Plasma Line Research Articles

Influence of the ionic electric field on Stark shifts of neutral helium lines in plasmas

In this work we provide a contribution to Stark shift for some lines of neutral helium in plasmas. The mentioned shift is caused by the collisions of the unbounded electrons with helium atoms in plasmas. We calculate this contribution by taking into account only weak collisions. This contribution takes into consideration the presence of the local electric microfield created by the ions that constitute in part the plasma. The effect of this microfield modifies the electron trajectory and therefore changes the shift formula developed early by using the straight trajectories in the case of neutral emitters. Our new contribution to the Stark shift caused by electron's collision is applied to some HeI lines: 3188 , 3888 , 6678 and 7065 . Our results are confronted with the experimental and theoretical data from the literature which clearly show that the influence of the local electric microfield created by the ions on the Stark shift caused by electron's collision is not negligible and must be taken into account. It turns out that the correction to the theoretical shift for the lines under consideration tends to red.

Electron Density Profile Derived From Ionogram Using Ray Tracing Inversion Method

AbstractThe ionosonde is widely used for detecting electron density profiles below the F2 peak altitude. Extracting precise profiles from ionograms is crucial, as it serves as a significant data source for ionospheric studies and applications. In our study, we utilized the ray tracing profile inversion method (RTPI) to derive more realistic electron density profiles from the ionosonde observations. By comparing the electron density profiles inverted by RTPI method with and without geomagnetic field against the profiles observed by Incoherent Scatter Radar (ISR) plasma lines, we validated the high precision of the RTPI with magnetic field effect method. The results showed that the average height difference and average peak height difference between profiles inverted by RTPI and plasma line observations are less than 10 and 5 km, respectively. Additionally, we quantified the errors associated with the geomagnetic field effect. It would cause an ∼8–10 km overestimation in true height and a ∼10%–15% underestimation in electron density if the geomagnetic field effect is not considered. These errors induced by the magnetic field accumulate with the frequency of the radio waves. Moreover, we conducted a comparative analysis of simulated echo traces using profiles with different E‐layer shapes. It was demonstrated that the key parameters of the bottom structure have a significant impact on ionogram retrieval, while the E‐layer shape has negligible influence on inversion. Furthermore, we analyzed echo traces simulated using ray tracing with and without collision. The collision effect has weak effect on the delay of the radio waves.

Resolving studies of Balmer alpha lines relevant to the LIBS analysis of hydrogen isotope retention

Utilizing Laser-Induced Breakdown Spectroscopy (LIBS) for detecting deuterium and tritium retention in fusion devices poses a significant challenge due to the experimental limitations in resolving hydrogen isotope Balmer alpha lines (Hα, Dα, and Tα). This study utilizes the Rayleigh criterion to distinguish Tα and Dα lines by determining the maximum line widths and corresponding plasma parameters. Experimental validation was performed through LIBS analysis of heavy water-doped graphite/silica gel targets in both argon and helium atmospheres to assess the predicted plasma parameters and line profile shapes. The optimization of laser pulse energy, gas pressure, delay, and gate times aimed at achieving fully resolved lines based on the intensity, width, and the dip between deuterium and hydrogen Balmer alpha lines. By fine-tuning these experimental parameters, the study successfully achieved a dip of less than 10 % between the Hα and Dα lines with a satisfactory signal-to-noise ratio, demonstrating the feasibility of fully resolving the Tα and Dα lines. These findings underscore the potential of LIBS in enhancing the detection of deuterium and tritium retention in fusion devices.

Description of the Stark Broadening of Spectral Lines in Plasmas Taking into Account the Nonstationary Ion Microfield within the Theory of Markov Processes

Description of the Stark Broadening of Spectral Lines in Plasmas Taking into Account the Nonstationary Ion Microfield within the Theory of Markov Processes

Global Coronal Plasma Diagnostics Based on Multislit Extreme-ultraviolet Spectroscopy

Full-disk spectroscopic observations of the solar corona are highly desired to forecast solar eruptions and their impact on planets and to uncover the origin of solar wind. In this paper, we introduce a new multislit design (five slits) to obtain extreme-ultraviolet (EUV) spectra simultaneously. The selected spectrometer wavelength range (184–197 Å) contains several bright EUV lines that can be used for spectral diagnostics. The multislit approach offers an unprecedented way to efficiently obtain the global spectral data but the ambiguity from different slits should be resolved. Using a numerical simulation of the global corona, we primarily concentrate on the optimization of the disambiguation process, with the objective of extracting decomposed spectral information of six primary lines. This subsequently facilitates a comprehensive series of plasma diagnostics, including density (Fe xii 195.12/186.89 Å), Doppler velocity (Fe xii 193.51 Å), line width (Fe xii 193.51 Å), and temperature diagnostics (Fe viii 185.21 Å, Fe x 184.54 Å, Fe xi 188.22 Å, and Fe xii 193.51 Å). We find a good agreement between the forward modeling parameters and the inverted results at the initial eruption stage of a coronal mass ejection, indicating the robustness of the decomposition method and its immense potential for global monitoring of the solar corona.

