We have demonstrated the world's highest average power, fully diode-pumped, petawatt-class peak power laser, the High-repetition-rate Advanced Petawatt Laser System (HAPLS) [1-3]. These first commissioning results at 16J (stretched) at 3%Hz fully validate projected performance of 30J/30fs (>1PW) at 10Hz. The laser has been operated at this intermediate level at Lawrence Livermore National Laboratory to demonstrate integrated performance of all subsystems and provide benchmarking data to laser performance models before further increasing energy and peak power. Data was obtained during multiple campaigns, exceeding several hours of run time, and a snapshot of 60min of data is shown in Fig. 1. The average pump laser 1ω (1053nm) energy was 97J with an rms stability of 0.7%, 2ω (527nm) energy at the Ti:sapphire power amplifier was 62J, and the average stretched short pulse energy was 16J. A full-aperture diagnostic suite allows simultaneous, single-shot measurement of energy, spectrum, beam quality, and pulse duration at full repetition rate. Single-shot SPIDER retrieved pulse shapes (Fig. 1 inset) with an average pulse duration over 12000 consecutive shots of 28.6fs (rms=1.4fs). The mean pulse duration is consistent with the measured spectral bandwidth and is ∼1.2× the transform limit. All results shown are raw data without filtering or averaging, demonstrating the exceptional pulse characteristics, repeatability, and stability of the entire laser system.

The HAPLS laser system has been commissioned to its first integrated performance milestone, delivering laser pulses with 16J sub-30fs duration at a 3⅓Hz repetition rate. This first all-diode-pumped petawatt-class laser offers the average powers required for secondary source applications.

Lawrence Livermore National Laboratory has many needs for high reliability, high peak current, high di/dt switches. Solid-state switch technology offers the demonstrated advantage of reliability under a variety of conditions. Light-triggered switches operate with a reduced susceptibility to electromagnetic interference commonly found within pulsed power environments. Despite the advantages, commercially available solid-state switches are not typically designed for the often extreme pulsed power requirements. Testing was performed to bound the limits of devices for pulsed power applications beyond the manufacturers' specified ratings. To test the applicability of recent commercial light-triggered solid-state designs, an adjustable high current switch test stand was assembled. Results from testing and subsequent selected implementations are presented.

The Plasma Electrode Pockels Cell (PEPC) subsystem is a key component of the National Ignition Facility, enabling the laser to employ an efficient four-pass main amplifier architecture. PEPC relies on a pulsed power technology to initiate and maintain plasma within the cells and to provide the necessary high voltage bias to the cells’ nonlinear crystals. Ultimately, nearly 300 high-voltage, high-current pulse generators will be deployed in the NIF in support of PEPC. Production of solid-state plasma pulse generators and thyratron-switched pulse generators is now complete, with the majority of the hardware deployed in the facility. An entire cluster (one-fourth of a complete NIF) has been commissioned and is operating on a routine basis, supporting laser shot operations. Another cluster has been deployed, awaiting final commissioning. Activation and commissioning of new hardware continues to progress in parallel, driving toward a goal of completing the PEPC subsystem in late 2007.

The Plasma Electrode Pockels Cell (PEPC) embodies technology essential to the National Ignition Facility (NIF). Together with a thin-film polarizer, PEPC functions as an optical switch for the main amplifier cavity, allowing optical pulses to be trapped, and then released, and enabling NIF to take advantage of the attendant gain and cost-savings. Details of the genesis, development, and prototyping of the PEPC are well documented. After moving from its laboratory setting to the NIF facility, PEPC--via its performance during the two-year NIF Early Light (NEL) campaign and its ongoing operation during facility build-out--has proven to be a fully functional system. When complete, NIF will accommodate 192 beams, capable of delivering 1.8 MJ to a fusion target. Forty-eight Plasma Electrode Pockels--driven by nearly 300 high-power, high-voltage pulse generators--will support this complement of beams. As deployed, PEPC is a complex association of state-of-the-art optics; low-voltage and high-voltage electronics; and mechanical, gas, and vacuum subsystems--all under computer control. In this paper, we briefly describe each of these elements, but focus on the pulse power aspects of the PEPC system.

The National Ignition Facility (NIF) Power Conditioning System (PCS) is a modular capacitive energy storage system that will be capable of storing nearly 400 MJ of electrical energy and delivering that energy to the nearly 8000 flashlamps in the NIF laser. The first sixteen modules of the power conditioning system have been built, tested and installed. Activation of the first nine power conditioning modules has been completed and commissioning of the first "bundle" of laser beamlines has begun. This paper will provide an overview of the power conditioning system design and describe the status and results of initial testing and activation of the first "bundle" of power conditioning modules.

A fully integrated test facility for the National Ignition Facility (NIF) Power Conditioning System (PCS) was completed in August of 2000 at LLNL. The system consists of the computer control and data acquisition subsystem, a 24kV 2.2-MJ Main Energy Storage Module (MESM), twenty 180ft lengths of high voltage transmission cable, and a standard NIF flashlamp, load (the Frame Assembly Unit or FAU). The MESM can contain up to 24 (20 nominal) 300uF energy storage capacitors. Stainless steel inductive/resistive (9uh/0.026 ohms) damping elements limit fault currents in the event of a capacitor or main bus failure. A single spark-gap switches the entire bank output through ballast inductors to the output cables. Each cable has it own ballast inductor to insure current sharing, the values of the inductors are varied with cable length. The test facility can be fired once every ten minutes with a total peak output current of 580kA at pulse width of 400/spl mu/s. We will present in detail tests performed to demonstrate that the system meets all specifications for operational performance well as statistical data verifying stability and reliability.

