JPS61274731A - Apparatus for separating isotope by laser - Google Patents

Abstract

PURPOSE:To enhance the separation efficiency of an isotope and to reduce the consumption of energy required in separation, by optimizing the irradiation time of dissociation beam. CONSTITUTION:The irradiation time with dissociation beam is set to the life of the exciting state of an excited atom or molecule or less. That is, the output signal from the optical probe 4 inserted in the exciting beam 5 emitted from a laser system 1 is amplified by an amplifying system 7 to be inputted to a control system 1 which, in turn, controls the oscillation of the laser system 2 on the basis of the signal from the optical probe 4. The life time of an excit ing state is preliminarily inputted to the control system 1 as a control parameter according to the parameter such as the pressure or temp. in a sample chamber 1. As a result, the separation efficiency of an isotope is enhanced and the con sumption of energy required in separation can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a laser isotope separation device, and particularly to a laser isotope separation device suitable for improving separation efficiency and reducing energy required for separation.

[Background of the invention]

In conventional laser isotope separation equipment, JP-A-1iV54-9
9899, 1989-99898, and 1982-13330, there were improvements regarding the atomization device and the selection method of the excitation light wavelength, but the optimization of the irradiation time of the excitation light and dissociation light and the associated separation were difficult. No consideration was given to improving efficiency or economic efficiency.

[Purpose of the invention]

An object of the present invention is to provide a method and apparatus for optimizing the irradiation time of dissociation light of a laser isotope separation apparatus, improving separation efficiency and reducing energy consumption required for separation.

[Summary of the invention]

Laser isotope separation takes advantage of the fact that the absorption spectra of atoms or molecules differ minutely depending on the isotope, and after selectively optically exciting only the atoms or molecules at the same position to be separated using a single wavelength laser beam, Dissociation light ionizes atoms or molecules of the isotope in an excited state. Target isotopes are separated by electrostatically separating ionized atoms or molecules. Therefore, in order to improve the separation efficiency of laser isotope separation, it is necessary to improve the efficiency of dissociating atoms or molecules in the excited state. Therefore, it is necessary to irradiate the excited atoms or molecules with dissociation light before they return to the ground state. Further, since the absorption cross section of the excited state is constant, in order to increase the number of dissociated atoms and molecules, it is desirable to irradiate dissociation light with as high an energy density as possible.

Generally, after irradiation with excitation light at time t, = O, the number of atoms or molecules that transition from the excited state to the ground state is the first
It changes as shown in the figure. Time 1. The position of the peak appearing at =τ changes depending on the pulse width of the excitation light. Furthermore, when the excitation light irradiation is stopped, the number of atoms or molecules that relax from the excited state to the ground state decreases exponentially, and it takes time to reach a ratio of e-1 to the maximum value (1 = τF). τ is called the lifetime of the excited state. As is clear from Figure 1,
After time 1, = 10, most of the atoms or molecules relax to the ground state, and even when irradiated with dissociation light, the number of atoms or molecules that are ionized is small. On the other hand, before time 16-τ, the majority of atoms or molecules in the excited state are not relaxed, and if dissociation light is irradiated during this period,
Excited atoms or molecules can be ionized efficiently. Therefore, by controlling the irradiation time of the dissociation light from the excitation light irradiation time 1 = 0 to = τ + τ, atoms or molecules in an excited state can be efficiently ionized.

Furthermore, τ0τ is usually at most 10° to 10” ns, and the light source of the dissociation light can be a pulsed laser. In a pulsed laser, the energy density for a waiting time of Qi is lower than that of a continuous light laser. That is, since the photon number density can be increased, it is possible to increase the number of atoms or molecules that are ionized from an excited state.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

Laser system 1 provides excitation light 5 and laser system 2 provides dissociation light 6. The excitation light and dissociation light enter the sample chamber 1 through the half mirror 3. Metal atoms containing the isotope to be separated (e.g. 90Z, Zr containing r
) is atomized by an atomization device and introduced into the sample chamber 1.

Isotopes ionized by the excitation light and dissociation light are ionized by the electromagnetic field in the sample chamber created by the electromagnetic field generator w2.
Directed to separator. The vacuum system of this apparatus is connected to a vacuum pump through a vacuum line 8, and is centrally managed by a control system 2. The control system 2 also controls the electromagnetic field generator and the atomization device 1 separator at the same time.

An optical probe 4 made of a photodiode is inserted into excitation light 5 emitted from the laser system 1. The output signal from the optical probe 4 is amplified by an amplification system 7,
It is input to the control system 1.

The control system 1 controls the oscillation of the laser system 2 using signals from the optical probe. In advance, the lifetime of the excited state is input to the control system 1 as a control parameter according to parameters such as pressure and temperature inside the sample chamber 1. Further, when the output waveform of the excitation light is a rectangular wave or the like, as shown in FIG. 1, it becomes impossible to ignore compared to the lifetime τ of the excited state. In this case, τ and τ are input as control parameters.

The laser system 2 is triggered by the signal from the optical probe 4 and emits a dissociation light pulse with a pulse width τ or τ+τ.

Time-resolved fluorescence spectroscopy and photoacoustic spectroscopy are used to measure the lifetime of the excited state. When the relaxation process is a radiative process, time-resolved fluorescence spectroscopy is used, and when it is a non-radiative process, photoacoustic spectroscopy is used.

〔Effect of the invention〕

According to the present invention, there are the following effects.

(1) Since both the excitation light source and the dissociation light source can be pulsed, the light energy density per unit time, that is, the photon number density can be improved, and the separation efficiency can be increased by -L. Even if the average output is the same, a pulsed light source can increase the optical energy density by about 6 orders of magnitude or more compared to a continuous light source.

(2) Since the excitation light source and the dissociation light source can be pulsed or have a rectangular wave, energy consumption of the light source can be reduced. For example, if the output is a rectangular wave with a duty cycle of 30%, the energy consumption will be reduced by about 70% compared to a continuous light source.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the temporal change in the number of relaxed atoms from an excited state, and FIG. 2 is a diagram showing the configuration of a laser isotope separation apparatus based on the present invention. 1... Sample chamber, 2... Electromagnetic field generator,
3... Half mirror 14... Optical probe, 5...
Excitation light, 6... Dissociation light, 7... Amplification system, 8... Vacuum line, 9... Optical window.

Claims (1)

[Claims] 1. A laser isotope consisting of an excitation light source for bringing atoms or molecules into an excited state, a dissociation light source for ionizing the excited atoms or molecules, and a separation device for separating the ionized atoms or molecules. A laser isotope separation device characterized in that the irradiation time of dissociation light is set to be less than the lifetime of the excited state of an excited atom or molecule. 2. A laser isotope separation apparatus according to claim 1, characterized in that excitation light and dissociation light are irradiated simultaneously. 3. In the laser isotope separation apparatus according to claim 1, the time from irradiation with excitation light until the number of atoms or molecules that relax from the excited state reaches the maximum, or during this time, the excited state A laser isotope separation device characterized by irradiating dissociation light only for a time corresponding to the lifetime of the laser isotope.