Table of contents

The National Ignition Facility (NIF) will be impacted by electromagnetic pulse (EMP) during normal long-pulse operation, but the largest impacts are expected during short-pulse operation utilizing the Advanced Radiographic Capability (ARC). Without mitigation these impacts could range from data corruption to hardware damage. We describe our EMP measurement systems on Titan and NIF and present some preliminary results and thoughts on mitigation.

We present the upgrading project ELFIE (Equipement Laser de Forte Intensité et Energie) based on the "100TW" mixed Nd:glass CPA laser system at 1μm at LULI, which includes an energy enhancement and the development of a short-pulse, high-energy, good temporal contrast beam line (50fs/5J). We report the first experimental step towards the short-pulse, high-energy beam line: spectral broadening above 60nm from 7nm and temporal pulse compression below 40fs from 300fs at 1μm through a Krypton-filled hollow fiber compressor.

We are converting a quad of NIF beamlines into eight, short-pulse (1–50 ps), petawatt-class beams for advanced radiography and fast ignition experiments. This paper describes progress toward completing this project.

Plasma mirror effect is demonstrated for short-pulse KrF lasers. It is shown that the reflectivity of the plasma starts to increase at the plasma threshold of 10¹²W/cm² and it saturates at 10¹⁴W/cm². The maximum reflectivity was ∼33% for 45° angle of incidence, and ∼50% was reached for 12.4°. This strong reflection allows even its direct application for short-pulse 248 nm systems whereas using it before the last amplifier may even clean the pulse from spatial inhomogeneities.

We have characterized the Advanced Radiographic Capability injection laser system and demonstrated that it meets performance requirements for upcoming National Ignition Facility fusion experiments. Pulse compression was achieved with a scaled down replica of the meter-scale grating ARC compressor and sub-ps pulse duration was demonstrated at the Joule-level.

The aim of this project is to establish a 10 PW facility on the Vulcan laser system capable of being focussed to intensities of at least 10²³ Wcm⁻² and integrate this into a flexible and unique user facility This paper will present progress made in Phase one developing the 10PW Front End as well as the concept for the new Vulcan 10 PW facility. The new facility will be configured in a unique way to maximise the scientific opportunities presented through a combination with the existing capabilities already established on Vulcan. This ground breaking development will open up a range of new scientific opportunities.

We present the design for a high-speed adaptive optics system that will be used to achieve the necessary laser pointing and beam-quality performance for initial fast-ignition coupling experiments. This design makes use of a 32×32 pixellated MEMS device as the adaptive optic and a two-channel interferometer as the wave-front sensor. We present results from a system testbed that demonstrates improvement of the Strehl ratio from 0.09 to 0.61 and stabilization of beam pointing from ∼75μrad to <2μrad.

We developed for the first time, very compact (<1 cm³) extremely low f-number (f/# = 0.4) confocal ellipsoid focusing systems. Direct measurement of the laser focal spot using a low-energy laser beam indicates 1/5 reduction of the spot size compared to standard focusing (using a f/2.7 optics). Such mirror is thus able to achieve significant enhancement of the focused laser intensity without modifying the laser system itself. The mirror is then used under plasma mirror regime which enables us to compactify the size, to liberate us from the anxiety of protecting the optics from target debris after shots, and to enhance the temporal contrast. In this paper, we focus our attention to designing and optimizing the geometry of such innovative plasma optics.

We present a diode-pumped chirped pulse amplification (CPA) system that generates multi-joule energy at a central wavelength of 1054 nm at a repetition rate of 10 Hz. The purpose of this laser is to serve as a pump source for non-collinear optical parametric chirped pulse amplification (NOPCPA). A Nd-doped glass slab with zigzag optical path was used as the gain medium of the main amplifier in this system to obtain multi-joule output with repeatable operation. The Nd:glass zigzag slab amplifier system consists of four-pass pre-amplification and four-pass power amplification. The seed pulse that is fed to the main amplifier was generated by a mode-locked fiber oscillator emitting at a 1053 nm central wavelength. The oscillator output was pulse-stretched to 2.7 ns duration with a 4.5 nm spectral bandwidth and amplified to 100 μJ by optical parametric amplification by use of type-I BBO crystals. After the main amplification, 2.4 J of energy in 3.7 nm of spectral bandwidth at 1 Hz repetition rate was obtained. This spectral bandwidth corresponds to a transform-limited pulse duration of 440 fs. This result indicates that our CPA laser is capable of delivering multi-joule pump light after pulse compression and frequency doubling for 30-TW NOPCPA system.

The OMEGA EP Laser System was completed in April 2008. It consists of four NIF-like beamlines that will each produce 6.5 kJ per beam at 351 nm. Two of the beamlines can be configured as high-energy petawatt beamlines that will each produce 2.6 kJ in a 10-ps laser pulse. This paper describes the current status of the OMEGA EP Laser System and some initial experimental results.

We propose a new single-shot third order correlator to measure the temporal contrast of pulses in the picosecond range of high power chain lasers. We use time-to-angular coding to transfer the temporal contrast information to a 3ω probe pulse. We determine the temporal window with the resolution obtained from this technique and predict via simulations the time-to-space coding as well as the time-to-frequency coding. We demonstrate the concept experimentally. The image acquisition is performed with a simple 16 bit CCD camera. An amplitude mask can easily improve the dynamics.

