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A model for a solid state nuclear pumped laser (SSNPL) has been developed. The laser model includes the spatial inhomogeneities of electron-hole pairs generated by fission products. A MCNP model was produced which transported the 20 most common U-235 fission fragments to dictate the 1-dimensional spatial inhomogeneity. The MCNP model included a variety of thicknesses to the layers involved. Core properties include a minimally critical cubic bare nuclear core which has dimensions less than one cubic meter on a side and laser thresholds in the sub-megawatt range. Laser efficiencies ranged from 2 to 5%. The SSNPL has the potential to be compact, low mass and efficient making it a promising space-based laser system.

The present paper deals with problems of the practical applications of high-power lasers in various industrial technologies. It is shown that creation of megawatt-range laser emitters based on the direct conversion of fission energy of heavy nuclei into energy of optical (laser) radiation in pulse reactor-laser systems will make it possible to considerably increase the efficiency of existing laser technologies and to extend the fields of their application.

A 500-J pulsed gas laser (laser module) pumped by uranium nuclear fission products has been created, which operates on xenon 5d[3/2]1 → 6p[3/2]1 transition with a wavelength of 2.03 μm. Experiments have been performed on a BARS-5 + RUN-2 complex comprising a fast aperiodic self-quenching reactor and a neutron multiplier reactor. A specific laser radiation energy in experiments achieved ∼32 J/dm3 at an efficiency of 3% (ratio of the laser output pulse energy and the energy transferred from fission fragments to gas medium).

The lasing characteristics of the Ar — Xe and He — Ar — Xe mixtures emitting at the transitions of the Xe atom at 1.73 and 2.026 mkm upon pumping by fission fragments in the BARS-6 pulsed reactor are studied. We describe an experimental setup and methods for measuring laser beam parameters and characteristics of the active medium of the nuclear-pumped laser in the free-running and master oscillator — amplifier regimes. The dependences of the laser pulse energy on the resonator parameters and the composition and pressure of the working mixture are studied in the free-running regime. A method of modulating the input signal of a single-pass amplifier is proposed for obtaining lasing characteristics of active mixtures. The lasing characteristics of the Ar — Xe and He — Ar — Xe mixtures (the unsaturated gain, saturation intensity, conversion efficiency, etc.) are determined from experiments in the amplifier — oscillator regime and compared with the results reported in other papers.

The efficiency of a master oscillator?amplifier scheme and the possibility of its using in multichannel nuclear-pumped laser systems are studied. The small-signal gain and saturation parameter are measured for the He:Ar:Xe = 380:380:1 mixture at a pressure of 1 atm at a wavelength of 2.03 ?m. It is shown that the small-signal gain increases linearly with the specific pump power density and achieves 1.1?1.2 m-1 at a pump density of 40 W cm-3. The saturation parameter is almost independent of the pump power and is equal to 70?90 W cm-2. It is found that at the pump-pulse maximum (40 W cm-3) the laser radiation power increases after amplification by 100%.

The nuclear-pumped laser (NPL) is a technology in which laser oscillation is accomplished using the energy of a nuclear reaction. We studied the possibility of developing a pulse reactor system for NPL using low-enriched uranium. It is possible to design a reactor system with 20% enriched uranium by making the pulse cores large, optimizing their position, and increasing their number. Such a system has uniform power distribution in the laser oscillation cells, which is desirable for laser pumping. The potential to solve the limit of energy efficiency and temperature in a nuclear reactor by NPL is also discussed.

Nuclear-pumped laser can directly convert nuclear energy to optical energy. A coupled reactor which consists of two pulse cores with highly enriched metallic uranium and a subcritical thermal laser module with highly enriched metallic uranium is one of the reactors for nuclear-pumped laser. In this paper, criticality analysis of a coupled reactor which consists of pulse cores with 20% enriched metallic uranium and a subcritical thermal laser module with 20% enriched metallic uranium was performed by Monte Carlo calculation. The result of criticality analysis showed the following three points. First, a coupled reactor with 20% enriched metallic uranium can achieve criticality. Second, using eight pulse cores in axial direction is effective to achieve flattened axial power distribution in the laser module. Third, less than 20% of the energy released from fissions in the whole coupled reactor has the possibility to be converted to optical energy for a coupled reactor with 100% enriched uranium, and less than 7% for a coupled reactor with 20% enriched uranium.

