Effects Of Plasma Temperature Research Articles

Dependence of spectral purity of Gd plasma emission around 6.7 nm on laser irradiation conditions

Gadolinium is a compelling candidate for the next-generation 6.x nanolithography light source. We present a systematically study on the spectral purity at 6.7 nm in the gadolinium laser produced plasma. Variations in extreme ultraviolet spectra are observed over a wide range of laser focal spot sizes and laser pulse energies due to the combined effect of plasma temperature and opacity. When varying laser focal spot size, ionic populations of Gd ions at different electron temperatures were estimated by the collisional-radiative model for the explanation of changes in the spectral profile. When adjusting the laser pulse energy, modifications in the electron density profile were measured through Nomarski interferometry, and the related optical depth was quantified assisted with a one-dimensional radiation transfer model. Results show that, appropriate laser energy and focal spot size are necessary to achieve the high spectral purity, and with a lens with focal length of f = 175 mm and a laser pulse energy of 100 mJ, a spectral purity of Gd plasma up to 3.7% over range of 5.5–10 nm is achieved.

Investigation on the origin of hot electrons in laser plasma interaction at shock ignition intensities

Shock Ignition is a two-step scheme to reach Inertial Confinement Fusion, where the precompressed fuel capsule is ignited by a strong shock driven by a laser pulse at an intensity in the order of 10^{16} W/cm^2. In this report we describe the results of an experiment carried out at PALS laser facility designed to investigate the origin of hot electrons in laser-plasma interaction at intensities and plasma temperatures expected for Shock Ignition. A detailed time- and spectrally-resolved characterization of Stimulated Raman Scattering and Two Plasmon Decay instabilities, as well as of the generated hot electrons, suggest that Stimulated Raman Scattering is the dominant source of hot electrons via the damping of daughter plasma waves. The temperature dependence of laser plasma instabilities was also investigated, enabled by the use of different ablator materials, suggesting that Two Plasmon Decay is damped at earlier times for higher plasma temperatures, accompanied by an earlier ignition of SRS. The identification of the predominant hot electron source and the effect of plasma temperature on laser plasma interaction, here investigated, are extremely useful for developing the mitigation strategies for reducing the impact of hot electrons on the fuel ignition.

Effects of Plasma Temperature in the Blowout Regime for Plasma Accelerators

Research on plasma accelerators for high-energy colliders has rapidly progressed over the past few decades. Plasma acceleration with a high repetition rate will enable higher collider luminosity, but results in a heated plasma. This study investigates two phenomena—beam breakup instability and ion motion—in the nonlinear blowout regime in plasma accelerators and how the plasma temperature affects them. It was found that increasing the plasma temperature enhances the beam breakup instability by reducing the blowout radius while suppressing the on-axis ion-density spike caused by ion motion. This imposes a stringent demand on alignment tolerances, but it offers promising prospects for mitigating ion motion.

Effect of Plasma Temperature on Major Element Prediction Accuracy From Laser‐Induced Breakdown Spectroscopy

AbstractLaser‐induced breakdown spectra (LIBS) were collected on a diverse suite of ∼2,600 geological standards using four laser energies (2.4–7.2 mJ) to assess how variations in irradiance from stand‐off distance affect prediction accuracy. Mismatches in laser energies and plasma temperatures between training and prediction datasets introduce substantial uncertainty in major element predictions. For example, using 2.4 mJ spectra to predict 7.2 mJ data results in errors of ±8.9, ±1.4, ±3.8, ±3.2, ±1.6, ±1.0, ±0.6, and ±1.0 wt% for SiO2, TiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, and K2O, respectively. When plasma temperatures of unknowns are represented in a multiple‐plasma‐temperature training set, prediction accuracies improve for the same oxides: ±3.0, ±0.3, ±1.3, ±1.4, ±1.0, ±0.7, ±0.5, and ±0.5 wt%. These results suggest that accuracies reported for Mars LIBS predictions based on single‐distance, single laser‐power calibration data may be overly optimistic except where Mars plasmas serendipitously match those acquired in the laboratory.

