Nuclear-pumped Lasers Research Articles

Kinetics of the active medium of a nuclear-pumped laser based on transitions in the cadmium atom

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.

Excitation mechanism of IR transitions in the xenon atom in a nuclear-pumped laser

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.

Simulation of NPL in experiments with e-beam pumping

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.

98/02140 Evaluations of radiation properties of gas media used in nuclear-pumped lasers

98/02140 Evaluations of radiation properties of gas media used in nuclear-pumped lasers

Kinetics of the active media of nuclear-pumped lasers based on transitions in carbon and nitrogen atoms

The first detailed time-dependent kinetic model of a nuclear-pumped laser is developed for transitions in carbon and nitrogen atoms present in Ne—Ar— N2—CO— H2— O2 mixtures. Numerical simulation is used to show that the main mechanism of pumping the upper active levels of carbon and nitrogen atoms in Ne—CO— N2 mixtures is three-body recombination of atomic carbon and nitrogen ions. Dissociative recombination of an ArC+ ion becomes the main pumping channel when argon is added to a mixture. The optimal conditions and the ultimate laser output characteristics are identified. The calculated results are in satisfactory agreement with experimental data.

Kinetics of the active medium of a nuclear-pumped laser based on IR transitions in the chlorine atom

A detailed transient kinetic model is proposed for the active medium and the results are given of numerical calculations of the output parameters of a nuclear-pumped laser emitting as a result of IR transitions in chlorine atoms in a high-pressure He—Ne—CCl4 mixture. A comparison of the calculated and experimental results is used to identify the mechanism of population inversion of the active transitions resulting in the emission at the wavelengths of 1.59 and 2.45 μm. The optimal lasing conditions are determined.

Analysis of a nuclear pumped lasing mechanism for application to nuclear radiation measurements

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.

Experiments for optical neutron detection using nuclear pumped laser

Since the nuclear pumped laser technique can be applied to optical detection of neutrons, numerical simulation 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 thermal neutron fluxes up to about 10/sup 12/ n/cm/sup 2//s at the JRR-4 reactor, JAERI. In these experiments, 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 numerical simulation. This system can be applied to optical neutron detection. The simulation results show that the population inversion between the 3p'[1/2]/sub 0/ and 3s'[1/2]/sub 0//sup 1/ levels of neon atoms 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.

Computer analysis of the stability of nuclear-pumped laser resonators

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.

Efficiency of energy deposition in lasers pumped by uranium fission fragments

An investigation was made of the efficiency of energy deposition by fission fragments in nuclear-pumped lasers. A comparison was made with results obtained by other authors. Possible reasons for the discrepancy between the experiment and theory were analysed.

Characteristics of nuclear-pumped lasers based on the 3p—3s transitions in the neon atom

An atmospheric-pressure neon laser pumped by uranium fission fragments was investigated. In the case of ternary He—Ne—Ar(Kr, Xe) mixtures the maximum radiation power (35 W) of the 585.3 nm line was obtained for the He : Ne : Ar = 250 : 5 : 2 mixture at 2 bar. The lasing parameters of binary Ne—Ar(Kr, Xe) mixtures were optimised separately for the 703.2 and 724.5 nm lines by varying the concentration of Ar (or Kr or Xe). In the red part of the spectrum the maximum power (40 W) was obtained for the 724.5 nm line in a mixture of the composition He : Ne : Kr = 90 : 300 : 1 at 1.3 bar. Lasing was not observed in He—Ne—H2 or Ne—H2 mixtures. A study was made of the influence of the H2 admixtures on the characteristics of He—Ne—Ar(Kr) lasers.

Kinetics of laser active media for NeI 3p-3s transitions pumped by a weak source of external ionization

The possibility of creating direct nuclear-pumped lasers on Ne 3p-3s transitions has been investigated. Spectroscopic investigations of radiation from a nuclear-induced He-Ne plasma and calculations of the kinetics of various physical-chemical processes have been carried out.

