Plasma Ion Energy Distribution Research Articles

A Pulsed Hollow Cathode Discharge Operated in an Ar/N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}/O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} Gas Mixture and the Formation of Nitric Oxide

A hollow cathode discharge with a CuNi (Cu50Ni50) cathode was operated in an Ar/N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}/O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} gas mixture. The energy distribution of plasma ions is investigated with the help of energy-resolved mass spectrometry. Formation of singly ionised Ar+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^+$$\\end{document} and of Cu+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^+$$\\end{document} and Ni+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^+$$\\end{document} ions is observed in pure argon. With the addition of N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} or O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} gas the additional formation of molecular N2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2^ +$$\\end{document} or O2+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2^+$$\\end{document} ions is observed. The intensity of these ions is reduced in the Ar+N2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document}+O2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} gas mixture and molecular NO+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^+$$\\end{document} ions become the most abundant ionic species. The formation of neutral NO molecules is confirmed by optical emission spectroscopy. Gas samples collected at the exhaust of the vacuum chamber confirm the formation of NO and, additionally, of NO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$_2$$\\end{document} molecules.Graphic Sample taken from the exhaust of the plasma chamber with a liquid-nitrogen-cooled glass container showing solid nitrogen oxide (blue).

Characteristics of a pulsed hollow cathode discharge operated in an Ar+O[formula omitted] gas mixture and deposition of copper nickel oxide thin films

A hollow cathode discharge with a CuNi (Cu50Ni50) cathode is operated inside a vacuum chamber with Ar gas flowing through its nozzle. O2 gas is admitted to the vaccum chamber. Typical Ar+O2 gas pressures are in the range of 2–50 Pa. The energy distribution of plasma ions is investigated with the help of energy-resolved mass spectrometry. Singly charged Ar+ and molecular O2+ ions are the most abundant ionic species. Deposition rate and heat flux to a substrate increase as function of discharge current. At high pressures, the deposition rate is further increased by the directional gas flow, which becomes more focused onto the substrate. Deposited and annealed thin films are analysed by X-ray diffraction and Raman spectroscopy. As-deposited films are composed of a mixed CuxNi1−xO cubic phase with a preferred (111) orientation. Upon annealing at 600 oC, the mixed CuxNi1−xO phase separates into two sub-phases composed of NiO and CuO. Annealed films display a photoelectrochemical (PEC) activity as a photocathode. The PEC activity deteriorates with time, however. This behaviour is related to the reduction of CuO to Cu2O.

Ion energy distribution of plasma ions of a hollow cathode discharge in Ar + N_2 and Ar + O_2 gas mixtures

A hollow cathode discharge with a Ti cathode and a positively biased ring anode was operated in Ar + N_2 or Ar + O_2 gas mixtures. The energy distribution of plasma ions is investigated with the help of energy-resolved mass spectrometry. Singly and doubly charged Ar^+ and Ar^{2+} ions and molecular N_2^+ or O_2^+ ions are the most abundant ionic species. The kinetic energy of all plasma ions is enhanced by a positive anode voltage.Graphical abstract

Peculiarities of measuring ion energy distribution in plasma with a retarding field analyzer.

Presented are the results from tailoring the retarding field energy analyzer to measure the degree of charge compensation and regular patterns in the separations of ions of different mass, with the multicomponent ion flow spreading out in the plasma-optical mass separator model.

Control of ordered mesoporous titanium dioxide nanostructures formed using plasma enhanced glancing angle deposition

Three dimensional nanostructures of mesoporous (pore diameter between 2-50nm) nanocrystalline titania (TiO2) were produced using glancing angle deposition combined with plasma ion assisted deposition, providing plasma enhanced glancing angle deposition eliminating the need for post-annealing to achieve film crystallinity. Electron beam evaporation was chosen to deposit nanostructures at various azimuthal angles, achieving designed variation in three dimensional nanostructure. A thermionic broad beam hollow cathode plasma source was used to enhance electron beam deposition, with ability to vary in real time ion fluxes and energies providing a means to modify and control TiO2 nanostructure real time with controlled density and porosity along and lateral to film growth direction. Plasma ion assisted deposition was carried out at room temperature using a hollow cathode plasma source, ensuring low heat loading to the substrate during deposition. Plasma enhanced glancing angle TiO2 structures were deposited onto borosilicate microscope slides and used to characterise the effects of glancing angle and plasma ion energy distribution function on the optical and nanostructural properties. Variation in TiO2 refractive index from 1.40 to 2.45 (@ 550nm) using PEGLAD is demonstrated. Results and analysis of the influence of plasma enhanced glancing angle deposition on evaporant path and resultant glancing angle deviation from standard GLAD are described. Control of mesoporous morphology is described, providing a means of optimising light trapping features and film porosity, relevant to applications such as fabrication of dye sensitised solar cells.