Optimization of single-needle red cell exchange in patients with sickle cell disease.

The hypercoagulable state associated with sickle cell disease (SCD) can be challenging for apheresis procedures. Among 62 single-needle red cell exchanges (SN-RCEs) performed over a 15-month period, 4 patients experienced 6 hemolytic events with a discolored plasma layer, elevated plasma/RBC interface in the centrifuge, and accompanying alarms of "Cells were detected in plasma line from centrifuge" or "AIM system detected RBC at top of connector." The hemolysis originated from the apheresis instrument because samples from the apheresis belt but not the patients' peripheral blood were positive for hemolysis. Further analysis showed the alarms occurred more often in SN-RCEs (20.4%) than double-needle RCEs (2.7%), and the hemolysis was probably secondary to clumping. To optimize SN-RCE, we increased the anticoagulant dosage by changing Inlet/AC ratio from 13 to 8 and lowered the inlet rate to the level comparable to double-needle RCE. The adjustments were well-tolerated with no more hemolysis.

Review of recent analytical advances in the spectroscopy of hydrogenic lines in plasmas

Abstract Broadening of hydrogenic spectral lines is an important tool in spectroscopic diagnostics of various laboratory and astrophysical plasmas. We review recent analytical advances in three areas. First, we review the analytical solution for the splitting of hydrogenic lines under the combination of a circularly polarized electromagnetic wave with a strong magnetic field. Practical applications of this solution relate to the spectroscopic diagnostic of the electron cyclotron waves and to the relativistic laser–plasma interactions. Second, we review analytical results concerning the Stark–Zeeman broadening of the Lyman-alpha (Ly-alpha) line in plasmas. These results allow for the Stark width of the Ly-alpha π-component to be used for the experimental determination of the ion density or of the root-mean-square field of a low-frequency electrostatic plasma turbulence in the situation where the Zeeman effect dominates over the Stark effects. Third, we review recent analytical advances in the area of the intra-Stark spectroscopy: three different new methods, based on the emergent phenomenon of the Langmuir-wave-caused structures (“L-dips”) in the line profiles, for measuring super-strong magnetic fields of the GigaGauss range developing during relativistic laser–plasma interactions. We also review the rich physics behind the L-dips phenomenon – because there was a confusion in the literature in this regard.

Laser Measurement of Anomalous Electron Diffusion in a Crossed-Field Plasma.

The anomalous diffusion of particles and energy in magnetized plasma systems is a widespread phenomenon that can adversely impact their operation and preclude predictive models. In this Letter, this diffusion is characterized noninvasively in a low-temperature, Hall-type plasma. Laser-induced fluorescence and incoherent Thomson scattering measurements are combined with a 1D generalized Ohm's law to infer the time-averaged inverse Hall parameter, a transport coefficient that governs cross-field diffusion. While the measured diffusion profile agrees with model-based estimates in magnitude, the measurements do not exhibit the steep "transport barrier" typically imposed in models. Instead, these results show that the electric field is primarily driven by a diamagnetic contribution due to the large peak electron temperature exceeding 75eV. This finding motivates a reconsideration of nonclassical energy transport across field lines in low-temperature plasmas.

Statistical analysis of magnetic divertor configuration influence on H-mode transitions

