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Interpretation of f({epsilon}) measurements by T. Kimura, K. Akatsuka and K. Ohe

Description: This note describes my analysis of the measurement of the electron energy distribution function in a DC glow discharge reported by T. Kimura, K. Akatsuka, and K. Ohe, in `Experimental and theoretical investigations of DC glow discharges in argon-nitrogen mixtures,`J. Phys. D: Appl. Phys. 27 (1994) 1664-1671. T. Kimura of the Department of Systems Engineering at the Nagoya Institute of Technology sent me this paper in 1994, as well as `Electron Energy Distribution Function in Neon-Nitrogen Mixture Positive Column,` T. Kimura, and K. Ohe, Jpn. J. Appl. Phys. Vol. 3 1, Part 1, No. 12A, December 1992, pp. 4051- 4052. I base my analysis on the data for a pure N{sub 2} discharge at p=1 torr in the 1994 paper. Figures 2 and 3 in that paper show a discrepancy between f({epsilon}) as measured by Langmuir probing and f({epsilon}) as calculated from E/N based on the measured axial field. Kimura et. al. explain their observation of hotter than expected electrons on superelastic collisions with vibrationally excited nitrogen. My fundamental point is that the radial field generated by ambipolar diffusion significantly augments E/N above the contribution from the axial field in this experiment, and creates a higher than expected radially averaged electron energy.
Date: November 26, 1996
Creator: Garcia, M.
Partner: UNT Libraries Government Documents Department

In-Situ Cleaning of Metal Photo-Cathodes in rf Guns

Description: Metal cathodes installed in rf guns typically exhibit much lower quantum efficiency than the theoretical limit. Experimenters often use some sort of in situ technique to ''clean'' the cathode to improve the QE. The most common technique is laser cleaning where the laser is focused to a small spot and scanned across the cathode surface. However, since the laser is operated near the damage threshold, it can also damage the cathode and increase the dark current. The QE also degrades over days and must be cleaned regularly. We are searching for a more robust cleaning technique that cleans the entire cathode surface simultaneously. In this paper we describe initial results using multiple techniques such as several keV ion beams, glow discharge cleaning and back bombarding electrons. Results are quantified in terms of the change in QE and dark current.
Date: January 3, 2007
Creator: Schmerge, J.F.; Castro, J.M.; Clendenin, J.E.; Colby, E.R.; Dowel, D.H.; Gierman, S.M. et al.
Partner: UNT Libraries Government Documents Department

Removal of CDP Mandrels from Sputter Coated Beryllium Capsules for NIF Targets

Description: Ablative targets for the National Ignition Campaign (NIC) have been fabricated by sputter coating spherical mandrels made of glow discharge polymer (GDP) with graded copper doped beryllium (Be) layers. The inner mandrel must be completely removed to meet specific ignition design requirements. The process of removing the mandrel requires elevated temperature in the presence of oxygen. However, elevating the temperature in air also oxidizes the Be and can cause blistering on the inner surface of the Be shell. This paper will discuss a refined technique, which removes the GDP mandrel without compromising the integrity of the inner Be surface. The oxygen gradient that develops during the mandrel removal and the impact of its presence will also be discussed.
Date: December 22, 2006
Creator: Laboratory, Lawrence Livermore National
Partner: UNT Libraries Government Documents Department


Description: Historically, glow discharge mass and optical spectrometric techniques have been used in industry for the characterization of processed metals, such as steels and other alloys. This technique is especially well suited for this type of product analysis because the glow discharge ionization source accommodates solid conducting samples with minimal or no sample preparation. This characteristic along with minimal matrix effect considerations makes the glow discharge source well suited for these types of applications.
Date: December 1, 1998
Creator: STEINER, R. & WAYNE, D.
Partner: UNT Libraries Government Documents Department

