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Fluid, Ions and Radiation Ensemble in Integrated Plasma Modelling

Final Report Summary - FIRE (Fluid, Ions and Radiation Ensemble in Integrated Plasma Modelling)

A primary goal of the project is the modeling of plasma produced by intense lasers and high-current pulsed discharges for plasma based radiation sources with applications in semiconductor extreme ultra-violet lithography (EUVL), for plasma diagnostics and for nanoparticle generation in nanotechnology. A computational code Z* was designed at EPPRA to model multicharged ion plasmas in experimental and industrial facilities, using a radiation-magnetohydrodynamics (RMHD) approach. In the European FP7 Industry-Academia Partnerships and Pathways (IAPP) project FIRE, the Z* code is substantially redeveloped to include improved atomic physics models and to pass from 2-D RMHD to full 3-D plasma simulation to evaluate plasma dynamics, spectral emission, radiation transport in non-equilibrium (nonLTE) plasma and the creation/transport of nanosize particles. Such modeling is a key factor to important scientific and technological solutions to EUV source optimization and their extension to subsequent nodes (16nm and beyond); and in the nanoparticles production, where the physical mechanisms leading to condensation and nucleation is elucidated.
The FIRE-project involves three main partners: R&D company EPPRA SAS from France; University College Dublin, National University of Ireland; Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences, Moscow. The project scope is very broad and includes radiative plasma dynamics, atomic physics, EUV & X-ray spectroscopy, pulsed power technology, nanotechnology, numerical methods and computer simulation, data mining, parallel computing architecture, as well as education, innovation, and IPR management. The research and transfer of knowledge is focused on two major applications: laser- , discharge- produced plasma EUV source optimization and nanoparticle production.
In synthesis, the project objectives implemented give an opportunity to be able to:
- Describe the high energy density laser- and discharge- produced plasmas (LPP, DPP) or their combinations taking into account non-equilibrium electron and radiation processes, including re-absorption in different elemental composition materials and plasmas, and to determine optimum parameters for plasma emission in the wavelength bands required;
- Yield emission (absorption) spectra of various substances and thermodynamic equation of state in a wide range of temperatures and densities of nonLTE plasmas by radiation generation in detailed spectra and the unresolved transition arrays (UTA);
- Calculate radiation spectral raytracing of plasma observation to compare with experimental measurement and interpret experimental data;
- Address problems in complex geometries (effect of targets, electrodes and insulators); possible sublimation (condensation) of solid materials and mixing. The vapor/plasma production from solid matter of targets or electrodes for selected LPP and DPP source parameters; optimum radiation generation while minimizing debris;
- Adapt the 3-D particle-in cell (PIC) code to two areas: (1) for hybrid code as a parallel processor to the main RMHD processing to calculate of charged particles acceleration in external and self-consistent electromagnetic field with possible collision processes; and (2) as a parallel post-processor of transport of nanoparticles after condensation and nucleation of the plasmas;
- Study the plasma-gas condition for production of size controlled nanoparticles through rapid quenching of energetic plasma expanding into a neutral gas.
Toward the objectives, the theoretical and computational works were performed with tin and xenon for EUV radiation at 13.5nm wavelength, gadolinium for BEUV radiation at 6.8 nm wavelength, zirconium and bismuth for the water-window range, gold etc targets using UTA and detailed spectra for a number of other elements as well. It was significant progress in research on i) production of atomic tables for: tin and galinstan (alloy of gallium, indium and tin), gadolinium, bismuth and zirconium and other materials for plasma radiation sources at certain spectral bands; ii) enhanced modelling of emission of nonLTE plasma of DPP and LPP; iii) the atomic tables for tin and galinstan have been used in simulations with Z*-code of experiments on laser assisted vacuum arc with ablated rotating electrodes in order to understand the physics behind and to optimize the EUV radiation sources. Maximum spectral efficiency of gadolinium plasma achieved is close to 6% in 0.6% waveband around 6.8 nm. Spectral emission efficiencies in EUV range based on plasma temperature and density were calculated for zirconium plasma. Intensive resonant transitions and satellites for XV – XXI Zr ions were investigated and precisely explored. Maximum spectral efficiency for emission in water window range (2.2-4.4nm wavelength) achieved was over 40% for plasma at temperature of 80eV and hotter. Absorption limits were studied.
