Direct Measurement of the Fuel Density-Radius Product in Laser-Fusion Experiments

Kacenjar, S.; Skupsky, S.; Entenberg, A.; Goldman, L. M.; Richardson, Martin

doi:10.1103/physrevlett.49.463

Cited by 47 publications

(23 citation statements)

References 8 publications

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“…The areal density qR was inferred using the knock-on technique. 276,277 The measured areal density, shown in Fig. 8-12(c) as a function of calculated convergence ratio, reached $20-35 mg/cm 2 at the highest convergence ratios.…”

Section: B Cryogenic Implosionsmentioning

confidence: 92%

“…(Neutron activation was developed by Campbell et al 275 at LLNL and used to measure the areal density of the glass shells surrounding the fuel for exploding-pusher 275 and indirect-drive 2,3 targets.) Two other diagnostics (knockons 276,277 and secondary reactions) were used, but they were limited to values of qR well below those of the bestperforming shots. (Knock-ons are energetic deuterium and tritium ions elastically scattered by the 14.1-MeV neutrons.)…”

Section: à3mentioning

confidence: 99%

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Direct-drive inertial confinement fusion: A review

et al. 2015

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The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. The problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 μm—the third harmonic of the Nd:glass laser—and 0.248 μm (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be nonlocal in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [Haynam et al., Appl. Opt. 46(16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.

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Section: B Cryogenic Implosionsmentioning

confidence: 92%

Section: à3mentioning

confidence: 99%

Direct-drive inertial confinement fusion: A review

et al. 2015

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“…3, have been used to measure the spectrum of knock-on deuterons ͑KO-D͒, elastically scattered by primary DT neutrons, from which fuel R can be inferred. [20][21][22] With the implementation of the MRS ͑Fig. 3͒, spectral measurements of the complementary particle, i.e., the downscattered neutron, are now possible.…”

Section: Probing Plastic and Cryogenic-dt Implosions At Omega Usmentioning

confidence: 99%

Probing high areal-density cryogenic deuterium-tritium implosions using downscattered neutron spectra measured by the magnetic recoil spectrometer

Frenje

Casey

et al. 2010

Physics of Plasmas

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For the first time high areal-density ͑R͒ cryogenic deuterium-tritium ͑DT͒ implosions have been probed using downscattered neutron spectra measured with the magnetic recoil spectrometer ͑MRS͒ ͓J. A. Frenje et al., Rev. Sci. Instrum. 79, 10E502 ͑2008͔͒, recently installed and commissioned on OMEGA ͓T. R. Boehly et al., Opt. Commun. 133, 495 ͑1997͔͒. The R data obtained with the MRS have been essential for understanding how the fuel is assembled and for guiding the cryogenic program at the Laboratory for Laser Energetics ͑LLE͒ to R values up to ϳ300 mg/ cm 2 . The R data obtained from well-established charged particle spectrometry techniques ͓C. K. Li et al., Phys. Plasmas 8, 4902 ͑2001͔͒ were used to authenticate the MRS data for low-R plastic capsule implosions, and the R values inferred from these techniques are in excellent agreement, indicating that the MRS technique provides high-fidelity data. Recent OMEGA-MRS data and Monte Carlo simulations have shown that the MRS on the NIF ͓G. H. Miller et al., Nucl. Fusion 44, S228͑2004͔͒ will meet most of the absolute and relative requirements for determining R, ion temperature ͑T i ͒ and neutron yield ͑Y n ͒ in both low-yield, tritium-rich, deuterium-lean, hydrogen-doped implosions and high-yield DT implosions.

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“…As illustrated by the S/B numbers shown in Table 2, the S/N ratios are dictated mainly by the signal. Both in terms of S/N and S/B, it is cle Table 2: Signal-to-noise (S/N) and signal-to-background (S/B) ratios for the different MRS configurations, shown in Table 1, planned to be used for the down-scattered neutron measurements (6)(7)(8)(9)(10) MeV) at OMEGA and the NIF. The CCT [Eq.…”

Section: Cmentioning

confidence: 99%