Effect of Boronization on Ohmic Plasmas in NSTX

Description: Boronization of the National Spherical Torus Experiment (NSTX) has enabled access to higher density, higher confinement plasmas. A glow discharge with 4 mTorr helium and 10% deuterated trimethyl boron deposited 1.7 g of boron on the plasma facing surfaces. Ion beam analysis of witness coupons showed a B+C areal density of 10 to the 18 (B+C) cm to the -2 corresponding to a film thickness of 100 nm. Subsequent ohmic discharges showed oxygen emission lines reduced by x15, carbon emission reduced by two and copper reduced to undetectable levels. After boronization, the plasma current flattop time increased by 70% enabling access to higher density, higher confinement plasmas.
Date: March 27, 2001
Creator: Skinner, C.H.; Kugel, H.; Maingi, R.; Wampler, W.R.; Blanchard, W.; Bell, M. et al.
Partner: UNT Libraries Government Documents Department

NSTX Filament Preionization and Glow Discharge Cleaning Systems

Description: Initial NSTX GDC experiments were performed with one moveable anode and a biased filament preionization system that allowed D2 and He Glow Discharge breakdowns at the actual operating pressure, voltage and current. The biased filament system was also operated continuously during ohmic operations, and used to reduce volt-sec consumption for February 1999 plasma discharges up to 280 KA. An upgraded system has been installed with 2 fixed wall anodes and 3 biased filaments; 2 on the mid-plane and one in the divertor region; all separately controllable remotely using a PLC system. Recent applications include assisting in preionization for 800 KA plasma discharges.
Date: November 1, 1999
Creator: H.W. Kugel, W. Blanchard, G. D'Amico, R. Gernhardt, T. Provost
Partner: UNT Libraries Government Documents Department


Description: OAK-B135 Thin glow discharge polymer (GDP) shells are currently used as the targets for cryogenic direct drive laser fusion experiments. These shells need to be filled with nearly 1000 atm of D{sub 2} and cooled to cryogenic temperatures without failing due to buckling and bursting pressures they experience in this process. Therefore, the mechanical and permeation properties of these shells are of utmost importance in successful and rapid filling with D{sub 2}. In this paper, they present an overview of buckle and burst pressures of several different types of GDP shells. These include those made using traditional GDP deposition parameters (standard GDP) using a high deposition pressure and using modified parameters (strong GDP) of low deposition pressure that leads to more robust shells.
Date: June 1, 2003
Partner: UNT Libraries Government Documents Department


Description: OAK A271 COATING AND MANDREL EFFECTS ON FABRICATION OF GLOW DISCHARGE POLYMER NIF SCALE INDIRECT DRIVE CAPSULES. Targets for the National Ignition Facility (NIF) need to be about 200 {micro}m thick and 2 mm in diameter. These dimensions are well beyond those currently fabricated on a routine basis. They have investigated fabrication of near NIF scale targets using the depolymerizable mandrel technique. Poly-alpha-methylstyrene (PAMS) mandrels, about 2 mm in diameter, of varying qualities were coated with as much as 125 {micro}m of glow discharge polymer (GDP). The surface finish of the final shells was examined using a variety of techniques. A clear dependence of the modal spectrum of final GDP shell on the quality of the initial PAMS mandrels was observed. isolated features were found to be the greatest cause for a shell not meeting the NIF standard.
Date: April 1, 2002
Partner: UNT Libraries Government Documents Department


Description: OAK A271 RECENT PROGRESS IN FABRICATION OF HIGH-STRENGTH GLOW DISCHARGE POLYMER SHELLS BY OPTIMIZATION OF COATING PARAMETERS. In this paper, the authors report the progress they have made in fabrication of high-strength thin-walled glow discharge polymer (GDP) shells for cryogenic experiments at OMEGA. They have investigated a number of different parameters involved in making such shells. Optimization of hydrogen to hydrocarbon precursor flow has been observed to be critical in obtaining strong shells. They can routinely make high-strength shells of OMEGA size (900 {micro}m in diameter) with thicknesses in the range of 1.0 to 1.5 {micro}m. The permeabilities of these shells to various gases have been found to be as much as three times higher than those of lower strength shells. Run to run variability and other batch statistics are discussed.
Date: April 1, 2002
Partner: UNT Libraries Government Documents Department