The numerical code was improved to adaptive grid and extended from 2D to 3D. Improvements of the code were developed with installation and benchmarking of the high-performance computer (HPC), parallel computations of the PIC code and the spectral ray-tracing module. Extensive numerical modelling has been carried out to optimize the performance of EUV sources, and successfully benchmarked with in-house and external experiments on LPP, DPP and LADPP. A work on benchmarking data and radiation source optimization with the latest version of Z*-code carried out for Sn and Gd, with both Nd:YAG and CO2 and combined laser produced plasmas under different laser power, pulse shapes, plasma conditions and target compositions. The detailed physics of the effects taking place in the laser-initiated discharge was studied. It was found that tin discharge was more reproducible than in galinstan due to higher plasma conductivity at the breakdown and pinching time matching to the current maximum was significant for the high EUV output and it was sensitive to the trigger laser energy.
The PIC 3-D code for modelling of fast ions, electrons and nanoparticles dynamics in self-consistent electromagnetic field with collision processes has been developed for parallel computation on a multiprocessor computer. To determine the electron, ion or nanoparticle distribution function a method of decomposition to generalized functions with random parameters using of numerical model with combination of Monte-Carlo and particle methods guaranteed conservation of charge and availability of non-uniform computational mesh was applied. The particle motion in the self-consistent electromagnetic field includes statistical effects, i.e. a particle moving in the electromagnetic field randomly with certain probability undergoes absorption (recombination), scattering, ionization, charge exchange or condensation/nucleation (for neutrals to nanoparticles). The algorithm realizes the Poisson stream of events. The flux of charged particles produces the self-consistent electromagnetic field variation according to Maxwell equations. The PIC code is combined with RMHD core processor as pre- and post-processor. The computational code Z* combined with PIC-code is used to simulate physical phenomena in hollow cathode triggered low-pressure capillary discharge at different phases of the process: electron beam generation, formation of a channel by ionization wave, and discharge dynamics together with ionization kinetics and plasma emission, particularly in EUV band. Run-away electrons in gas-filled capillary discharge with hollow cathode play an important role both in ionization wave propagation, and in ionization of multicharged ions in discharge plasma. The electron beam prepares a tight ionized channel. The fast electrons shift the ionization equilibrium in discharge plasma increasing the EUV emission from relatively low-temperature plasma of xenon. The electron flow is simulated in 3-D PIC model. At discharge stage, the plasma is described by the RMHD with ionization kinetics and radiation transfer.
It was studied experimentally a synthesis of gold, silver nanoparticles in liquids and titanium nanoparticles formed in plasma by laser ablation of targets with selected materials with possible applications in materials science and bio-technology. Laser synthesized nanoparticles were applied for the possible use as Surface Enhanced Raman Spectroscopy (SERS) media for the signal enhancement. Porphyrim molecule has been detected in colloid silver nanoparticle system with the SERS method. Dual-pulse laser synthesis of the nanoparticles of silver and gold has been also studied. It allows much better control of the size-distribution of the nanoparticles shifting the distribution towards lower values and making distribution more uniform and repeatable. The other aspect of the work was related to the laser produced plasmas in vacuum with the aim to study thin films produced and data on nanoparticles formation. Dual-pulse laser ablation to produce thin films and SAXS and XRD measurements of the films were performed. Films deposited with the dual-pulse and with appropriate time-delay between first and second pulse are of better characteristics that forms produced with 'classical' pulsed laser deposition using one pulse only.
The first results of tungsten 5MA Z-pinch 3D RMHD modeling with upgraded Z*-code show the pinch behavior at the final stage of the pinch. Due to development of the radiative-thermal instability, the initially azimuthally isotropic current breaks up to many filaments with a current less than Pease-Briaginskii current limit in each. These filaments become banded as a result of MHD kink and higher mode instabilities (m>1) generating poloidal magnetic field and formation of a global equilibrium with quasi-forceless configuration of the pinch. Banding of the current lines and the current filamentation increases the effective resistance of the pinch. This can explain the discrepancy between dissipation of the energy observed in Angara-5, Z-machine experiments and joule heating calculated from measured pinch parameter.
The results obtained during the project were reported at dozens of International Conferences and Workshops, and published in ten scientific journals and proceedings. The project outcomes will impact both the research and the industrial communities in the EUV, BEUV and soft X-rays by establishing detailed radiation mechanisms and physical parameters; and the nanotechnology, whenever mono-disperse and chemically pure nanoparticles are required.