To realize a pulsed-power discharge plasma using a liquid metal, we investigated the dependence of the diameter on the flow velocity of a liquid metal flow consisting of a U-alloy. The plasma temperature was measured using a pyrometric method. The results show that the flow velocity estimated by the parabolic corresponds to a theoretical value derived from the difference between the gas pressure and

The phenomenon of electron runaway in a dense semiclassical plasma was investigated on the basis of the effective potentials of particle interactions. These effective potentials take into account the quantum-mechanical effect of diffraction and static or dynamic screening. The results of numerical calculations of the effective collision frequency, mean free path and friction force for various values

This paper presents an exploration of potential mitigation methods for the gas fuel fill tube in Inertial Confinement Fusion implosions (ICF) at the National Ignition Facility (NIF), and the impact of hydrodynamic growth seeded from other target imperfections using a specialized low convergence implosion experiment. Enhanced x-ray self- emission of this experiment design allows the impact of hydrodynamic

To clarify a regeneration process of fast electrons in a Malmberg-Penning trap device, a numerical simulation was carried out using a multi-particle tracking code. The numerical simulations reproduced the fast particle regeneration by the rapid relaxation process observed in the experiment. In comparison with the experimental and the numerical results, it was considered that the rapid relaxation process

In order to enhance the conversion efficiency of ultra-intense laser energy into plasma leading to ion acceleration, we have performed an experiment with over-picosecond laser pulses having a relativistic intensity interacting with foam targets. We adjust the prepulse of the laser to control the plasma density near the critical density. The combination of hydrodynamic and particle-in-cell simulations

Low-mode asymmetries represent an important obstacle to achieving high-gain inertial confinement fusion implosions. As a step in learning how to control such effects, an OMEGA experiment with imposed mode 2 laser drive asymmetries was done to study the expected signatures of this type of asymmetry [M. Gatu Johnson et al., PRE 2018]. In the present work, a 3D xRAGE simulation including the stalk mount

Radiation-hydrodynamics simulations are used to design laser-driven cylindrical implosion experiments to directly measure hydrodynamic instability growth in convergent geometry. Designs for two different size targets, varying in radial dimension by a factor of three, are presented. A set of beam pointings and powers are identified for each scale design that result in a nearly axially uniform implosion

A solenoidal magnetic field has been used to enhance the ion flux of a laser ion source. However, the dependence of the increase in ion current on the charge-state has not been clarified. In this study, to control the purity of the charge-state in the laser ion source, we investigated the effect of a solenoidal magnetic field on the charge-state distribution of ions in laser ion sources with a solenoid

The inertial confinement fusion (ICF) program toward ignition in China has made great progress since 1993. After research work on SG series with laser energy of tens kJ, SG-III laser facility with energy output of hundreds kJ is being used to study target physics prior to ignition. A new hybrid drive (HD) approach combined indirect drive (ID) and direct drive (DD) provides the HD pressure far greater

We examine the anomalous absorption effect due to ion–acoustic turbulence (IAT) driven by the return current instability in a plasma corona in relation to relevant conditions of the direct-drive inertial confinement fusion scheme of the Russian megajoule-energy level laser facility. We find that for the plasma corona created by a carbon ablator, the IAT contributes not more than 10% to absorption for

Creation of hot dense highly charged plasma is key to realizing novel radiation sources, e.g., high Z ion beams and intense hard x-rays. We study the formation of dense silver plasma driven by an ultrashort petawatt laser using one-dimensional Particle-in-Cell (PIC) simulations take into account physics of collisional energy transport, ionizations, and radiations byproducts. For this purpose, we implemented

An ion beam has a unique feature to deposit its main energy inside a human body to kill cancer cells or inside material. In this paper, a future intense laser ion accelerator is discussed to make the laser-based ion accelerator compact and controllable. The issues in the laser ion accelerator include the energy efficiency from the laser to the ions, the ion beam collimation, the ion energy spectrum

We have performed refraction enhanced radiography (RER) measurements of indirect drive layered high density carbon capsule implosions relevant for inertial confinement fusion. Streaked RER data using a 5 µm wide imaging slit, backlit by a 7.8 keV Ni He-α laser driven x-ray source, shows features due to inflight density gradients in the ablator and fuel ice that are not visible in absorption only radiographs