Application of accelerator in research of condensed lasants for nuclear pumped lasers

A technique for measuring a conversion efficiency η, a lifetime of working level τ and the position and width of spectral lines of activator ions during excitation of media by nuclear reaction products is presented. The 14-MeV neutrons from the reaction 3H(d, n) 4He have been used for the homogeneous excitation of condensed lasants. The charged particles produced by the interaction of the fast neutrons react with the atomic nuclei of the medium. This technique has been tested on the laser crystal Y 3Al 5O 12:Nd 3+ and has been used for the investigation of laser-active inorganic liquids.

Kinetics of the active media of nuclear-pumped lasers

Numerical simulation of active media nuclear-pumped lasers on noble gases and their mixtures with metal vapors are presented. Prospects of creation of high-power short-wavelength nuclear-pumped excimer lasers are discussed.

Nuclear-pumped gas lasers at temperatures up to 800˚C

This article describes the design of a laser setup excited by 3He(n, p)3H reaction products and intended for investigations of the laser characteristics of 3He mixtures with metal vapors or other gases at temperatures up to 800˚C. This setup could also be used to study the effect of the medium heating on the characteristics of nuclear-pumped gas lasers.

Pulsed nuclear reactors in nuclear-pumped laser research

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.

Experimental and theoretical works performed by the Institute of Physics and Power Engineering on the physics of nuclear-induced plasmas

In review, general results obtained by Institute of Physics and Power Engineering (IPPE) during 1981–1992 are presented in the field of physics of nuclear-induced plasmas in the following directions: processes of primary ionization of different media by nuclear reaction products; function of electron distribution in nuclear-induced plasmas; processes of excitation and relaxation; track structure of nuclear-induced plasmas. Prospects of study progress are discussed with a view to improve the current concepts of physics of elementary processes occurring in nuclear-induced plasmas and obtain experimental and theoretical data on process constants needed to calculate the nuclear-pumped lasers.

Overview of nuclear-pumped lasers

The first demonstration of a nuclear-pumped laser (NPL) dates back to the mid-1970s while theoretical studies started earlier. This history will be briefly reviewed, followed by a discussion of the present status of various NPL concepts. Both physics and engineering issues are noted. Most attention has been given to gaseous media due to problems associated with radiation damage in liquid- and solid-state media. Various pumping methods, ranging from direct pumping of the laser medium to the use of nuclear-pumped flashlamps, will be discussed. Recent experimental results on pumping of O2(1Δ), the first demonstration of a nuclear-pumped flashlamp-driven laser XeBr*-I, and the new 3He-Ne-H2 NPL will be presented. Potential applications and corresponding NPL requirements, e.g., the long delay time requirements for an inertial fusion driver based upon NPLs, will be reviewed.

Practical, visible wavelength nuclear-pumped laser

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.

Heavy-ion beam pumping as a model for nuclear-pumped lasers

Heavy-ion accelerators can provide various beams from protons to uranium ions with energies ranging from a few keV/u to more than 1 GeV/u. The Munich Tandem van de Graaff accelerator has been used for most of the experiments described in this article. It can provide continuous or pulsed beams of almost all elements with particle energies of about 3.5 MeV/u. The pulse width is typically 2 ns. Maximum DC-beam currents of the order of 10 μA can be obtained, for example, for 32S ions. When the beam is focused to a beam spot of about 3 mm diameter, the flux of the ions is comparable to the flux of fission fragments used for nuclear-pumped lasers. Ion beam pumping is therefore well suited for model experiments of nuclear-pumped lasers. Technical aspects of ion beam-pumped lasers are discussed and the results of the lasers that have thus far been pumped by this method aresummarized. As ion beams are available either continuous or at high-pulse repetition rates ranging from tens of kHz to MHz, detailed spectroscopic and time-resolved studies of the emission of light induced by heavy-ion excitation of the target material can easily be performed. Experiments in which the emission by rare gas excimers and line radiation from atoms and ions has been studied are described. Lifetime measurements of excited levels at different target densities were used to measure collisional rate constants.