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At least 199 records · Page 11

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DOE OSTI2016

Electronic transitions of C{sub 5}H{sup +} and C{sub 5}H: neon matrix and CASPT2 studies

Two electronic transitions at 512.3 and 250 nm of linear-C{sub 5}H{sup +} are detected following mass-selective deposition of m/z = 61 cations into a 6 K neon matrix and assigned to the 1 {sup 1}Π←X {sup 1}Σ{sup +} and 1 {sup 1}Σ{sup +}←X {sup 1}Σ{sup +} systems. Five absorption systems of l-C{sub 5}H with origin bands at 528,7, 482.6, 429.0, 368.5, and 326.8 nm are observed after neutralization of the cations in the matrix and identified as transitions from the X {sup 2}Π to 1 {sup 2}Δ, 1 {sup 2}Σ {sup −}, 1 {sup 2}Σ{sup +}, 2 {sup 2}Π, and 3 {sup 2}Π electronic states. The assignment to specific structures is based on calculated excitation energies, vibrational frequencies in the electronic states, along with simulated Franck–Condon profiles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

TRACING HIGH-ENERGY RADIATION FROM T TAURI STARS USING MID-INFRARED NEON EMISSION FROM DISKS

High-energy radiation from T Tauri stars (TTS) influences the amount and longevity of gas in disks, thereby playing a crucial role in the creation of gas giant planets. Here we probe the high-energy ionizing radiation from TTS using high-resolution mid-infrared (MIR) Spitzer Infrared Spectrograph neon forbidden line detections in a sample of disks from IC 348, NGC 2068, and Chamaeleon. We report three new detections of [Ne III] from CS Cha, SZ Cha, and T 54, doubling the known number of [Ne III] detections from TTS. Using [Ne III]-to-[Ne II] ratios in conjunction with X-ray emission measurements, we probe high-energy radiation from TTS. The majority of previously inferred [Ne III]/[Ne II] ratios based on [Ne III] line upper limits are significantly less than 1, pointing to the dominance of either X-ray radiation or soft extreme-ultraviolet (EUV) radiation in producing these lines. Here we report the first observational evidence for hard EUV-dominated Ne forbidden line production in a T Tauri disk: [Ne III]/[Ne II] {approx} 1 in SZ Cha. Our results provide a unique insight into the EUV emission from TTS, by suggesting that EUV radiation may dominate the creation of Ne forbidden lines, albeit in a minority of cases.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2024

Comparative study of boron and neon injections on divertor heat fluxes using SOLPS-ITER simulations

Here, based on the EAST equilibrium, the effects of boron (B) and neon (Ne) injected at different locations on the target heat load, and the distributions of B and Ne particles were investigated by transport code SOLPS-ITER. It was found that the B injection was more sensitive to the injection location for heat flux control than impurity Ne. The high electron and ion densities near the inner target in the discharge with impurity B injected from over X-point (R 1 ) led to plasma detachment only at the inner target, and the localized B ions in the cases with injection from outer target location (R 2 ) and upstream location (R 3 ) led to far-SOL detachment at the outer target, but not at the inner target. In contrast, for Ne, the spatial distributions of Ne ions and electrons were found to be similar in all the cases at the three injection locations, and the detached plasma was achieved at the inner target and the electron temperature was reduced at the outer target. For locations R 2 and R 3 , impurity B showed a more pronounced effect on the heat flux at the far-SOL of the outer target. Further analysis indicated that Ne atoms came mainly from the recycling sources, whereas B atoms came mainly from injection, and that their distinct atomic distributions resulted from the difference in the ionization threshold and ionization mean free path. In addition, the radiation proportion of B in the divertor region was larger than that of Ne when the total radiation power was similar, which suggests that B has less influence on the core region.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2026

Simultaneous ELM suppression and divertor detachment via synergistic boron powder and neon injection in EAST