In this presentation, we report an improvement technique in our 700TW Ti:sapphire laser facility. In order to improve the contrast ratio, we designed a long cavity ring preamplifier. With careful alignment in each dimension of grating, we got a good focal spot after compressor. The size of focal spot was about 25μm with an f/10 off-axis-parabolic mirror (OAP). Using an f/3 OAP to focus the laser beam in experiment, we expect the laser intensity of 10²¹W/cm² could be realized on the target.

A 50 TW high-intensity laser (aka "Leopard" laser) was developed for experiments with the 1 MA z-pinch generator at the University of Nevada, Reno. The laser produces short pulses of 0.35 ps; energy is 15 J. Long pulses are 1 ns; energy is 30 J. The output beam diameter is 80 mm. The Leopard laser applies chirped pulse amplification technology. The laser is based on the 130 fs Ti:Sapphire oscillator, Öffner-type stretcher, Ti:Sapphire regenerative amplifier, mixed Nd:glass rod and disk amplifiers, and vacuum grating compressor. An adaptive optics system ameliorates focusing ability and augments the repetition rate. Two beam terminals are available for experiments: in the vacuum chamber of the z-pinch generator (aka "Zebra"), and a laser-only vacuum chamber (aka "Phoenix" chamber). The Leopard laser coupled to the Zebra z-pinch generator is a powerful diagnostic tool for dense z-pinch plasma. We outline the status, design, architecture and parameters of the Leopard laser, and its coupling to Zebra. We present the methods of laser-based z-pinch plasma diagnostics, which are under development at the University of Nevada, Reno.

The possibility of the same large-aperture KrF laser driver to amplify simultaneously both nanosecond pulses for thermonuclear target implosion and picosecond ones for fuel ignition is discussed relative to KrF-based Fusion Test Facility. In this way experiments were performed at hybrid Ti:Sapphire/KrF GARPUN-MTW facility on amplification of subpicosecond pulses. 2-TW, 330-fs pulses were produced with beam divergence 20 μrad in direct double-pass amplification scheme. Peak power as high as 30–40 TW can be achieved in 50-fs pulses, being combined with long pulses (of a few ns to 100 ns) of ∼1 GW power.

The current status of the LUCIA laser program is discussed. While aiming at 100J, 10Hz, 10ns, a first milestone is set at 10 Joules with a repetition rate of 1–3 Hz. 7ns long, sub-mJ pulses generated by a cavity-dumped oscillator are first preamplified at the sub-J level. Thermal effects limit amplification and repetition rate at this stage. These pulses will be injected into the main amplifier, where amplification is limited by amplified spontaneous emission. It is expected that these pulses reach energy level of ∼10J.

A LIFE laser driver needs to be designed and operated which meets the rigorous requirements of the NIF laser system while operating at high average power, and operate for a lifetime of >30 years. Ignition on NIF will serve to demonstrate laser driver functionality, operation of the Mercury laser system at LLNL demonstrates the ability of a diode-pumped solid-state laser to run at high average power, but the operational lifetime >30 yrs remains to be proven. A Laser Technology test Facility (LTF) has been designed to specifically address this issue. The LTF is a 100-Hz diode-pumped solid-state laser system intended for accelerated testing of the diodes, gain media, optics, frequency converters and final optics, providing system statistics for billion shot class tests. These statistics will be utilized for material and technology development as well as economic and reliability models for LIFE laser drivers.

The Laser Megajoule (LMJ), is under construction by the French Commissariat à l'Energie Atomique (CEA) at CESTA laboratory near Bordeaux. The LMJ is an important part of the French "Simulation Program". The LMJ is dedicated to high energy density physics experiments, and it is designed to obtain ignition and fusion of a DT fuel capsule. The laser and target systems have been designed to meet the specifications needed for these experiments, in an overall optimization including the fusion target. The current status of the LMJ project is presented.

The generation of neutron/gamma radiation, electromagnetic pulses (EMP), debris and shrapnel at mega-Joule class laser facilities (NIF and LMJ) impacts experiments conducted at these facilities. The complex 3D numerical codes used to assess these impacts range from an established code that required minor modifications (MCNP - calculates neutron and gamma radiation levels in complex geometries), through a code that required significant modifications to treat new phenomena (EMSolve - calculates EMP from electrons escaping from laser targets), to a new code, ALE-AMR, that is being developed through a joint collaboration between LLNL, CEA, and UC (UCSD, UCLA, and LBL) for debris and shrapnel modelling.

