Plasma Energy Loss Research Articles

Properties of a continuous optical discharge sustained by short-wave infrared laser radiation in high pressure argon

Abstract The paper is devoted to the experimental study of the characteristics of continuous optical discharge (COD) sustained by high power continuous wave laser radiation at a wavelength λ = 1.08 μm in high pressure argon. New data on COD threshold laser power dependence on argon pressure in the range 20-50 bar are obtained. COD threshold laser power is shown to be in good agreement with the data obtained by other authors and theoretical evaluations provided the contribution of plasma energy loss due thermal radiation is taken into account properly. A study of the convective plume oscillations around COD in argon has been carried out. It was found that in a pressure range 25-35 bar the growth of the laser radiation power leads to a decrease in convection oscillation frequency from 33 to 29 Hz, while the radius of the convective plume grows accordingly. The oscillation frequency ν and characteristic radius of the convective plume r0 were found to obey the similarity relation previously established in experiments with COD in xenon.

Influence of temperature and momentum on heavy quark energy loss

We investigated the correlation between temperature and momentum, as well as the impact of temperature and momentum on energy loss in quark-gluon plasma (QGP), along with the primary mechanisms of energy dissipation. Our findings reveal that the threshold momentum increases with rising temperatures, indicating a greater possibility to energy loss at higher temperatures and momenta. Numerical estimates of the losses show that the energy loss in the hot matter is greater than the energy loss in the cold matter. Upon considering energy loss due to polarization, radiation, and collision, we observe that under low transverse momentum conditions, polarization dominates the energy loss, whereas under high transverse momentum conditions, radiation takes precedence. In addition, we found that heavy quarks with lower mass are more prone to energy loss because of the faster thermalization rate.

Color chiral Cherenkov radiation and energy loss in the quark-gluon plasma

We introduce and investigate the color chiral Cherenkov effect which consists in radiation of the circularly polarized gluons by a fast color charge moving with constant velocity in the presence of the chiral magnetic current. We derive the transition rates for all gluon polarizations. We compute the contribution of the color chiral Cherenkov effect to the parton energy loss in the quark-gluon plasma. Published by the American Physical Society 2024

Fast ion relaxation in ITER mediated by Alfvén instabilities

We address the critical issue for future burning plasmas of whether high-energy fusion products or auxiliary heating-beam ions will be confined for a sufficiently long time to compensate for thermal plasma energy losses. This issue can be mitigated by one of the most deleterious collective phenomena—the instability of low, sub-cyclotron frequency Alfvén eigenmodes (AEs), such as toroidicity-induced AEs and reversed-shear AEs in the ITER steady-state scenario. Using a revised quasi-linear (QL) theory applied to energetic particle (EP) relaxation in the presence of AEs, we find that the AE instabilities can affect both neutral beam ions and alpha particles, although the resulting fast ion transport is expected to be modest if classical particle slowing down is assumed. On the other hand, the QL theory predicts that the AE amplitudes will be enhanced by the background microturbulence, although this topic remains outside our scope due to the significant numerical effort required to evaluate these effects. We report our results for EP relaxation dynamics obtained utilizing several tools: (i) a comprehensive linear stability study of the sub-cyclotron Alfvénic spectrum as computed by ideal magnetohydrodynamic NOVA simulations for the AE eigenproblem, (ii) drift kinetic NOVA-C calculations for wave–particle interaction and AE growth/damping rates, and (iii) predictive QL modeling coupled with the global transport code TRANSP to assess the EP relaxation on the equilibrium timescale.

