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Characterization of high power flashlamps and application to Nd:glass laser pumping

Description: Detailed spectral and temporal measurements of the output radiation from Xe flashlamps are reported together with their use in predicting the pumping efficiency of Nd-doped laser glass. We have made absolute spectral-intensity measurements for 0.5, 1.5, and 4.2-cm-bore flashlamps for input powers ranging from 5 to 90 kW/cm/sup 2/ and pulselengths of 600 ..mu..s. Under quasi-stationary conditions these flashlamps emit essentially identical spectra when excited at equal input power per unit-area of the bore. This behavior is characteristic of an optically-thick radiator although it is not completely clear why flashlamps should behave this way. A simple model is also described which accounts for the transient response of flashlamps by characterizing the output spectra and radiation efficiencies in terms of the radiant output power rather than the electrical input power. 23 refs., 16 figs.
Date: January 17, 1986
Creator: Powell, H.T.; Erlandson, A.C. & Jancaitis, K.S.
Partner: UNT Libraries Government Documents Department

Survey of Laser Markets Relevant to Inertial Fusion Energy Drivers, information for National Research Council

Description: Development of a new technology for commercial application can be significantly accelerated by leveraging related technologies used in other markets. Synergies across multiple application domains attract research and development (R and D) talent - widening the innovation pipeline - and increases the market demand in common components and subsystems to provide performance improvements and cost reductions. For these reasons, driver development plans for inertial fusion energy (IFE) should consider the non-fusion technology base that can be lveraged for application to IFE. At this time, two laser driver technologies are being proposed for IFE: solid-state lasers (SSLs) and KrF gas (excimer) lasers. This document provides a brief survey of organizations actively engaged in these technologies. This is intended to facilitate comparison of the opportunities for leveraging the larger technical community for IFE laser driver development. They have included tables that summarize the commercial organizations selling solid-state and KrF lasers, and a brief summary of organizations actively engaged in R and D on these technologies.
Date: February 24, 2011
Creator: Bayramian, A. J.; Deri, R. J. & Erlandson, A. C.
Partner: UNT Libraries Government Documents Department

The LIFE Laser Design in Context: A Comparison to the State-of-the-Art

Description: The current point design for the LIFE laser leverages decades of solid-state laser development in order to achieve the performance and attributes required for inertial fusion energy. This document provides a brief comparison of the LIFE laser point design to other state-of-the-art solid-state lasers. Table I compares the attributes of the current LIFE laser point design to other systems. the state-of-the-art for single-shot performance at fusion-relevant beamline energies is exemplified by performance observed on the National Ignition Facility. The state-of-the-art for high average power is exemplified by the Northrup Grumman JHPSSL laser. Several items in Table I deal with the laser efficiency; a more detailed discussion of efficiency can be found in reference 5. The electrical-to-optical efficiency of the LIFE design exceeds that of reference 4 due to the availability of higher efficiency laser diode pumps (70% vs. {approx}50% used in reference 4). LIFE diode pumps are discussed in greater detail in reference 6. The 'beam steering' state of the art is represented by the deflection device that will be used in the LIFE laser, not a laser system. Inspection of Table I shows that most LIFE laser attributes have already been experimentally demonstrated. The two cases where the LIFE design is somewhat better than prior experimental work do not involve the development of new concepts: beamline power is increased simply by increasing aperture (as demonstrated by the power/aperture comparison in Table I), and efficiency increases are achieved by employing state-of-the-art diode pumps. In conclusion, the attributes anticipated for the LIFE laser are consistent with the demonstrated performance of existing solid-state lasers.
Date: March 21, 2011
Creator: Deri, R. J.; Bayramian, A. J. & Erlandson, A. C.
Partner: UNT Libraries Government Documents Department