This paper describes a set of analyses and tests performed to evaluate approaches to provide a safe and robust grounding approach for the main Power Conditioning System (PCS) in the National Ignition Facility (NIF) facility presently under construction at the Lawrence Livermore National Laboratory (LLNL). The Power Conditioning System consists of up to 192 capacitor bank modules, each storing 2.2 MJ and capable of producing a peak current over 500 kA. The grounding system must minimize touch potentials associated with operation of the Power Conditioning System. In the event of severe faults, the system must assure that the energy delivered to a person through contact with "grounded" structures is very low. Based on computer modeling and low-voltage, low current tests, we have concluded that the most effective approach is a set of metal enclosures around the output cables (effectively heavy-wall closed cable trays) extending from the capacitor bank modules to their flashlamp loads. This paper will discuss the safety standards identified for this application, the approach to meeting the standards, and the predicted performance of the safety system.

The National Ignition Facility (NIF) Power Conditioning System (PCS) is a modular capacitive energy storage system that provides over 34 kilojoules of energy to each of the nearly 8000 flashlamps in the NIF laser. Up to 400 megajoules of energy can be stored in the NIF PCS system, discharged through spark gaps and delivered to the flashlamps through a coaxial transmission line system requiring nearly 100 miles of high-voltage cable. The NIF PCS has been under development for nearly 4 years. During this time, the system was developed and designed by Sandia National Laboratory in Albuquerque, NM (SNLA) in conjunction with Lawrence Livermore National Laboratory (LLNL). Extensive reliability testing was performed at SNLA on the First Article NIF Test Module (FANTM) test facility and design improvements were implemented based on FANTM test results, leading to the final design presently undergoing system reliability testing at LLNL. Low-cost energy-storage capacitors, charging power supplies, and reliable, fault-tolerant components were developed through partnerships with numerous contractors. Extensive reliability and fault testing of components has also been performed. This paper provides an overview of the many efforts that have culminated in the final design of the NIF PCS. The PCS system design will be described and the cost tradeoffs discussed. Plans for fabrication and installation of the NIF PCS system over the next 6 years will be presented.

Many pulse power systems rely on large numbers of inductively isolated high voltage capacitors configured in parallel for energy storage. Often when an energy storage capacitor fails there is little or no external indication. Identifying the failed component can be a time consuming and potentially hazardous operation. We have developed a new noninvasive (i.e. no dismantling of the bank is required) technique that greatly improves personnel safety as well reducing troubleshooting time. We present the theory of operation, a complete description of the battery-powered hardware, test results and techniques of operation.

This paper describes design and operation of the flashlamp test system, used to evaluate the primary laser flashlamps on the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) in Livermore, California. The tester delivers repetitive high voltage pulses to a series pair of flashlamps at levels closely simulating those encountered in normal operation. Each lamp pair is subjected to a pre-ionization and main pulse shot sequence, with two minute intervals between shots. This capability allows the manufacturer to test and evaluate the flashlamps for infant mortality and longevity before delivery to NIF [1]. All operations are under computer control with fully automated test and data acquisition capabilities requiring minimal operator input. The system is designed to operate continuously. Typical pre-ionization and main pulse outputs are Pre-ionization Pulse: V/sub chg/=27kV, I/sub peak/=3kA, E=2.4kJ, Pulse Width: (10%-90%)=200us Main Pulse: V/sub chg/=23kV, I/sub peak/=24kA, E=78.6kJ, Pulse Width: (10%-90%)=350us.

The laser glass for the National Ignition Facility (NIF) main amplifier system is pumped by a system of 192 pulsed power/flash lamp assemblies. Each of these 192 assemblies consists of a 1.6 MJ (nominal) capacitor bank working with a pre-ionization/lamp check (PILC) pulser to drive an array of 40 flash lamps. This paper describes the predicted performance of these power conditioning system (PCS) modules in concert with flashlamp assemblies in NIF. Each flashlamp assembly consists of 20 parallel sets of lamps in series pairs. The sensitivity of system performance to various design parameters of the PILC pulser and the main capacitor bank is described. Results of circuit models are compared to sub-scale flashlamp tests and to measurements taken in tests of a PCS module driving a flashlamp assembly in the First Article NIF Test Module facility at Sandia National Laboratories. Also included are predictions from a physics-based, semi-empirical amplifier gain code.

The purpose of this paper is to describe the current state of avalanche transistor-based Pockels cell driver development at LLNL and to provide the reader with a set of useful design guidelines. A general description of the units is followed by a short section on the circuit design of avalanche transistor pulsers. Techniques for delivering either 1/4 or 1/2 wave voltages to a Pockels cell are covered. Recently these units have been modified for use at repetition rates up to 10 kHz. Operating at high repetition rates presents problems for both the driver and the Pockels cell. Design solutions for the pulser are presented as well as a discussion of Pockels cell acoustic resonance.