We have developed a new 3D multi-physics multi-material code, ALE-AMR, for modeling laser/target effects including debris/shrapnel generation. The code combines Arbitrary Lagrangian Eulerian (ALE) hydrodynamics with Adaptive Mesh Refinement (AMR) to connect the continuum to microstructural regimes. The code is unique in its ability to model hot radiating plasmas and cold fragmenting solids. New numerical techniques were developed for many of the physics packages to work efficiency on a dynamically moving and adapting mesh. A flexible strength/failure framework allows for pluggable material models. Material history arrays are used to store persistent data required by the material models, for instance, the level of accumulated damage or the evolving yield stress in J2 plasticity models. We model ductile metals as well as brittle materials such as Si, Be, and B4C. We use interface reconstruction based on volume fractions of the material components within mixed zones and reconstruct interfaces as needed. This interface reconstruction model is also used for void coalescence and fragmentation. The AMR framework allows for hierarchical material modeling (HMM) with different material models at different levels of refinement. Laser rays are propagated through a virtual composite mesh consisting of the finest resolution representation of the modeled space. A new 2nd order accurate diffusion solver has been implemented for the thermal conduction and radiation transport packages. The code is validated using laser and x-ray driven spall experiments in the US and France. We present an overview of the code and simulation results.

The HiPER project [1] is in a preliminary phase and a risk assessment is being conducted for a generic HiPER beamline concept – this is based on an anticipated requirement for a single beamline (or focal spot unit) drawn from the best available knowledge we have to date of the fusion physics requirement. For the moment the general architecture is to first order independent of the specific beamline implementation (i.e compression phase or ignition phase) as the fundamental requirements are very similar. In this paper we are describing the laser beamline as a bundle of unit beams (or beamlets) and we are explaining that optical zooming is quite possible especially in the case of shock ignition.

The performance of a high-resolution deformable mirror ("HRDM") is analyzed for wavefront correction on the CEA high-power laser baselines in France : the Laser Mégajoule (LMJ), the Laser Integration Line (LIL) and the Petawatt Aquitaine Laser (PETAL). This study is achieved using monochromatic numerical simulations with the CEA "MIRÓ" laser propagation code. When compared to the LMJ deformable mirror used alone, the HRDM located at the L-turn is shown to give equivalent performance at filtering pinholes whereas the HRDM located at injection is less efficient. The use of an HRDM improves the impulse response of the LIL/LMJ main amplifier section. As a consequence, on the PETAL 1ω focal spot, it gives a reduction of factor 2.7 of the radius at 80% of encircled energy and an increase up to 40% of the peak intensity. Finally, maximum mechanical amplitude of 10 nm is numerically evaluated for sinusoidal phase technological defects in the case of the HRDM located at the L-turn.

ALE-AMR is a new hydrocode that we are developing as a predictive modeling tool for debris and shrapnel formation in high-energy laser experiments. In this paper we present our approach to implementing laser ray tracing in ALE-AMR. We present the basic concepts of laser ray tracing and our approach to efficiently traverse the adaptive mesh hierarchy.

The laser-induced damage thresholds in silica glasses at different temperature conditions (123 K – 473 K) by Nd:YAG laser fundamental (wavelength 1064 nm) and third harmonic (wavelength 355 nm) 4 ns of pulses were measured. In the results, the damage thresholds increased at low temperature. At 1064 nm, the temperature dependence became strong by the concentration of impurities. However, at 355 nm, the temperature dependences of almost sample were almost the same for different concentration of impurities.

Spectral broadening is required on high power lasers to avoid Stimulated Brillouin Scattering in the laser chains and to smooth the focal spot. Up to now, spectral broadening has been obtained by sinusoidal phase modulations. However, it leads to non-homogeneous spectra, which is not optimal. In this paper we show that, thanks to non-sinusoidal phase modulations, performance of high power lasers may be enhanced. Furthermore, we demonstrate theoretically and experimentally that adjusting non-sinusoidal phase modulations may be almost as simple as adjusting sinusoidal ones.

Analyses were performed to characterize the radiation field in the vicinity of the Final Optics Assemblies (FOAs) at the National Ignition Facility (NIF) due to neutron activation following Deuterium-Deuterium (DD), Tritium-Hydrogen-Deuterium (THD), and Deuterium-Tritium (DT) shots associated with different phases of the NIF operations. The activation of the structural components of the FOAs produces one of the larger sources of gamma radiation and is a key factor in determining the stay out time between shots to ensure worker protection. This study provides estimates of effective dose rates in the vicinity of a single FOA and concludes that the DD and THD targets produce acceptable dose rates within10 minutes following a shot while about 6-days of stay out time is suggested following DT shots. Studies are ongoing to determine the combined effects of multiple FOAs and other components present in the Target Bay on stay-out time and worker dose.

Theoretical background of stimulated Brillouin scattering (SBS) seeded by a spatially localized optical interference pattern was investigated. Performed analysis revealed that the SBS may have its origin in the acoustic standing wave produced as a transient state between the initial optical interference field and the resulting stationary density modulation. Acquired knowledge can be found valuable in optimization of laser beam combination scheme considered e.g. for IFE applications.