Toxic Elements Behavior during Plasma Treatment for Waste Collected from Power Plants

The subject of this work is the treatment of solid waste collected from power plants using thermal plasma technology. Inductively coupled plasma (ICP), X-ray fluorescence (XRF), and energy-dispersive X-ray spectroscopy (EDX) were used to characterize the waste before and after the treatment. The results show that waste is formed essentially from carbon, but it also contains sulfur and toxic elements like lead, cadmium, zinc, and arsenic. For this reason, a plasma reactor was used to separate carbon from the heavy metals by a pyrolysis/combustion plasma system. After the plasma treatment, the mass of the waste was reduced by more than 85% and the metals were collected in the filter bag. A computer code was used to study the toxic element volatility during the treatment. With this code, the effects of plasma temperature, confinement matrix, and the composition of the carrier gas on the volatility of lead and arsenic were determined. The code results show that arsenic remains in the liquid phase for temperatures less than 2000 K, whereas for temperatures beyond 2100 K, arsenic becomes very volatile. For lead, any increase in temperature increases its vaporized quantity and its vaporization speed. The addition of oxygen in the carrier gas leads to the heavy metal incorporation in the confinement matrix. The increase of the quantity of Ba in the containment matrix strengthens the confinement of as in the matrix.

Effect of plasma temperature and electron number density on signal enhancement observed in nanoparticle enhanced LIBS

The present work aims to understand the signal enhancement observed in nanoparticle (NP)-enhanced laser induced breakdown spectroscopy (NELIBS) due to changes in the plasma parameters as a result of improved atomization and excitation. A systematic study on signal enhancements during NELIBS using simultaneous spectroscopy and imaging is investigated by varying the experimental parameters like particle size and laser fluence. We have observed similar enhancements in spectroscopy and imaging channels regardless of NP size at different laser fluences. Although the plume size in NELIBS was marginally more prominent than the LIBS at the same laser fluence, the corresponding intensity in NELIBS is significantly higher. This agrees with the hypothesis of efficient atomization and excitation of plasma in the case of NELIBS. Therefore, we performed a sensitivity analysis using simulated LIBS signal to understand changes in experimentally observable plasma parameters (excitation temperature and electron number density) on signal enhancement. We have shown that the enhancements in the emission intensities of typically one order of magnitude can be explained as a result of the change in electron number density and plasma temperature. A comparison of the expected enhancement due to this change with experimental observation for a Cu I line is also presented.

Characterizing Spectral Channels of Visible Emission Line Coronagraph of Aditya-L1

Aditya-L1 is India’s first solar mission with the Visible Emission Line Coronagraph (VELC), which consists of three spectral channels taking high-resolution spectroscopic observations of the inner corona up to 1.5 Rʘ at 5,303, 7,892, and 10,747 Å. In this work, we present a strategy for the slit width optimization of the VELC using synthetic line profiles by taking into account the instrument characteristics and coronal conditions for log(T) varying from 6 to 6.5. The synthetic profiles are convolved with simulated instrumental scattered light and noise to estimate the signal-to-noise ratio (SNR), which will be crucial to designing the future observation plans. We find that the optimum slit width for VELC turns out to be 50 μm, providing sufficient SNR for observations in different solar conditions. We also analyzed the effect of plasma temperature on the SNR at different heights in the VELC field of view for the optimized slit width. We also studied the expected effect of the presence of a CME on the spectral channel observations. This analysis will help to plan the scientific observations of VELC in different solar conditions.

Numerical Simulation of Plasma‐Propellant Interaction Under the Non‐Fourier Model

AbstractDue to the signicant characteristics of shorter and more reproducible ignition delay, plasma ignition becomes one of the key technologies of electrothermal‐chemical (ETC) propulsion. Plasma ignition is a complex heat transfer process, characterized by high temperature, high pressure, micro‐scale and extremely short duration. Under such extreme conditions, the assumption that the propagation speed of thermal disturbance is infinite in Fourier's law is no longer applicable. As such, for accurate prediction the non‐Fourier model with dual‐phase‐lag (DPL) is adopted to describe the interaction process between the plasma and the propellant. The temperature history of propellant is obtained by Dufort‐frankel numerical difference method. The numerical results obtained by DPL model are compared with the results by the Fourier model and Cattaneo‐Vernotte (C−V) model, it shows that the DPL model occupies preferable prediction performance. Additionally, the effects of plasma temperature, particle radius and absorber thickness on ignition delay are discussed. It finds that the ignition delay decreases with the increase of plasma temperature, increases with the increase of particle radius, and increases with the increase of absorber thickness. The numerical results based on DPL model are verified by the experimental results as well.

Saturation of Raman scattering in nonlinear regime

Saturation of Raman scattering of laser pulses in plasma, which is expected for hohlraum targets in ICF, is investigated. Trapping and Langmuir decay instability are two major candidates for saturation of Raman scattering in nonlinear regime. Coupled equations of plasma and scattered waves are derived and solved analytically in nonlinear regime where the effect of Landau damping and nonlinear frequency shift is considered. The solution leads to derivation of scattered waves growth and their reflectivity. Plots of reflectivity of scattered waves under various laser beam and plasma conditions are presented. The effects of plasma temperature and its density, as well as, laser frequency, its intensity and pulse duration on reflectivity are discussed.