Gratings for Increasing Solid-State Laser Gain and Efficiency

Description: We introduce new concepts for increasing the efficiency of solid state lasers by using gratings deposited on laser slabs or disks. The gratings improve efficiency in two ways: (1) by coupling out of the slab deleterious amplified spontaneous emission (ASE) and (2) by increasing the absorption efficiency of pump light. The gratings also serve as antireflective coatings for the extracting laser beam. To evaluate the potential for such coatings to improve laser performance, we calculated optical properties of a 2500 groove/mm, tantala-silica grating on a 1cm x 4cm x 8cm titanium-doped sapphire slab and performed ray-trace calculations for ASE and pump light. Our calculations show substantial improvements in efficiency due to grating ASE-coupling properties. For example, the gratings reduce pump energy required to produce a 0.6/cm gain coefficient by 9%, 20% and 35% for pump pulse durations of 0.5 {micro}s, 1{micro}s and 3{micro}s, respectively. Gratings also increase 532-nm pump-light absorption efficiency, particularly when the product slab overall absorption is small. For example, when the single-pass absorption is 1 neper, absorption efficiency increases from 66%, without gratings, to 86%, when gratings are used.
Date: April 16, 2010
Creator: Erlandson, A C; Britten, J A & Bonlie, J D
Partner: UNT Libraries Government Documents Department

NIF laser bundle review. Final report

Description: We performed additional bundle review effort subsequent to the completion of the preliminary report and are revising our original recommendations. We now recommend that the NIF baseline laser bundle size be changed to the 4x2 bundle configuration. There are several 4x2 bundle configurations that could be constructed at a cost similar to that of the baseline 4x12 (from $11M more to about $11M less than the baseline; unescalated, no contingency) and provide significant system improvements. We recommend that the building cost estimates (particularly for the in-line building options) be verified by an architect/engineer (A/E) firm knowledgeable about building design. If our cost estimates of the in-line building are accurate and therefore result in a change from the baseline U-shaped building layout, the acceptability of the in-line configuration must be reviewed from an operations viewpoint. We recommend that installation, operation, and maintenance of all laser components be reviewed to better determine the necessity of aisles, which add to the building cost significantly. The need for beam expansion must also be determined since it affects the type of bundle packing that can be used and increases the minimum laser bay width. The U-turn laser architecture (if proven viable) offers a reduction in building costs since this laser design is shorter than the baseline switched design and requires a shorter laser bay.
Date: September 15, 1995
Creator: Tietbohl, G.L.; Larson, D.W. & Erlandson, A.C.
Partner: UNT Libraries Government Documents Department

Thermal recovery measurements on multi-segment amplifiers

Description: We present the results of a series of experiments to measure the thermal recovery times of a flashlamp-pumped, Nd:Glass multi-segment laser amplifier. In particular, we investigated the thermal recovery times under the following cooling options: (1) passive cooling; (2) active cooling of the flashlamp cassettes, and (3) active cooling of the flashlamp cassettes and gas flow in the pump cavity.
Date: September 21, 1995
Creator: Rotter, M.D.; McCracken, R.W.; Erlandson, A.C. & Brown, D.
Partner: UNT Libraries Government Documents Department

Gain measurements on a prototype NIF/LMJ amplifier pump cavity

Description: We are currently developing large-aperture amplifiers for the National Ignition Facility (NIF) and Laser Megajoules (LMJ) lasers. These multisegment amplifiers are of the flashlamp-pumped, Nd:Glass qW and are designed to propagate a nominally 36 cm square beam. The apertures within a particular amplifier bundle are arranged in a four- high by two-wide configuration and utilize two side lamp arrays and a central flashlamp array for pumping. The configuration is very similar to that used in the Beamlet laser, a single-beam prototype for the NIF/LMJ lasers, which has four apertures arranged in a two- high by two-wide configuration.
Date: December 1, 1996
Creator: Rotter, M.D.; McCracken, R.; Erlandson, A. & Guenet, M.
Partner: UNT Libraries Government Documents Department

Effect of amplifier component maintenance on laser system availability and reliability for the US National Ignition Facility

