Self-consistent and precise measurement of time-dependent radiative albedo of gold based on specially symmetrical triple-cavity Hohlraum

A self-consistent and precise method to determine the time-dependent radiative albedo,i.e.,the ratio of the reemission flux to the incident flux,for an indirect-drive inertial confinement fusion Hohlraum wall material is proposed.A specially designed symmetrical triple-cavity gold Hohlraum is used to create approximately constant and near-equilibrium uniform radiation with a peak temperature of 160 eV.The incident flux at the secondary cavity waist is obtained from flux balance analysis and from the shock velocity of a standard sample.The results agree well owing to the symmetrical radiation in the secondary cavity.A self-consistent and precise time-dependent radiative albedo is deduced from the reliable reemission flux and the incident flux,and the result from the shock velocity is found to have a smaller uncertainty than that from the multi-angle flux balance analysis,and also to agree well with the result of a simulation using the HYADES opacity.

The effects of incident light wavelength difference on the collective stimulated Brillouin scattering in plasmas

The first laser–plasma interaction experiment using lasers of eight beams grouped into one octad has been conducted on the Shenguang Octopus facility.Although each beam intensity is below its individual threshold for stimulated Brillouin backscattering(SBS),collective behaviors are excited to enhance the octad SBS.In particular,when two-color/cone lasers with wavelength separation 0.3 nm are used,the backward SBS reflectivities show novel behavior in which beams of longer wavelength achieve higher SBS gain.This property of SBS can be attributed to the rotation of the wave vectors of common ion acoustic waves due to the competition of detunings between geometrical angle and wavelength separation.This mechanism is confirmed using massively parallel supercomputer simulations with the three-dimensional laser–plasma interaction code LAP3D.

Progress in octahedral spherical hohlraum study

In this paper,we give a review of our theoretical and experimental progress in octahedral spherical hohlraum study.From our theoretical study,the octahedral spherical hohlraums with 6 Laser Entrance Holes(LEHs)of octahedral symmetry have robust high symmetry during the capsule implosion at hohlraum-to-capsule radius ratio larger than 3.7.In addition,the octahedral spherical hohlraums also have potential superiority on low backscattering without supplementary technology.We studied the laser arrangement and constraints of the octahedral spherical hohlraums,and gave a design on the laser arrangement for ignition octahedral hohlraums.As a result,the injection angle of laser beams of 50°-60°was proposed as the optimum candidate range for the octahedral spherical hohlraums.We proposed a novel octahedral spherical hohlraum with cylindrical LEHs and LEH shields,in order to increase the laser coupling efficiency and improve the capsule symmetry and to mitigate the influence of the wall blowoff on laser transport.We studied on the sensitivity of the octahedral spherical hohlraums to random errors and compared the sensitivity among the octahedral spherical hohlraums,the rugby hohlraums and the cylindrical hohlraums,and the results show that the octahedral spherical hohlraums are robust to these random errors while the cylindrical hohlraums are the most sensitive.Up till to now,we have carried out three experiments on the spherical hohlraum with 2 LEHs on Shenguang(SG)laser facilities,including demonstration of improving laser transport by using the cylindrical LEHs in the spherical hohlraums,spherical hohlraum energetics on the SGIII prototype laser facility,and comparisons of laser plasma instabilities between the spherical hohlraums and the cylindrical hohlraums on the SGIII laser facility.

Corrigendum to“First demonstration of improving laser propagation inside the spherical hohlraums by using the cylindrical laser entrance hole”[Matter Radiation Extremes 1(1)(2016)2-7]

Corrigendum Text:On page 2 of this letter,there is a misprint in the unit.The unit of the geometrical dimension of the spherical hohlraums on this page should always be“mm”rather than“mm”,i.e.in the second paragraph,“…with 800 J per beam at 0.35 mm…”should be“…with 800 J per beam at 0.35 mm…”,“The slit of 400 mm width is parallel…”should be“The slit of 400 mm width is parallel…”,“The laser focal diameter is about 500 mm…”should be“The laser focal diameter is about 500 mm…”;in the third paragraph,“…we take 850 mm as the radius…”should be“…we take 850 mm as the radius…”,“The LEH radius R_(L) is 400 mm…”should be“The LEH radius R_(L) is 400 mm…”,“…the radius of the cylindrical LEH outer ring is taken as 1.5 R_(L)=600 mm”should be“…the radius of the cylindrical LEH outer ring is taken as 1.5 R_(L)=600 mm”.This mistake does not affect any of the main results of the original letter.

