Heights integrated model as instrument for simulation of hydHeights Integrated Model as Instrument for Simulation of Hydrodynamic, Radiation Transport, and Heat Conduction Phenomena of Laser-Produced Plasma in EUV Applications.

The HEIGHTS integrated model has been developed as an instrument for simulation and optimization of laser-produced plasma (LPP) sources relevant to extreme ultraviolet (EUV) lithography. The model combines three general parts: hydrodynamics, radiation transport, and heat conduction. The first part employs a total variation diminishing scheme in the Lax-Friedrich formulation (TVD-LF); the second part, a Monte Carlo model; and the third part, implicit schemes with sparse matrix technology. All model parts consider physical processes in three-dimensional geometry. The influence of a generated magnetic field on laser plasma behavior was estimated, and it was found that this effect could be neglected for laser intensities relevant to EUV (up to {approx}10{sup 12} W/cm{sup 2}). All applied schemes were tested on analytical problems separately. Benchmark modeling of the full EUV source problem with a planar tin target showed good correspondence with experimental and theoretical data. Preliminary results are presented for tin droplet- and planar-target LPP devices. The influence of three-dimensional effects on EUV properties of source is discussed

Effect of Dual Ion Beam Irradiation (Helium and Deuterium) on Tungsten–Tantalum Alloys Under Fusion Relevant Conditions

The selection of tungsten (W) as a divertor material in ITER is based on its high melting point, low erosion, and strong mechanical properties. However, continued investigation has shown W to undergo severe morphology changes in fusion-like conditions. Recent literature suggests alloying W with other ductile refractory metals, viz. tantalum (Ta) may resolve some of these issues. These results provide further motivation for investigating W–Ta alloys as a plasma-facing component (PFC) for ITER and future DEMO reactors. Specifically, how these alloy materials respond to simultaneous He+ and D+ ion irradiation, and what is the effect on the surface morphology when exposed to fusion relevant conditions. In the present study, the surface morphology changes are investigated in several W–Ta targets (pure W, W-1%Ta, W-3%Ta, and W-5% Ta) due to simultaneous He+ and D+ ion irradiations. This comprehensive work allows for deeper understanding of the synergistic effects induced by dual ion irradiation on W and W–Ta alloy surface morphology. Pure W and W–Ta alloys were irradiated simultaneously by 100 eV He+ and/or D+ ions at various mixture ratios (100% He+, 60% D+ + 40% He+, 90% D+ + 10% He+ ions and 100% D+ ions), having a total constant He fluence of 6 × 1024 ion m−2, and at a target temperature of 1223 K. This work shows that slight changes in materials composition and He/D content have significant impact on surface morphology evolution and performance. While both the pure W and W–Ta alloys exhibit very damaged surfaces under the He+ only irradiations, there is a clear suppression of the surface morphology evolution as the ratio of D+/He+ ions is increased

Structural Distortion-Induced Magnetoelastic Locking in Sr\u3csub\u3e2\u3c/sub\u3eIrO\u3csub\u3e4\u3c/sub\u3e Revealed through Nonlinear Optical Harmonic Generation

We report a global structural distortion in Sr2IrO4 using spatially resolved optical second and third harmonic generation rotational anisotropy measurements. A symmetry lowering from an I41/acd to I41/a space group is observed both above and below the Néel temperature that arises from a staggered tetragonal distortion of the oxygen octahedra. By studying an effective superexchange Hamiltonian that accounts for this lowered symmetry, we find that perfect locking between the octahedral rotation and magnetic moment canting angles can persist even in the presence of large noncubic local distortions. Our results explain the origin of the forbidden Bragg peaks recently observed in neutron diffraction experiments and reconcile the observations of strong tetragonal distortion and perfect magnetoelastic locking in Sr2IrO4

A structural distortion induced magneto-elastic locking in Sr2_2IrO4_4 revealed through nonlinear optical harmonic generation