DIII-D plasmas are compared for two upper divertor configurations: with the outer strike point on the small angle slot (SAS) divertor target and with the outer strike point on the horizontal divertor target (HT). Scanning the vertical distance between the magnetic null point and the divertor target over a range 0.10–0.16 m is shown to increase the threshold power, Pth , and edge plasma power, PLoss , for the low-to-high confinement (L–H) and H–L transitions respectively, by up to a factor of 1.4. The X-point height scans were performed at three L-mode core plasma line average electron densities, n¯e= 1.2, 2.2 and 3.6 ×1019m−3 , to investigate the density dependence of divertor magnetic configuration influence on Pth . The X-point height, Zx-pt , was further extended across the range 0.16–0.22 m with the more open HT divertor configuration, for which a clear decrease in Pth with increasing Zx-pt is observed. The dependence of Pth on divertor magnetic geometry is further investigated using a time-dependent probability density function (PDF) model and information geometry to elucidate the roles played by pedestal plasma turbulence and perpendicular velocity flows. The degree of stochasticity of the plasma turbulence is observed to be sensitive to the plasma heating rate. The calculated square of the information rate shows changes in the relative density fluctuations and perpendicular velocity PDFs begin 2–5 ms prior to the L–H transition for three plasmas; providing a crucial measurement of the dynamic timescale of external transport barrier formation. Additionally, both information length and rate provide potential predictors of the L–H transition for these plasmas.

Abstract 5017: Analytical performance of contrived samples for validation of liquid biopsy assays

Abstract Introduction: Cell-free DNA (cfDNA) extracted from plasma is critical for the analytical validation of liquid biopsy assays. cfDNA is comprised of genetic material from tumor and non-tumor cells, which can be highly variable across tumor types and disease stage. Relative to tumor tissue, cfDNA yield is lower and may not always capture all clinically relevant variants (e.g. gene fusions). Supplementing analytical validation studies with contrived samples prepared from cell line derived DNA to mimic the features of cfDNA allows for more robust testing of rare variants in clinical samples. To determine the commutability of contrived sample DNA to clinical plasma sample cfDNA, a retrospective analysis of sensitivity studies using two methods of contrived sample preparation was performed. Methods: The PGDx elio Plasma Focus assay was used to compare sample base size post library preparation and limit of detection (LoD) of clinically relevant variants. Both methods used fragmented cell line DNA with a variant of interest and for method #1, cell line DNA was spiked into noncancerous donor plasma, which was then extracted resulting in a cfDNA and cell line DNA mixture. This contrived sample was diluted using wild-type (WT) DNA extracted from noncancerous donor plasma to obtain a target variant allele frequency (VAF). Method #2 used fragmented cell line DNA diluted with fragmented WT cell line DNA to obtain a target VAF. This retrospective data analysis will include a minimum of 28 samples run in replicate (3-20) across multiple studies. Results: Data obtained from a DNA fragment analyzer post library preparation show similarities between fragmented cell line DNA spiked into plasma, fragmented cell line DNA, and clinical plasma cfDNA, with fragment peaks ranging from 290-320 base pair (bp). The median LoDs across the three sample types (n=28) were also similar for single nucleotide variants (SNVs) at VAFs of 0.70%, 0.76%, 0.72%, indels at VAFs of 0.70%, 1.0%, 0.78%, amplifications at folds of 1.4, 1.3, 1.5, and translocations at fusion read fractions of 0.5%, 0.61%, 0.55%. When comparing the same variants in a contrived sample functional characterization study, the call rates of various dilution levels were similar. A Fisher’s Exact Test of the Hit Rate showed no significant difference for KRAS G12V SNV, ERBB2 amplification, and RET translocation between cell line DNA and clinical cfDNA. Conclusions: This data demonstrates that contrived samples perform with general equivalence to and may be an appropriate substitute for clinical plasma samples, though certain DNA sources may influence overall performance. Overall, fragmented cell line DNA spiked into plasma and fragmented cell line DNA diluted with WT fragmented cell line DNA performed similarly to clinical cfDNA samples representative of the intended use population. Citation Format: Amanda E. Harvey, Cindy K. Maddox, Sonomi O. Dillon, Omar T. Khawar, Ellen L. Verner, Amy Greer, Kenneth C. Valkenburg, Brian J. Caveney, Shakti Ramkissoon. Analytical performance of contrived samples for validation of liquid biopsy assays [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5017.

Electron collisional excitation cross-section measurements and modeling for select Ni-like to Ge-like gold transitions

We have experimentally determined the electron collisional excitation cross-sections for several 3d→4f and 3d→5f excitations in Ni- to Ge-like Au at energies of ∼ 0.4, 1, 2, and 3 keV above threshold energy, ET, for the 3d→4f excitations ( ET ∼ 2.5 keV) and ∼ 0.2, 1, and 2 keV above threshold energy for the 3d→5f excitations ( ET ∼ 3.3 keV). The cross-section measurements are possible by using the GSFC micro-calorimeter to record emission spectra from beam plasmas created in the Livermore EBIT-I electron beam ion trap. The cross-sections are experimentally determined from the ratio of the measured intensities of the collisionally excited lines to the intensities of the radiative recombination lines in monoenergetic electron distribution EBIT-I plasmas. The effects of polarization and Auger processes in the beam plasmas are accounted for in the cross-section determination. Experimentally determined cross-sections are compared with those from HULLAC, DWS, and FAC calculations. The measurements exhibit significant differences with the calculations of these excitation cross-sections.