The Neutralized Drift Compression Experiment II (NDCX II) is an induction accelerator planned for initial commissioning in 2012. The final design calls for a ∼3 MeV, ∼30 A Li⁺ ion beam, delivered in a bunch with characteristic pulse duration of 1 ns, and transverse dimension of order 1 mm. The purpose of NDCX II is to carry out experimental studies of material in the warm dense matter regime, and ion beam/hydrodynamic coupling experiments relevant to heavy ion based inertial fusion energy. In preparation for this new machine, we have carried out hydrodynamic simulations of ion-beam-heated, metallic solid targets, connecting quantities related to observables, such as brightness temperature and expansion velocity at the critical frequency, with the simulated fluid density, temperature, and velocity. We examine how these quantities depend on two commonly used equations of state.

As a technique for heating matter to high energy density, intense beams of heavy ions are capable of delivering precise and uniform beam energy deposition to a relatively large sample. The US heavy ion fusion science program has developed techniques for heating and diagnosing warm dense matter (WDM) targets. We have developed a WDM target chamber and a suite of target diagnostics including a fast multi-channel optical pyrometer, optical streak camera, VISAR, and high-speed gated cameras. Initial WDM experiments heat targets by both the compressed and uncompressed parts of the NDCX-I beam, and explore measurement of temperature, droplet formation and other target parameters. Continued improvements in beam tuning, bunch compression, and other upgrades are expected to yield higher temperature and pressure in the WDM targets. Future experiments are planned in areas such as dense electronegative targets, porous target homogenization and two-phase equation of state.

An alternative concept for Heavy Ion Inertial Fusion (HIF) is the use of a recirculator to accelerate ion beams to energies in the range of 50–100 GeV [1]. The physics of an ion recirculator can be explored by means of scaled experiments in a compact machine like the existing University of Maryland Electron Ring (UMER). UMER has been successfully used for the study of the fundamental physics of space-charge-dominated transport using a 10 keV electron beam with up to 100 mA of current (or 10 nC per a 100 ns pulse) [2]. Due to the low energy and high perveance, the UMER beam accesses the same range of intensities as an HIF driver. In this paper we report on a computational study for the design of an acceleration stage for UMER using an induction cell. Using the two-dimensional transverse slice model in the particle-in-cell code WARP we show that it is possible to accelerate the UMER beam up to 20 keV without major modifications to the machine. Such acceleration enables future experiments on transverse resonance crossing and studies on longitudinal pulse behavior.

The shaping of the x-ray radiation pulse is very important in both radiation physics research and Inertial Confinement Fusion studies. The novel planar wire array (PWA) was found to be the effective radiator tested at the university-scale 1.6 MA, 100 ns Zebra generator. The single PWA consists of a single row of wires that are parallel to each other, while the double planar wire array (DPWA) and triple planar wire array (TPWA) include two or three parallel plane wire rows, respectively. All multi-planar geometries resulted in a cascade-type array implosion with a complicated multi-step precursor formation before plasma stagnation. The PWAs (without additional core foam target) feature a dynamic precursor evolution that is a powerful tool for x-ray pulse shaping. The shape and timing of the x-ray pulse from different PWAs were theoretically predicted and experimentally analyzed for a variety of planar wire arrays.

University-scale Z-pinch devices are able to produce plasmas with a broad range of sizes, temperatures, densities, their gradients, and opacity properties. Radiative properties of such plasmas depend on material, mass, and configuration of the wire array loads. Experiments with two different types of loads, double planar wire arrays (DPWA) and X-pinches, performed on the 1 MA Zebra generator at UNR are analyzed. X-pinches are made from Stainless Steel (69% Fe, 20% Cr, and 9% Ni) wires. Combined DPWAs consist of one plane from SS wires and another plane from Alumel (95% Ni, 2% Al, 2% Si) wires. The main focus of this work is on the analysis of plasma jets at the early phase of plasma formation and the K-and L-shell radiation generation at the implosion and stagnation phases in experiments with the two aforementioned wire loads. The relevant theoretical tools that guide the data analysis include non-LTE collisional-radiative and wire ablation dynamics models. The astrophysical relevance of the plasma jets as well as of spectroscopic and imaging studies are demonstrated.

The BUCKY 1-D radiation hydrodynamics code has been used to simulate the dynamic thermo-mechanical interaction between a xenon gas-filled chamber and tungsten first-wall armor with an indirect-drive laser fusion target for the LIFE reactor design.

Two classes of simulations were performed: (1) short-time (0–2 ms) simulations to fully capture the hydrodynamic effects of the introduction of the LIFE indirect-drive target x-ray and ion threat spectra and (2) long-time (2–70 ms) simulations starting with quiescent chamber conditions characteristic of those at 2 ms to estimate xenon plasma cooling between target implosions at 13 Hz.

The short-time simulation results reported are: (1) the plasma hydrodynamics of the xenon in the chamber, (2) dynamic overpressure on the tungsten armor, and (3) time-dependent temperatures in the tungsten armor. The ramifications of local thermodynamic equilibrium (LTE) vs. non-LTE opacity models are also addressed.