The isotope Am242m is an interesting nuclide as it shows one of the known highest neutron fission cross section. This could be useful in some special applications, like the nuclear reactor for space propulsion proposed by C. Rubbia. A detailed measurement of the energy transfer from the fission fragments to the gas as a function of the path and the gas type is an important item for the evaluation of the engine performances. This was carried out by means of an ionisation chamber. However the Am242m availability, in particular at high isotopic abundance, is still at present a serious drawback. A production model, experimentally tested in thermal nuclear reactors, has been used to evaluate the achievable isotopic abundances. The results are quite below 70% and advise the use of separation techniques for further enrichment. The use of Am242m for other applications like nuclear pumped laser is suggested.

The model of a nuclear — optically — pumped liquid laser is constructed and the laser characteristics are analysed for different parameters of the setup and pump pulse, compositions of the converter media and active elements. The lasing parameters of the liquid laser using heavy-water solution of 245Cm as the converter medium and neodymium-containing phosphorous oxychloride (phosphoryl chloride) as the active element are calculated. It follows from the results of calculations that lasing can be achieved in these media pumped by neutrons from the BARS-6 reactor.

The distribution of the two-dimensional gas velocity inside ion-irradiated laser cells is considered for low ion energy deposits into the gas. It is shown that, if the energy deposit is smoothly nonuniform, the twodimensional motion has two quasi-one-dimensional components: the longitudinal gas velocity is practically uniform across the cell and depends on the transversely averaged energy deposit, while the transverse velocity component depends on the difference between the local energy deposit and energy deposit averaged over the transverse direction.

In Chap. 2 we examined rather simple NPL designs for searching for and studying characteristics of laser active media, but there are also more complex nuclear laser devices. As a rule, they are structural elements of multichannel reactor lasers operating in stationary or pulsed modes, and are intended to study the specifics of their operation. This chapter examines some of these devices, whether in operation or still being designed.

This book primarily discusses NPL research in Russia. The Russian program has been larger and remains active whereas work in the United States and elsewhere has dwindled. Shortly after the end of the Cold War, two circumstances combined to cause stoppage of NPL work. While the military need ceased, public opposition to nuclear power mounted following the Three Mile Island Nuclear reactor accident in the United States. Such concerns clearly carried over to a reactor pumped laser, i.e. to NPLs. Here we briefly review earlier work is the United States, prior to a build-up of effort as part of the “Star Wars” program as cold war tension grew.

A kinetic model of the active medium is developed for a nuclear-pumped laser (with an He — Cd — CCl4 mixture) based on transitions in the cadmium ion and atom. The results of numerical modelling give the distribution of the relaxation flux between excited states of the cadmium atom. A study is reported of the mechanisms responsible for the influence of the addition of carbon tetrachloride on the evolution of relaxation processes in an He — Cd plasma and on stimulated emission of the λ = 325.0 nm line. It is shown that the main factor hindering lasing as a result of the 4d9 5s2 2D3/2 → 4d10 5p 2P1/2 transition is the parasitic absorption of the stimulated radiation by metastable cadmium atoms.

The main goals of this review article are to show, on the basis of the results accumulated in this field, achievements in simulating the processes in nuclear pumped laser (NPL) active media by experiments on e-beam pumping, and to give a number of characteristic experimental examples, when this simulation has improved understanding of the inversion population processes in NPL active media (Cd+, Xe-lasers) or generated interest in experiments with fission fragments excitation (Ne-laser). In the case of the population of laser operation levels in non-equilibrium recombinating plasma, one can say with sufficient accuracy that the inversion population mechanism is identical for both excitation types.

The present status of standard neutron fields in the YAYOI reactor are reviewed. The research topics using the standard neutron fields are also introduced on the development of advanced nuclear measurement technique in application of the latest technology on lasers, optical fibers and digital signal processing.

A nuclear pumped laser is attractive as a self-powered and visible radiation sensor which is capable of processing information with coherent light signals. The development of highly efficient and low-threshold nuclear pumped lasers was advanced in an 3He/Ne/Ar gas mixture. This paper presents the analytic results of the lasing mechanisms of the 3He/Ne/Ar nuclear pumped laser through numerical simulations and reactor experiments.