Relativistic atomic structure calculations and study of plasma parameters for Na-like Se XXIV

Extensive calculations of energy levels and radiative data such as transition wavelengths, radiative rates, oscillator strengths, and line strengths for electric dipole (E1) transitions have been performed for Se XXIV using the multiconfiguration Dirac–Fock method. For other types of transitions, namely, magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2), only the radiative rates (A) are listed. The importance and effect of valence-valence and core-valence correlations on the excitation energies have been studied. For additional accuracy assessments, analogous calculations have been carried out by employing the flexible atomic code and configuration interaction technique. Comparisons are made with the available experimental and theoretical data in the literature. Close agreement has been found ensuring the accuracy and reliability of our results. The effect of plasma temperature on the line intensity ratio, electron density, plasma frequency, and skin depth has been analyzed for hot dense plasma (HDP) in local thermodynamic equilibrium. The present work might be beneficial in the modeling and characterization of HDP.

Experimental investigation on electrical characteristics and dose measurement of dielectric barrier discharge plasma device used for therapeutic application.

In this research, a Dielectric Barrier Discharge (DBD) plasma device operating in air has been made. The electrical characteristics of this device like instantaneous power, dissipated power, and discharge capacitance have been measured. Also, the effects of applied voltage on the dissipated power and discharge capacitance of the device have been investigated. The determination of electrical parameters is important in DBD plasma device used in living tissue treatment for choosing the proper treatment doses and preventing the destructive effects. The non-thermal atmospheric pressure DBD plasma source was applied for studying the acceleration of blood coagulation time, in vitro and wound healing time, in vivo. The citrated blood drops coagulated within 5 s treatment time by DBD plasma. The effects of plasma temperature and electric field on blood coagulation have been studied as an affirmation of the applicability of the constructed device. Also, the effect of constructed DBD plasma on wound healing acceleration has been investigated.

Analysis of Raman scattering of self-focused Gaussian laser beam in plasma without WKB approximation

The self-focusing and propagation of intense Gaussian laser beams in plasmas are investigated, and the explicit form of intensity of self-focused laser beams is derived without the use of WKB approximation. Propagation of self-focused laser beams in plasmas is strongly affected by Raman scattering and Brillouin scattering that are expected for hohlraum targets in inertial confinement fusion. The intensity of Raman and Brillouin scattered waves is derived in paraxial approximation where the effect of plasma temperature and Landau damping is considered through the kinetic theory of plasmas. The effect of plasma temperature and its density, as well as laser wavelength and its intensity, on self-focusing and spatial growth of scattered waves is considered.

Effect of Plasma Temperature and Nonlinearity of the Adiabatic Compressibility Index on Flow Parameters for Hypersonic Aerosol Expansion Following a Plasma Disruption

Future fusion reactors are expected to experience hard current disruptions that quench the confined plasma and depositing the energy on the plasma facing materials, thus causing surface ablation and the evolving aerosol expands into the reactor chamber. The plasma flow following a disruption event can be simulated experimentally and computationally using confined capillary discharges, which generate heat fluxes (up to ~80 GW/m2) typical to those expected in fusion reactors during a disruption. Computational technique to investigate the effect of plasma temperature on the adiabatic compressibility index has been investigated using a pulsed disruptive capillary electrothermal plasma source with a converging–diverging transition nozzle at the exit attached to the expansion regions. The plasma is formed in the capillary due to thermal decomposition of the ablating inner wall followed by subsequent ionization of the decomposed material. This work is particular to the cases where the ejected particulates coming out from a heat-load affected surface or arc-triggered plasma source orifice are at the sonic speed. The converging section in the nozzle provides a transition from the capillary exit subsonic condition to sonic state, which allows for observing the effect of temperature on the supersonic isentropic expansion. Mathematical model has been developed for effective atomic number (Z eff ) as function of the plasma temperature and has been used to model the adiabatic compressibility index (γ p ) of the plasma. Plasma parameters along the axial direction of the flow in the transition and the expansion regions are obtained.

Improvement on Quantitative Measurement of Fly Ash Contents Using Laser-Induced Breakdown Spectroscopy

Contents of fly ash are important factors for the operation of coal-fired plants. Real-time monitoring of coal and fly ash such as unburned carbon in fly ash can be an indicator of the combustion conditions. Because of the strong signal intensity and the relative simplicity of the LIBS (Laser- Induced Breakdown Spectroscopy) technique, LIBS can be applicable for real-time composition measurement of coal and fly ash. This research presented here focused on the clarification of the effects of plasma temperature and coexisting materials on quantitative measurement of fly ash contents. Quantitative capability of LIBS was improved using the proposed plasma temperature correction method. The CO2 effect was also discussed to accurately evaluate unburned carbon in fly ash in exhausts. Using the results shown in this study, quantitative measurement of fly ash contents has been improved for wider applications of LIBS to practical fields.