Numerical study on spark characteristics and evolution of plasma jet igniter

In this paper, a compressible spark plasma simulation model with fully coupled electromagnetic, flow, and thermal multi-physics process is developed based on COMSOL, and the evolution of spark properties during the spark plasma development of embedded plasma jet igniter is investigated by combining high-speed ICCD experimental data. The results show that in the early stage of spark plasma discharge, strong electric field distortion occurs in the near cathode electrode area, current density and temperature rise sharply, which develop close to each other and subsequently form spark plasma discharge channels; during the discharge development period, under the continuous Joule heat deposition, the plasma channel temperature rises and volume expands, and the plasma high pressure channel formed has obvious ‘shockwave-like’ pressure interrupted surface with the surrounding environment, and the ‘shockwave-like’ pressure interrupted surface propagates and reflects in the igniter cavity, driving the plasma cluster to move outward. The energy is gradually dissipated as the spark cluster rolls outside the igniter cavity sucking in the surrounding cold air. The energy loss of the spark plasma comes mainly from the heat exchange with the surrounding environment and the partial stay in the igniter cavity of the ignition plasma cluster that fails to participate in the ignition.

Flavor hierarchy of parton energy loss in quark-gluon plasma from a Bayesian analysis

The quenching of light and heavy flavor hadrons in relativistic heavy-ion collisions probes the color and flavor dependences of parton energy loss through a color-deconfined quark-gluon plasma (QGP), and thus offers an important test of QCD-based calculation at extremely high density and temperature. By combining a next-to-leading order perturbative QCD calculation of parton production, a general ansatz of parton energy loss functions and parton fragmentation functions, we calculate the nuclear modification of various hadron species – charged hadrons, D mesons and B-decayed J/ψ – over a wide transverse momentum regime. Comparing our calculations to the experimental data using the Bayesian statistical analysis, we perform a first simultaneous extraction of the energy loss functions of gluons (g), light quarks (q), charm quarks (c) and bottom quarks (b) inside the QGP. We find that the average parton energy loss at high energies follows the expected hierarchy of 〈ΔEg〉>〈ΔEq〉∼〈ΔEc〉>〈ΔEb〉, while the parton energy loss distribution can further test the QCD calculations of parton interaction with the dense nuclear matter. We also find that the reduction of experimental uncertainties can significantly improve the precision of the extracted parton energy loss functions inside the QGP.

Plasma Energy Loss by Cathode Heat Conduction in a Vacuum Arc: Cathode Effective Voltage

The importance of understanding the energy loss specifics by the cathode for vacuum arc metallic plasma generation and its applications were emphasized. To this end, the heat conduction losses per unit current were characterized by the cathode effective voltage uef, which is weakly dependent on the current. In this paper, a physical model and a mathematical approach were developed to describe the energy dissipation due to heat conduction in the cathode body, which is heated by energy outflowed from the adjacent plasma. The arc plasma generation was considered by taking into account the kinetics of the heavy particle fluxes in the non-equilibrium layer near the vaporizing surface. The phenomena of electric sheath, heat and mass transfer at the cathode were taken into account. The self-consistent numerical analysis was performed with a system of equations for a copper cathode spot. The transient analysis starts from the spot initiation, modeled by the plasma arising at the initial time determined by the kind of arc triggering, up to spot development. The results of the calculations show that the cathode effective voltage uef is determined by the cathode temperature as a function of spot time. The calculated evolution of the voltage uef shows that the steady state of uef is approximately 7 V, and it is reached when the cathode temperature reaches a steady state at approximately one microsecond. This essential result provides an explanation for the good agreement with the experimental cathode effective voltage (6–8 V) measured for the arc duration from one millisecond up to a few seconds.

Measurement of electrons from open heavy-flavor hadron decays in Au+Au collisions at sqrt{s_{textrm{NN}}} = 200 GeV with the STAR detector

We report a new measurement of the production of electrons from open heavy-flavor hadron decays (HFEs) at mid-rapidity (|y| < 0.7) in Au+Au collisions at sqrt{s_{textrm{NN}}} = 200 GeV. Invariant yields of HFEs are measured for the transverse momentum range of 3.5 < pT< 9 GeV/c in various configurations of the collision geometry. The HFE yields in head-on Au+Au collisions are suppressed by approximately a factor of 2 compared to that in p + p collisions scaled by the average number of binary collisions, indicating strong interactions between heavy quarks and the hot and dense medium created in heavy-ion collisions. Comparison of these results with models provides additional tests of theoretical calculations of heavy quark energy loss in the quark-gluon plasma.