The computational results for the main parameters of the energy model of the laser system pumped from a pulsed reactor show that a quite high energy of the laser beam can be achieved. An experimental demonstration of this possibility is now one of the most important stages for further development of investigations in the region of direct conversion of fission energy into laser radiation. This problem can be solved when the stand with a power model of the reactor-laser system, developed at the Main Science Center of the Russian Federation — Physics and Power Engineering Institute, is put into operation at the end of 1996. We thank A. P. Barzilov and O. F. Kukharchuk for assisting in the calculations and in organizing the present paper.

A simplified method for analysis of changes in the stability of nuclear-pumped laser resonators is proposed. This method ensures a reasonable qualitative agreement between changes in the output power and a function representing the stability.

Possibility to perform experiments for nuclear pumped laser oscillation by using low enriched uranium is investigated. Kinetic analyses are performed for two types of reactor design, one is using highly enriched uranium and the other is using low enriched uranium. The reactor design is based on the experiment reactor in IPPE. The results show the oscillation of nuclear pumped laser in the case of low enriched uranium reactor is also possible. The use of low enriched uranium in the experiment will make experiment easier.

An overview of nuclear-pumped laser programs conducted on various pulsed reactor types has been presented. The independent research undertaken in Russia and the United States have confirmed the concept of energy conversion from nuclear exothermal reactions to coherent optical radiation as feasible.

A practical, visible nuclear-pumped laser (NPL) has been sought at the University of Illinois and other laboratories for a number of years. Yet, the results from successful visible NPLs to date have not been fully satisfactory, e.g., the threshold pumping power is too high for conventional applications. Progress in recent studies of 3He-Ne-H2 as a candidate NPL operating in the visible region at 585.3 nm on the 2P1,-1S2 Ne transition is described. We obtained lasing on the above transition for 3He-Ne-H2 concentrations of 1,140, 588, and 412 torr, respectively, with the laser cavity placed in the beamport of the University of Illinois TRIGA reactor. The threshold thermal neutron flux is 1014 n/cm2-s, corresponding to a threshold pumping power of 5 W/cm3.

In an earlier preliminary design study, we proposed a novel nuclear-pumped laser-driven (NPL) inertial confinement fusion (ICF) power reactor that represents an important variation on the “neutron feedback” concept for ICF. This NPL-driven ICF concept also included an advanced, DT-seeded, D3He-fueled pellet and magnetic protection of the first wall of the reactor chamber. Advantages that were demonstrated for this approach included increased efficiency for laser-to-target energy coupling, increased efficiency for thermalto-electric energy conversion, and reduced neutron activation and waste. The coupling efficiency is enhanced because a nuclear-pumped flashlamp is directly pumped by fission fragments from uranium micropellets within the lamp medium. The thermal conversion efficiency is greater because a large fraction of the ICF pellet&s fusion yield is in charged Finally, the fraction of the fusion yield carried by neutrons is significantly reduced in comparison with pure D-T-fueled pellets; thus, neutron-induced activity in the first wall is decreased and safety is increased. The initial study indicated these factors could result in a required driver energy of 5 MJ (vice 10 MJ currently projected) and a pellet gain of only 50 (vice 100 currently projected) for a feasible l,000-MWe power reactor operating with approximately six pellets per second. The current study includes a refined analysis of an NPL-driven ICF power reactor of this type. A cylindrical design for the fission/NPL blanket is selected as a “natural” geometry for pumping the NPL. Required enrichments and criticalities are then predicted for the multiplication of the fusion neutron yield needed to pump the NPL. Based upon these results, we report a more detailed parametric study of the efficiencies for converting neutron, X-ray, and plasma yields from advanced ICF pellets into electrical and optical energy flows required in this concept. We also examined breeding tritium in a lithium blanket layer. Results from these studies help define topics and parameter spaces for further research on this unique reactor concept.

A computer model has been developed and benchmarked for the nuclear-pumped atomic carbon laser. Experiments have been performed with the atomic carbon laser and with the radiolysis of CO2 as a benchmark for the model. The results of the CO2 radiolysis are described.

New neutron detection methods using the 3HeNe lasing are proposed. These methods are mainly based on two types of lasing: nuclear pumped laser (NPL) and radiation triggered laser (RTL). In the NPL mode, the charged particles produced by neutron reactions directly excite the laser gas, and then the lasing occurs. The direct NPL output power and the optical gain are available as signals to measure the thermal neutron flux. In the RTL mode, the neutron irradiation raises the discharge of the laser gas when a specific voltage is applied, and then the lasing occurs. This method is based on the variation of the lasing voltage by the neutron irradiation. Experimental results, obtained for both of these two methods, show the feasibility of a new neutron detection system, using the laser light signal, and which can be applied to in-core neutron monitoring in the fission reactor.

