1.1 Chronology of Main Events. Initial Phases of Research

This section briefly examines the last 50 years of research in the field of transfor­mation of the kinetic energy of products of nuclear reactions into laser radiation, that is, nuclear-pumped lasers (NPL). NPLs include lasers in the optical spectral range, which are excited directly by nuclear radiation or by using intermediate devices, for example, nuclear-optical converters (nuclear-excited plasma, scintillators).

The discussion of the problem of direct conversion of nuclear energy into laser radiation began in the 1960s, immediately after creation of the first lasers. Interest in this problem was prompted by the possibility of using powerful, compact, high — energy sources of nuclear energy (nuclear reactors, nuclear explosions) for laser pumping, and accordingly, the fundamental possibility of creating powerful lasers. At present, the concept of the reactor-laser (RL) is the most common embodiment of this new technology. The core of the RL consists of fissionable material and the laser medium. There the direct conversion of the escaping nuclear energy into laser radiation occurs, bypassing the intermediate stage of thermal energy.

Early experimental and theoretical studies of NPLs were primarily carried out in the United States and Russia. Table 1.1 shows the basic phases of NPL develop­ment. In some cases, the dates of events are provided (if they are reliably known to the authors), but not the dates of articles about these events. Articles sometimes appeared considerably later, since roughly until the end of the 1980s, because research on NPLs in certain laboratories was carried out in accordance with classified programs. The sequence by which individual articles reached the open press may be traced from the list of references.

In Russia, research on problems of NPLs began in the late 1960s virtually simultaneously at three institutes—VNIIEF (Sarov), the Kurchatov IAE (Moscow), and the MGU Institute of Nuclear Physics (Moscow). The neutron sources were pulsed reactors of VNIIEF and IAE. Roughly from the start of the 1970s,

© Springer Science+Business Media New York 2015 S. P. Melnikov et al., Lasers with Nuclear Pumping, DOI 10.1007/978-3-319-08882-2_1

Date	Event	Scientific organization (authors)	References
1964	Calculated estimation of a nuclear-laser device using a mixture of He-Ne (k = 633 nm)	UAC (L. O. Herwig)	[1]
1965-1972	US experiments to find active NPL media (condensed media, mixtures of He-Ne, CO2-N2- He, Ne-O2, Ar, Ne, Xe, Kr, etc.)	ANL, NL, UI, UF, NASA, NARC, GA, МС et al. (J. A. De Shong, J. W. Eerkins, J. R. Rusk, G. H. Miley, J. C. Guyot, R. T. Schneider, E. Matovich, D. M. Compton, V. E. Derr, et al.)	[2-5]
1968-1971	Investigations at VNIIEF to find laser media for NPLs (condensed media, CO2-N2- He, CO) and assessment of different variants of nuclear laser devices	VNIIEF (A. M. Voinov, A. T. Kazakevich, V. N. Krivonosov, M. F. Kostenko, A. N. Sizov, V. M. Karyuk, L. M. Pavlovskaya, A. A. Sinyanskiy, et al.)	[6-8]
1970	Attempt to achieve lasing in a mixture of 3He-Hg (k = 615 nm)	MGU, IAE (V. M. Andriyakhin, V. D. Pismennyy, V. Ye. Khvostionov, et al.)	[9]
1970	Achievement of lasing at transitions of Ne and Xe atoms with pumping of atmospheric — pressure gas mixtures with an electron beam	IYaF SO AN (G. G. Dolgov- Savelyev, B. A. Knyazev, Yu. L. Kozminykh, V. V. Kuznetsov, A. M. Orishich)	[10]
1971	First experiments to pump lasers with y — radiation of a nuclear explosion (liquid xenon medium)	VNIIEF (O. V. Korniyenko, I. G. Zhidov, V. V. Varaksin, A. P. Morovov, Ye. K. Bonyushkin, et al.)	[un-published]
1972	Achievement of super­luminescence with excitation of a laser based on europium chelate with n, y-radiation of a pulsed reactor	VNIIEF (T. A. Babicheva, A. M. Voinov, L. Ye. Dovbysh, A. A. Sinyanskiy, L. M. Pavlovskaya, et al.)	[6, 7]
1972	First successful experiments to develop an NPL (mixture of He-Xe, k и 3 pm)	VNIIEF (A. A. Sinyanskiy, A. M. Voinov, A. T. Kazakevich, S. P. Melnikov, L. Ye. Dovbysh); GOI (I. V. Podmoshenskiy)	[6, 11]
1973	Experiments on pumping a mixture of SF6-C2H6 (LANL) and gaseous xenon (LLNL) with y-radiation of a nuclear explosion	LANL (P. B. Lyons, J. S. Clarke, D. S. M. Metzger); LLNL (P. J. Ebert, J. L. Ferderber, et al.)	[12—14]

