Millimeter-sized CD foils fielded close (order mm) to inertial confinement fusion (ICF) implosions have been proposed as a game-changer for improving energy resolution and allowing time-resolution in neutron spectrum measurements using the magnetic recoil technique. This paper presents results from initial experiments testing this concept for direct drive ICF at the OMEGA Laser Facility. While the foils are shown to produce reasonable signals, inferred spectral broadening is seen to be high (∼5 keV) and signal levels are low (by ∼20%) compared to expectation. Before this type of foil is used for precision experiments, the foil mount must be improved, oxygen uptake in the foils must be better characterized, and impact of uncontrolled foil motion prior to detection must be investigated.

Experiments on the National Ignition Facility (NIF) to study hohlraums lined with a 20-mg/cc 400-μm-thick Ta_{2}O_{5} aerogel at full scale (hohlraum diameter = 6.72 mm) are reported. Driven with a 1.6-MJ, 450-TW laser pulse, the performance of the foam liner is diagnosed using implosion hot-spot symmetry measurements of the high-density carbon (HDC) capsule and measurement of inner beam propagation through a thin-wall 8-μm Au window in the hohlraum. Results show an improved capsule performance due to laser energy deposition further inside the hohlraum, leading to a modest increase in x-ray drive and reduced preheat due to changes in the x-ray spectrum when the foam liner is included. In addition, the outer cone bubble uniformity is improved, but the predicted improvement in inner beam propagation to improve symmetry control is not realized for this foam thickness and density.

The next-generation Magnetic Recoil Spectrometer, called MRSt, will provide time-resolved measurements of the deuterium-tritium-neutron spectrum from inertial confinement fusion implosions at the National Ignition Facility. These measurements will provide critical information about the time evolution of the fuel assembly, hot-spot formation, and nuclear burn. The absolute neutron spectrum in the energy range of 12-16 MeV will be measured with high accuracy (∼5%), unprecedented energy resolution (∼100 keV) and, for the first time ever, time resolution (∼20 ps). Crucial to the design of the system is a CD conversion foil for the production of recoil deuterons positioned as close to the implosion as possible. The foil-on-hohlraum technique has been demonstrated by placing a 1-mm-diameter, 40-μm-thick CD foil on the hohlraum diagnostic band along the line-of-sight of the current time-integrated MRS system, which measured the recoil deuterons. In addition to providing validation of the foil-on-hohlraum technique for the MRSt design, substantial improvement of the MRS energy resolution has been demonstrated.

Polar-direct-drive exploding pushers are used as a high-yield, low-areal-density fusion product source at the National Ignition Facility with applications including diagnostic calibration, nuclear security, backlighting, electron-ion equilibration, and nucleosynthesis-relevant experiments. In this paper, two different paths to improving the performance of this platform are explored: (i) optimizing the laser drive, and (ii) optimizing the target. While the present study is specifically geared towards nucleosynthesis experiments, the results are generally applicable. Example data from T2/3He-gas-filled implosions with trace deuterium are used to show that yield and ion temperature (Tion) from 1.6 mm-outer-diameter thin-glass-shell capsule implosions are improved at a set laser energy by switching from a ramped to a square laser pulse shape, and that increased laser energy further improves yield and Tion, although by factors lower than predicted by 1 D simulations. Using data from D2/3He-gas-filled implosions, yield at a set Tion is experimentally verified to increase with capsule size. Uniform D3He-proton spectra from 3 mm-outer-diameter CH shell implosions demonstrate the utility of this platform for studying charged-particle-producing reactions relevant to stellar nucleosynthesis.

We present narrow-band self-emission x-ray images from a titanium tracer layer placed at the fuel-shell interface in 60-laser-beam implosion experiments at the OMEGA facility. The images are acquired during deceleration with inferred convergences of ∼9-14. Novel here is that a systematically observed asymmetry of the emission is linked, using full sphere 3D implosion modeling, to performance-limiting low mode asymmetry of the drive.

Planar components made from glow discharge polymer (GDP) are commonly used in laser inertial fusion experiments. The thickness profile of GDP coatings on flat substrates follows a nearly Gaussian distribution with a full-width at half-maximum only 20 nun across, restricting the number of usable components with the same thickness that can be made from each substrate. A new coating method to improve the thickness uniformity and increase the usable area of GDP coatings has been simulated and involves rotating the planar substrate while it is offset from the center of the coating chamber. While the coating rate drops to about 40% at the center, the thickness variation is less than 10% out to a radius of 10 mm, increasing the usable area by a factor of over 7, thereby increasing the number of components that can be made from a single coating.

The Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility measures the DT neutron spectrum from cryogenically layered inertial confinement fusion implosions. Yield, areal density, apparent ion temperature, and directional fluid flow are inferred from the MRS data. This paper describes recent advances in MRS measurements of the primary peak using new, thinner, reduced-area deuterated plastic (CD) conversion foils. The new foils allow operation of MRS at yields 2 orders of magnitude higher than previously possible, at a resolution down to ∼200 keV FWHM.

