A. Kritcher, D. Schlossberg, C. Weber, C. Young, E. Dewald, A. Zylstra, O. Hurricane, A. Allen, B. Bachmann, K. Baker, S. Baxamusa, T. Braun, G. Brunton, D. Callahan, D. Casey, T. Chapman, C. Choate, D. Clark, J.-M. Di Nicola, L. Divol, M. Edwards, S. Haan, T. Fehrenbach, S. Hayes, D. Hinkel, M. Hohenberger, K. Humbird, O. Jones, E. Kur, B. Kustowski, C. Kong, O. Landen, D. Larson, X. Lepro-Chavez, J. Lindl, B. MacGowan, S. Maclaren, M. Marinak, M. Millot, A. Nikroo, R. Nora, A. Pak, P. Patel, J. Ralph, M. Ratledge, M. Rubery, S. Sepke, M. Stadermann, D. Strozzi, T. Suratwala, R. Tommasini, R. Town, B. Woodworth, B. Van Wonterghem, C. Wild
An exciting use of high powered lasers is to inertially confine fusion plasmas in the laboratory. This presentation describes the first design to achieve controlled fusion target gain exceeding one using high powered lasers in the inertial confinement fusion approach and recent experimental results on the NIF (National Ignition Facility). In these experiments, laser beams incident on the inside of a cylindrical can (Hohlraum) generates an intense x-ray radiation bath that is used to spherically implode pellets containing Deuterium and Tritium. On Dec 5th 2022, the imploded pellet generated more fusion energy (3.15 MJ) than laser energy incident on the target (2.05 MJ), reaching a milestone for the field that was more than six decades in the making. Follow on experiments in this platform using 2.2 MJ of laser energy have generated >5 MJ and >2x target gain.
The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory contains a 192-beam 4.2 MJ neodymium glass laser (around 1053 nm or 1w) that is frequency converted to 351nm light or 3w. It was built to access the extreme high energy density conditions needed to support the nation’s nuclear stockpile in the absence of further underground nuclear tests, including studying Inertial Confinement Fusion (ICF) and ignition in the laboratory.
Over the last year, important results have been obtained demonstrated a fusion yield of 1.35MJ with 1.9MJ of laser energy (and 440 TW power) injected in the target, bringing the NIF to the threshold of ignition [2-3]. As the yield curve near ignition is steep, the laser performance team has focused on providing improved power accuracy and precision (better shot-to-shot reproducibility) with a high-fidelity pulse shaping system (HiFiPS), and also on extending the NIF operating power and energy space by 15% to 2.2MJ and 500TW.
The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory contains a
192-beam 4.2 MJ neodymium glass laser (around 1053 nm or 1w) that is frequency converted to
351nm light or 3w. It has been designed to support the study of Inertial Confinement Fusion (ICF)
and High Energy Density Physics (HEDP). The NIF Precision Diagnostic System (PDS) was reactivated and new
diagnostic packages were designed and fielded that offer a more comprehensive suite
of high-resolution measurements. The current NIF laser performance will be presented as well as the preliminary results obtained with the various laser experimental campaigns using the new diagnostic tool suites.
This talk will provide an overview of high power laser research at Lawrence Livermore National Laboratory (LLNL). It will discuss the status of the National Ignition Facility (NIF) laser. In addition, the talk will describe other laser development activities such as the development of high average power lasers and novel fiber lasers.
The National Ignition Facility (NIF) has been in service since 2007 and operating with > 1 MJ energies since 2009. During this time the facility has transitioned to become an international user facility and increased the shot rate from ~150 target shots per year to greater than 400 shots per year. Today, the NIF plays an essential role in the US Stockpile Stewardship Program, providing data under the extreme conditions needed to validate computer models and train the next generation of stockpile stewards. Recent upgrades include the Advanced Radiographic Capability (ARC), a high energy short pulse laser used to do high resolution radiography.
In addition to the NIF, this talk will include an overview of progress on the high average power laser development, recent results from fiber laser development activities and improvements to laser design and computational capabilities.
The National Ignition Facility (NIF) is designed with its high-value optical systems in cassettes called line-replaceable Units (LRUs). Virtually all of NIF's active components are assembled in one of approximately 4000 electrical and optical LRUs that serve between two and eight of NIF's 192 laser beamlines. Many of these LRUs are optomechanical assemblies that are roughly the size of a telephone booth. The primary design challenges for this hardware include meeting stringent mechanical precision, stability, and cleanliness requirements. Pre-production units of each LRU type have been fielded on the first bundle of NIF and have been used to demonstrate that NIF meets its performance objectives. This presentation provides an overview of NIF LRUs-and their design and production plans for building out the remaining NIF bundles.
Alvin Erlandson, H. Lambert, Luis Zapata, L. Pedrotti, Doug Larson, Mark Rotter, W. Dallum, Stephane Seznec, Geoffroy LeTouze, Eric Grebot, O. Carbourdin, J. Fornerod, P. Bosch
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 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.
The National Ignition Facility (NIF) is a high energy glass laser system and target chamber that will be used for research in inertial confinement fusion. The 192 beams of the NIF laser system are pumped by over 8600 Xenon flashlamps. The power conditioning system for NIF must deliver nearly 300 MJ of energy to the flashlamps in a cost effective and reliable manner. The present system design has over 200 capacitive energy storage modules that store approximately 1.7 MJ each and deliver that energy through a single switch assembly to 20 parallel sets of two series flashlamps. Although these are many possible system designs, few will meet the aggressive cost goals necessary to make the system affordable. Sandia National Laboratory and Lawrence Livermore National Laboratory are developing the system and component technologies that will be required to build the power conditioning system for the National Ignition Facility. This paper will describe the ongoing development activities for the NIF power conditioning system.
The tolerance of the circuit topology proposed for the National Ignition Facility (NIF) power conditioning system to specific fault conditions is investigated. A new pulsed power circuit is proposed for the NIF which is simpler and less expensive than previous ICF systems. The inherent fault modes of the new circuit are different from the conventional approach, and must be understood to ensure adequate NIF system reliability. A test-bed which simulates the NIF capacitor module design was constructed to study the circuit design. Measurements from test- bed experiments with induced faults are compared with results from a detailed circuit model. The model is validated by the measurements and used to predict the behavior of the actual NIF module during faults. The model can be used to optimize fault tolerance of the NIF module through an appropriate distribution of circuit inductance and resistance. The experimental and modeling results are presented, and fault performance is compared with the ratings of pulsed power components. Areas are identified which require additional investigation.
We have modeled dynamic stresses in the envelopes of pulsed xenon flashlamps, treating stresses produced by three different sources: the heating of the envelope by the plasma; the pressure rise of the xenon gas; and magnetic forces, due to currents flowing in nearby lamps. The heat-induced stresses were calculated by the finite element method, using uniform heating rates for the inside surface of the envelope that were inferred from flashlamp radiant efficiency measurements. Pressure-induced stresses were calculated analytically, using empirical relationships for temperature and pressure in terms of current density. Magnetically-induced stresses were also calculated analytically, for flashlamps packed parallel to each other in linear arrays.
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