Table 1.1 (continued) Date Event Scientific organization (authors) References 1974 Statement in open press on possibility of creating a reac­tor-laser FIAN (L. I. Gudzenko, S. I. Yakovlenko) [15] 1974-1976 Cycle of experimental investi­gations of NPLs at IR transi­tions of atoms Xe, Kr, and Ar (acquiring an efficiency of up to 2 %) VNIIEF (A. M. Voinov, A. A. Sinyanskiy, V. N. Krivonosov, S. P. Melnikov, et al.); GOI (I. V. Podmoshenskiy) [6, 11, 16] 1975 First successful experiments in the United States using pulsed reactors to develop NPLs: CO laser (X = 5.1-5.6 pm) and laser with mixture of He-Xe (X = 3.51 pm) Sandia (D. A. McArthur, P. B. Tollefsrud); LANL, UF (H. H. Helmick, J. L. Fuller, R. T. Schneider) [13, 17, 18] 1975 Proposal to use mixtures of rare gases with vapors of metals (Mg, Hg, Cd, etc.) as prospective NPL media VNIIEF (A. A. Sinyanskiy) [16] 1976-1977 Creation of NPLs at transi­tions of atoms N and C in near IR spectral range UI (G. H. Miley, M. A. Prelas, R. J. DeYoung, F. P. Boody, W. E. Wells, et al.) [19, 20] 1977 First NPL in visible range (mixture of He-Hg, X = 615 nm) Sandia (M. A. Akerman, D. A. McArthur); UI (G. H. Miley) [21] 1977-1984 Development and investiga­tions of powerful HF and XeF lasers, excited by y-radiation of a nuclear explosion VNIIEF (Ye. K. Bonyushkin, A. I. Pavlovskiy, A. P. Morovov, B. V. Lazhintsev, V. V. Varaksin, A. Ye. Lakhtinov, et al.) [22, 23] 1979 Achieving lasing in the mix­ture He-Cd (X = 534 and 538 nm) pumped by 3He(n, p)3H reaction products MIFI (A. I. Miskevich, B. S. Salamakha, V. A. Stepanov, et al.) [24] 1979 Start of computational and theoretical investigations of the appearance and evolution of optical non-uniformities in NPLs VNIIEF (A. N. Sizov) [25] 1981 Creation of NPLs pumped by fast neutrons (He-Xe mixture) VNIIEF (S. P. Melnikov, A. M. Voinov, A. A. Sinyanskiy, A. S. Koshelev) [6, 11] 1981 Achieving lasing in a solid — state neodymium NPL pumped by the radiation of a CsI scintillator VNIIEF (A. M. Voinov, L. Ye. Dovbysh, A. A. Sinyanskiy, et al.) [6]