Superconducting multicell cavity development program at Los Alamos

Description: The superconducting rf (SCRF) cavity Development Program at Los Alamos has designed, fabricated, and tested single-cell niobium cavities at 3-GHz and 805-MHz. This work is being done in preparation for procuring and testing a multicell niobium cavity. The multicell cavity is designed to accelerate protons at {beta} = 0.9; initial tests will be without beam. Progammmatic changes have required us to modify our plans to install a 6800-liter helium cryostat and a 12.8-g/s helium pump. We will use an installed cryostat to test the multicell cavity. Also, the cavity will be modified from a seven-cell to a four-cell structure to match the dimensions of the installed cryostat. Previous reports concentrated on 3-GHz results. In this paper, some of the latest results of the 805-MHz cavity tests are presented. Modifications to allow high pulsed power (HPP) testing on 805-MHz single- and four-cell cavities are proceeding. Glow discharge cleaning of an 805-MHz niobium cavity resulted in a decrease in cavity performance. The cavity was restored to previous performance levels with buffered chemical polishing (bcp). Initial results with high-pressure water cleaning show the process is useful in restoring cavity performance.
Date: June 1, 1993
Creator: Rusnak, B.; Spalek, G.: Gray, E.; DiMarco, J. N.; DeHaven, R.; Novak, J.; Walstrom, P. et al.
Partner: UNT Libraries Government Documents Department

New hollow-cathode electrode for high-power copper lasers

Description: Multiple hollow-cathode slots were utilized on a profiled solid-copper electrode taht extended stable glow discharge to higher pressures in copper lasers. This novel electrode design, which dramatically reduced discharge jitter and window contamination, has been run for more than 8000 hours with very little degradation.
Date: March 9, 1994
Creator: Chang, J. J.; Alger, T. W.; Anderson, A. T. & Arnold, P. A.
Partner: UNT Libraries Government Documents Department

Development of NSTX Particle Control Techniques

Description: NSTX High Harmonic Fast Wave (HHFW) current drive discharges will require density control for acceptable efficiency. We have compared boronization on hot and cold surfaces, varying helium glow discharge conditioning (HeGDC) durations, and brief morning boronization with between discharge boronization for improving density control. Access to Ohmic H-modes was enabled by boronization on hot surfaces, however, the duration of the effectiveness of hot and cold boronization was comparable. A 15 min HeGDC between discharges was needed for reproducible L-H transitions. Brief morning boronization followed by a comparable duration of applied HeGDC restored and enhanced good conditions. Additional short boronizations between discharges did not improve plasma performance (reduced recycling, reduced impurity luminosities, earlier L-H transitions, longer plasma current flattops, higher stored energies) if conditions were already good. Between discharge boronization requires increases in the duty cycle due to the need for additional HeGDC to remove co-deposited D{sub 2}.
Date: June 15, 2004
Creator: Kugel, H; Maingi, R; Bell, M; Gates, D; Hill, K; LeBlanc, B et al.
Partner: UNT Libraries Government Documents Department

Glow Discharge Mass Spectrometry Analysis of LX-17 and PBX-9502 High Explosive Samples

Description: As part of the Campaign 4 effort in A Division we have done an analysis of several high explosives that are used in the current nuclear stockpile. In particular we have looked at samples of LX-17 and PBX-9502. The analysis was done using the glow discharge mass spectrometer that is currently located in B132N and operated by Mark Lane of the Chemistry and Material Science (CMS) Directorate. George Overturf from CMS obtained small samples of high explosive for the measurements. From the analysis we wanted to verify the actual atomic composition of the high explosive, see how that compared with the nominal composition, and understand whether any significant impurities existed in the samples. We present the analysis of several LX-17 and PBX-9502 samples using the glow discharge mass spectrometer to measure both the main constituents of the high explosive as well as any trace materials that may be present.
Date: December 16, 2002
Creator: Nilsen, J; Castor, J I; Lane, M A & Overturf, G E
Partner: UNT Libraries Government Documents Department