A new type of in-core neutron monitor using the 3HeNe nuclear pumped laser (NPL) is proposed and the optimum design and characteristics of this detector are discussed, especially for application to the fast breeder reactor (FBR). Through this optimum design study, a highest efficiency monitor has been found to show the simple and practical relation of PR = 3.54 [atom cm], where P and R are the 3He pressure and the diameter of a laser cell, respectively. The response function of this detector has been estimated, which shows the linearity to the neutron flux level above the threshold level for the NPL operation. The life of this detector is found to be rather long when considering the tritium β-decay to the 3He gas.

A two‐dimensional, time‐dependent model has been developed to determine the coupled fluid dynamic and charged particle transport behavior of a flowing gas, nuclear pumped laser cavity. Stationary results are presented for a typical cavity that uses a flowing He buffer gas pumped with charged particles produced by the 10B(n,α)7Li reaction. The boron is coated on fuel plates mounted parallel to the flow direction. The effects of changing the buffer gas inlet flow velocity and outlet pressure are investigated. For a fixed inlet velocity, the results presented show that the gradients of the charged particle energy deposition and density increase in magnitude primarily in the direction perpendicular to the gas flow, i.e., normal to the fuel plates, as the outlet pressure is increased. With increasing inlet velocity and a fixed outlet pressure, the density variations decrease, whereas the variations in energy deposition increase in the direction perpendicular to the flow and decrease in the direction parallel t...

The achievable beam quality resulting from heavy charged particle pumping of transverse flow, gas laser amplifiers is presented. The charged particles are generated by nuclear reactions in either B4C or UO2 coated on plates parallel to the lasant flow. The character of the laser medium aberration resulting from the nonuniform energy deposition and fluid dynamic effects is discussed as well as the effects on the far‐field beam quality of the amplifier. Pumping from plates parallel to the flow produces a medium aberration which is dominated by a cylindrical focus perpendicular to the flow, and a tilt in the flow direction. Beam qualities of better than 2 times diffraction limited (TDL) are obtained with a B4C fueled 1‐m‐long amplifier pumped at an average power deposition of 100 W/cm3 with an inlet 0.1‐MPa helium flow at 100 m/s. Amplifiers using UO2 fuel coatings to pump argon under the same flow conditions with fission fragments have similar qualitative laser medium aberrations but with larger magnitude, ...

The opportunity of populating of Hg and N 2 levels due to ion-ion recombination is considered. Spectra of a luminescence of mixtures 3 He + N 2 + NF 3 (CCl 4 ) are investigated on nuclear reactor installation. It was supposed, that populating of N 2 (C 3 Π u ) in processes: N 2 + + F - (Cl - ) + M → N 2 (C 3 Π u ) + F (Cl) + M, will lead to increase of the intensity of the second positive system of nitrogen. However measurements have shown that molecular bands of nitrogen don't amplify at addition of electro-negative gases. Spectra of luminescence of mixtures He + Hg + O 2 (CO 2 ) are investigated on installation with excitation by α-particles of 210 Po. It was supposed, that in processes of recombination: Hg + + O - + M→ Hg* + O + M Hg + + O 2 - + M→ Hg ** + O 2 + M will be populated 7 3 S 1 and probably 6D levels of Hg. The observed increase in intensity of triplet lines of mercury at addition of CO 2 to a mixture 3 He + Hg, apparently, is connected with recombination of ions Hg + and O - .

Optimization studies of optical and power performances of nuclear pumped lasers are performed. It is shown that the laser mix pump rate speed-up from 7 to 30 m/s and laser channel width reduction from 2 to 1 cm allows increasing the average specific energy input by the factor of 1.6 and narrowing the refraction factor measuring interval for 4 times.

A numerical simulation is used to show that new experimental data on the rate constants of xenon atoms in metastable and resonant states lead to a revision of the existing views on the mechanism of excitation of the upper active levels of a laser operating on IR transitions in xenon.