Table 1.1 (continued) Date Event Scientific organization (authors) References 1982 Achieving lasing in a He-Cd mixture (k = 442, 534, and 538 nm) pumped by uranium fission fragments VNIITF (E. P. Magda, V. A. Kryzhanovskiy, L. V. Semkov, et al.); VNIIEF (A. A. Sinyanskiy, S. P. Melnikov) [26] 1982 First experimental investiga­tions of optical non-uniformities in gas NPLs VNIIEF (V. V. Borovkov, B. V. Lazhintsev, S. P. Melnikov, A. A. Sinyanskiy, V. A. Nor-Arevyan, et al.) [27] 1983 Achieving lasing in a He-Zn mixture (k = 748 nm) VNIIEF (A. M. Voinov, S. P. Melnikov, A. A. Sinyanskiy, et al.); MIFI (A. I. Miskevich, B. S. Salamakha, et al.) [6, 16, 28] 1985 Achieving lasing in the visible spectral range at transitions of the Ne atom (k = 585, 703 and 725 nm) VNIIEF (S. P. Melnikov, A. M. Voinov, A. A. Sinyanskiy, et al.); MIFI (A. I. Miskevich) [11, 16] 1985 Achieving a minimal lasing threshold of NPLs with a thermal-neutron flux density of around 2 x 1012 cm-2-s-1 (0.02 W/cm3) VNIIEF (A. M. Voinov, S. P. Melnikov, A. A. Sinyanskiy, A. I. Konak, V. G. Zobnin, I. N. Mochkayev [11, 16] 1985-1990 Development of kinetic models of NPLs with various active media IOFAN (S. I. Yakovlenko, A. V. Karelin, et al.); VNIIEF (S. P. Melnikov, A. A. Sinyanskiy, A. M. Voinov) [28, 29] 1986 Formulation of concept of a laser system with pumping from a pulsed reactor (nuclear pumped laser amplifier, OKUYaN) FEI (A. V. Zrodnikov, P. P. Dyachenko, A. V. Gulevich, et al.) [30] 1987-2007 Experimental and theoretical investigations of optical non-uniformities in gas-flowing NPLs VNIIEF (V. V. Borovkov, A. N. Korzenev, B. V. Lazhintsev, V. Yu. Matyev, A. N. Sizov, A. A. Sinyanskiy, et al.) [31—33] 1988-1993 Computational and theoretical investigations in the United States of optical non-uniformities in NPLs Sandia (J. R. Torczynski, D. R. Neal, et al.) [34, 35] 1989 Obtaining of an intrinsic effi­ciency of ~3 % for NPLs using mixtures of Ar-Xe and He-Ar- Xe (k = 1.73 and 2.03 pm) Sandia (WJ. Alford, G. N. Hays) [36]

Table 1.1 (continued) Date Event Scientific organization (authors) References 1989-1994 US development of kinetic models of NPLs operating on transitions of atoms Xe, Ar, and Ne UI (M. J. Kushner, M. Ohwa, J. W. Shon, T. J. Moratz, R. L. Rhoads) [37—39] 1991 Creation of a photodissocia­tion iodine laser (X = 1.315 pm), initiated by radiation of XeBr* molecules UI (W. H. Williams, G. H. Miley) [40] 1992 Creation of NPLs based on the transition of the Hg atom in a He-Xe-Hg-H2 mixture (X = 546 nm) VNIITF (A. V. Bochkov, E. P. Magda, V. A. Kryzhanovskiy, S. L. Mukhin, et al.) [41] 1991-1993 A series of experimental investigations of xenon NPLs in the United States Sandia (W. J. Alford, G. N. Hays, G. A. Hebner) [42—44] 1994 Activation of the LM-4/BIGR setup, obtaining of cw lasing in gas flowing mode VNIIEF (A. M. Voinov, A. A. Sinyanskiy, S. L. Turutin, B. V. Lazhintsev, V. V. Porkhayev, A. N. Sizov, A. N. Pokalo, et al.) [45] 1996 First NPL in UV spectral range (He-N2-H2 mixture, X = 391 nm) VNIITF (N. M. Barysheva, E. P. Magda, A. V. Bochkov, V. A. Kryzhanovskiy, et al.) [46] 1999 Start-up of demonstration model of OKUYaN reactor — laser system FEI (A. V. Zrodnikov, P. P. Dyachenko, A. V. Gulevich, et al.) [30] 1986-2007 Development of reactor IKAR—model of stationary reactor-laser VNIIEF (A. M. Voinov, A. N. Sizov, A. A. Sinyanskiy, V. N. Krivonosov, I. A. Nikitin, V. I. Turutov et al.) [47]