Fourier Transform Infrared Spectroscopic Analysis Of Plastic Capsule Materials Exposed To Deuterium-Tritium (DT) Gas

Description: Planar samples of varying thicknesses of both CH and CD glow discharge polymer have been measured with Fourier transform infrared (FTIR) spectroscopy before and after exposure to deuterium-tritium (DT) gas at elevated temperature and pressure. Planar samples of polyimide films made from both hydrogenated and deuterated precursors have also been examined by FTIR before and after DT exposure. The post-exposure FTIR spectra demonstrated no measurable exchange of hydrogen with deuterium or tritium for either polymer. Evidence for oxidation of the glow discharge polymer due to atmospheric oxygen was the only chemical change indicated by the FTIR data.
Date: June 16, 2005
Creator: Schoonover, J R; Steckle, Jr., W P; Elliot, N; Ebey, P S; Nobile, A; Nikroo, A et al.
Partner: UNT Libraries Government Documents Department

Biocompatible Silver-containing a-C:H and a-C coatings: AComparative Study

Description: Hydrogenated diamond-like-carbon (a-C:H) and hydrogen-free amorphous carbon (a-C) coatings are known to be biocompatible and have good chemical inertness. For this reason, both of these materials are strong candidates to be used as a matrix that embeds metallic elements with antimicrobial effect. In this comparative study, we have incorporated silver into diamond-like carbon (DLC) coatings by plasma based ion implantation and deposition (PBII&D) using methane (CH4) plasma and simultaneously depositing Ag from a pulsed cathodic arc source. In addition, we have grown amorphous carbon - silver composite coatings using a dual-cathode pulsed filtered cathodic-arc (FCA) source. The silver atomic content of the deposited samples was analyzed using glow discharge optical spectroscopy (GDOES). In both cases, the arc pulse frequency of the silver cathode was adjusted in order to obtain samples with approximately 5 at.% of Ag. Surface hardness of the deposited films was analyzed using the nanoindentation technique. Cell viability for both a-C:H/Ag and a-C:/Ag samples deposited on 24-well tissue culture plates has been evaluated.
Date: April 1, 2007
Creator: Endrino, Jose Luis; Allen, Matthew; Escobar Galindo, Ramon; Zhang, Hanshen; Anders, Andre & Albella, Jose Maria
Partner: UNT Libraries Government Documents Department


Description: A series of high-stability neon glow discharge tubes (OG3/85A2) was used to stabilize 1685 volts for the dynode resistance divider of a photomultiplier tube to an accuracy of plus or minus 0.2%. The limit of stability and the aging phenomena for the tube operating at reduced currents are discussed but not understood. (auth)
Date: October 14, 1958
Creator: Neher, L.K.
Partner: UNT Libraries Government Documents Department


Description: OAK A271 COMPOSITION AND STRUCTURAL STUDIES OF STRONG GLOW DISCHARGE POLYMER COATINGS. An investigation of the chemical composition and structure of strong glow discharge (GDP) polymer shells made for cryogenic experiments at OMEGA is described. The investigation was carried out using combustion and Fourier Transform Infrared Spectroscopy (FTIR) analysis. The strongest coatings were observed to have the lowest hydrogen content or hydrogen/carbon H/C ratio, whereas the weakest coatings had the highest hydrogen content or H/C ratio. Chemical composition results from combustion were used to complement FTIR analysis to determine the relative hydrogen content of as-fabricated coatings. Good agreement was observed between composition results obtained from combustion and FTIR analysis. FTIR analysis of coating structures showed the strongest coatings to have less terminal methyl groups and a more double bond or olefinic structure. Strong GDP coatings that were aged in air react more with oxygen and moisture than standard GDP coatings. In addition to a more olefinic structure, there may also be more free-radial sites present in strong GDP coatings, which leads to greater oxygen uptake.
Date: April 1, 2002
Partner: UNT Libraries Government Documents Department