Study of charged particle production at high pT using event topology in pp, p–Pb and Pb–Pb collisions at [formula omitted] TeV

This letter reports measurements which characterize the underlying event associated with hard scatterings at mid-pseudorapidity (|η|<0.8) in pp, p–Pb and Pb–Pb collisions at centre-of-mass energy per nucleon pair, sNN=5.02TeV. The measurements are performed with ALICE at the LHC. Different multiplicity classes are defined based on the event activity measured at forward rapidities. The hard scatterings are identified by the leading particle defined as the charged particle with the largest transverse momentum (pT) in the collision and having 8 <pT<15GeV/c. The pT spectra of associated particles (0.5 ≤pT<6GeV/c) are measured in different azimuthal regions defined with respect to the leading particle direction: toward, transverse, and away. The associated charged particle yields in the transverse region are subtracted from those of the away and toward regions. The remaining jet-like yields are reported as a function of the multiplicity measured in the transverse region. The measurements show a suppression of the jet-like yield in the away region and an enhancement of high-pT associated particles in the toward region in central Pb–Pb collisions, as compared to minimum-bias pp collisions. These observations are consistent with previous measurements that used two-particle correlations, and with an interpretation in terms of parton energy loss in a high-density quark gluon plasma. These yield modifications vanish in peripheral Pb–Pb collisions and are not observed in either high-multiplicity pp or p–Pb collisions.

Transverse oscillations and an energy source in a strongly magnetized sunspot

The solar corona is two to three orders of magnitude hotter than the underlying photosphere, and the energy loss of coronal plasma is extremely strong, requiring a heating flux of over 1,000 W m−2 to maintain its high temperature. Using the 1.6 m Goode Solar Telescope, we report a detection of ubiquitous and persistent transverse waves in umbral fibrils in the chromosphere of a strongly magnetized sunspot. The energy flux carried by these waves was estimated to be 7.52 × 106 W m−2, three to four orders of magnitude stronger than the energy loss rate of plasma in active regions. Two-fluid magnetohydrodynamic simulations reproduced the high-resolution observations and showed that these waves dissipate significant energy, which is vital for coronal heating. Such transverse oscillations and the associated strong energy flux may exist in a variety of magnetized regions on the Sun, and could be the observational target of next-generation solar telescopes.

Measurement of beauty production via non-prompt D0 mesons in Pb-Pb collisions at sqrt{{textrm{s}}_{textrm{NN}}} = 5.02 TeV

The production of non-prompt D0 mesons from beauty-hadron decays was measured at midrapidity (|y| < 0.5) in Pb-Pb collisions at a nucleon-nucleon center-of-mass energy of sqrt{{textrm{s}}_{textrm{NN}}} = 5.02 TeV with the ALICE experiment at the LHC. Their nuclear modification factor (RAA), measured for the first time down to pT = 1 GeV/c in the 0–10% and 30–50% centrality classes, indicates a significant suppression, up to a factor of about three, for pT> 5 GeV/c in the 0–10% central Pb-Pb collisions. The data are described by models that include both collisional and radiative processes in the calculation of beauty-quark energy loss in the quark-gluon plasma, and quark recombination in addition to fragmentation as a hadronisation mechanism. The ratio of the non-prompt to prompt D0-meson RAA is larger than unity for pT> 4 GeV/c in the 0–10% central Pb-Pb collisions, as predicted by models in which beauty quarks lose less energy than charm quarks in the quark-gluon plasma because of their larger mass.