First-of-a-kind experiments on cluster/aerosol formation by colliding ablation plumes have been conducted, radiating Al, Cu and C with 3ω-YAG laser at power densities between 2∼30 J/cm²/pulse. Visible spectroscopy indicates that the excitation light intensities of Cu and Al plumes are not necessarily be doubled in collision, but can rather be weakened due to atomic and molecular reactions. For colliding C plumes, Swan band radiation has been observed, indicative of C₂ and/or C₂⁺ formation, and ion mass spectrometry has identified C_n⁺-clusters, including C⁺, C₂⁺, C₃⁺, C₄⁺ and C₅⁺. From ICCD camera observations, C plumes generated at power densities above ∼15 J/cm²/pulse tend to split into two components with respective velocities, only the slow component of which appears to be interactive to form clusters. Nano structures like CNT have been identified in deposits from colliding C plumes.

Current status of SBS PCM based IFE approach proposed recently as an alternative to the IFE classical approach is presented. This technology is of particular importance to the direct drive scheme taking care of automatic self-navigation of every individual laser beam on the injected pellets with no need for any final optics adjustment. Conceptual design of one typical laser driver is shown and its features discussed. In comparison with the earlier design an upgraded scheme was developed with the low energy illumination laser beam (glint) entering the reactor chamber through the same entrance window as used by the corresponding high energy irradiation laser beam. Results of experimental verification of this improved design are reported. In these experiments for the fist time a complete setup including the pellet (realized by the static steel ball) was employed. The pellet survival conditions in the period between its low energy illumination and subsequent high energy irradiation were studied and the upper limits on the allowed energies absorbed were found for both DD and DT fuels.

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.

Our recent research has developed a technique for imbedding ultra high density deuterium "clusters" (D cluster) in Palladium (Pd) thin film. Experiments have shown that in Pd these condensed matter state clusters approach metallic conditions, exhibiting super conducting properties. This deuterium cluster is achieved through electrochemically loading-unloading deuterium into a thin metal film, such as Palladium (Pd). During the loading process, Palladium lattice expands significantly due to invasion of deuterium into the interstitial sites. With the large enough stress, some linear lattice imperfections, called dislocations, form at / transformation interface. These dislocation defects form a strong potential trap causing deuterium to condense. In the present study, a new method employing nano-structuring of the Pd is proposed to significantly improve the site density over the target volume, suggesting that a sizable region of the compressed target deuterium can reach densities an order of magnitude higher than possible with prior target designs. This improved cluster packing fraction will enable a significant increase of the fusion reaction burn density, hence the target burn-up efficiency.

To carry out laser plasma experiments on CEA laser facilities, a R&D program was set up and is still under way to deliver complex targets. For a decade, specific developments are also dedicated to "Ligne d'Intégration Laser" (LIL) in France and Omega facilities (USA). To prepare the targets intended for the first experiments on the Laser "Mégajoule" (LMJ) facility, new developments are required, such as cocktail hohlraum fabrication, gas barrier coating and foam shells developments. For fusion experiments on LMJ, an important program is also under way to elaborate the Cryogenic Target Assembly (CTA), to fill and transport the CTA and to study the conformation process of the DT layer.

This paper reports on way to fabricate a gas-tight targets dedicated for the first stage of Fast Ignition Realization Experiment (FIREX-I) at the Institute of Laser Engineering (ILE), Osaka University. It was found that a Ti;sapphire laser machining can be used to fabricate the target. The performance of the laser machining using a fs Ti;sapphire laser was examined on shell materials. The conditions for accurate machining were determined. Michelson interferometer with two different wavelengths which imitates a white light interferometer is an excellent tool for confirming the gas-tightness of the target after assembly.

A new procedure of fuel layering for the Fast Ignition Realization Experiment (FIREX) target is proposed. A conical laser guide heating technique was experimentally demonstrated in principle as the followings. It employed the target consisting of a polystyrene (PS) shell, a fill tube and a conical laser guide. At first, liquid fuel was fed into the shell and existed around the conical laser guide because the surface tension of the fuel must cause it. Then, it was solidified. The laser light provided a heat source to the conical laser guide so that the solid fuel was moved to the other interior of the shell. This process resulted in missing solid fuel around the conical laser guide. To fill the vacant space, liquid fuel was added as temperature was raised to the melting point. After the liquid fuel addition, temperature was lowered to the solidification point again. During this process, most of the solid fuel could survive.

Current ICF and HED targets are fielded on Omega, Z, and Trident; future campaigns will also be fielded on NIF. NIF will field less than 2 shots per day. With such few experiments, target fabrication and alignment accuracy, enhanced metrology and advanced component machining will be even more important. Future target designs are also becoming more complex and more stringent in terms of both manufacturing accuracy and precision. Several steps have been taken to improve the fabrication and characterization of targets, such as instituting an automated assembly station with 3 μm tolerances, utilizing non-destructive characterization tools for rapid component metrology and target assembly, and advancing machining capabilities. Recapitalization of target fabrication infrastructure is continuous.

Experimental results are presented on the neutron scintillating properties of a custom-designed Praseodymium-doped Lithium-6 glass for a new deuterium-deuterium (DD) fusion scattered-neutron detector. Luminescence was observed at 278 nm-wavelength, and time-resolved measurement yielded ∼5.4 ns decay time for neutron excitation. Actual time-of-flight data in laser fusion experiments at the GEKKO XII facility at the Institute of Laser Engineering (ILE), Osaka University reveal that it can clearly discriminate fusion primary-neutrons from the x-ray signals. This material promises the realization of more accurate DD fusion scattered-neutron diagnostics. Design work for a scattered-neutron detector is being conducted for the Fast Ignition Realization Experiment (FIRE-X) at ILE.