Various energy sources, including both solar and nuclear systems, have been considered for laser power beaming. Nuclear systems (i.e. Nuclear Pumped Lasers) have unique advantages for space applications, since they can combine the power source and the laser in a single compact unit. Sale of electricity produced by combined plant offsets the high capital cost required for the laser system. For power beaming, a good beam quality is crucial. Here, the authors propose some novel improvements in the NPL beam quality. Desired characteristics for good beam quality are diffraction limited beams-minimum spot size, high extraction volume, and minimum gas lensing. A large extraction volume can be achieved by use of unstable resonators, while the spot size can be decreased by use of shorter wavelengths. Finally, gas lensing effects can be corrected by use of combined wall and volume pumping together with adaptive optics. The first step towards correcting for gas lensing is the study of dynamic conditions during reactor pumping. The theoretical modeling allows a time-dependent calculation of the density variations and the corresponding index-of-refraction variations. These results are then used to calculate, by means of ray tracing, the beam distortion due to gas lensing. Extension of the theoretical modelingmore » and the experiments from nuclear pumped cells to laser cavities (such as unstable resonators) is the second step in the study. Results from the work will be used to develop a combined pumping and adaptive optics method to improve beam quality.« less

During the last few years, important experimental investigations have been made concerning the possibility of induced nuclear fission of high-Z elements by electromagnetic interaction (photofission, electron fission, neutron fission). Fast ions, neutrons and fission fragments from such interactions can be used to pump a laser medium, to produce energy from the 232Th–233U nuclear fission cycle. The main aim of the present work is to study a three-step process, in a relatively new experimental scheme, in order to improve the number of both neutrons and fast ions. In the proposed scheme, high-energy particles and photons are produced by high-intensity laser beam interaction with a solid or gas target, which are utilized later on to trigger the nuclear reactions for the production of (photo) neutrons. These neutrons can give rise to fission of 232Th that leads through a cascade of decays to 233U —a highly fissionable material. Such a process will enhance, by an important factor, the final neutron flux and the energetic fission fragments. The use of a high intensity pulsed laser beam will control the turn-on and turn-off of the nuclear reactions and allow one to ensure the security of the whole operation. Finally, the produced neutrons are used to accomplish a major population inversion in an appropriate gas medium for the last stage of amplification of a high-contrast ultra-short laser seed pulse.

Experimental and theoretical investigations were made of an XeF laser pumped by a travelling ionising wave originating from a nuclear explosion. The results indicated that an efficiency, in terms of the input energy, could reach 1–3%.

It is proposed that multiple sub-critical cylindrical-geometry nuclear-pumped laser (NPL) arrays, with longitudinal cooing flow, driven by pulsed reactors at low duty cycle (100 ms pulses at 1 Hz). He did not discuss the effects of pump intensity and solid-state laser (SSL) pulse rate on SSL efficiency or pump intensity on SSL cooling, which is very important at higher duty cycle. A 200-MW CW module for up-conversion pumping Pr/sup +3/:LaCl/sub 3/ is discussed in a companion paper.

One of the principles at nuclear pumping of lasers is the excitation of active media by uranium fission fragments. So it means that these lasers doesn't contain such a traditional for nuclear energetics safety barrier as keeping of fission products inside the solid state fuel matrix, The absence of this barrier leads to accumulation of radioactive products in the active laser volume, so the activity of these products may be quite significant. The feature of nuclear pumped laser gas media is the absence of aerosols, so the fission products are existing there only in forms of single atoms and molecules. To develop the necessary methods of protection from radiation for works on researching of nuclear pumped laser and for development of design of powerful nuclear pumped laser for fusion energetics it was needed to understand physicochemical and radiation properties of laser gas media. So there were carried out series of experiments the results of which are given.

The concept for an inertial confinement fusion (ICF) system is presented, which is driven by laser output power amplifiers designed as pulse nuclear reactor-pumped lasers. A brief review is given of the current status of research in this field at the Institute of Physics and Power Engineering, Obninsk, Russia. The development of a pulsed nuclear reactor-pumped laser system, based on all ignition reactor module in the form of a two-core fast-burst reactor and a thermal subcritical laser module employing an Ar-Xe laser active medium, is reported.

