scholarly journals Observation and Modeling of Optical Emission Patterns and Their Transitions in a Penning Discharge

2008 ◽  
Vol 2008 ◽  
pp. 1-7 ◽  
Author(s):  
C. C. Klepper ◽  
R. C. Hazelton ◽  
F. Barakat ◽  
M. D. Keitz ◽  
J. P. Verboncoeur
Keyword(s):  
Fusion Energy ◽  
Optical Emission ◽  
Nonlinear Dependence ◽  
Sensor Technology ◽  
Gaseous Species ◽  
Optical Signals ◽  
Particle In Cell ◽  
Neutral Gas ◽  
Minority Species ◽  
Mode Transitions

A Penning discharge tube has been used as the excitation source for optical detection of gaseous species concentrations in a neutral gas. This type of diagnostic has been primarily used in magnetic fusion energy experiments for the detection of minority species in the effluent gas (e.g., for helium detection in a deuterium background). Recent innovations (US Patent no. 6351131, granted February 26, 2002) have allowed for extension of the operation range from <1 Pa to as high as 100 Pa and possibly beyond. This is done by dynamically varying the gauge magnetic field and voltage to keep the optical signals nearly constant (or at least away from a nonlinear dependence on the pressure). However, there are limitations to this approach, because the Penning discharge can manifest itself in a number of modes, each exhibiting a different spatial emission pattern. As a result, varying the discharge parameters can cause the gauge to undergo transitions between these modes, disrupting any intended monotonic dependence of the overall emission on the varied parameter and hence any predicable impact on the emission. This paper discusses some of the modes observed experimentally using video imaging of the discharge. It also presents a first successful application, a particle-in-cell (PIC) code, to simulate these modes and a mode transition. The hope is that a good understanding of the physics involved in the mode transitions may allow for methods of either avoiding or suppressing such transitions. This would aid in broadening the use of this plasma-based sensor technology.

scholarly journals Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas

2020 ◽  
Vol 6 (27) ◽  
pp. eaay9711 ◽  
Author(s):  
D. Krishnarao ◽  
R. A. Benjamin ◽  
L. M. Haffner
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Center ◽  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Hydrogen Gas ◽  
Emission Lines ◽  
Neutral Gas ◽  
Optical Line ◽  
Tilted Disk

Optical emission lines are used to categorize galaxies into three groups according to their dominant central radiation source: active galactic nuclei, star formation, or low-ionization (nuclear) emission regions [LI(N)ERs] that may trace ionizing radiation from older stellar populations. Using the Wisconsin H-Alpha Mapper, we detect optical line emission in low-extinction windows within eight degrees of Galactic Center. The emission is associated with the 1.5-kiloparsec-radius “Tilted Disk” of neutral gas. We modify a model of this disk and find that the hydrogen gas observed is at least 48% ionized. The ratio [NII] λ6584 angstroms/Hα λ6563 angstroms increases from 0.3 to 2.5 with Galactocentric radius; [OIII] λ5007 angstroms and Hβ λ4861 angstroms are also sometimes detected. The line ratios for most Tilted Disk sightlines are characteristic of LI(N)ER galaxies.

Petascale particle-in-cell simulations of kinetic effects in inertial fusion energy plasmas

2019 ◽  
Vol 61 (4) ◽  
pp. 044007
Author(s):  
H Wen ◽  
F S Tsung ◽  
W B Mori ◽  
R A Fonseca ◽  
L O Silva
Keyword(s):  
Fusion Energy ◽  
Inertial Fusion ◽  
Inertial Fusion Energy ◽  
Particle In Cell ◽  
Kinetic Effects

Electrostatic particle-in-cell simulation of heat flux mitigation using magnetic fields