We present an overview of recent experiments fielded on the LIL facility. A key issue for mega-joule class laser facilities is shrapnel fragment generation. A specific collector was therefore developed to capture debris in aerogel and dedicated shots were done to quantitatively evaluate target fragmentation phenomena. The LIL panel of transmitted and backscattered light diagnostics is well suited for laser-plasma interaction (LPI) experiments. This include gas-filled hohlraum configurations relevant to Indirect Drive ignition targets in order to test the specific LMJ longitudinal SSD technique, as well as LPI experiments with foam targets for laser beam smoothing in underdense plasma in the context of Direct Drive. After Visar commissioning a campaign was dedicated to boron Equation of State (EOS).

Results are shown from recent experiments at the Omega laser facility, using 40 Omega beams driving the hohlraum with 3 cones from each side and up to 19.5 kJ of laser energy. Beam phasing is achieved by decreasing the energy separately in each of the three cones, by 3 kJ, for a total drive energy of 16.5 kJ. This results in a more asymmetric drive, which will vary the shape of the imploded symmetry capsule core from round to oblate or prolate in a systematic and controlled manner. These results show the sensitivity of capsule implosion symmetry for implosions in "high temperature" (275 eV) hohlraums at Omega. Dante measurements confirmed the predicted peak drive temperatures of 275 eV. Implosion core time dependent x-ray images were obtained from framing camera data which show the expected change in symmetry due to beam imbalance and which also agree well with post processed hydro code calculations.

We are developing a target platform that utilizes short-pulse (10 ps) generated hot electrons (∼200 keV) to isochorically heat solid density beryllium up to temperatures of several 10 eV. We use x-ray Thomson scattering to characterize the plasma conditions. X-rays from a Cl Ly-α line source at 2.96 keV are scattered off the plasma in forward direction where the inelastically scattered signal is sensitive to plasma oscillations. Besides Landau-damping the strong energy down-shifted plasmon signal is also broadened by electron-ion collisions which, in turn, allows to infer the collision rate and thus the conductivity in these plasmas. A precise knowledge of the collisionality in the parameter regime we are aiming at with these experiments is important to correctly model the conditions encountered during capsule implosions at the National Ignition Facility.

Triature Photon Doppler Velocimetry (TDV) is an adaptation of Photonic Doppler Velocimetry (PDV) that rejects common-mode data noise after splitting PDV three ways, with each signal 120° out of phase from each other. Testing has demonstrated that the TDV also improves temporal resolution from the typical five-nanoseconds of PDV to a subnanosecond range. This paper compares the temporal response of TDV with that of PDV and VISAR [velocity interferometer system for any reflector] in an experiment with a subnanosecond (∼120-picosecond rise time) shock source.

Laboratory tests were performed using a high-power laser on targets of copper and aluminum. A fast VISAR with a single-point PDV and a prototype TDV were used. A special probe that combined PDV, TDV, and fast VISAR made simultaneous velocity measurements. Breakout velocities of 1.3 km/second on copper and 2.5 km/second on aluminum were observed, where TDV resolved rise times of ∼200 ps. This resolution was better than that of a fast VISAR, which can achieve ∼500 ps temporal resolution. Test methods and results are presented.

At the recently completed National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, the initial set of diagnostics to be deployed are focused on measuring neutrons and γ's generated by d(t,n)α reactions in the imploded capsule. Although valuable for understanding pre-ignition experiments, this abbreviated diagnostic suite provides an incomplete picture of the plasma conditions obtained. Prompt radiochemical techniques, based on induced neutron and charged particle reactions within the imploded target, provide a novel and interesting new perspective. To enable these techniques requires the collection and assay of activated target material. In Nov. 2008, experiments were performed using the Omega Laser at the University of Rochester to study the efficiency of collecting debris from directly driven targets. Results from these experiments indicate that target debris was successfully collected, and the debris thermalization and transport scheme enhanced the debris collection up to 347% over direct collection.