First experimental comparisons of laser-plasma interactions between spherical and cylindrical hohlraums at SGⅢ laser facility

We present our recent laser-plasmas instability(LPI)comparison experiment at the SGIII laser facility between the spherical and cylindrical hohlraums.Three kinds of filling are considered:vacuum,gas-filling with or without a capsule inside.A spherical hohlraum of 3.6 mm in diameter,and a cylindrical hohlraum of 2.4 mm?4.3 mm are used.The capsule diameter is 0.96 mm.A flat-top laser pulse with 3 ns duration and up to 92.73 kJ energy is used.The experiment has shown that the LPI level in the spherical hohlraum is close to that of the outer beam in the cylindrical hohlraum,while much lower than that of the inner beam.The experiment is further simulated by using our 2-dimensional radiation hydrodynamic code LARED-Integration,and the laser back-scattering fraction and the stimulated Raman scatter(SRS)spectrum are post-processed by the high efficiency code of laser interaction with plasmas HLIP.According to the simulation,the plasma waves are strongly damped and the SRS is mainly developed at the plasma conditions of electron density from 0.08 n_(c) to 0.1 n_(c) and electron temperature from 1.5 keV to 2.0 keV inside the hohlraums.However,obvious differences between the simulation and experiment are found,such as that the SRS back-scattering is underestimated,and the numerical SRS spectrum peaks at a larger wavelength and at a later time than the data.These dif-ferences indicate that the development of a 3D radiation hydrodynamic code,with more accurate physics models,is mandatory for spherical hohlraum study.

Determination of laser entrance hole size for ignition-scale octahedral spherical hohlraums

A recently proposed octahedral spherical hohlraum with six laser entrance holes(LEHs)is an attractive concept for an upgraded laser facility aiming at a predictable and reproducible fusion gain with a simple target design.However,with the laser energies available at present,LEH size can be a critical issue.Owing to the uncertainties in simulation results,the LEH size should be determined on the basis of experimental evidence.However,determination of LEH size of an ignition target at a small-scale laser facility poses difficulties.In this paper,we propose to use the prepulse of an ignition pulse to determine the LEH size for ignition-scale hohlraums via LEH closure behavior,and we present convincing evidence from multiple diagnostics at the SGIII facility with ignition-scale hohlraum,laser prepulse,and laser beam size.The LEH closure observed in our experiment is in agreement with data from the National Ignition Facility.The total LEH area of the octahedral hohlraum is found to be very close to that of a cylindrical hohlraum,thus successfully demonstrating the feasibility of the octahedral hohlraum in terms of laser energy,which is crucially important for sizing an ignition-scale octahedrally configured laser system.This work provides a novel way to determine the LEH size of an ignition target at a small-scale laser facility,and it can be applied to other hohlraum configurations for the indirect drive approach.

First demonstration of improving laser propagation inside the spherical hohlraums by using the cylindrical laser entrance hole

The octahedral spherical hohlraums have natural superiority in maintaining high radiation symmetry during the entire capsule implosion process in indirect drive inertial confinement fusion.While,in contrast to the cylindrical hohlraums,the narrow space between the laser beams and the spherical hohlraum wall is usually commented.In this Letter,we address this crucial issue and report our experimental work conducted on the SGIII-prototype laser facility which unambiguously demonstrates that a simple design of cylindrical laser entrance hole(LEH)can dramatically improve the laser propagation inside the spherical hohlraums.In addition,the laser beam deflection in the hohlraum is observed for the first time in the experiments.Our 2-dimensional simulation results also verify qualitatively the advantages of the spherical hohlraums with cylindrical LEHs.Our results imply the prospect of adopting the cylindrical LEHs in future spherical ignition hohlraum design.

Type 1 interferon-induced IL-7 maintains CD8＋ T-cell responses and homeostasis by suppressing PD-1 expression in viral hepatitis

Type 1 interferon （IFN-I） promotes antigen-presenting cell maturation and was recently shown to induce hepatic IL-7 production during infection. Herein, we further explored the underlying mechanisms used by I FN-I to orchestrate antiviral immune responses in the liver. Acute viral hepatitis was induced by i.v. injection of adenovirus （Ad） in IFN-a receptor knockout （IFNAR-/-） and control mice. To disrupt signaling, monoclonal antibodies （mAbs） against IL-7 receptor alpha （IL-7Re） or PD-L1 were i.p. injected. We found that CD8＋ T cells in IFNAR-/- mice were less effective than those in control mice. The reduced T-cell function was accompanied by increased levels of PD-1 expression, apoptosis and decreased IFN-7 production. The lack of IFN-I signaling also impaired the expression of accessory molecules in both intrahepatic dendritic cell （DCs） and hepatocytes. PD-L1 was comparably and highly expressed on hepatocytes in both IFNAR-/- and control mice. Injection of PD-Ll-specific mAb in IFNAR-/- mice reversed the compromised immune responses in the liver. Further investigation showed that hepatic IL-7 elevation was less pronounced in IFNAR-/- mice compared to the controls. A treatment with recombinant IL-7 suppressed PD-1 expression on CD8＋ T cells in vitro. Accordingly, blocking IL-7R signaling in vivo resulted in increased PD-1 expression on CD8＋ T cells in Ad-infected mice. Collectively, the results suggest that IFN-I-induced hepatic IL-7 production maintains antiviral CD8＋ T-cell responses and homeostasis by suppressing PD-1 expression in acute viral hepatitis.