2016 ◽  
Vol 82 (5) ◽  
Author(s):  
Karl Felix Lüskow ◽  
S. Kemnitz ◽  
G. Bandelow ◽  
J. Duras ◽  
D. Kahnfeld ◽  
...  
Keyword(s):  
Heat Flux ◽  
Magnetic Fields ◽  
Turbulent Transport ◽  
Optical Emission ◽  
Emission Region ◽  
Transport Channel ◽  
Particle In Cell ◽  
Heat Deposition ◽  
Cell Simulation ◽  
Pic Method

The particle-in-cell (PIC) method was used to simulate heat flux mitigation experiments with partially ionised argon. The experiments demonstrate the possibility of reducing heat flux towards a target using magnetic fields. Modelling using the PIC method is able to reproduce the heat flux mitigation qualitatively. This is driven by modified electron transport. Electrons are magnetised and react directly to the external magnetic field. In addition, an increase of radial turbulent transport is also needed to explain the experimental observations in the model. Close to the target an increase of electron density is created. Due to quasi-neutrality, ions follow the electrons. Charge exchange collisions couple the dynamics of the neutrals to the ions and reduce the flow velocity of neutrals by radial momentum transport and subsequent losses. By this, the dominant heat-transport channel by neutrals gets reduced and a reduction of the heat deposition, similar to the experiment, is observed. Using the simulation a diagnostic module for optical emission is developed and its results are compared with spectroscopic measurements and photos from the experiment. The results of this study are in good agreement with the experiment. Experimental observations such as a shrank bright emission region close to the nozzle exit, an additional emission in front of the target and an overall change in colour to red are reproduced by the simulation.

scholarly journals Numerical studies on terahertz radiation generated from two-color laser pulse interaction with gas targets

2011 ◽  
Vol 29 (4) ◽  
pp. 447-452 ◽  
Author(s):  
H.W. Du ◽  
M. Chen ◽  
Z.M. Sheng ◽  
J. Zhang
Keyword(s):  
Intensity Ratio ◽  
Second Harmonic ◽  
Electromagnetic Emission ◽  
Current Theory ◽  
Particle In Cell ◽  
Neutral Gas ◽  
Ionization Model ◽  
The Difference ◽  
Gas Targets ◽  
Proper Values

AbstractBased upon the Ammosov-Delone-Krainov ionization model, it is shown that two-color laser interaction with neutral gas generates strong ionization currents, which lead to electromagnetic emission at terahertz frequency when the gas density is at proper values. The emission efficiency depends on the difference of the phases between the fundamental and its second harmonic. The intensity ratio between the two pulses also affects the emission strength. An optimum intensity ratio has been found within our parameter region. The above ionization current theory is in agreement with one-dimensional particle-in-cell simulations with field ionization included.

Optical Sensing of Lean Blowout Precursors in a Premixed Swirl Stabilized Dump Combustor

2003 ◽  
Author(s):  
Thiruchengode M. Muruganandam ◽  
Jerry M. Seitzman
Keyword(s):  
Optical Fibers ◽  
Optical Emission ◽  
Transient Behavior ◽  
Sensor Technology ◽  
Loop Control ◽  
Turbine Engine ◽  
Lean Blowout ◽  
Dump Combustor ◽  
Closed Loop Control System ◽  
Loop Control System

The work described here is part of an effort to detect and prevent lean blowout in turbine engine combustors. The approach uses optical emission, primarily chemiluminescence, to identify blowout precursor events, and is demonstrated in a premixed, swirl-stabilized dump combustor. The results show that the transient behavior of the flame as lean blowout is approached is characterized by short duration, localized extinction and reignition events. These events increase in frequency and duration, and spatial extent, as LBO is approached. Several methods can be used to detect these events in the raw sensor output, including signal thresholding and frequency analysis. The paper describes examples of how these analysis techniques can be used to calculate a simple LBO proximity measure that would be ideally suited for use in an active (closed-loop) control system. The LBO proximity sensing is also demonstrated using sensor technology that is close to what would be required in a realistic turbine engine environment, specifically, optical fibers to collect the chemiluminescence and miniature, metal package PMTs for detection. Possible detection locations within the combustor are discussed and various locations are compared, based on their practicality and sensitivity to LBO precursor detection. It was found that the best detection was from fiber that was mounted on the head end and viewed downstream.