Description: We have analyzed the availability and reliability of the flashlamp- pumped, Nd:glass amplifiers that, as a part of a laser now being designed for future experiments, in inertial confinement fusion (ICF), will be used in the National Ignition Facility (NIF). Clearly , in order for large ICF systems such as the NIF to operate effectively as a whole, all components must meet demanding availability and reliability requirements. Accordingly, the NIF amplifiers can achieve high reliability and availability by using reliable parts, and by using a cassette-based maintenance design that allows most key amplifier parts to be 1744 replaced within a few hours. In this way, parts that degrade slowly, as the laser slabs, silver reflectors, and blastshields can be expected to do, based on previous experience, can be replaced either between shots or during scheduled maintenance periods, with no effect on availability or reliability. In contrast, parts that fail rapidly, such as the flashlamps, can and do cause unavailability or unreliability. Our analysis demonstrates that the amplifiers for the NIF will meet availability and reliability goals, respectively, of 99.8% and 99.4%, provided that the 7680 NIF flashlamps in NIF have failure rates of less than, or equal to, those experienced on Nova, a 5000-lamp laser at Lawrence Livermore National Laboratory (LLNL).
Date: December 1, 1996
Creator: Erlandson, A.C.; Lambert, H. & Zapata, L.E.
Partner: UNT Libraries Government Documents Department

Preliminary report: NIF laser bundle review

Description: As requested in the guidance memo {sup 1}, this committe determined whether there are compelling reasons to recommend a change from the NIF CDR baseline laser. The baseline bundle design based on a tradeoff between cost and technical risk, which is replicated four times to create the required 192 beams. The baseline amplifier design uses bottom loading 1{times}4 slab and flashlamp cassettes for amplifier maintenance and large vacuum enclosures (2.5m high {times} 7m wide in cross-section for each of the two spatial filters in each of the four bundles. The laser beams are arranged in two laser bays configured in a u-shape around the target area. The entire bundle review effort was performed in a very short time (six weeks) and with limited resources (15 personnel part-time). This should be compared to the effort that produced the CDR design (12 months, 50 to 100 personnel). This committee considered three alternate bundle configurations (2{times}2, 4{times}2, and 4{times}4 bundles), and evaluated each bundle against the baseline design using the seven requested issues in the guidance memo: Cost; schedule; performance risk; maintainability/operability; hardware failure cost exposure; activation; and design flexibility. The issues were reviewed to identify differences between each alternate bundle configuration and the baseline.
Date: August 31, 1995
Creator: Tietbohl, G.L.; Larson, D.W. & Erlandson, A.C.
Partner: UNT Libraries Government Documents Department

Laser Systems for Orbital Debris Removal

Description: The use of a ground based laser for space debris cleaning was investigated by the ORION project in 1996. Since that study the greatest technological advance in the development of high energy pulsed laser systems has taken place within the NIF project at LLNL. The proposed next laser system to follow the NIF at LLNL will be a high rep rate version of the NIF based on diode-pumping rather than flashlamp excitation; the so called 'LIFE' laser system. Because a single 'LIFE' beamline could be built up in a few year time frame, and has performance characteristics relevant to the space debris clearing problem, such a beamline could enable a near term demonstration of space debris cleaning. Moreover, the specifics of debris cleaning make it possible to simplify the LIFE laser beyond what is required for a fusion drive laser, and so substantially reduce its cost. Starting with the requirements for laser intensity on the target, and then considering beam delivery, we will flow back the laser requirements needed for space debris cleaning. Using these derived requirements we will then optimize the pulse duration, the operational regime, and the output pulse energy of the laser with a focus of simplifying its overall design. Anticipated simplifications include operation in the heat capacity regime, eliminating cooling requirements on the laser gain slabs, and relaxing B-integral and birefrigence requirements.
Date: February 5, 2010
Creator: Rubenchik, A M; Barty, C P; Beach, R J; Erlandson, A C & Caird, J A
Partner: UNT Libraries Government Documents Department

Flashlamp for NIF: Russian variant

Description: A variant of the flashlamp for NIF was developed on the base of the experience of manufacture and application of high-power flashlamps in Russia. Features of flashlamp design as well as first test results of the experimental samples are presented.
Date: November 1, 1996
Creator: Erlandson, A.C.; Nikiforov, V.G.; Nikolaevskii, V.G.; Gerasimov, V.A. & Zapata, L.E.
Partner: UNT Libraries Government Documents Department