Critical Mach Numbers for Magnetohydrodynamic Shocks with Accelerated Particles and Waves

The first critical fast Mach number is defined for a magnetohydrodynamic shock as the Mach number where the shock transitions from subcritical, laminar behavior to supercritical behavior, characterized by incident ion reflection from the shock front. The ensuing upstream waves and turbulence are convected downstream, leading to a turbulent shock structure. Formally, this is the Mach number where plasma resistivity can no longer provide sufficient dissipation to establish a stable shock, and is characterized by the downstream flow speed becoming subsonic. We revisit these calculations, including in the MHD jump conditions terms modeling the plasma energy loss to accelerated particles and the presence of waves associated with these particles. The accelerated particle contributions make an insignificant change, but the associated waves have a more important effect. Upstream waves can be strongly amplified in intensity on passing through the shock, and they represent another means of shock dissipation. The presence of such waves therefore increases the first critical fast Mach number, especially at quasi-parallel shock where wave excitation is strongest. These effects may have significance for the solar regions where shock waves accelerate particles and cause Type II and Type III radio bursts, and they could also contribute to the event-to-event variability of SEP acceleration.

B2.5-Eunomia simulations of Magnum-PSI detachment experiments: II. Collisional processes and their relevance

Detachment is achieved in Magnum-PSI by increasing the neutral background pressure in the target chamber using gas puffing. The plasma is studied using the B2.5 multi fluid plasma code B2.5 coupled with Eunomia, a Monte Carlo solver for neutral species. This study focuses on the effect of increasing neutral background pressure to the plasma volumetric loss of particle, momentum and energy. The plasma particle and energy loss almost linearly scale with the increase of neutral background pressure, while the momentum loss does not scale as strongly. Plasma recombination processes include molecular activated recombination (MAR), dissociative attachment, and atomic recombination. Atomic recombination, which includes radiative and three-body recombination, is the most relevant plasma process in reducing the particle flux and, consequently, the heat flux to the target. The low temperature where atomic recombination becomes dominant is achieved by plasma cooling via elastic H+−H2 collisions. The transport of vibrationally excited H2 molecules out of the plasma serves as an additional electron cooling channel with relatively small contribution. Additionally, the transport of highly vibrational H2 has a significant impact in reducing the effective MAR and dissociative attachment collision rates and should be considered properly. The relevancy of MAR and atomic recombination occupy separate electron temperature regimes, respectively, at eV and eV, with dissociative attachment being relevant in the intermediary. Plasma cooling via elastic H+−H2 collisions is effective at eV.

Mitigation of disruption on IR-T1 tokamak by means of low-energy neutral beam injection to control runaway electron generation

In a tokamak, the poloidal magnetic field provided by the toroidal plasma current forms an essential part of the magnetic field confining the plasma. However, instabilities of magnetohydrodynamic equilibrium can lead to an uncontrolled sudden loss of plasma current and energy, which is called a disruption. Disruptions are of significant concern to future devices due to the large amount of energy released during the rapid quenching of the plasma. One important consequence of disruption is the generation of significant current carried in multi-MeV runaway electrons that are eventually lost into plasma components. They can damage the tokamak walls and its structure if they are not controlled. Disruption control by neutral beam injection has been performed on IR-T1 to study the effect on runaway electron generated by plasma disruptions. Noble gases are used for injection, pure Hydrogen, Helium and Argon. The use of these non-reactive gases for disruption control ensures they fast removed from the vessel after the termination of a tokamak discharge. A piezo-valve is used for injection which has the precision of 1 ms. The effect of runaway electron generation control during disruption is studied using a comparison between reference disruptive discharge and a discharge into which different impurity species are injected. The data collected can then be used to optimize the performance of these energetic electrons control generated in disruption.

Heavy quark energy loss in the quark-gluon plasma in the Moller theory

We study the energy loss of a heavy quark propagating in the quark-gluon plasma (QGP) in the framework of the Moller theory, including possible large Coulomb logarithms as a perturbation to BDMPSZ bremsstrahlung, described in the harmonic oscillator (HO) approximation. We derive the analytical expression that describes the energy loss in the entire emitted gluon frequency region. In the small frequencies region, for angles larger than the dead cone angle, the energy loss is controlled by the BDMPSZ mechanism, while for larger frequencies it is described by N = 1 term in the GLV opacity expansion. We estimate corresponding quenching rates for different values of the heavy quark path length and different m/E ratios.

