LA-7328-PR Progress Report a . Laser Fusion Program July 1—December 31, 1977 ,- .. .. .. ..-— — DO NOT CIRCULATE PERMANENT RETENTION ! REQUIREDBY CONTRACT v LOS ALAMOS SCIENTIFIC LABORATORY Lail!lik — post Office Box 1663 Los Alamos, New Mexico 87545 An AffumativeAction/EqualOpportunityEmployex . The four most recent reports in this series,un- classified, are LA-65 10-PR, LAY6 16-PR, LA4834-PR, and LA-6982-PR. This work was supported by the US Department of Energy, Office of Laser Fusion. TM. report was prep.rcd as m .CLWUII1O( work sponsored by the United SUICS Go”enlme”l. Neither the Un,ted Stiles I nor the United Slates Department cd Enersy. nor any of their employees. nor any 0( their CO.114C10rS. subcontrar tom. or their ●w.loyecs. makes any warranty. .xD,,!s O, irnPlled. ., P .isume. any Iesal Ii. biiity or responsibkbw for the accuracy. cmnpletcncm. y usefulness of any information. app.; .t.s. product. or Pro..= dl=losed. or rrpreacnm that its w would “.1 i“fri”le privately owned rlthls. UNITED STATES DEPARTMENT OF CNCRGV CONTRACT W-7408 -CNO. S6 LA-7328-PR Progress Report UC-21 IssI,W: December 1978 . Laser Fusion Program at LASL July 1—December 31, 1977 Compiled by Frederick Skoberne 4 .! L-. — .— - . ABSTRACT . ...”” 1 SUMMARY . ...0000oo 2 Introduction . 2 CO, Laser Program . 2 Antares . 2 CO, Laser Technology . 3 Laser Fusion Theory, Experiments, and Target Design . 3 Laser Fusion Target Fabrication . 4 1, CO, LASER PROGRAM . 6 Single-Beam System . 6 llvo-Beam System . 6 Eight-Beam System . 8 II. ANTARES-HIGH-ENERGY GAS IJM3ERFAClLITY . 16 Introduction . 16 Prototype Power Amplifier . 16 Antares System . 19 III. CO, LASER TECHNOLOGY . 34 Gas Isolator Development . 34 CO, Laser Physics . 47 Oscillator Development . 60 Optical Damage Studies . 64 References . 66 Iv. LASER FUSION EXPERIMENT, TARGET DESIGN, THEORY, AND MILITARY APPLICATION . 68 Target Experiments . 68 Target Design . 105 Double-Shell Target Designs forLASL EBB . 109 Theoretical Support and Direction . 114 Military Applications,Experiments,and Studies . 120 References . 123 h I v. LASER FUSION TARGET FABRICATION . ● Introduction . Target Assembly Alignment and PostShot Analysis . 126 Microballoon Separation, Measurement, Characterization, and Fabrication . iv Development of New Target Material . ...132 Coating Technique Development . ...135 Mandrels for Freestanding Metal Microballoon Fabrication . 142 Cryogenic Targets . 142 References . 147 . VI. TARGET DIAGNOSTICS . 149 Introduction . 149 Developments . 149 References . 161 VU. APPLICATIONS OF LASER FUSION—FEAWEHLITY AND SYSTEMS STUDIES . 163 Hydrodynamic Waves in a Liquid Lithium Blanket . 163 Propagation of Laser Light in a Commercial Reactor Chamber . 168 Economic Modeling FORTRAN Program INDEXER . 169 Electrothermochemical Hydrogen Production by Water-Splitting Using Laser Fusion Reactors as the Source of High-Temperature Process Heat . 171 References . 175 VIII. RESOURCES, FACILITIES, AND OPERATIONAL SAFETY . 176 Manpower Distribution . 176 Operational Safety . 176 Facilities . 176 Ix. PATENTS, PRESENTATIONS, AND PUBLICATIONS . 177 Patent Issued . 177 Application Filed . 177 Presentations . 177 Publications . 181 v LASER FUSION PROGRAM AT LASL JULY l—DECEMBER 31, 1977 Compiled by Frederick Skoberne ABSTRACT Progress in the development of high-energy short-pulse CO, laser systems for fusion research is reported. Among the achievements discussed are an increase in on-target energy of the Two-Beam System to 375 J per beam; operation of one Eight-Beam System module at the design point of 1.2 kJ at a power of > 2 TW; and the on-schedule development of our 100- to 200-TW laser Antares. Technology and research efforts are summarized, which led to the incorporation of an effective broadband isolater in both the Two- Beam System and the Eight-Beam System. Target designs based on the LASNEX code incorporating new theoretical insights are described, culminating in a double-shell exploding-pusher target that attains a high degree of symmetry through hot-electron tran- sport in an exploding outer shell. Significant improvements in the fabrica- tion and inspection of targets are reported, as well as advances in the development of promising new materials such as low-density, small-cell plastic foams and ammonia borane, which was formed successfully into microballoons for the first time. Studies of laser light absorption are outlined, which confmmed that the values for COZ are nearly identical to those obtained with Nd:glass lasers, and that ion loss is not a severe concern for laser fusion application as had been feared earlier. Unique diagnostics are described, which allow us to measure properties of x-ray emission not previously accessible, and which provide absorption data of sufficient accuracy for direct comparison with