A novel approach for simultaneous power exhaust and edge-localized mode (ELM) control is presented in the Experimental Advanced Superconducting Tokamak discharges, which utilize an ITER-like tungsten divertor. Real-time injection of boron (B) powder and neon (Ne) gas overcomes their limitations encountered when used separately. Pure Ne seeding leads to a narrow operational window constrained by core impurity accumulation and H-mode to L-mode back transitions, while pure solid B injection (SBI) is insufficient for effective divertor cooling. In comparison, their combined use achieves a stable, stationary, ELM-suppressed H-mode with adequate power exhaust. This synergistic scenario features partial energy detachment at the outer divertor while maintaining good plasma confinement (H 98 ∼ 1) with minimal degradation. Two key features of this scenario are: (1) the SBI triggers a persistent Edge Harmonic Mode (EHM), which provides a crucial continuous particle transport channel, preventing Ne and tungsten/molybdenum accumulation without flushing out by ELM, and (2) the B + Ne mixture allows for active optimization of the radiated power profile. Core radiation can be reduced by substituting a portion of the Ne with B, leveraging their complementary non-coronal equilibrium radiation efficiencies. This combined B + Ne injection scheme presents a promising pathway toward integrated core-edge scenarios, offering the potential to minimize total impurity throughput while leveraging an actuator (powder injection) already being considered for ITER.

Boron↗

DOE OSTI2020

Quantum electronics and optics at the interface of solid neon and superfluid helium

Here, we predict a new quantum electronic structure at the interface between two condensed phases of noble-gas elements: solid neon and superfluid helium. An excess electron injected onto this interface self-confines its wavefunction into a nanometric dome structure. Its size varies with pressure and optical transitions cover a broad mid-infrared spectrum. A collection of such electrons can form a classical Wigner crystal resembling a quantum-dot array on a triangular lattice. Under ultrafast laser illumination, this Wigner crystal can exhibit the quantum optical phenomenon of superradiance in the picosecond time scale. The ultralong spin-coherence time and micron-scale deterministic configurability allow the electrons in this system to serve as quantum information carriers. Their spin states can be controlled and readout by on-chip single-electron devices.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2022

Electron spin coherence on a solid neon surface

We report a single electron floating on the surface of a condensed noble-gas liquid or solid can act as a spin qubit with ultralong coherence time, thanks to the extraordinary purity of such systems. Previous studies suggest that the electron spin coherence time on a superfluid helium (He) surface can exceed 100 s. In this paper, we present theoretical studies of the electron spin coherence on a solid neon (Ne) surface, motivated by our recent experimental realization of single-electron charge qubit on solid Ne. The major spin decoherence mechanisms investigated include the fluctuating Ne diamagnetic susceptibility due to thermal phonons, the fluctuating thermal current in normal metal electrodes, and the quasi-statically fluctuating nuclear spins of the 21 Ne ensemble. We find that at a typical experimental temperature about 10 mK in a fully superconducting device, the electron spin decoherence is dominated by the third mechanism via electron–nuclear spin–spin interaction. For natural Ne with 2700 ppm abundance of 21 Ne, the estimated inhomogeneous dephasing time ${T}_{2}^{*}$ is around 0.16 ms, already better than most semiconductor quantum-dot spin qubits. For commercially available, isotopically purified Ne with 1 ppm of 21 Ne, ${T}_{2}^{*}$ can be 0.43 s. Under the application of Hahn echoes, the coherence time T 2 can be improved to 30 ms for natural Ne and 81 s for purified Ne. Therefore, the single-electron spin qubits on solid Ne can serve as promising new spin qubits.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2017