Effects of density distribution on the Stark width and shift of spectral lines in plasma

A plasma density distribution that arises due to a finite observation volume or is inherent due to turbulence, needs to be accounted for when using spectral lines for plasma diagnostics. Such a distribution distorts line shapes in a non-trivial way and alters their intensities. In the present study, these effects are analyzed. The results are presented analytically and also tabulated for two types of the density distribution, Gaussian and log-normal, over a wide range of the distribution variance. The results are applicable to practically any type of spectral lines used for plasma density diagnostics. Provided also are considerations for choosing spectral lines to minimize uncertainties if a density distribution is expected but its extent is unknown. In addition, an approach for inferring the density distribution based on the line-shape asymmetry is suggested.

Characterization of Magnetized-Plasma System Induced by Laser

This study investigated the effect of applying an external magnetic field on the characteristics of laser-induced plasma, such as its parameters plasma, magnetization properties, emission line intensities, and plasma coefficients, for plasma induced from zinc oxide: aluminum composite (ZO:AL) at an atomic ratio of 0.3 %. Plasma properties include magnetization and emission line intensities. The excitation was done by a pulsed laser of Nd:YAG with 400 mJ energy at atmospheric pressure. Both the electron temperature and number density were determined with the help of the Stark effect principle and the Boltzmann-Plot method. There was a rise in the amount of (ne) and (Te) that was produced by applying a magnetic field and, on the other hand, using the 532 nm wavelength rather than the fundamental wavelength of a laser. The emission lines in the atmosphere's plasma have an appearance of Lorentzian shape. The 532 nm laser exhibited a decrease in both the Larmor radius and the confinement factor compared with the 1064 nm laser. By applying the magnetic field, the Laser Induced Breakdown Spectroscopy (LIBS) intensities increased by 1.44 times when compared to the emissions before applying the field. In addition, the spectral line intensities improved with the fundamental wavelength compared to the second harmonic frequency as a result of the increase in the extracted materials. This is due to the increase in the absorbance of the laser by the target, as some of these materials are excited, so they act as emission sources, which makes them more detectable.

Identification of the melting line in the two-dimensional complex plasmas using an unsupervised machine learning method

Machine learning methods have been widely used in the investigations of the complex plasmas. In this paper, we demonstrate that the unsupervised convolutional neural network can be applied to obtain the melting line in the two-dimensional complex plasmas based on the Langevin dynamics simulation results. The training samples do not need to be labeled. The resulting melting line coincides with those obtained by the analysis of hexatic order parameter and supervised machine learning method.

Plasma line detected by Voyager 1 in the interstellar medium: Tips and traps for quasi-thermal noise spectroscopy

The quasi-thermal motion of plasma particles produces electrostatic fluctuations, whose voltage power spectrum induced on electric antennas reveals plasma properties. In weakly magnetised plasmas, the main feature of the spectrum is a line at the plasma frequency – proportional to the square root of the electron density – whose global shape can reveal the electron temperature, while the fine structure reveals the suprathermal electrons. Since it is based on electrostatic waves, quasi-thermal noise spectroscopy (QTN) provides in situ measurements. This method has been successfully used for more than four decades in a large variety of heliosphere environments. Very recently, it has been tentatively applied in the very local interstellar medium (VLISM) to interpret the weak line discovered on board Voyager 1 and in the context of the proposed interstellar probe mission. The present paper shows that the line is still observed in the Voyager Plasma Wave Science data, and concentrates on the main features that distinguish the plasma QTN in the VLISM from that in the heliosphere. We give several tools to interpret it in this medium and highlight the errors arising when it is interpreted without caution, as has recently been done in several publications. We show recent solar wind data, which confirm that the electric field of the QTN line in a weakly magnetised stable plasma is not aligned with the local magnetic field. We explain why the amplitude of the line does not depend on the concentration of suprathermal electrons, and why its observation with a short antenna does not require a kappa electron velocity distribution. Finally, we suggest an origin for the suprathermal electrons producing the QTN and we summarise the properties of the VLISM that could be deduced from an appropriate implementation of QTN spectroscopy on a suitably designed instrument.