Herein, a two-dimensional magnetohydrodynamic (MHD) simulation has been performed to understand the MHD and the generated magnetic field (B-field) behaviors of a capacitor-coil target. The results showed that a peak B-field strength was generated in the capacitor-coil target, followed by a current peak. This B-field depends on a peak current with a pulse duration of 2 ns. For a peak current of 2 ns

At National Ignition Facility (NIF), yield amplification due to alpha particle heating approached ~3 in the highest performing inertial confinement fusion (ICF) implosions, while yield amplification of ~15-30 is needed for ignition. Hydrodynamic instabilities are a major factor in degradation of implosions while understanding and mitigation of the instabilities are critical to achieving ignition. This

In the Shock Ignition scheme, the spike pulse intensity is well above the threshold of parametric instabilities, which produce a considerable amount of hot electrons that could be beneficial or detrimental to the ignition. To study their impact, an experiment has been carried out on the LMJ-PETAL facility with a goal to generate a strong shock inside a plastic layer under plasma conditions relevant

The U.S. Naval Research Laboratory (NRL) has built a 137 J electron beam pumped argon fluoride (ArF) laser operating at 193 nm utilizing the Electra facility. This paper highlights initial ArF oscillator measurements in the context of significant benefits of ArF laser characterization for inertial confinement fusion target performance and development of a kinetics code with predictive capabilities

We demonstrated 117-J laser output in a nanosecond regime with a diode-pumped Yb:YAG ceramic laser amplifier. The repetition rate was 0.05 Hz, and the pulse duration was around 40 ns. 5-J input energy was amplified by two cryogenically cooled Yb:YAG ceramic laser heads. Six Yb:YAG ceramic disks in each laser head were cooled by cryogenic helium gas with a temperature of 175 K. The output energy of

A magnetic nozzle, which is a convergent-divergent magnetic field to control a plasma flow, has been investigated for application to plasma propulsion systems in spaceships. In the magnetic nozzle, plasma thermal energy is converted to one-directional kinetic energy by Lorentz force to generate thrust. Although magnetic field structure and strength are optimized for improvement of the thrust performance

Typical inertial confinement fusion (ICF) plasmas have ultra-high energy density state (UHEDs) with an energy density exceeding 1 × 108 Jcm−3, which corresponds to a pressure of beyond 1 Gbar. In previous investigation, it is suggested that such an UHEDs condition could be generated with a tabletop ultrahigh intensity laser, by irradiating onto a nanowire array. In this research, we have developed

A newly available ns-gated laser-entrance-hole (GLEH) imager in the National Ignition Facility provides a routine, non-perturbative measurement of hohlraum x-ray emission from inner and outer laser beam deposition regions. The GLEH records the x-ray flux integrated over complex interactions of various part of hohlraum plasma that evolves on a sub-nanosecond time scale. To use these images to unravel

A Li-like Al soft x-ray laser oscillation (15.47 nm) by means of recombination plasma scheme was investigated to enhance the gain coefficent of lasing medium. In this study, we employed a Nd:YAG laser pulse composed of 8-pulse train, in which each pulse width was 400 ps and its interpulse time was 400 ps. The laser beam was tightly line-focused into 50 μm in height and 12 mm in length on Al slab target

A Monte Carlo (MC) code simulating the kinetics of two-particle collisions has shown to have certain advantages in the spectral analysis of neutrons from fast-ignition inertial confinement fusion (ICF). The MC code quickly displays neutron spectra produced in the expected fusion plasma kinetics (incl. ion energy spectrum, anisotropy, and collision geometry). This allows to explore various potential

Active control of laser-produced relativistic electron beams (REB) transport is crucial for the success of the fast isochoric heating, which requires efficient energy transfer from REB to a small pre-compressed plasma core. In general, the laser-produced REB has a large divergence angle, thus only a small portion of REB interacts with the small core. We observed experimentally that the REB can be guided