The magnetic recoil spectrometer uses a deuterated polyethylene polymer (CD2) foil to measure neutron yield in inertial confinement fusion experiments. Higher neutron yields in recent experiments have resulted in primary signal saturation in the detector CR-39 foils, necessitating the fabrication of thinner CD2 foils than established methods could provide. A novel method of fabricating deuterated polymer foils is described. The resulting foils are thinner, smoother, and more uniform in thickness than the foils produced by previous methods. These new foils have successfully been deployed at the National Ignition Facility, enabling higher neutron yield measurements than previous foils, with no primary signal saturation.

Capsules for inertial confinement fusion require precise measurement of isolated features and domes on the capsule's outer suiface. Features that are too large must be removed. A 4pi capsule mapping and characterization system has been developed to map, identify, and measure domes using a Leica confocal microscope. An ultraviolet wavelength laser was integrated to laser-ablate the offending domes that exceed the allowable mix mass. Current process methods to remove domes require three different stations in different locations. The 4pi system achieves automated capsule handling, metrology, and laser polishing/ablation of domes on one device without losing track of the capsule's orientation. The measurement technique and metrology accuracy are compared to patch atomic force microscopy scans and phase-shifting diffraction inteiferometer measurements with good correlation. The laser polishing method has demonstrated analogous results to the current process methods, but in an automated fashion. Additionally, the 4pi capsule-handling capability of the system has been used to laser-ablate purposeful engineered designs into specialty capsules.

Deuterated polyethylene films as thin as 50 mu m have been produced using a four-post heated press method. These films are then cut into the desired shape (foil) and are used for the magnetic recoil spectrometer (MRS). The MRS is a diagnostic tool for inertial confinement fusion (ICF) experiments at the National Ignition Facility (NIF) and at the OMEGA Laser Facility at the University of Rochester Laboratory for Laser Energetics. The films produced by this method are more uniform and have fewer defects than foils prepared by previous methods. Whereas traditional films had a thickness limitation of 100 mu m, this new heat pressing method allows the fabrication of 50-mu m films, which is the desired thickness for MRS foils. The foils produced and characterized by General Atomics have decreased the neutron measurement uncertainty of the MRS instrument by a factor of 2 compared to the previous foils. This work has also been extended to fabricate thin polymer films and films with sinusoidal patterns from other polymeric materials for ICF experiments. This paper will discuss the heat pressing technique used in the fabrication of these films for the NIF and OMEGA MRS as well as other patterned and flat polymer films. The morphology of these foils and the advantages that they provide will also be discussed.

Abstract Energy partitioning, energy coupling (EPEC) is one of the new experimental platforms being investigated at the National Ignition Facility (NIF) to provide valuable data for national security applications. The EPEC target is a 7-μm-thick silver spherical halfraum driven by a single NIF quad. This paper will describe the fabrication of the hollow spherical target, starting with the selection of the mandrel, the single-point diamond turning process used to achieve the desired thickness, and the final processing to remove the mandrel. Also discussed will be the metrology technique, X-ray opacity, used to determine the wall thickness and wall uniformity and how this nondestructive technique was benchmarked by two destructive characterization techniques, dual focused ion beam and scanning electron microscope, for wall thickness determination.

Capsules for the National Ignition Facility require measurement of isolated defects on the capsule surface. A phase-shifting diffraction interferometer (PSDI) is used to identify, locate, and measure defects by capturing 71 overlapping similar to 500-mu m-diam charge coupled device height maps for software analysis. Using capsules with drilled holes for the purpose of alignment, PSDI data were con firmed with atomic force microscopy by comparing defect data from corresponding equatorial bands. We explored the limitations of the PSDI resulting from unwrapping errors caused by defect slopes greater than the Nyquist sampling theorem. White light interferometry proved to be a useful complementary tool to measure defects that could not be unwrapped by the analysis software. Implementing the PSDI in conjunction with the shell flipper, both developed at Lawrence Livermore National Laboratory, allowed for full mapping of shell surfaces by mounting corresponding hemispheres onto the PSDI within a 2-deg accuracy.

The inertial confinement fusion program requires the uniformity of multilayered samples to be measured to high accuracy. We currently use a reflection spectroscopy tool to measure optically transparent shells with no more than two layers. The method cannot measure opaque samples such as beryllium shells, low-reflection samples such as foam shells, or any shells with more than two layers such as National Ignition Facility specification Ge-CH shells. We also use a white-light interferometer to measure transparent samples with multiple layers, but only at the North/South Poles for a given orientation. To complement these existing tools, we developed an X-ray technique based on a commercial X-ray microscope (Xradia MicroXCT). MicroXCT is capable of providing high-contrast, high-resolution images and allows the samples to be precision aligned and angular indexed. Dimension accuracy is achieved through the calibration of the projection magnification and the lens distortion. From each X-ray image, a wall thickness trace along the great circle is obtained by converting Cartesian coordinates into cylindrical coordinates, and edge-finding algorithms are developed for a contact radiography project. Three-dimensional reconstruction and wall thickness display allow the visualization of the sample nonuniform The method has a 0.3 mu m measurement precision and, through phase contrast calibration, can achieve 0.3 mu m accuracy.