Note: Nomenclature of scientific organizations

UAC United Aircraft Corporation (United States), ANL Argonne National Laboratory (United States), NL Northrop Laboratories (United States), UI University of Illinois (United States), UF University of Florida (United States), NASA, NASA Langley Research Center (United States), NARC North American Rockwell Corporation (United States), GA General Atomic (United States), MC Martin Company (United States), VNIIEF All-Russian Scientific Research Institute of Experimental Physics (Sarov), MGU Moscow State University (Moscow), IAE Kurchatov Institute of Atomic Energy, IYaF SO AN Institute of Nuclear Physics, Siberian Department, Academy of Sciences (Novosibirsk), GOI Vavilov State Optical Institute (St Petersburg), LLNL Lawrence Livermore National Laboratory (United States); Sandia: Sandia National Laboratories (United States), LANL Los Alamos National Laboratory (United States), FIAN Lebedev Physics Institute, USSR Academy of Sciences (Moscow), MIFI Moscow Engineering and Physics Institute (Moscow), VNIITF All-Russian Scientific Research Institute of Technical Physics (Snezhinsk), IOFAN General Physics Institute, USSR Academy of Sciences (Moscow), FEI Physics and Power Engineering Institute (Obninsk)

investigations into the problems of NPLs began to be conducted at MIFI (Moscow), from the end of the 1970s at VNIITF (Snezhinsk), and from the start of the 1980s at FEI (Obninsk). Some experiments using a stationary reactor and calculations of the kinetics of certain types of NPLs were carried out at the Nuclear Physics Institute of the Academy of Sciences of Kazakhstan (Alma-Ata).

In parallel with the experiments, theoretical investigations of NPLs were carried out, in which FIAN (Moscow) and IOFAN (Moscow) participated, in addition to the institutes mentioned previously. Experimental investigations were carried out with the use of electron beams at FIAN (Moscow), the Institute of High Current Electronics of the Siberian Division of the Russian Academy of Sciences (ISE SO RAN) (Tomsk), the Scientific Research Center for Technological Lasers (Moscow), and the Institute of Electrophysics of the Ural Division of the Russian Academy of Sciences (Yekaterinburg).

Elsewhere, experimental and theoretical investigations of NPLs were mainly carried out in the United States (see Table 1.1). The first proposals regarding NPLs and the first experimental investigations began somewhat earlier than in Russia. The most substantial contribution to the development and creation of NPLs was made by investigations carried out at the Sandia National Laboratories, University of Illinois, NASA Langley Research Center, and University of Florida. In addition to the laboratories and universities indicated in Table 1.1, a number of NPL investigations were carried out in the United States at the University of Missouri — Columbia, the Idaho National Engineering Laboratory, Oak Ridge National Labo­ratory, North Carolina State University, and Vanderbilt University. Some individ­ual investigations of NPLs were carried out in France (Laboratoire de Physique des Gaz et des Plasmas), China (Institute of Nuclear Physics and Chemistry of CAEP), and Japan (University of Tokyo, Tokyo Institute of Technology).

To model the conditions that occur in gas media of NPLs, in joint experiments carried out in Germany (Technische Universitat Miinchen) and in the United States (Rutgers University), beams of heavy ions (4He+, 32S+, 132Xe+, etc.) were used. A number of interesting studies (basically of a high-pressure xenon laser) were also carried out using fast electron beams at the University of Twente (The Nether­lands), Stanford University (United States), Naval Research Laboratory (United States), and Science Research Laboratory (United States).

The majority of published data relate to the search for NPL media and the study of their characteristics. Basic efforts were directed toward obtaining maximal efficiency of conversion of deposited nuclear energy into laser radiation (ці) and low lasing thresholds (qth). The maximal values of ці and the lowest lasing thresholds were registered for a laser based on IR transmissions of the atom Xe: П = 2-3 % (VNIIEF, 1976 [6, 11, 16]; Sandia Laboratory, 1989 [36]), qth ~0.02 W/cm3 (VNIIEF, 1985 [6, 11, 16]).

