[en] The field of nuclear diagnostics for Inertial Confinement Fusion (ICF) is broadly reviewed from its beginning in the seventies to present day. During this time, the sophistication of the ICF facilities and the suite of nuclear diagnostics have substantially evolved, generally a consequence of the efforts and experience gained on previous facilities. As the fusion yields have increased several orders of magnitude during these years, the quality of the nuclear-fusion-product measurements has improved significantly, facilitating an increased level of understanding about the physics governing the nuclear phase of an ICF implosion. The field of ICF has now entered an era where the fusion yields are high enough for nuclear measurements to provide spatial, temporal and spectral information, which have proven indispensable to understanding the performance of an ICF implosion. At the same time, the requirements on the nuclear diagnostics have also become more stringent. To put these measurements into context, this review starts by providing some historical remarks about the field of ICF and the role of nuclear diagnostics, followed by a brief overview of the basic physics that characterize the nuclear phase and performance of an ICF implosion. A technical discussion is subsequently presented of the neutron, gamma-ray, charged-particle and radiochemistry diagnostics that are, or have been, routinely used in the field of ICF. This discussion is followed by an elaboration of the current view of the next-generation nuclear diagnostics. Since the seventies, the overall progress made in the areas of nuclear diagnostics and scientific understanding of an ICF implosion has been enormous, and with the implementation of new high-fusion-yield facilities world-wide, the next-generation nuclear diagnostics will play an even more important role for decades to come. (topical review)

[en] The basis for a time-of-flight neutron spectrometer for inertial confinement fusion (ICF) experiments using recoils from a shaped scattering foil is presented. It is shown that the number of elastic recoils can be substantially increased by utilizing a large scattering foil in the shape of an ellipsoid, with the curvature of the ellipsoid being determined by the mass of the recoil particle. This shape allows the time-of-flight dispersion -- present originally in the neutrons -- to be maintained in the recoils despite the large foil area. The feasibility of using this design on current ICF experiments is discussed

[en] Spectral measurements have been made of charged fusion products produced in deuterium + helium-3 filled targets irradiated by the OMEGA laser system [T. R. Boehly , Opt. Commun. 133, 495 (1997)]. Comparing the energy shifts of four particle types has allowed two distinct physical processes to be probed: Electrostatic acceleration in the low-density corona and energy loss in the high-density target. When the fusion burn occurred during the laser pulse, particle energy shifts were dominated by acceleration effects. Using a simple model for the accelerating field region, the time history of the target electrostatic potential was found and shown to decay to zero soon after laser irradiation was complete. When the fusion burn occurred after the pulse, particle energy shifts were dominated by energy losses in the target, allowing fundamental charged-particle stopping-power predictions to be tested. The results provide the first experimental verification of the general form of stopping power theories over a wide velocity range

[en] The use of measured spectra of secondary fusion protons for studying physical characteristics of D₂-filled inertial confinement fusion capsules is described theoretically and demonstrated with data from implosions in the OMEGA 60-beam laser facility. Spectra were acquired with a magnet-based charged-particle spectrometer and with a range-filter-based spectrometer utilizing filters and CR39 nuclear track detectors. Measurement of mean proton energy makes possible the study of a capsule's total areal density (ρR), since that is what affects the energy loss suffered by protons as they pass through fuel and shell while leaving the capsule. Details of specific shots will be presented. It is also shown that similar techniques should prove useful for diagnosis of future experiments with cryogenic D₂-filled capsules

[en] Fast protons ∼>1 MeV have been observed on the 60-beam, 30 kJ OMEGA laser [T. R. Boehly , Opt. Commun. 133, 495 (1997)] at an intensity I≅10¹⁵ W/cm² and a wavelength λ=0.35 μm. These energies are more than 5 times greater than those observed on previous, single-beam experiments at the same Iλ². The total energy in the proton spectrum above 0.2 MeV is ∼0.1% of the laser energy. Some of the proton spectra display intense, regular lines which may be related to ion acoustic perturbations in the expanding plasma