PIC simulation for dense high Z plasma formation with ultrashort petawatt laser including radiation processes

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 the algorithm of radiation energy loss in hot plasmas enabling self-consistent PIC simulations of the silver plasma formation with radiation cooling. We demonstrated the highly charged silver plasma formation with a pressure of ~ 10 petapascal by irradiating a petawatt laser with peak intensity of 1021 W/cm2 in 30 femtoseconds. The energy stored in the hot silver plasma is released as hard X-rays photons in a few picosecond time scale with radiation intensity of 1017 W/cm2. The energy conversion from the laser to the emitted X-rays reaches ~ 10%.

Radiation energy losses in a single chamber three phase plasma torch with rod electrodes

The paper deals with the results of the study of the plasma energy loss in a chamber of the three phase alternating current arc plasma torch at pressures above atmospheric. It is shown that the loss due to radiation takes the main share. A time-averaged estimation of the radiation power per unit length of the arcs and its dependence on pressure was obtained based on the results of calorimetric measurements of the heat flux into the end part of the plasma torch. The dependence of the fraction of energy loss by radiation versus the total loss in the plasma torch chamber depending on the pressure and gas flow rate are presented. The dependence of the efficiency of the plasma torch versus the gas flow rate and pressure is also given. Studies were conducted on a plasma torch over the power range from 50 to 200 kW. The working gas was nitrogen.

Beam Dynamics Simulation for the Plasma Investigation on the Experimental Facility HIPr-1

The HIPr-1 (Heavy-Ion Prototype) beam transport channel was designed for performing experiments to measure the energy losses in plasma, which was developed considering the results of the beam dynamics simulation.

Study of end-cell plasma parameters of GAMMA 10/PDX by the LINDA code

This research numerically investigates the plasma behavior during neutral gases puffing into the west end-cell of the linear plasma confinement device GAMMA 10/PDX. A multi-fluid code named ‘LINDA’ is developed and applied at the west end-cell of the device to explore the processes of plasma detachment and energy loss mechanism during plasma-neutral interactions. The ion heat flux limiter is newly introduced in the LINDA code. In the paper, we investigate the influence of the ion heat flux limiter in our divertor plasma models to understand how the ion heat flux limiter affects the computed plasma parameters. The upstream plasma parameters are The effect of ion heat flux limiting reduces the ion temperature and heat flux in the direction of the target plate. The ion temperature profile is shown to be similar when the heat flux limiting factor (αi) is varied from 0.2 to 2.0. The effect of Hydrogen (H) and Argon (Ar) gas puffing has been investigated under the condition of ion heat flux limiting factors αi = 1.0. The ion temperature is shown to be similar between Ar and without Ar puffing. On the other hand, Te reduces remarkably for Ar puffing by enhancing the radiation cooling of Ar. The ion and electron loss are greatly enhanced for combined puffing of Ar and H. The ionization loss is found to be slightly higher and the charge-exchange loss is found to be slightly lower during the ion heat flux limiting case. These outcomes may contribute to understanding the plasma detachment processes in fusion devices.

Neutron Time-of-Flight Measurements of Charged-Particle Energy Loss in Inertial Confinement Fusion Plasmas.

Neutron spectra from secondary ^{3}H(d,n)α reactions produced by an implosion of a deuterium-gas capsule at the National Ignition Facility have been measured with order-of-magnitude improvements in statistics and resolution over past experiments. These new data and their sensitivity to the energy loss of fast tritons emitted from thermal ^{2}H(d,p)^{3}H reactions enable the first statistically significant investigation of charged-particle stopping via the emitted neutron spectrum. Radiation-hydrodynamic simulations, constrained to match a number of observables from the implosion, were used to predict the neutron spectra while employing two different energy loss models. This analysis represents the first test of stopping models under inertial confinement fusion conditions, covering plasma temperatures of k_{B}T≈1-4 keV and particle densities of n≈(12-2)×10^{24} cm^{-3}. Under these conditions, we find significant deviations of our data from a theory employing classical collisions whereas the theory including quantum diffraction agrees with our data.