CS229846B1 - A method for obtaining a chemical laser inversion - Google Patents

Abstract

The invention relates to a method for obtaining inversion of a chemical laser, which would allow the use of high energy density contained in metastable states of molecules, arising, for example, by a chemical reaction, to obtain inversion by exciting active centers with a sufficient speed for use in high-energy pulsed lasers. Free atoms, for example, can serve as active centers. Such lasers are used for research into controlled thermonuclear fusion. The required light pulses range in the range of units to tens of nanoseconds and their energy to tens of kJ.

Description

The present invention relates to a method of obtaining a chemical laser inversion that allows the use of the high energy density contained in metastable states of molecules, for example resulting from a chemical reaction, to obtain inversion by activating active centers with sufficient speed for use in high energy pulsed lasers. For example, free atoms can serve as active centers. Such lasers are used for the research of controlled thermonuclear fusion. The required light pulses range in units of up to tens of nanoseconds and their energy to tens of kj.

For example, resonant energy transfer between the metastable level of the oxygen molecule O ₂ (and ¹ A _g ) and the iodine I atom is currently being used:

O ₂ (aU _g ) + 1 ( ^from P3 / 2) - I * ( ² Pi / 2) + O ₂ (X ³ £ g-) (1) ki = 7.6.10 “ ¹¹ cm ³ / s

The natural lifetime of O2 (a ¹ A _g j is 45 min.) Can therefore be prepared chemically, for example by chemical reaction:

Cl2 + H2O2 + 2NaOH-O2 (aU _q ) + 2NaCl + + 2HaO (2j with an efficiency of 95 + 5 ° / o. Atomic iodine for the reaction (1j is obtained on the basis of reactions:

O2 * (Ag ¹⁾ + 02 * ⁽¹ Ag) - O2 ** (BQ) ⁺ g) + O2 ⁽³ X £ _g ~) k3 - 2nd ΊΟ-w cm ³ / sec

G ** ₂ (b ^{1 +} 2 g) + I2 - * O2 (X ^{3 _} 2Jg) + 2Ι (Ρ3 ^2/2) (4) k == 2.3.TO ^-10 cm ³ / s

Therefore, it is possible to obtain the necessary inversion in this laser by mixing the molecular iodine vapors with the flowing O2 (a ¹ A _g j).

This laser was operated at a partial pressure of 02 (aUJ 130 130 Pa. For operation)

- This laser has some limiting factors that make it impossible to increase the I * ( ² Pj / ₂ ) concentration and thereby achieve the desired inversion level for the high power pulse mode. Above all, the low concentration of O2 ** (biŠ ₈ ⁺ L) is important, which does not allow to increase the amount of I2 in the system.

1 * ⁽² Pi / 2) + I I2- ⁽² P3 / 2) + I2 (5) ks - 3.6.10-11 _om 3 / _s

With increasing concentration OAU and ^L A) shortens the lifetime of this state and the system requires technically difficult reachable speed agitation iodine vapors with oxygen. There is an influence of reactions

O ₂ * (AIA _g) + I * (P ² _{j / 2)} -02'JbiL /] + L ⁽² P _3/2) (6) ks = 6.2 IO-1 ⁴ cm3 / s 0.2 ** (b.i2; g ⁺ ) -> O2 (X ³ Xg-j + hv (7) k7 == 7.7.10-2.S-1 Oz ** ( bi £ g ⁺ ) + M-O 2 (aiA _g ) + M (8) k & = 1.0.10 ~ 17 cm ³ / s

Furthermore, the effect of admixtures in gases and quenching of metastable states by collisions of molecules with walls is apparent. Abroad, a theoretical possibility has been proposed to increase the accumulated energy density while preserving life, at a technically fair value on the basis of substantial supercooling of the laser mixture, in order to reduce the rate of individual reactions in an appropriate manner. The overall efficiency was estimated, including the recovery of used chemicals around 6%. Estimated extracted energy of 100 kj (15 J / lj with twenty times the light pass through the amplifier. The time between each light pass is about 200 ns, so that the energy can be exchanged according to equation (lj.

The disadvantage of this system is the sophisticated cooling system and the need for rapid mechanical mixing of the iodine vapor with oxygen, which limits the increase in the concentration [OW] [I] and thus the reaction rate (lj). Extracting energy from the amplifier Shortening this time would also simplify the design of the amplifier Obtaining atomic iodine based on reaction (4) is also not optimal due to the low concentration Ο2 ** (^ 2 _? ⁺ ] and reaction (5).

At present, a photodissociating iodine laser is also used in which excited states of iodine atoms are obtained by photodissociation with UV radiation of C3F7I type compounds. The laser iodine transition corresponds to a wavelength of 1.315 µm and the UV radiation corresponding to the maximum cross section of the photodissociation has a wavelength of 273 nm. Useful UV bandwidth 41 nm.