Advances in dielectric barrier discharge-optical emission spectrometry for the analysis of trace species

2015 ◽  
Vol 7 (5) ◽  
pp. 1660-1666 ◽  
Author(s):  
Yong-Liang Yu ◽  
Yu-Ting Zhuang ◽  
Jian-Hua Wang
Keyword(s):  
Aqueous Medium ◽  
Dielectric Barrier Discharge ◽  
Barrier Discharge ◽  
Optical Emission ◽  
Optical Emission Spectrometry ◽  
Emission Spectrometry ◽  
Gaseous Species ◽  
Dielectric Barrier ◽  
Trace Species

This mini-review presents and discusses the progress of dielectric barrier discharge-optical emission spectrometry systems in the analysis of gaseous species and those in an aqueous medium.

Breakdown Process of Pseudospark Discharge Using the Various Discharge Module

2014 ◽  
Vol 670-671 ◽  
pp. 1012-1015
Author(s):  
Xiao Wei Gu
Keyword(s):  
Gas Phase ◽  
Theoretical Foundation ◽  
Secondary Electron Emission ◽  
Design Parameters ◽  
Physical Processes ◽  
Particle In Cell ◽  
Breakdown Process ◽  
Neutral Gas ◽  
Pseudospark Discharge ◽  
Electrons And Ions

A argon Pseudospark discharge is studied and modelled with our developed simulation program. The structure of our code is flexible and transparent. The modular structure is divided into three main parts: electromagnetics module which forms the heart of the model, the neutral gas module, and the chemical reaction module. The above three parts with the plasma module are controlled by the user. The strong modularity makes the code easy to handle and easy to adjust or expand. This project will do in-depth numerical simulation for the study of the inception of breakdown characteristics via a electrostatic particle-in-cell plus Monte-Carlo collision method. The model tracks the trajectories of both electrons and ions, including ionizing collisions in the gas phase by electrons and ions, and secondary electron emission by ions on surfaces. The result indicated the pseudospark discharge breakdown process mainly induced by field emission.The peak discharge current is found to be dependent on gas pressure,electrode borehole diameter. The effect of these design parameters on the peak anode current has been analysed. Simulate the discharge breakdown physical processes for the Pseudospark in order to lay the theoretical foundation for the optimize and improve the pulse power electron beam.

Ion-Focused Propagation of Relativistic Electron Beam in the Self-Generated Plasma in the Atmosphere

2022 ◽  
Author(s):  
Hao Jian-Hong ◽  
Xue Bi-Xi ◽  
Zhao Qiang ◽  
Zhang Fang ◽  
Fan Jie-Qing ◽  
...  
Keyword(s):  
Electron Beam ◽  
Relativistic Electron ◽  
Long Range ◽  
Relativistic Electron Beam ◽  
Beam Quality ◽  
Pulse Length ◽  
Space Environment ◽  
Long Distance ◽  
Particle In Cell ◽  
Neutral Gas

Abstract It is known that ion-focused regime can effectively suppress the expansion of relativistic electron beam (REB). By using particle in cell-Monte Carlo collision (PIC-MCC) method, the propagation of REBs in neutral gas is numerically investigated. The numerical results demonstrate that the beam body is charge neutralization and a stable IFR can be established. As a result, the beam transverse dimensions and longitudinal velocities keep close to the initial parameters. We also calculated the charge and current neutralization factors of REBs. Combined with envelope equations, we obtained the variations of beam envelopes, which agree well with the PIC simulations. However, both the energy loss and instabilities of REBs may lead to a low transport efficiency during long-range propagation. It has been proved that decreasing the initial pulse length of REBs can avoid the influence of electron avalanche. Using parts of REB pulses to build a long-distance IFR in advance can improve the beam quality of subsequent pulses. Further, a long-distance IFR may contribute to the implementation of long-range propagation of REBs in the space environment.

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