Perturbation of the ECR plasma ion energy distribution function during the interaction with a laser-generated plasma

The electron cyclotron resonance coupled to a laser ion source for charge state enhancement method, based on the coupling of a laser ion source with an electron cyclotron resonance (ECR) ion source in order to produce highly charged ions of metallic elements, demonstrated its validity some years ago, although some aspects remained unclear, in particular the optimization of the ion capture probability through ion–ion scattering. Another crucial item that determines the efficiency of the coupling is the variation of the energy content of the electron cyclotron resonance ion source (ECRIS) plasma: when the ions produced by means of the laser ablation are captured, they deposit a great amount of energy into the magnetically confined plasma. The released energy perturbs the ECR plasma, thus increasing the losses onto the chamber walls and the emittance of the extracted beam. Only a rough estimation of the energy content perturbations has been available up to now, so Monte Carlo simulations have been used to improve the description of the ion capture mechanism and the energy perturbation. The real magnetic field structure of ECRIS and a realistic plasma density distribution have been taken into account, as the code considers the ECR plasma properties emerging from particle in cell (PIC) simulations and from experimental measurements that permit one to determine locally the energy perturbation. The effects of electric fields on the ion stream coming from the laser-ablated target have been also considered, resulting in better coupling after the ion energy decrease.

Ion Distribution Function Evaluation Using Escaping Neutral Atom Kinetic Energy Samples

A reliable method to evaluate the probability density function of escaping atom kinetic energies is required for analyzing neutral particle diagnostic data used to study the fast ion distribution function in fusion plasmas. In this paper, digital processing of solid state detector signals is proposed as an improvement of the simple histogram approach. Probability density function of kinetic energies of neutral particles escaping from plasma has been derived in a general form, taking into consideration the plasma ion energy distribution, electron capture and loss rates, superposition along the diagnostic sight line, and the magnetic surface geometry. A pseudorandom number generator has been realized to simulate a sample of escaping neutral particle energies for given plasma parameters and experimental conditions. Empirical probability density estimation code has been developed and tested to reconstruct the probability density function from simulated samples assuming Maxwellian ion energy distribution shapes for different temperatures and classical slowing down distributions with different slowing down times. The application of the developed probability density estimation code to the analysis of experimental data obtained by the novel Angular-Resolved Multi-Sightline Neutral Particle Analyzer has been studied to obtain the suprathermal particle distributions. The optimum bandwidth parameter selection algorithm has also been realized.

Ion-Energy Diagnostics in an SPT-100 Plume from Thrust Axis to Backflow

Of primary concern with the integration of Hall thrusters on conventional satellite designs is the possible damaging effect of high-energy exhaust ions impinging upon spacecraft surfaces. This paper reports on measurements of plasma ion-energy distributions within the plume of an SPT-100 Hall thruster using a custom-designed molecular beam mass spectrometer. With this instrument ion energy was measured over a complete 360-deg circumference about the thruster at 0.5-m radius from the exit plane and over a total inclusive arc of 260 deg at 1.0-m radius. These data uncovered the existence of high-energy ions departing the thruster at angles exceeding 90 deg from the thrust vector and continuing well into the backflow region of the plume. Through an analysis of the energy structure the evidence of charge-exchange collisions occurring between plume ions and background neutrals was documented; such collisions produced anomalous distributions of ions having voltages greater than that applied to the thruster discharge.

Computer-Controlled System for Plasma Ion Energy Auto-Analyzer

A computer-controlled system for plasma ion energy auto-analyzer was technically studied for rapid and online measurement of plasma ion energy distribution. The system intelligently controls all the equipments via a RS-232 port, a printer port and a home-built circuit. The software designed by Lab VIEW G language automatically fulfils all of the tasks such as system initializing, adjustment of scanning-voltage, measurement of weak-current, data processing, graphic export, etc. By using the system, a few minutes are taken to acquire the whole ion energy distribution, which rapidly provides important parameters of plasma process techniques based on semiconductor devices and microelectronics.

Ion-Energy Diagnostics in the Plasma Exhaust Plume of a Hall Thruster

Of primary concernwiththeintegration of Hall thrusterson conventional satellitedesigns isthepossibledamaging effect of high-energy exhaust ions impinging upon spacecraft surfaces. This paper reports on measurements of plasma ion-energy distributions within the plume of an SPT-100 Hall thruster using a custom-designed molecularbeam mass spectrometer. With this instrument ion energy was measured over a complete 360-deg circumference about the thruster at a radius of 0.5 m from the exit plane and over a total inclusive arc of 260 deg at 1.0-m radius. These data uncovered the existence of high-energy ions departing the thruster at angles exceeding 90 deg from the thrust vector and continuing well into the backe ow region of the plume. Through an analysis of the energy structure, the evidence of charge-exchange collisions occurring between plume ions and background neutrals was documented; such collisions produced anomalous distributions of ions having voltages greater than that applied to the thruster discharge. Nomenclature Ac = area of collector, m 2 d = analyzer plate separation, m Ei = ion energy, J or eV e = elementary charge, C f (ui) = ion velocity distribution, s/m f (Vi) = ion voltage distribution, s/m GCEM = gain of electron multiplier K45 = spectrometer constant k = Boltzmann constant, J/K L = analyzer interslit distance, m mi = mass of ion, kg ni = ion density, m i 3 q = ion integer charge state r = radial distance from thruster, m ui = ion velocity, m/s Vb = main distribution voltage, V Vi = ion voltage, V Vm = most-probable voltage, V Vp = repelling plate voltage, V w = analyzer slit width, m x = spatial coordinate, m y = spatial coordinate, m h = angle, deg s i = distribution half-width at e i 1 point, V