theory. Finally, various feasibility and systems studies are summarized, such as the succes- sful modeling of short-pulse amplification in large three-pass COZ laser amplifiers, as verified experimentally. SUMMARY (R. B. Perkins and Laser Fusion Staff’) . INTRODUCTION development of a suitable mixture, which permitted us to operate the EBS at the design point of 1.2 kJ, . The Laser Fusion Program at the Los Alamos at a power >2 TW on one module. The front end is Scientific Laboratory (LASL) is pursuing the dual essentially complete. The target chamber and optics goal of investigating military and commercial ap- are installed and the cryogenic vacuum system is plications of inertial confinement fusion. For both operational. All four dual-beam modules are assem- goals it is essential to achieve scientific breakeven, bled and have been operating simultaneously that is, a fusion output that equals the laser energy through the computer operations program. The incident on the target. For this purpose, we have in- target insertion mechanism and vacuum interlock vented, and are developing, high-power short-pulse are installed. carbon-dioxide gas lasers, which offer the advantage Progress toward completion of the 100-kJ Antares of exhibiting adequate efficiency combined with a laser continued, with the objective of extending pre- repetition-rate capability that holds promise for sent CO* laser capabilities to power levels at which their eventual use in commercial power plants. In fusion experiments can be expected to yield ther- support of pellet burning experiments, which we ex- monuclear energy release in the range of scientific pect will successfully culminate in breakeven, we breakeven. are expending significant effort in target design, target fabrication, laser facility support, and diagnostics development. A modest experimental ef- ANTARES fort directed toward military applications is under way to identify the feasibility of various types of The Antares system comprises a six-beam, 100-to relevant experiments. Finally, a systems group is 200-TW CO, laser (100 kJ in 1 ns or 50 kJ in 0.25 ns) exploring design concepts for future commercial fu- and associated target-irradiation facilities. Ex- sion reactor systems and subsystems to identify cellent progress was made in system design and in potential problems at an early date. construction of the various large buildings to house the system. Most noteworthy were the successful conclusion of the prototype power-amplifier (PA) CO, LASER PROGRAM program; the start of all construction; the comple- tion of the Antares PA optical and elec- During the current reporting period we have made tromechanical design layouts to the point where substantial progress in many areas. In the C02 laser detailed design was begun; and the release of program, we have continued the use of the Single- specifications for the target vacuum system to the Beam System (SBS) and Two-Beam System (TBS) Department of Energy (DOE) in the form of a Re- for target experiments. The upgrading of the TBS quest for Proposals (REP). continued with incorporation of an improved All objectives of the prototype PA programs have saturable gas isolator cell between the laser final been attained. Evaluation of the electromechanical amplifier and the target chamber, permitting the characteristics of the chambers and of the cylin- L on-target energy to be raised to 375 J per beam. The drical electron gun; characterization of the gas dis- SBS was shut down at the end of November 1977, charges, with specific identification of magnetic ef- and the personnel was transferred within the divi- fects; and laser gain measurements demonstrated . sion to support more urgent tasks. the correctness of the designs. Operational tests of Effort continued at a vigorous level on the Eight- the improved electron-beam foil-support structure Beam System (EBS) to meet facility completion in were completely successful. Parasitic-gain standoff April 1978. Highlights of achievement include the in excess of Antares requirements was achieved. evaluation of gaseous saturable absorbers and the 2 The Antares PA design incorporated all ● Double-shell exploding-pusher targets have operational and design experience gained in the been designed to attain a high degree of sym- prototype programs. In addition, an optical-path metry through hot-electron transport in an ex- < layout was developed that included optical design ploding outer shell. Energy delivered to an inner concepts that substantially reduced the sensitivity shell by hot and cold electron transport and by . to misalignment, vibration, and mechanical defor- hydrodynamic motions then drives an ablative mations, and which will successfully control target implosion of the inner shell. backscatter, thereby eliminating damage to optical A.