Several key issues were uncovered and addressed in the problem of searching for and studying active NPL media. These included specific features of gas medium pumping with heavy charged particles and the problem of severe optical non-uniformities. Computational and theoretical investigations [25, 48—50], and then later also experimental investigations of this type were begun at VNIIEF in

1970. Later on there were reports about the conduct of analogous investigations in the United States [34, 35].

Apart from the work related to the search for NPLs and study of their various characteristics, one should also note other issues studied relating to development of powerful NPLs:

• Investigations into the properties of nuclear-excited plasma (track structure of plasma, kinetics of plasma processes, luminescence characteristics).

• Selection of radiation-resistant optical and structural materials for NPLs.

• Development and creation of various nuclear-laser devices.

• Development of the fabrication method of thin-film uranium fuel (radiator of fission fragments and fuel for the reactor-laser (RL).

• Selection of the optimal design for a RL and creation of its experimental model.

• Evaluation of possible applications of nuclear-laser devices of various types. Many of the studies done in these areas are also considered in this book.

In the history of development of NPLs, some special scientific conferences have been organized to discuss the results of research into their characteristics, prospects for development, and possible applications. The most significant of these were:

1. Second Symposium on Uranium Plasmas: Research and Applications, Atlanta (USA), 15-17 November 1971.

2. First International Symposium on Nuclear Induced Plasmas and Nuclear Pumped Lasers, Orsay (France), 23-25 May 1978.

3. The specialist conference Physics of Nuclear-Excited Plasma and Problems of Nuclear-Pumped Lasers, Obninsk (Russia), 26-29 May 1992.

4. The second international conference Physics of Nuclear-Excited Plasma and Problems of Nuclear-Pumped Lasers, Arzamas-16 (Russia), 26­30 September 1994.

5. The third international conference Problems of Nuclear-Pumped Lasers and Pulsed Reactors, Snezhinsk (Russia), 16-20 September 2002.

6. The fourth international conference Problems of Nuclear-Pumped Lasers and Pulsed Reactors, Obninsk (Russia), 18-21 September 2007.

The widest international representation was involved in the last four confer­ences, in which scientists from Russia, the United States, Germany, France, China, and Japan participated.

Despite the large volume of research carried out with regard to NPL problems, the number of survey papers is comparatively small, namely: K. Thom, R. T. Schneider [2] (1972); V. Ya. Pupko [51] (1981); N. W. Jalufka [3] (1983); R. T. Schneider, F. Hohl [52] (1984); D. A. McArthur [13] (1991); A. I. Miskevich [53] (1991); G. H. Miley [40] (1992); E. G. Batyrbekov [54] (1994); A. A. Sinyanskiy [6] (1995); A. V. Karelin, A. A. Sinyanskiy, S. I. Yakovlenko [28] (1997); A. A. Sinyanskiy, S. P. Melnikov, [11] (1998); E. P. Magda [55] (1998). Most of the surveys were published some time ago; many of them contain infor­mation only about research by individual laboratories. The most complete survey