Integrated process modeling for the laser inertial fusion Energy (LIFE) generation system

Description: A concept for a new fusion-fission hybrid technology is being developed at Lawrence Livermore National Laboratory. The primary application of this technology is base-load electrical power generation. However, variants of the baseline technology can be used to 'burn' spent nuclear fuel from light water reactors or to perform selective transmutation of problematic fission products. The use of a fusion driver allows very high burn-up of the fission fuel, limited only by the radiation resistance of the fuel form and system structures. As a part of this process, integrated process models have been developed to aid in concept definition. Several models have been developed. A cost scaling model allows quick assessment of design changes or technology improvements on cost of electricity. System design models are being used to better understand system interactions and to do design trade-off and optimization studies. Here we describe the different systems models and present systems analysis results. Different market entry strategies are discussed along with potential benefits to US energy security and nuclear waste disposal. Advanced technology options are evaluated and potential benefits from additional R&D targeted at the different options is quantified.
Date: October 22, 2009
Creator: Meier, W R; Anklam, T M; Erlandson, A C; Miles, R R; Simon, A J; Sawicki, R et al.
Partner: UNT Libraries Government Documents Department

Z-Beamlet (ZBL) Multi-Frame Back-lighter (MFB) System for ICF/Plasma Diagnostics

Description: Z-Beamlet [1] is a single-beam high-energy Nd:glass laser used for backlighting high energy density (HED) plasma physics experiments at Sandia's Z-accelerator facility. The system currently generates a single backlit image per experiment, and has been employed on approximately 50% of Z-accelerator system shots in recent years. We have designed and are currently building a system that uses Z-Beamlet to generate two distinct backlit images with adjustable time delay ranging from 2 to 20 ns between frames. The new system will double the rate of data collection and allow the temporal evolution of high energy density phenomena to be recorded on a single shot.
Date: September 8, 2005
Creator: Caird, J A; Erlandson, A C; Molander, W A; Murray, J E; Robertson, G K; Smith, I C et al.
Partner: UNT Libraries Government Documents Department

Atmospheric tarnishing of silver-plated laser mirrors

Description: Purified air is being considered as a cost-effective alternative to evaporated liquid nitrogen for cooling laser amplifiers in the National Ignition Facility (NIF). Atmospheric corrosion of the associated flashlamp reflectors could cause significant degradation of overall laser performance. Therefore, a comprehensive study has been undertaken to address this important problem. Specific contributions include: (1) a detailed literature search, with a critical analysis of published data; (2) Predictive calculations based on the published data, as well as new measurements made a Lawrence Livermore National Laboratory (LLNL); (3) Analyses of proposed coolant gases to determine the actual concentrations of H2S, SO2, COS, CS2, H2O, NO2, Cl2, and organic forms of sulfur; and (4) Investigations of both ultra-filtration of air and protective optical coatings as possible means of preventing mirror tarnish.
Date: October 1, 1997
Creator: Farmer, J.; Thomas, N.; Siekhaus, W.; Gregg, H.; Erlandson, A.; Marshall, C. et al.
Partner: UNT Libraries Government Documents Department

Pump-induced wavefront distortion in prototypical NIF/LMJ amplifiers-modeling and comparison with experiments

Description: In large-aperture laser amplifiers such as those envisioned for the National Ignition Facility (NIF) and Laser Megajoules (LMJ) lasers, the geometry is such that the front and back faces of the laser slab are heated unevenly by the pump process. This uneven heating results in a mechanical deformation of the laser slab and consequent internal stresses. The deformation and stresses, along with a temperature-dependent refractive index variation, result in phase variations across the laser beam (so-called pump-induced wavefront distortions). These phase variations lead to beam steering which may affect frequency conversion as well as energy-on-target. We have developed a model which allows us to estimate the pump-induced wavefront distortion for a given amplifier configuration as well as the spatially-resolved depolarization. The model is compared with experiments taken in our amplifier development laboratory, AMPLAB
Date: September 1, 1998
Creator: Erlandson, A; Jancaitis, K; LeTouze, G; Marshall, C; Rotter, M; Seznec, S et al.
Partner: UNT Libraries Government Documents Department