Microwave Propagation in Warm, Collisional Magnetoionic Media

In this paper, we present the derivation of the magnetoionic dispersion equation and the corresponding index of refraction and propagation constant for characterizing wave propagation in warm plasma immersed in a uniform magnetic field. To demonstrate the effects of plasma temperature on wave propagation and attenuation, a numerical example of the developed theory has been given. It is well known that there are two forward propagating modes of cold plasma: one is weakly attenuated and the other is weakly amplified. By comparing the cold plasma complex propagation constant of the classical Appleton-Hartree theory with the propagation constant obtained for the warm plasma case, we observed that the attenuated mode is thermally enhanced while the amplification of the other mode decreases by increasing the temperature where it becomes damped beyond a certain electron thermal speed.

The Effect of Ar/H2 Plasma Pretreatments on Porous K=2.0 Dielectrics for Pore Sealing by Self-Assembled Monolayers Deposition

Self-assembled monolayers (SAMs) deposition is being recently explored to help sealing the pores of a k=2.0 material. In order to enable a covalent chemical low-k surface functionalization by SAMs, a hydroxyl groups density as high as 1 to 2.5 OH groups/nm2 is required. This surface modification must be carefully controlled to confine the k below 10%. In this paper, the effects of plasma temperature, time and power on the SAMs deposition and plasma-induced damage are investigated. The main findings are that there is always a trade-off between surface hydroxyl groups density and bulk damage. A thick modified layer allows the SAM molecules to penetrate inside the pores which results in a decreased porosity and an increased k value with respect to correspondent plasma-treated pristine substrates.

Propagation characters of Gaussian laser beams in collisionless plasma: Effect of plasma temperature

This paper presents an investigation of the propagation characters of Gaussian laser beam in cold collisionless plasma by considering the plasma temperature variation. The ponderomotive nonlinearity is involved and induces the nonlinear self-focusing against spatial diffraction. The second-order differential equation of dimensionless beam width parameter f(ξ) in terms of plasma temperature is established from Maxwell’s equations with paraxial approximation. The initial (P0,ρ0) plane, behaviors of f(ξ) parameter, and perturbed density n/nn0n0 of different plasma temperatures are plotted and analyzed. The plasma temperature is divided into four regions, which leads to different propagation characters including oscillatory divergence, self-trapping, self-focusing, and steady divergence. The plasma density distribution modified by the electric field intensity and plasma temperature is discussed.

Effect of temperature on ion motion in future plasma wakefield accelerators

We study the effect of plasma temperature on ion motion in a plasma wakefield accelerator with parameters typical of a future high-energy accelerator. We show that the collapse of the plasma ions caused by the extremely high fields of ultradense electron bunches can be prevented only by a very high plasma ion temperature.

Stability of an ion-ring distribution in a multi-ion component plasma

The stability of a cold ion-ring velocity distribution in a thermal plasma is analyzed. In particular, the effect of plasma temperature and density on the instability is considered. A high ring density (compared to the background plasma) neutralizes the stabilizing effect of the warm background plasma and the ring is unstable to the generation of waves below the lower-hybrid frequency even for a very high temperature plasma. For ring densities lower than the background plasma density, there is a slow instability where the growth rate is less than the background-ion cyclotron frequency and, consequently, the background-ion response is magnetized. This is in addition to the widely discussed fast instability where the wave growth rate exceeds the background-ion cyclotron frequency and hence the background ions are effectively unmagnetized. Thus, even a low density ring is unstable to waves around the lower-hybrid frequency range for any ring speed. This implies that effectively there is no velocity threshold for a sufficiently cold ring.

Fluid Mechanics and Heat Transfer of Liquid Precursor Droplets Injected into High-Temperature Plasmas

Thermo-physical processes in liquid ceramic precursor droplets in plasma were modeled. Models include aerodynamic droplet break-up, droplet transport, as well as heat and mass transfer within individual droplets. Droplet size, solute concentration, and plasma temperature effects are studied. Results are discussed with the perspective of selecting processing conditions and injection parameters to obtain certain types of coating microstructures. Small droplets ( 5 microns) tend to surface precipitate-forming shells with liquid core. They may be subjected to internal pressurization leading to shattering of shells and secondary atomization of liquid within. They arrive at the substrate as broken shells and unpyrolized material.