Reaction history measurements, such as nuclear bang time and burn width, are fundamental components of diagnosing ICF implosions and will be employed to help steer the National Ignition Facility (NIF) towards ignition. Fusion gammas provide a direct measure of nuclear interaction rate (unlike x-rays) without being compromised by Doppler spreading (unlike neutrons). Gas Cherenkov Detectors that convert fusion gamma rays to UV/visible Cherenkov photons for collection by fast optical recording systems have established their usefulness in illuminating ICF physics in several experimental campaigns at OMEGA. In particular, bang time precision better than 25 ps has been demonstrated, well below the 50 ps accuracy requirement defined by the NIF. NIF Gamma Reaction History (GRH) diagnostics are being developed based on optimization of sensitivity, bandwidth, dynamic range, cost, and NIF-specific logistics, requirements and extreme radiation environment. Implementation will occur in two phases. The first phase consists of four channels mounted to the outside of the target chamber at ∼6 m from target chamber center (GRH-6m) coupled to ultra-fast photo-multiplier tubes (PMT). This system is intended to operate in the 10¹³–10¹⁷ neutron yield range expected during the early THD campaign. It will have high enough bandwidth to provide accurate bang times and burn widths for the expected THD reaction histories (> 80 ps fwhm). Successful operation of the first GRH-6m channel has been demonstrated at OMEGA, allowing a verification of instrument sensitivity, timing and EMI/background suppression. The second phase will consist of several channels located just inside the target bay shield wall at 15 m from target chamber center (GRH-15m) with optical paths leading through the cement shield wall to well-shielded streak cameras and PMTs. This system is intended to operate in the 10¹⁶–10²⁰ yield range expected during the DT ignition campaign, providing higher temporal resolution for the expected burn widths of 10–20 ps associated with ignition. Multiple channels at each phase will allow for increased redundancy, reliability, accuracy and flexibility. In addition, inherent energy thresholding capability combined with this multiplicity will allow exploration of interesting gamma-ray physics well beyond the ignition campaign.

A micro-channel plate based temporally-gated x-ray camera (framing camera) is one of the most versatile diagnostic tools of inertial confinement fusion experiments; particularly for observation of the shape of x-ray self emission from compressed core of imploded capsules. However, components used in an x-ray framing camera have sensitivity to various kinds of secondary radiation induced by neutron. On early low-yield capsule implosions at the National Ignition Facility (NIF), the expected neutron production is about 5×10¹⁴. Therefore, the expected neutron fluence at a framing camera located ∼ 150 cm from the object is 2×10⁹ neutrons/cm². To obtain gated x-ray images in such harsh neutron environments, quantitative understanding of neutron-induced backgrounds is crucial.

Experiments resulting in a significant neutron yield are scheduled to start in 2010 at the National Ignition Facility (NIF). A wide range of diagnostics will be used to measure several parameters of implosion such as the core and fuel shape, temperatures and densities, and neutron yield. Accurate evaluations of the neutron and gamma backgrounds are important for several diagnostics. Several Monte-Carlo simulations were performed to identify the expected signal to background ratios at several potential locations for the High Energy X-ray Imager (HEXRI) diagnostics. Gamma backgrounds were significantly reduced by using tungsten collimators. The collimators resulted in the reduction of the gamma background at the HEXRI scintillators by more than an order of magnitude during the first 40 ns following a Tritium-Hydrogen-Deuterium (THD) shot.

A secondary gamma experiment was carried out using a Gas Cherenkov Detector (GCD) at the OMEGA laser facility. The primary experimental objective was to simulate neutron-induced secondary gamma production (n-γ) from a NIF implosion capsule, hohlraum, and thermo-mechanical package. The high-band width of the GCD enabled us to detect time delayed and Doppler broadened n-γ signals from five different puck materials (Si, SiO₂, Al, Al₂O₃, Cu) placed near target chamber center. These measurements were used for MCNP & ITS ACCEPT code validation purposes. By a simple change of the GCD CO₂ gas pressure the system can effectively eliminate signals induced by n-γ reactions and thereby allow quality measurements of DT fusion γ-rays that are produced at NIF (National Ignition Facility).

Neutron imaging is currently being developed as a primary diagnostic for inertial fusion studies at the National Ignition Facility (NIF). It is an attractive diagnostic for measuring asymmetries in the burn region and will be able to operate at neutron fluences found during ignition scale implosions. The most straightforward technique for imaging of the spatial distribution of deuterium-tritium (DT) fusion neutrons utilizes a simple pinhole aperture, which blocks all neutrons outside of the solid angle defined by the pinhole and results in a blurred image at the detector. We are currently investigating source image reconstruction techniques from detector images. Source reconstructions from Monte Carlo neutron transport (MCNP) calculations are shown to emulate hydrodynamic simulations with imposed Legendre asymmetries to high accuracy.

Gas Cherenkov detectors have been used to convert fusion gammas into photons to record gamma reaction history measurements. These gas detectors include a converter, pressurized gas volume, relay collection optics, and a photon detector. A novel design for the National Ignition Facility (NIF) using 90° off-axis parabolic mirrors efficiently collects signal from fusion gammas with 8-ps time dispersion. Fusion gammas are converted to Compton electrons, which generate broadband Cherenkov light (response is from 250 to 700 nm) in a pressurized gas cell. This light is relayed into a high-speed detector using three parabolic mirrors. The relay optics collect light from a 125-mm-diameter by 600-mm-long interchangeable gas (CO₂ or SF₆) volume. The parabolic mirrors were electroformed instead of diamond turned to reduce scattering of the UV light. All mirrors are bare aluminum coated for maximum reflectivity. This design incorporates a 4.2-ns time delay that allows the detector to recover from prompt radiation before it records the gamma signal. At NIF, a cluster of four channels will allow for increased dynamic range, as well as different gamma energy thresholds.