Dusty plasmas

Description: This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project has been to develop a fundamental understanding of dusty plasmas at the Laboratory. While dusty plasmas are found in space in galactic clouds, planetary rings, and cometary tails, and as contaminants in plasma enhanced fabrication of microelectronics, many of their properties are only partially understood. Our work has involved both theoretical analysis and self-consistent plasma simulations to understand basic properties of dusty plasmas related to equilibrium, stability, and transport. Such an understanding can improve the control and elimination of plasma dust in industrial applications and may be important in the study of planetary rings and comet dust tails. We have applied our techniques to the study of charging, dynamics, and coagulation of contaminants in plasma processing reactors for industrial etching and deposition processes and to instabilities in planetary rings and other space plasma environments. The work performed in this project has application to plasma kinetics, transport, and other classical elementary processes in plasmas as well as to plasma waves, oscillations, and instabilities.
Date: May 1, 1996
Creator: Jones, M.E.; Winske, D.; Keinigs, R. & Lemons, D.
Partner: UNT Libraries Government Documents Department

Recent trends in inorganic mass spectrometry

Description: The field of inorganic mass spectrometry has seen substantial change in the author`s professional lifetime (over 30 years). Techniques in their infancy 30 years ago have matured; some have almost disappeared. New and previously unthought of techniques have come into being; some of these, such as ICP-MS, are reasonably mature now, while others have some distance to go before they can be so considered. Most of these new areas provide fertile fields for researchers, both in the development of new analytical techniques and by allowing fundamental studies to be undertaken that were previously difficult, impossible, or completely unforeseen. As full coverage of the field is manifestly impossible within the framework of this paper, only those areas with which the author has personal contact will be discussed. Most of the work originated in his own laboratory, but that of other laboratories is covered where it seemed appropriate.
Date: October 1, 1996
Creator: Smith, D.H.; Barshick, C.M.; Duckworth, D.C. & Riciputi, L.R.
Partner: UNT Libraries Government Documents Department

Metal Mesh Smear Sampling for Glow Discharge Analytical Spectroscopy

Description: Metal mesh smear sampling is being developed and evaluated for use in a number of glow discharge and other optical and mass spectrometric techniques. Sensitive elemental and isotopic analyses thus will be coupled with a convenient sampling scheme similar to one that is common for radiological surveys.
Date: June 1, 2000
Creator: Shaw, R.W.; Barshick, C.M.; Ramsey, J.M. & Smith, D.H.
Partner: UNT Libraries Government Documents Department

Processing of O.F.E. copper beam chambers for PEP-II high energy ring

Description: Using laboratory scale and full size PEP-II vacuum chambers, chemical cleaning, glow discharge and thermal process effects were evaluated using surface analysis by x-ray photoelectron spectroscopy (XPS). These processes were optimized to reduce surface carbon and thereby minimize photodesorption gas loads. The relation of surface carbon to ion dose was investigated and compared for pure argon, 5% oxygen in argon, and pure hydrogen plasmas. Argon incorporation was noted only when the copper was oxidized in the mixed gas. Surfaces, stable in ambient atmosphere, were obtained having surface carbon values less than 10%. These optimized recipes will be used in processing copper vacuum chambers for the PEP-II B-Factory.
Date: August 1, 1995
Creator: Hoyt, E.; Hoyt, M.; Kirby, R.; Perkins, C.; Wright, D. & Farvid, A.
Partner: UNT Libraries Government Documents Department