Since the nuclear pumped laser technique can be applied to the optical detection of neutrons, numerical simulations and demonstration experiments have been carried out for He-Ne-Ar mixtures. Test cells filled with /sup 3/He gas (1140 torr), Ne gas (540 torr) and Ar gas (208 torr) were irradiated with a thermal neutron flux up to about 10/sup 12/ n/cm/sup 2//s at JRR-4 reactor, JAERI. In these experiments, an optical output of 585.3 nm from Ne 3p-3s transitions was clearly observed. Its intensity was almost proportional to the thermal neutron flux, and these results agree with those of the numerical simulation. This system can be applied to optical neutron detection. The simulation results show that the population inversion between 3p'[1/2]/sub 0/, and 3s'[1/2]/sub 0//sup 1/ levels of neon atom for the cell can be achieved at the thermal neutron flux of much higher than 10/sup 12/ n/cm/sup 2//s. It is also estimated that the threshold thermal neutron flux for the population inversion is about 3/spl times/10/sup 12/ n/cm/sup 2//s for the gas cell filled with optimized gas mixtures.

An investigation was made of a quasi-cw low-threshold laser utilizing an Ar–Xe mixture (λ = 2.03 and 2.65 μm) excited by uranium fission fragments. When an Ar:Xe = 400:1 mixture at a pressure of 0.25 atm was excited, the λ = 2.03 μm lasing threshold was reached at a thermal neutron flux density of 1.5 × 1012 (cm2 s) − 1, corresponding to a specific pump power of ~ 0.02 W/cm3. It was found that this laser could be pumped also by α particles from 210Po and 242Cm radionuclide sources.

A hybrid “nuclear light bulb” gaseous core reactor that can radiantly transfer energy to a propellant or alternately activate laser action is proposed for advanced space missions. The propellant mode would be employed in the phases of the mission requiring a higher thrust. However, for the bulk of the travel, the propellant would be turned off and the ultrahigh specific impulse laser mode of operation would be employed. The concept is reviewed, research and development issues are identified, and steps necessary for a feasibility demonstration are discussed.

Conception of a high-power pulsed laser system based on the optical quantum amplifier pumped by the IBR-type reactor for space applications is discussed. The development of an energy model of RPLS consisting of the ignition two-core fast-burst reactor module and a thermal subcritical laser module filled with a laser active medium is reported. The basic components of nuclear pumped laser system such as: laser active element, pulsed reactor, laser module of nuclear pumped quantum amplifier are described. Some of the calculation and experimental data are presented.

Experimental setup configuration and lasing experiments results on fission fragments pumping of gas lasers are presented. The IPPE’s fast burst reactor BARS-6 has been used as a neutron source for nuclear pumping of lasers. Experimental results on nuclear pumping of «master oscillator-amplifier» pulse laser system and energy parameters of 1.73 μm 5d-6p Xel transition of Ar-Xe laser and amplifier are presented. Neutron characteristics of system were compared with computed ones. It was shown that experimental and calculated results are in a good agreement.

A Nuclear Pumped Laser (NPL) using 3He/Ne/Ar gas mixture is investigated for a purpose of applying to an optical self‐powered neutron detector. Reactor experiments and simulations on lasing mechanism have been made to estimate the best gas pressure and mixture ratios on the threshold input power density (or thermal neutron flux) in 3He/Ne/Ar mixture. Calculational results show that the best mixture pressure is 3He/Ne/Ar=2280/60/100 Torr and thermal neutron flux threshold 5×1012 n/cm2 sec, while the reactor experiments made in the research reactor ‘‘YAYOI’’ of the University of Tokyo and ‘‘JRR‐4’’ of JAERI also demonstrate that excitational efficiency is maximized in a similar gas mixture predicted by the calculation.

In present report there are assumed the results of nuclear pumped laser (NPL) active media experimental studying with electron beam excitation and the analysis is made for emission characteristics and kinetic processes of more perspective lasers, which are operating at low pumping power close to NPL excitation conditions. Basic attention is paying to experimental data, obtained for e‐beam pumped low‐threshold active media, which have allowed to accelerate the understanding of the inversion population creation processes in NPL and which have predetermined new future experiments with NPL. It has been shown that in spit of same differences in plasma creation processes for e‐beam pumping and fission fragment excitation, operating level and inversion population creation processes in nonequilibrium recombinant plasma are similar for both types of excitation at compatible pumping power and pulse duration.

Possible physical reasons of overheating of Ar‐Xe direct nuclear pumped laser were investigated. The time‐dependent Ar‐Xe laser output was measured at temperatures 20, 150, 220 and 260 °C. It was shown that the true reason of temperature anomalies are the pollution of Ar‐Xe active media by water vapour which was desorbed from the walls of the laser cell at high temperature.