Quasi-thermal Noise Spectroscopy Analysis of Parker Solar Probe Data: Improved Electron Density Model for Solar Wind

We present a comprehensive analysis of electron density measurements in the solar wind using quasi-thermal noise (QTN) spectroscopy applied to data from the first 15 encounters of the Parker Solar Probe mission (2018 November–2023 March). Our methodology involves the identification of the plasma line frequency and the calculation of plasma density based on in situ measurements. By analyzing over 2.1 million data points, we derive a power-law model for electron density as a function of radial distance from the Sun in the range of 13 to 50 R ☉: n e(r) = (343,466 ± 19921) × r (−1.87±0.11). This model provides improved estimates for localizing interplanetary solar radio bursts. Moreover, obtained electron densities can be used for calibrating particle instruments on board the Parker Solar Probe. We discuss its limitations and potential for further refinement with additional Parker Solar Probe encounters.

Visible and Ultraviolet Plasma Lines of the He–Ne Gas Laser

A study of helium–neon laser plasma lines was done using a double grating spectrometer and a helium-neon laser with an emission wavelength of 632.8 nm (15 802 cm−1). The absolute wavenumber, measured to within [Formula: see text]0.2 cm−1, and wavelength of each plasma line are presented, along with intensity and shift relative to the main laser line. Several of the measured lines have not been reported in the literature and are observed at shifts between 0 and 1500 cm−1 from the laser line, a spectral region commonly probed by optical Raman scattering experiments. Accounting for the possibility of second-order diffraction permitted many previously unassigned lines to be attributed to known neon electronic transitions with wavelengths in the ultraviolet region of the electromagnetic spectrum.

Radiative cooling effects on reverse shocks formed by magnetized supersonic plasma flows

We study the structure of reverse shocks formed by the collision of supersonic, magnetized plasma flows driven by an inverse (or exploding) wire array with a planar conducting obstacle. We observe that the structure of these reverse shocks varies dramatically with wire material, despite the similar upstream flow velocities and mass densities. For aluminum wire arrays, the shock is sharp and well-defined, consistent with magneto-hydrodynamic theory. In contrast, we do not observe a well-defined shock using tungsten wires, and instead we see a broad region dominated by density fluctuations on a wide range of spatial scales. We diagnose these two very different interactions using interferometry, Thomson scattering, shadowgraphy, and a newly developed imaging refractometer that is sensitive to small deflections of the probing laser corresponding to small-scale density perturbations. We conclude that the differences in shock structure are most likely due to radiative cooling instabilities, which create small-scale density perturbations elongated along magnetic field lines in the tungsten plasma. These instabilities grow more slowly and are smoothed by thermal conduction in the aluminum plasma.

Hot spots of the main limiter induced by fast ions in experimental advanced superconducting tokamak (EAST)

The main limiter in EAST was observed to endure a high heat load and was cracked near the midplane at the right side during the plasma operation. To explore the heat load carried by fast ion loss toward the main limiter, the neutral beam injection (NBI) and radio frequency power proportion experiment was conducted in EAST where the plasma stored energy and line integrated density were kept almost constant. The hot spot at the right side of the main limiter was observed to be enhanced by co-current perpendicular (co-perp) NBI. An NBI ion loss simulation was performed in the presence of the toroidal field ripple and the Coulomb collision by using the orbit code GYCAVA and the NBI code TGCO. The result indicates that the NBI ion loss by ripple and collision mainly causes a bright area below the midplane of the right side of the main limiter as observed in the EAST experiment. The peak heat load of lost fast ions generated by co-perp NBI is ∼0.5 MW/m2 as obtained by 1 MW of NBI deposited power and comparable with the heat load carried by fast electrons induced by lower hybrid current drive. In addition, increasing the gap between the separatrix and the first-wall limiters in the simulation is found to reduce this heat load.

Comment on Blagoveshchenskaya et al. Artificial Ducts Created via High-Power HF Radio Waves at EISCAT. Remote Sens. 2023, 15, 2300

The claim that incoherent scatter radar data show electron density enhancements of 50–80% during some ionospheric heating experiments in a recent paper is questioned. The backscatter from the monostatic radar can indeed be enhanced during these experiments, but the conclusion that a large electron density increase is the cause is almost certainly wrong. Some natural plasma line data are presented in support of our claim. Previously published studies of similar events and a possible explanation for the observed increases in backscattered power are pointed out.