We report a global structural distortion in Sr$_2$IrO$_4$ using spatially resolved optical second and third harmonic generation rotational anisotropy measurements. A symmetry lowering from an $I4_{1}/acd$ to $I4_{1}/a$ space group is observed both above and below the N\'{e}el temperature that arises from a staggered tetragonal distortion of the oxygen octahedra. By studying an effective super-exchange Hamiltonian that accounts for this lowered symmetry, we find that perfect locking between the octahedral rotation and magnetic moment canting angles can persist even in the presence of large non-cubic local distortions. Our results explain the origin of the forbidden Bragg peaks recently observed in neutron diffraction experiments and reconcile the observations of strong tetragonal distortion and perfect magneto-elastic locking in Sr$_2$IrO$_4$.Comment: 6 pages, 4 figure

Extreme Conditions for Plasma-Facing Components in Tokamak Fusion Devices

Abstract-Safe and reliable operation is still one of the major challenges in the development of fusion energy. In magnetic fusion devices, perfect plasma confinement is difficult to achieve. During transient loss of plasma confinement, high plasma power and particle beams (power densities up to hundreds of gigawatts per square meter in time duration on the order of milliseconds) strike the reactor walls, particularly the divertor plate, and can significantly damage the exposed surfaces and also indirectly damage nearby components. To predict the resulting damage of the direct plasma impact on the divertor plate, comprehensive multiphysics multiphase models are developed, integrated, and implemented in the High Energy Interaction with General Heterogeneous Target Systems computer simulation package. The evolution of the divertor material, resulting vaporization, heating and ionization of vapor plasma to higher temperatures, and, consequently, the resulting photon radiation, transport, and deposition around the divertor area are calculated for typical instability parameters of the edge-localized modes and disruption for an ITER-like geometry. Index Terms-Computer simulation, plasma density, plasma temperature, radiation effects, reactor design, Tokamak devices. W E SIMULATED the evolution of an edge-localized mode (ELM) plasma impact onto the divertor surface of an ITER-like geometry with strong and inclined magnetic field configuration using the High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS) computer simulation package with extensive integrated models [1]- We studied the effect of ELMs on the divertor plate with different durations of 1, 0.5, and 0.1 ms. The ELM durations of 0.5 and 1 ms correspond to deposition powers of 0.92 MW/cm 2 and 0.46 MW/cm 2 , respectively. The shorter ELM initiates intense surface vaporization. The produced plasma cloud has a high temperature (up to 60 eV) and is very effective in forming a stable vapor/plasma shielding for the ELM incoming particles because of the insufficient time for vapor MHD motion and expansion/transport. The plasma shielding layer acts as an absorption layer for the rest of the ELM impact near the strike point location. The ELM particles decelerate, scatter, and deviate from the initial impinging direction in the plasma cloud that results in a significant decrease in erosion depth directly at the strike point and to a broadening of the whole erosion area. Because the plasma cloud is located near the strike point and relatively in confined position, the processes of plasma radiation and transport are evolved in this confined area around the divertor strike point but relatively far from nearby components. The impact ELM energy is consumed mostly for vaporization because of insufficient time for thermal relaxation and heat conduction inside the divertor plate. The MHD role and the expansion of the evolved vapor plasma increase appreciably with ELM impact duration. The plasma cloud has sufficient time for motion and expansion in the dome area [see We calculated the incident photon fluxes along the dump and dome surfaces using our Monte Carlo radiation transport model implemented in HEIGHTS. For the same impact of total ELM energy of 12.6 MJ, higher radiation deposition was predicted for the longer impact duration of 1.0 ms. The maximum energy deposited reaches values up to 40 J/cm 2 . These values are 0093-3813/$26.0

Robust spin correlations at high magnetic fields in the harmonic honeycomb iridates

The complex antiferromagnetic orders observed in the honeycomb iridates are a double-edged sword in the search for a quantum spin-liquid: both attesting that the magnetic interactions provide many of the necessary ingredients, while simultaneously impeding access. Focus has naturally been drawn to the unusual magnetic orders that hint at the underlying spin correlations. However, the study of any particular broken symmetry state generally provides little clue about the possibility of other nearby ground states. Here we use magnetic fields approaching 100 Tesla to reveal the extent of the spin correlations in.-lithium iridate. We find that a small component of field along the magnetic easy-axis melts long-range order, revealing a bistable, strongly correlated spin state. Far from the usual destruction of antiferromagnetism via spin polarization, the high-field state possesses only a small fraction of the total iridium moment, without evidence for long-range order up to the highest attainable magnetic fields