Table 1.2 Experimental research to find gas media for NPLs performed before 1972 Scientific organization, reference Pumping method Laser medium Results University of Illinois [2, 3] (G. H. Miley, J. C. Guyot, et al. 1967) TRIGA reactor, a particles (layer 10B) He-Ne (<0.13 atm) In the opinion of the authors, amplification was observed at к = 3.39 pm Northrop Laboratories [2, 3, 57] (J. R. Rusk, J. W. Eerkins, J. A. DeJuren, et al. 1968) TRIGA reactor, a particles and uranium fission fragments (layer 235U and 10B) 1. Ne-O2 (~0.1 atm) 2. CO2-N2- He 3. Ne, Ar, Kr, Xe (<0.4 atm) An increased level of luminescence was observed in rare gases, which the authors attribute to stimulated radiation MGU and IAE [2, 3, 58] (V. M. Andriyakhin, V. D. Pismennyy, et al. 1968) Proton beam with energy of 3 MeV CO2-N2-3He (0.013 atm) A threefold increase in lasing power was observed upon irradiation with a proton beam of a gas-discharge CO2 laser MGU and IAE [2, 9] (V. M. Andriyakhin, V. D. Pismennyy, et al. 1970) IIN pulsed reactor, nuclear reaction prod­ucts 3He(n, p)3H 3He-Hg (~0.5 atm); cell temper­ature 150 °С Observed radiation power at к = 615 nm substan­tially exceeds the level of spontaneous radiation, in the opinion of the authors University of Florida, NASA Langley Research Center [2, 3, 59] (F. Allario, H. S. Rhoads, R. T. Schneider, 1971) Stationary reactor, nuclear reaction prod­ucts 3He(n, p)3H CO2-N2-3He (0.008 atm) A twofold increase in las­ing power and efficiency was observed with irradi­ation of a gas-discharge CO2 laser University of Illinois [60] (T. Ganley, J. T. Verdeyen, G. H. Miley, 1971) TRIGA reactor, a particles (layer 10B) CO2-N2-He (<1 atm) An increase in lasing power was observed with irradiation of gas-discharge CO2 lasers at both low and high pressures VNIIEF (A. A. Sinyanskiy, A. T. Kazakevich et al. 1971) VIR-2 reactor, fission fragments (layer 235U) Ar, Xe (<0.5 atm) CO2-(N2)- He (<1 atm) No lasing

[28] is dedicated to the energy and threshold characteristics only gas NPLs excited with the use of pulsed reactors, and to certain problems of the RL.

To create effective NPLs, it is necessary to use high pressures of the gas medium, close to atmospheric, because it is at such pressures that effective absorp­tion of the kinetic energy of nuclear particles (uranium fission fragments, a parti­cles) becomes possible at the path length of several centimeters, which is comparable with the characteristic transverse dimensions of laser cells. This is why, in the initial stages of research into NPLs, when atmospheric pressure gas lasers were still unknown, primary attention was given to liquid — and solid-state laser media. Studies dealt primarily with the condensed media known at the time: ruby and neodymium lasers, liquid lasers based on organic solvents activated with europium, and inorganic aprotonic solvents activated with neodymium. Attempts to achieve lasing during pumping of condensed media with nuclear radiation did not yield positive results, although in VNIIEF’s experiments with the pulsed TIBR reactor, superluminescence was registered (X ~610 nm) with the use of a solution of Eu(BTFA)4 HDPhH in acetone [6,7]. The principal reason for the absence of lasing with the use of condensed media was their radiation damage: radiation defects of the crystal lattice in solid-state lasers, radiolysis and the formation of gas bubbles on the tracks of nuclear particles in liquid lasers. The problems of such NPLs are examined in detail in Chap. 11.

Interest in the study of gas NPLs grew in the late 1960s, when powerful gas-discharge CO2 lasers (X = 10.6 ^m) were developed with a gas pressure of around 1 atm (for example, see monograph [56]) and lasing was obtained in the IR spectral range with excitation of atmospheric-pressure rare-gas mixtures with an electron beam [10]. The results of experiments performed before 1972, in which attempts were made to pump gas media with nuclear radiation, are shown in Table 1.2. As is noted in the review paper [2], none of these experiments unequiv­ocally demonstrated the presence of lasing, although indirect evidence was cited. Table 1.2 also includes experiments on the study of the influence of nuclear radiation on the parameters of gas-discharge CO2 lasers, which can be viewed as a preliminary phase on the path to finding gas NPLs.

The initial unsuccessful attempts at direct pumping of gas media with nuclear radiation did not stop studies to find gas media for NPLs, and soon after, in 1972 [6, 11] (Russia, VNIIEF, He-Xe mixture) and in 1974 [12, 13] (United States, LANL, SF6-C2H6) lasing was achieved when gas media were pumped with uranium fission fragments and with y-radiation from a nuclear explosion, respectively.