We propose an approach to Inertial Confinement Fusion (ICF) that could potentially lead to high levels of thermonuclear burn in the laboratory. The proposal is based upon the concept of pulsed power X ray driven hohlraums together with indirectly-driven ICF capsule designs that are scaled up in size from those typically used in laser indirect-drive ICF experiments at the National Ignition Facility

The propagation of transverse Electromagnetic (EM) waves along a high energy relativistic electron beam passing through a neutralizing heavy ion background is investigated in the presence of an external axial magnetic field. By making use of the linearized fluid equations coupled with Maxwell’s equations the dielectric tensor and the dispersion relation of excited modes are derived. Since the electron

A new density functional theory, average atom based model for the electrical conductivity of dense plasmas with a mixture of ion species, containing no adjustable parameters, is presented. The model takes the temperature, mass density and relative abundances of the species as input. It takes into account partial ionization, ionic structure, and core-valence orthogonality, and uses quantum mechanical

Kinetic physics has the potential to impact the performance of indirect-drive inertial confinement fusion (ICF) experiments. In near vacuum hohlraums (or vacuum hohlraums), the high-Z plasma expands from the hohlraum wall and collides with the blow-off from the capsule (or the low-density fill-gas). Such collision produces conditions in which kinetic effects may dominate since the ion-ion mean free

The yield and fuel compression trends for the NIF indirect-drive cryogenically-layered DT implosions is empirically examined across all ablators (CH, C and Be) and design in-flight adiabats between 1.5 and 3. Higher compression is observed for a lower design adiabat. Within a design adiabat, compression increases for shorter coast implosions but only if have optimized shock timing. The sensitivity

We experimentally demonstrate the generation of an electron beam with the charge of about 200 pC, the divergence of about 7 mrad and the maximum energy of about 320 MeV from helium gas via self-injection induced by self-evolved laser pulses (3 J, 30 fs) in the plasma channel. Based on the experimental electron beam parameters, the Monte Carlo simulation code Geant4 was used to optimize the thicknesses

Coherent x-rays via the Burst Intensification by Singularity Emitting Radiation (BISER) mechanism are generated from relativistic plasma in helium gas target. A broad modulation of the BISER spectrum, which is significantly wider than the harmonic order, is observed and characterized. In particular, we found that the modulation period can be as large as 41 eV.

We have implemented laser Thomson scattering for local plasma measurement of electron and ion temperatures, electron density, flow velocity, and charge state. The electron density increases by two times in the interaction of two plasma flows, indicating collisionless interaction. The density and velocity show fluctuations only at t=40 ns, and the density suddenly decreases, indicating the plasma ejection

We report on femtosecond petawatt laser pulses at 0.1 Hz that combine both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric CPA (OPCPA) techniques. High temporal contrast of 1012 prior to the main pulse of 10 J output energy has been demonstrated with a cleaned high-energy seeded low gain OPCPA preamplifier. Intensities as high as 1022 W∕cm2 on target have been achieved by focusing

The scattering of laser light due to cross-beam energy transfer (CBET) is an undesirable process in direct-drive inertial confinement fusion (ICF) that degrades both the compression and symmetry of the imploding target. Here, we present results from laser-plasma interaction simulations performed with the wave-based code LPSE that explore two techniques for suppressing CBET in frequency-tripled, Nd:glass

The properties of hot, dense plasmas generated by the irradiation of GaAs targets by the Titan laser at Lawrence Livermore National Laboratory were determined by the analysis of high resolution K shell spectra in the 9 keV to 11 keV range. The laser parameters, such as relatively long pulse duration and large focal spot, were chosen to produce a steady-state plasma with minimal edge gradients, and

Experiments were performed at the LLNL Titan laser to measure the propagation direction of the energetic electrons that were generated during the interaction of the polarized laser beam with solid targets in the case of normal incidence. The energetic electrons propagated through vacuum to spectator metal wires in the polarization direction and in the perpendicular direction, and the K shell spectra

We review the 9th NLTE code comparison workshop, which was held in the Jussieu campus, Paris, from November 30th to December 4th, 2015. This time, the workshop was mainly focused on a systematic investigation of iron NLTE steady-state kinetics and emissivity, over a broad range of temperature and density. Through these comparisons, topics such as modeling of the dielectronic processes, density effects