On the reaction of muon transfer from protium to neon at low collision energies

The reaction of direct muon transfer from protium to neon at thermal collision energies is considered. The question of whether it is possible to reconstruct the energy dependence of the reaction rate on the basis of available experimental data is discussed. A model based on the following two assumptions is proposed: (i) The reaction in question proceeds within an interaction sphere beyond which the entrance channel and the muon-transfer channel decouple. (ii) For s and p waves, the complex logarithmic derivatives of radial wave functions for the entrance channel at the surface of the interaction sphere are independent of energy at low collision energies. Two logarithmic-derivative values that comply with experimental data on the reaction rate at the temperatures of 20 and 300 К are found upon taking into account the s-wave contribution alone. In this temperature range, the reaction rates calculated at the resulting two values do not differ substantially. Sizable distinctions arise only at temperatures of a few kelvin units. The problem of choosing one specific value of the logarithmic derivative is solved by comparing the energy dependence of the S matrix with the results of an earlier calculation. Thereby, the proposed procedure can be viewed as a means for correcting calculations in the low-energy region.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2011

Effect of natural convection on the current-voltage characteristic of a DC discharge in neon at intermediate pressures

The parameters of the positive column of a glow discharge in neon are calculated with allowance for the induced hydrodynamic motion. It is shown that natural convection in the pressure range of {approx}0.1 atm significantly affects the profiles of the parameters of the positive column and its current-voltage characteristic. The convection arising at large deposited energies improves heat removal, due to which the temperature in the central region of the discharge becomes lower than that calculated from the heat conduction equation. As a result, the current-voltage characteristic is shifted. With allowance for convection, the current-voltage characteristic changes at currents much lower than the critical current at which a transition into the constricted state is observed. This change is uniquely related to the Rayleigh number in the discharge. Thus, a simplified analysis of thermal conduction and diffusion, even with detailed account of kinetic processes occurring in the positive column, does not allow one to accurately calculate the current-voltage characteristic and other discharge parameters at intermediate gas pressures.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2013

Optical characteristics and parameters of gas-discharge plasma in a mixture of mercury dibromide vapor with neon

Results are presented from studies of the optical characteristics and parameters of plasma of a dielectric barrier discharge in a mixture of mercury dibromide vapor with neon—the working medium of a non-coaxial exciplex gas-discharge emitter. The electron energy distribution function, the transport characteristics, the specific power losses for electron processes, the electron density and temperature, and the rate constants for the processes of elastic and inelastic electron scattering by the working mixture components are determined as functions of the reduced electric field. The rate constant of the process leading to the formation of exciplex mercury monobromide molecules is found to be 1.6 × 10{sup −14} m{sup 3}/s for a reduced electric field of E/N = 15 Td, at which the maximum emission intensity in the blue-green spectral region (λ{sub max} = 502 nm) was observed in this experiment.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2017

Specific features of a single-pulse sliding discharge in neon near the threshold for spark breakdown

Experimental data on the spatial structure of a single-pulse sliding discharge in neon at voltages below, equal to, and above the threshold for spark breakdown are discussed. The experiments were carried at gas pressures of 30 and 100 kPa and different polarities of the discharge voltage. Photographs of the plasma structure in two discharge chambers with different dimensions of the discharge zone and different thicknesses of an alumina dielectric plate on the surface of which the discharge develops are inspected. Common features of the prebreakdown discharge and its specific features depending on the voltage polarity and gas pressure are analyzed. It is shown that, at voltages below the threshold for spark breakdown, a low-current glow discharge with cathode and anode spots develops in the electrode gap. Above the breakdown threshold, regardless of the voltage polarity, spark channels directed from the cathode to the anode develop against the background of a low-current discharge.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2019

AmeriFlux US-xKZ NEON Konza Prairie Biological Station (KONZ)

This is the AmeriFlux version of the carbon flux data for the site US-xKZ NEON Konza Prairie Biological Station (KONZ). Site Description - Konza Prairie Biological Station (KPBS) was established to provide a "natural laboratory" to conduct ecological research and is located on a 3,487 hectare native tallgrass prairie preserve. KPBS is a field research station dedicated to conservation, education and long-term ecological research. Over 1,580 scientific papers have been published by scientists conducting studies at KPBS. The study of ecological patterns and processes in native tallgrass prairie ecosystems is the primary subject of research.