Interactions of high-intensity femtosecond lasers with deuterium clusters leading to Coulombic explosions and subsequent production of fusion neutrons attracted in recent years considerable attention. In order to maximize the neutron yield finding a dependence of clusters size and their spatial distribution on experimental conditions became very important. In this paper a possibility to measure the deuterium clusters spatial distributions experimentally was analyzed. In combination with experiments recently performed in the Laboratory of Quantum Optics at the Korea Atomic Energy Research Institute (KAERI) interferometry was identified as the diagnostics suitable for such measurements.

Polar-drive (PD) target implosions have been designed for neutron diagnostic development on the NIF. These experiments use thin, room-temperature glass shells filled with low pressures of DT. Initial target implosions on the NIF will produce DT yields in the range of a few 10¹⁴ neutrons. The predicted yields are consistent with earlier data (10¹⁴ neutrons at 30 kJ) and recent PD scoping experiments performed on OMEGA. The experiments will use existing x-ray-drive phase plates with judicious repointing and defocusing to drive the implosions as uniformly as possible. These implosions have been modeled with three codes: LILAC, to optimize the 1-D design; SAGE, to optimize the pointing uniformity; and DRACO, to predict the yield from 2-D implosion simulations. Current simulation results indicate that the required yields will be obtained using up to 200-kJ UV light formed into a 1500-ps Gaussian pulse. Large-diameter glass shells (∼1500-μm OD) are under development and fabrication at General Atomics. As tritium and environmental conditions evolve, similar target designs, with larger diameters and higher laser energies, are expected to produce thermonuclear yields approaching 10¹⁶ neutrons.

We present the details of the analog fiber-optic data link that will be used in the chamber-mounted Gamma Reaction History (GRH) diagnostic at the National Ignition Facility (NIF) located at the Lawrence Livermore Laboratory in Livermore, California. The system is based on Mach-Zehnder (MZ) modulators integrated into the diagnostic, with the source lasers and bias control electronics located remotely to protect the active electronics. A complete recording system for a single GRH channel comprises two MZ modulators, with the fiber signals split onto four channels on a single digitizer. By carefully selecting the attenuation, the photoreceiver, and the digitizer settings, the dynamic range achievable is greater than 1000:1 at the full system bandwidth of greater than 10 GHz. The system is designed to minimize electrical reflections and mitigate the effects of transient radiation darkening on the fibers.

A novel x-ray imager, consisting of two toroidally bent Bragg crystals and a 2D image sampler using a conventional x-ray streak camera, has been demonstrated for use in fast ignition resaerch. Sequential and 2D monochromatic x-ray images of laser-imploded core plasma were successfully obtained with a temporal resolution of 20 ps, a spatial resolution of 31 μm, and a spectral resolution of over 200, simultaneously.

Lasnex calculations and x-ray flux measurements are presented for a series of NIF vacuum hohlraum experiments that were among the first targets shot on NIF as part of the facility commissioning. An important result is that the hohlraum x-ray fluxes are significantly higher than predicted by pre-shot Lasnex calculations employing the baseline "configuration managed" physics packages used in the NIF ignition target calculations. A possible explanation for the high-flux vacuum hohlraum result has been explored via post-shot calculations in which non-baseline emissivity and heat conduction models are used.

An analytic model for the gamma reaction history (GRH) diagnostic to be fielded on the National Ignition Facility is described. The application of the GRH diagnostic for the measurement of capsule rho-R during burn using 4.4 MeV carbon gamma rays is demonstrated by simulation.

Measurements of yield and spatial distribution of fast neutrons are of extreme importance in the inertial confinement fusion research to estimate the spatial distribution of temperature in core plasma. In experiments using an ultra intense laser light such as fast ignition research, strong electromagnetic pulses generated by the laser irradiation make it very difficult to use a detector with an electric circuit. In order to avoid this problem, we have developed several detectors to measure fast electrons, X-ray, and so on under these environments using an imaging plate (IP). Here, we demonstrate the simple fast neutron detection method by using a stack of IPs. In the experiment using a monochromatic 14MeV neutron source, the IP has linear response to quantity of incident neutrons within the fluence from 10⁴ to 10⁹. The minimum neutron yield measureable by the detector is estimated to 10³ or less depending on detection efficiency.

We report on experiments aimed at obtaining laser-imploded core plasma temperature maps using two color, monochromatic x-ray imager. This instrument uses two toroidally bent Bragg crystals and a high-speed sampling imager to provide spatial resolution of 25 μm, temporal resolution of 20 ps, and spectral resolution over 200, simultaneously. Using a deuterated plastic shell target filled with CHClF₂ gas, time-resolved monochromatic x-ray images in the Cl-He_β and Cl-Ly_β were successfully obtained.

Imaging of nuclear reaction region is important to clarify heating mechanism in a fast-ignition plasma. The nuclear reaction region can be identified by hard x-ray and neutron images, which are emanated from the heated region. We proposed a novel penumbral imaging that is suitable for imaging quanta having strong penetrating power, such as hard x ray and neutron. Using multiple penumbral apertures arranged with M-sequence leads to two orders of magnitude higher detection efficiency than that with a single aperture. In addition, a heuristic method was introduced to a image reconstruction procedure for reducing artifacts caused by noise in a penumbral image. A proof-of-principle experiment indicates that the proposed imaging is superior to the conventional one.