[en] A fusion-product source, utilizing a 150 kV Cockraft-Walton linear accelerator, has been refurbished to provide a reliable nuclear diagnostic development tool to the national inertial confinement fusion (ICF) research program. The accelerator is capable of routinely generating DD reaction rates at ∼10⁷/s when using a 150 kV, 150 μA deuterium (D) beam onto an erbium (Er) or titanium (Ti) target doped with D, and D³He reaction rates at ∼5x10⁵/s when using a using a 120 kV, ∼100 μA D beam onto a Er or Ti target doped with ³He. The new accelerator is currently being used in a number of projects related to the national ICF program at the OMEGA Laser Fusion Facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], which includes the wedge range filter charged-particle spectrometry program [F. H. Seguin et al., Rev. Sci Instrum. 75, 3520 (2004)] and the magnetic recoil neutron spectrometer [J. A. Frenje et al., Rev. Sci. Instrum. 72, 854 (2001)]

[en] Charging of inertial confinement fusion (ICF) targets generates a potential well that traps energetic electrons within the target. Trapped electrons can preheat the fuel, raise the adiabat, degrade compression and perhaps have an effect on achieving the high areal densities (ρR) required for ignition and gain. The decay time of this potential is thus an important parameter for any calculations of preheat. A nonlinear model of electrical discharging of ICF capsules has been developed and is presented here. The empirical model, which captures the essential dynamics of the target voltage decay, incorporates previous charged-particle spectroscopic and radiographic measurements of the fields surrounding the target. On the basis of this model, it is shown that the decay time is weakly dependent on the initial voltage of the target. In addition, it is shown that currents through the target support fiber aid target discharging. Implications of these findings for inertial fusion energy targets without support fibers are discussed. (paper)

[en] The cone-in-shell approach to fast ignition (FI) uses a re-entrant cone to keep the path of the ignition pulse clear of plasma, allowing the ultrafast laser to propagate close to the dense core of compressed fuel. The core must be assembled close to the tip of the cone to be effectively heated with the hot electrons produced by the fast-ignition pulse. Gas-tight, direct-drive FI targets consisting of a ∼24-μm-thick CH shell with a t0 degree centigree-or 30 degree centigree-opening-angle gold cone inserted and filled with ∼ 10 atm of DD or D''3He have been used on OMEGA to study the implosion dynamics and fuel assembly. The targets were implored by direct illumination with up to 21 kJ of 351-nm laser light. A backlighter was used on some experiments to observe the fuel assemble. An areal density of-60 mg/cM''2 was inferred for the core plasma using both fusion products and backlit images, which is more than 50% of the calculated 1-D (clean) areal density. No significant mixing of the cone material into the assembled core was observed. to ascertain that the inside of the cone stays free of plasma until the time of peak compression, a passive shock-breakout diagnostic was used to record the time of shock transit through the gold cone. A preliminary data set shows no measurable heating (T<1 eV) inside the cone and a shock breakout∼500 ps after peak compression. This work was supported by the U. S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. De-Fc-92SF19460, the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article. (Author)

[en] Solid-state nuclear track detectors, such as CR-39, are widely used in physics and in many inertial confinement fusion (ICF) experiments. In the ICF experiments, the particles of interest, such as D³He-protons, have ranges of order of the detector thickness. In this case, the dynamic range of the detector can be extended by recording data on both the front and back sides of the detector. Higher energy particles which are undetectable on the front surface can then be measured on the back of the detector. Studies of track formation under the conditions on the front and back of the detector reveal significant differences. Distinct front and back energy calibrations of CR-39 are therefore necessary and are presented for protons. Utilizing multiple surfaces with additional calibrations can extend the range of detectable energies on a single piece of CR-39 by up to 7-8 MeV. The track formation process is explored with a Monte Carlo code, which shows that the track formation difference between front and back is due to the non-uniform ion energy deposition in matter.

[en] Wedge Range Filter (WRF) proton spectrometers are routinely used on OMEGA and the NIF for diagnosing ρR and ρR asymmetries in direct- and indirect-drive implosions of D³He-, D₂-, and DT-gas-filled capsules. By measuring the optical opacity distribution in CR-39 due to proton tracks in high-yield applications, as opposed to counting individual tracks, WRF dynamic range can be extended by 10² for obtaining the spectral shape, and by 10³ for mean energy (ρR) measurement, corresponding to proton fluences of 10⁸ and 10⁹ cm⁻², respectively. Using this new technique, ρR asymmetries can be measured during both shock and compression burn (proton yield ∼10⁸ and ∼10¹², respectively) in 2-shock National Ignition Facility implosions with the standard WRF accuracy of ±∼10 mg/cm²