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| 1 | Laser-direct-drive program: Promise, challenge, and path forward显示文摘Along with laser-indirect(X-ray)-drive and magnetic-drive target concepts,laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion.In the United States,a national program has been established to demonstrate and understand the physics of laser direct drive.The program utilizes the Omega Laser Facility to conduct implosion and coupling physics at the nominally 30-kJ scale and lasereplasma interaction and coupling physics at the MJ scale at the National Ignition Facility.This article will discuss the motivation and challenges for laser direct drive and the broad-based program presently underway in the United States. | E.M.Campbell V.N.Goncharov T.C.Sangster S.P.Regan P.B.Radha R.Betti J.F.Myatt D.H.Froula M.J.Rosenberg I.V.Igumenshchev W.Seka A.A.Solodov A.V.Maximov J.A.Marozas T.J.B.Collins D.Turnbull F.J.Marshall A.Shvydky J.P.Knauer R.L.McCrory A.B.Sefkow M.Hohenberger P.A.Michel T.Chapman L.Masse C.Goyon S.Ross J.W.Bates M. Karasik J.Oh J.Weaver A.J.Schmitt K.Obenschain S.P.Obenschain S.Reyes B.Van Wonterghem | 2017 | Matter and Radiation at Extremes2017，2，2： | 10 |
| 2 | Conceptual design of a 15-TW pulsed-power accelerator for high-energy-densityephysics experiments显示文摘We have developed a conceptual design of a 15-TW pulsed-power accelerator based on the linear-transformer-driver(LTD)architecture described by Stygar[W.A.Stygar et al.,Phys.Rev.ST Accel.Beams 18,110401(2015)].The driver will allow multiple,high-energy-density experiments per day in a university environment and,at the same time,will enable both fundamental and integrated experiments that are scalable to larger facilities.In this design,many individual energy storage units(bricks),each composed of two capacitors and one switch,directly drive the target load without additional pulse compression.Ten LTD modules in parallel drive the load.Each module consists of 16 LTD cavities connected in series,where each cavity is powered by 22 bricks connected in parallel.This design stores up to 2.75 MJ and delivers up to 15 TW in 100 ns to the constant-impedance,water-insulated radial transmission lines.The transmission lines in turn deliver a peak current as high as 12.5 MA to the physics load.To maximize its experimental value and flexibility,the accelerator is coupled to a modern,multibeam laser facility(four beams with up to 5 kJ in 10 ns and one beam with up to 2.6 kJ in 100 ps or less)that can provide auxiliary heating of the physics load.The lasers also enable advanced diagnostic techniques such as X-ray Thomson scattering and multiframe and three-dimensional radiography.The coupled accelerator-laser facility will be the first of its kind and be capable of conducting unprecedented high-energy-densityephysics experiments. | R.B.Spielman D.H.Froula G.Brent E.M.Campbell D.B.Reisman M.E.Savage M.J.Shoup III W.A.Stygar M.L.Wisher | 2017 | Matter and Radiation at Extremes2017，2，4： | 5 |
| 3 | Implementation of a Faraday rotation diagnostic at the OMEGA laser facility显示文摘Magnetic field measurements in turbulent plasmas are often difficult to perform. Here we show that for kG magnetic fields, a time-resolved Faraday rotation measurement can be made at the OMEGA laser facility. This diagnostic has been implemented using the Thomson scattering probe beam and the resultant path-integrated magnetic field has been compared with that of proton radiography. Accurate measurement of magnetic fields is essential for satisfying the scientific goals of many current laser–plasma experiments. | A.Rigby J.Katz A.F.A.Bott T.G.White P.Tzeferacos D.Q.Lamb D.H.Froula G.Gregori | 2018 | High Power Laser Science and Engineering2018，6，3： | 0 |
| 4 | Insensitivity of a turbulent laser-plasma dynamo to initial conditions显示文摘It has recently been demonstrated experimentally that a turbulent plasma created by the collision of two inhomogeneous,asymmetric,weakly magnetized,laser-produced plasma jets can generate strong stochastic magnetic fields via the small-scale turbulent dynamo mechanism,provided the magnetic Reynolds number of the plasma is sufficiently large.In this paper,we compare such a plasma with one arising from two pre-magnetized plasma jets whose creation is identical save for the addition of a strong external magnetic field imposed by a pulsed magnetic field generator.We investigate the differences between the two turbulent systems using a Thomson-scattering diagnostic,x-ray selfemission imaging,and proton radiography.The Thomson-scattering spectra and x-ray images suggest that the external magnetic field has a limited effect on the plasma dynamics in the experiment.Although the external magnetic field induces collimation of the flows in the colliding plasma jets and although the initial strengths of the magnetic fields arising from the interaction between the colliding jets are significantly larger as a result of the external field,the energies and morphologies of the stochastic magnetic fields post-amplification are indistinguishable.We conclude that,for turbulent laser-plasmas with supercritical magnetic Reynolds numbers,the dynamo-amplified magnetic fields are determined by the turbulent dynamics rather than the seed fields or modest changes in the initial flow dynamics of the plasma,a finding consistent with theoretical expectations and simulations of turbulent dynamos. | A.F.A.Bott L.Chen P.Tzeferacos C.A.J.Palmer A.R.Bell R.Bingham A.Birkel D.H.Froula J.Katz M.W.Kunz C.-K.Li H-S.Park R.Petrasso J.S.Ross B.Reville D.Ryu F.H.Séguin T.G.White A.A.Schekochihin D.Q.Lamb G.Gregori | 2022 | Matter and Radiation at Extremes2022，7，4： | 0 |
| 5 | Measurements of the ablation-front trajectory and low-mode nonuniformity in direct-drive implosions using x-ray self-emission shadowgraphy显示文摘Self-emission x-ray shadowgraphy provides a method to measure the ablation-front trajectory and low-mode nonuniformity of a target imploded by directly illuminating a fusion capsule with laser beams. The technique uses time-resolved images of soft x-rays(>1 ke V) emitted from the coronal plasma of the target imaged onto an x-ray framing camera to determine the position of the ablation front. Methods used to accurately measure the ablation-front radius(δ R= ±1.15 μm), image-to-image timing(δ( t)= ±2.5 ps) and absolute timing(δt= ±10 ps) are presented.Angular averaging of the images provides an average radius measurement of δ( Rav)= ±0.15 μm and an error in velocity of δV / V= ±3%. This technique was applied on the Omega Laser Facility [Boehly et al., Opt. Commun. 133, 495(1997)] and the National Ignition Facility [Campbell and Hogan, Plasma Phys. Control. Fusion 41, B39(1999)]. | D.T.Michel A.K.Davis W.Armstrong R.Bahr R.Epstein V.N.Goncharov M.Hohenberger I.V.Igumenshchev R.Jungquist D.D.Meyerhofer P.B.Radha T.C.Sangster C.Sorce D.H.Froula | 2015 | High Power Laser Science and Engineering2015，3，3： | 0 |
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