Investigating Radio Frequency Plasmas Used for the Modification of Polymer Surfaces

By use of Langmuir probes and energy-resolved mass spectrometry, the properties of a cold plasma suitable for the surface treatment of polymers are investigated. The 13.56 MHz radio frequency (rf) excitation is provided by an external coil, and we demonstrate that a plasma of Ar gas is capacitively coupled to the source coil. The spatial distributions of plasma and floating (self-bias) potentials, electron temperature Te, and plasma density ne have been investigated for a range of input powers (1−50 W) and gas pressures (10-3−10-1 Torr) using compensated Langmuir probes. Estimates of the rf potential amplitudes are also given. The energy distribution of plasma ions at plasma boundaries has also been measured, and the effect of the perturbation to the plasma parameters due to the presence of the polymer sample and the spectrometer has been quantified. A feature of these plasmas is the presence of large rf potentials (up to about 25Te) and high self-bias potentials (up to 80 V). We show that the presence of a mass spectrometer changes the plasma potential and alters the level of rf fluctuation in the plasma and thereby affects the ion energy distribution function at the sample surface. Estimates of ion and photon energy fluxes are made, and the relative importance of these two fluxes in terms of polymer modification at a pressure of 10-2 Torr is discussed.

Ion energy distribution in an ECR plasma chamber

The plasma ion energy distribution in an ECR plasma chamber, operated from a 2.45 GHz microwave supply, has been measured by a new plasma ion energy analyzer composed of a screened plate, a repel grid, an analyzer grid and a collector grid plate. The ion energy distribution in nitrogen ranged from 15 to 47 eV at gas pressures from 0.06 to 0.1 Pa, being lowest at higher pressure. The ion energy and the ion current flowing to the analyzer rose with increasing microwave power. No high-energy ions were observed in the ECR plasma confirming its value for ion processing under controlled impingement energy.

Energetic neutral atom imaging of space plasmas

Experimental techniques and instrumentation for space plasma imaging in fluxes of energetic neutral atoms (ENAs) are reviewed. ENAs are born in charge exchange collisions between space plasma energetic ions and background neutral gas. ENAs are ubiquitous in the space environment and their energies are in the range from a few eV up to >100 keV.Contrary to charged particles, ENAs can travel large distances through space with minimal disturbance, and by recording ENA fluxes as a function of observational direction, one can reconstruct a global image of a planetary magnetosphere or the heliosphere. Plasma ion energy distribution and ion composition can be remotely established by measuring ENA energies and masses. ENA imaging opens a new window on various phenomena in space plasmas with a promise to qualitatively improve our understanding of global magnetospheric and heliospheric processes. At first we review ENA fluxes in space and their properties, and present a brief history of ENA experimental studies and the evolution of experimental approaches. The concepts of ENA imaging and particle identification are considered and followed by comparison with corpuscular diagnostics of fusion plasmas. Basic ENA techniques and instrument components are then described in detail and critically evaluated; performance characteristics, limitations, and requirements to key instrumental elements are discussed. And finally, representative ENA instruments are shown, and promising instrumental approaches are identified.

Comparative characteristics of atomic particle analyzers with solid and gaseous targets when used at large fusion facilities

The capabilities of atomic particle analyzers with solid and gaseous targets for measurements of plasma ion energy distribution functions at large fusion facilities are analyzed. It is shown that analyzers with a solid target have a number of advantages over the analyzers with a gaseous target and that their sensitivity at energies above 5 keV can be to 10–100 times higher. They are smaller in size. This makes it easier to shield them against X-ray and neutron irradiation and they are simpler in their design and maintenance.

Detailed measurements of anisotropic mirror plasma ion energy distributions during drift cyclotron loss-cone instability

Using improved computer filtering and a reconstruction analysis we have been able to extract additional details on a mirror plasma’s midplane ion energy distribution from the current–voltage (I–V) curve of a voltage-swept electrostatic end loss analyzer (ELA). For the University of Maryland’s MIX-1 plasma [Phys. Fluids 23, 3439 (1976)], the diagnostic technique has provided us with important information on the ‘‘loss-cone region’’ of an anisotropic ion distribution during drift cyclotron loss-cone (DCLC) instability experiments. Observations include convincing verification of ion distribution modification during DCLC evolution and an enhancement of the loss-region boundary over that predicted by simplified trapping theory. The reconstruction analysis involves matching the differentiated I–V curves (i.e., dI/dV vs V) to theoretically predicted curves based on model midplane ion distribution functions. The theoretical curves are obtained from the model midplane distributions by a mapping transformation based on conservation of magnetic moment and total energy of each ion along lines of magnetic flux.