Prevention of corrosion of silver reflectors for the National Ignition Facility

Description: A durable protected silver coating was designed and fabricated for possible use on flashlamp reflectors in the National Ignition Facility (NIF) to avoid tarnishing under corrosive conditions and intense visible light (10 J/cm{sup 2}, 360 {micro}s). This coating provides a valuable alternative for mirror coatings where high reflectance and durability are important requirements. This paper describes a protected silver coating having high reflectance from 400 mn to 10,000 mu. The specular reflectance is between 95% and 98% in the visible region and 98% or better in the infrared region.
Date: July 1, 1999
Creator: Thomas, N; Siekhaus, W; Farmer, J; Gregg, H; Erlandson, A; Marshall, C et al.
Partner: UNT Libraries Government Documents Department

Accelerated thermal recovery for flash-lamp-pumped solid-state laser amplifiers final report for 97-ERD-133

Description: We have developed a cost-effective method for accelerating the thermal wavefront recovery and shot rate of large, flashlamp-pumped, Nd:glass, Brewster-angle slab lasers of the type used for studying inertial confinement fusion (ICF) and laser-plasma interactions. This method removes waste pump heat by flowing slightly-chilled, turbulent gas over the flashlamps and blastshields after each shot, with the cooled blastshields serving as heat sinks for radiatively extracting residual heat deposited in the laser slabs. We performed both experiments and modeling to characterize residual optical distortions arising from both temperature gradients within the laser slabs as well as from buoyantly-driven convection currents in the amplifier cavity and attached beam tubes. The most rapid thermal recovery was achieved by reducing the temperature of the cooling gas by 0.5-1 C below the ambient temperature for about two hours after the shot. Model predictions for the 1.8-MJ National Ignition Facility (NIF) laser now being built at Lawrence Livermore National Laboratory (LLNL) show that such chilled-gas cooling would increase the thermal-distortion-limited shot rate from about one shot every eight hours to one shot every three to four hours, thus significantly increasing the potential scientific productivity of this major Department of Energy (DOE) facility.
Date: September 3, 1999
Creator: Erlandson, A C; London, R; Manes, K; Marshall, C; Petty, C; Pierce, R et al.
Partner: UNT Libraries Government Documents Department

Flashlamp pumping of Nd:glass disk amplifiers

Description: We present experimental results and a model of Nd:glass disk amplifiers which are used in inertial confinement fusion research. We first review our previous measurements on pulsed xenon flashlamps. We then discuss out measurements on the enhancement of the Nd fluorescence decay rate in laser disks by amplified spontaneous emission. Using these data, we have constructed a model of flashlamp pumping which treats the transfer efficiency of pump light from the flashlamps to the disks as an empirical function. We have found a simple description of this cavity transfer function which provides an excellent fit to the amplifier results for various pump pulselengths. We discuss the concept of the pump area ratio for describing the flashlamp packing density and show that amplifier performance is optimized for values of this parameter near unity. We finally present results for both a single-segment and a multisegment disk amplifier. We have used these devices to investigate new amplifier designs for a large scale fusion driver. 11 refs., 13 figs.
Date: June 12, 1990
Creator: Powell, H.T.; Erlandson, A.C.; Jancaitis, K.S. & Murray, J.E.
Partner: UNT Libraries Government Documents Department

Inertial Fusion Energy's Role in Developing the Market for High Power Laser Diodes

Description: Production-cost models for high-power laser-diodes indicate systems of 10GW peak power coupled with facilitization of semi-conductor manufacturing capacity could yield costs below $0.02/Watt. This is sufficient to make IFE competitive with other nuclear power technologies.
Date: November 29, 2007
Creator: Ladran, A L; Ault, E R; Beach, R J; Campbell, J H; Erlandson, A C; Felker, A J et al.
Partner: UNT Libraries Government Documents Department