The disadvantage of the photodissociation laser is its low efficiency due to the disadvantageous ratio of the energy of the quantities needed for photodissociation (flax) and the quantum of laser radiation (hia) · '= 4.82 h in _L

There is also a low efficiency of the UV sources needed for photodissociation and the low energy stored in capacitor batteries. Current capacitors achieve 100 J / l (0.1 J / g) and a laser efficiency of 0.1%. Thus, a 10 kJ laser amplifier requires a 10 MJ capacitor battery, which is technically very difficult to implement. By way of comparison, current exits oxygen chemical generators allow to generate energy of 100 J / g.

These drawbacks of the purely chemical laser and of the phiotodissociation laser do not have the present invention, the object of which is to provide an inversion of a chemical laser utilizing energy transfer from metastable state molecules to active centers whose excited states are used for stimulated laser emission. SUMMARY OF THE INVENTION The present invention provides a process in which free active centers are obtained by photodissociation of molecules containing these centers in the working volume of molecules in the metastable state. The invention further relates to a process in which, in the metastable state, ozone molecules ( ^I ) and atoms (I) obtained by photodissociation of iodide are treated. The present invention utilizes a so-called hybrid inversion pumping process comprising adding a compound containing active centers in the bound inactive state to a mixture comprising molecules in the metastable state. After filling the appropriate cuvette of the laser system with this mixture, by photodissociation of this compound, the required concentration of free active centers for resonant energy transfer from the metas-tabular states of the molecules is obtained in a pulsed manner in the volume of the working medium. These excited centers can be used for stimulated emission in the laser system. The long lifetime of the molecules in the metastable states in the absence of active centers before the start of the photodissociation and the small effect of the compounds containing these centers on the lifetime of the molecules in the metastable state are used to obtain the inversion. An example of a hybrid inversion pumping method is a mixture containing oxygen in the metastable state of O2 (a ¹ A _g ) and an RI type compound used in photodissociating iodine lasers (eg C3F7IJ) utilizing resonance energy transfer to active centers formed by iodine atoms obtained by photodissociation:

RI + hv -> R + I *

On the first pass of the laser beam, the atoms return to the ground state due to stimulated emission and are again energized by resonant energy transfer from metastable levels of O 2 (O 2) according to equation (1). The stored energy at the metastable levels of the molecules is converted to the light energy of the laser radiation at each pass of laser light.

An advantage of the arrangement according to the invention is that it eliminates the need for rapid mechanical mixing of the mixture that requires a conventional chemical laser. It allows for a fast pulsed method of obtaining inversion across the entire volume of working medium required for the pulse mode of the laser, while maintaining the advantages of the high energy density of chemical lasers. In the pulsed method of obtaining active centers in the working volume of the molecules in the metastable state, higher concentrations of these molecules can be used, thereby increasing the energy density stored in the laser system and increasing the energy transfer rate between metastable states of the molecules and active centers. This solution also eliminates the disadvantage of the photodissociation laser and hence the low efficiency, since most of the stored energy is contained in the metastable levels of the molecule and only a fraction of the energy is obtained by photodissociation. Molecules at metastable levels can be obtained chemically with up to 100% yield. This solution also eliminates the need for significant cooling of the mixture, since real mixing time is not a determining factor in achieving high energy densities, as in conventional chemical lasers. Removing large capacitor batteries, reducing cooling requirements, and laser gas velocities will greatly simplify the technical implementation of large laser modules (for 10 kj energies).

A particular embodiment of the invention can be illustrated by the construction of a photodissociation laser pumped by a discharge lamp, wherein the quartz cuvette with the working charge is illuminated by UV radiation of pulsed xenon lamps. In such a laser, photodissociation of the excited iodine concentration of 4.10 ¹⁶ cim ^-3 is achieved. The working substance used is n-C3F7l with a concentration of 5.10 ¹⁷ cm ³ . This corresponds to the gain for the small signal g = 0.04 cm ^-1 . The method of obtaining an inversion according to the invention consists of impregnating oxygen in the metastable state of OztaiAg) at a partial pressure of 2 kPa with n-CsF7l vapors in a ratio of 1: 1 into the cuvette of said arrangement sc. iodine concentration obtained by photodissociation after lamp exposure. Therefore, the extracted energy in the laser radiation will also be in a corresponding ratio higher than for a classical photodissociation laser.

Currently iodine photodissociation lasers with energies of 1 kj are realized. Using the proposed hybrid inversion acquisition method, it is possible to increase the energy and efficiency of these lasers so that they become perspective for the realization of a controlled thermonuclear reaction. Because the energy flux density of chemical generators of molecules in metastable states is very high (MJ / L), these generators, together with the proposed method of obtaining inversion of high repetition rate lasers and energies of 100 J, make relatively simple and inexpensive technical means possible. Such lasers are promising in industry as a source of X-rays for lithography, or for annealing semiconductors after implant implantation.

Claims (2)

Subject A method of obtaining a chemical laser inversion utilizing transfer from molecules in a metastable state to active centers, the excited states of which are used for stimulated laser emission, characterized in that the free active centers are obtained in the workload volume of the metastable molecules. center. 2. The method of obtaining the inversion of a chemical laser according to claim 1, characterized in that in the metastable state, the molecules of Ozazi and the atoms of I. obtained by photodissociation of iodine are treated.