed and to suppress the loss due to charge exchange. When performing ion recovery by the conventional technique, the moving speed of ions is determined by the ion temperature and electron temperature of plasma due to the influence of space charge. In this case, the ion temperature and electron temperature of the plasma generated by the photoionization by the laser beam are as low as about 0.1 eV, so that the moving speed of the charged particles is relatively slow, and it takes some time to extract the ions from the plasma to the electrode. Will be needed. Therefore, in order to collect ions at high speed using the electrostatic field, a high voltage must be applied to the collecting electrode.

However, if the ion density is increased in order to increase the ion recovery rate, the voltage applied to the recovery electrode must also be increased. At this time, due to the sputtering phenomenon of ions that have obtained high energy, the voltage is applied to the electrode surface. Recovered isotopes may be ejected.

Further, since the ions are collected while the high voltage is applied, it is expected that the energy consumed during the collection will be large.

[0005]

In view of the above problems, it is an object of the present invention to provide a method for efficiently collecting ions when the temperature of the photoionization plasma is low and the recovery time is long.

[0006]

[Means for Solving the Problems] In order to solve the above problems,
According to the present invention, in a method of separating an isotope of interest of an atom with an electric field by irradiating a vapor atom having an isotope with a laser beam to generate a photoionization plasma, the plasma is irradiated with an electromagnetic wave. A method is provided which comprises raising the temperature of the plasma to recover the isotope in a short time.

[0007]

As described above, since the temperature of the plasma photoionized by the irradiation of the laser beam is low, the moving speed of the ions in the electric field becomes relatively slow, and it takes some time to extract the ions from the plasma. Becomes When this plasma is irradiated with an electromagnetic wave, the charged particles in the plasma, that is, ions and electrons absorb the electromagnetic wave, so that the temperature of these charged particles rises and the momentum in the plasma increases. As a result, the ions are easily attracted to the electrode, and the time until the ions are attracted to the electrode is reduced, and the ions can be recovered in a shorter time than the conventional isotope separation method using laser light.

The frequency of the electromagnetic wave with which the plasma is irradiated is not particularly limited as long as it can raise the temperature of the plasma, but when the frequency of the electromagnetic wave is lower than the plasma frequency, the electrons in the plasma can be efficiently heated. Therefore, it is preferable. This is because if the frequency of the applied electromagnetic wave is higher than the plasma frequency, the electromagnetic wave will pass through the plasma, and the heating efficiency of the plasma will decrease.

The laser light to be applied may be any one that can selectively ionize the target vapor atom in synchronization with the resonance wavelength of the vapor atom, and is applied in a pulsed or steady manner.
In the present invention, a pulse laser is preferably used to selectively photoionize the atoms.

The method of applying the electromagnetic wave is not particularly limited, and for example, an antenna or a waveguide may be installed near the recovery electrode, or the electromagnetic wave may be applied to one or both of the electrodes. Then, the electromagnetic wave may be applied in a pulsed or standing wave.

The type of atom recovered by the method of the present invention is not particularly limited as long as it has an isotope, but the method of the present invention is used for the isotope separation of alkali metal, alkaline earth metal or transition metal. It is preferable to use.

[0012]

EXAMPLE A schematic diagram of an apparatus for carrying out the method of the present invention is shown in FIG. A heat pipe having a length of 30 cm was installed in the separation chamber 1, and parallel plate electrodes 2 for ion collection were arranged on both sides of the heat pipe. A predetermined voltage was applied from the high voltage recovery power supply 6 to both electrodes. Pulsed laser light (-600 μJ, 10 ns, 2 mm, which was made to resonate with D ₂ line of sodium atom, was added to metallic sodium vapor enclosed in a heat pipe.
φ) was irradiated to ionize sodium atoms by multiphoton absorption to generate plasma 3. The sodium ions ionized in this manner were collected in a parallel plate electrode to which a low voltage was applied. A coil electrode was installed as an electromagnetic wave generating antenna 5 near the center of the electrode, and a high frequency electromagnetic wave was applied using an electromagnetic wave generator. The frequency of electromagnetic waves is 14
It was 0 MHz. The plasma frequency at this time was about 300 MHz. The time waveform of the ionic current flowing through the electrode 2 was observed, and the relationship between the applied high frequency electromagnetic wave and the ionic current waveform was measured. The result is shown in FIG.

FIG. 2 shows the waveform of the ion current flowing through the electrode 2 when the high frequency electromagnetic wave is applied to the plasma and when it is not applied. From this figure, it can be seen that the application of high frequency electromagnetic waves accelerates the rise of the pulse of the ion current. It can also be seen that the collection time is shortened as the output of the high frequency electromagnetic wave is increased.

[0014]

As described above, according to the present invention, even when the plasma density is high, ions can be rapidly collected in the electrode within a predetermined time, and as a result, the efficiency and product amount of isotope separation by laser light can be increased. Can be increased.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for carrying out the present invention.

FIG. 2 is a diagram showing a relationship between a high-frequency electromagnetic wave to be applied and an ion current waveform.

[Explanation of symbols]

 1 Separation Chamber 2 Recovery Electrode 3 Photoionization Plasma 4 Electromagnetic Wave 5 Antenna 6 High Voltage Recovery Power Supply 7 Electromagnetic Wave Generator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Yoichiro Maruyama, Shirahone, Shirahone, Tokai-mura, Naka-gun, Ibaraki Prefecture, Japan 4 Inside the Tokai Research Institute, Japan Atomic Energy Research Institute (72) Takashi Arisawa, Tokai-mura, Naka-gun, Ibaraki Prefecture 4 at Shirane No. 4 Inside the Japan Atomic Energy Research Institute Tokai Research Institute

Claims (3)

[Claims] 1. A method for separating an isotope of interest of an atom with an electric field by irradiating a vapor atom having an isotope with a laser beam to generate a photoionization plasma, and irradiating the plasma with an electromagnetic wave. A method comprising raising the temperature of plasma to recover the isotope in a short time. 2. The method according to claim 1, wherein the frequency of the radiating electromagnetic wave is lower than the plasma frequency. 3. The method according to claim 1, wherein the atom is an alkali metal, an alkaline earth metal or a transition metal.