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in subjects: "Electron Density"

open access

The multipulse Thomson scattering diagnostic on the DIII-D tokamak

This paper describes the design and operation of a 40-spatial channel Thomson scattering system that uses multiple 20 Hz Nd:YAG lasers to measure the electron temperature and density profiles periodically throughout an entire plasma discharge. Interference filter polychromators disperse the scattered light which is detected by silicon avalanche photodiodes. The measurable temperature range from 10 eV to 20 keV and the minimum detectable density is about 2 {times} 10{sup 18} m{sup {minus}3}. Las… more

Date: September 1, 1991

Creator: Carlstrom, T. N.; Campbell, G. L.; DeBoo, J. C.; Evanko, R. G.; Evans, J.; Greenfield, C. M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electron heating and confinemet measurements in EBT-S using Thomson scattering

Thomson scattering of ruby laser light was used to measure electron temperatures and densities in the ELMO Bumpy Torus-Scale (EBT-S) at Oak Ridge National Laboratory. The measurements were made primarily during May 1980, although some were taken during January 1980. The scattering system, which was designed for very low electron density measurements, features a 14-J ruby laser, a high-throughput spectrometer, and 15% quantum efficiency photomultipliers. The measured electron densities lie in th… more

Date: September 1, 1980

Creator: Bighel, L. & Cobble, J. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The solar flare of 18 August 1979: Incoherent scatter radar data and photochemical model comparisons

Measurements of electron density at seven D-region altidues were made with the Arecibo radar during a Class-X solar flare on 18 August 1979. Measurements of solar x-ray fluxes during the same period were available from the GOES-2 satellite (0.5 to 4 /angstrom/ and 1 to 8 /angstrom/) and from ISEE-3 (in four bands between 26 and 400 keV). From the x-ray flux data we computed ionization rates in the D-region and the associated chemical changes, using a coupled atmospheric chemistry and diffusion … more

Date: April 1, 1988

Creator: Zinn, J.; Sutherland, C. D.; Fenimore, E. E. & Ganguly, S.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Recent beam probe measurements on EBT, TMX, and RENTOR

It is noted that beam probe systems can provide accurate, reliable measurments of plasma space potential and nf(T/sub e/). Over some temperature range, at least, it should be possible to separate n and T/sub e/ by measuring the multiple ionization reaction products. It is also an ideal diagnostic for studying fluctuations since it provides a simultaneous measurement of phi and nf(T/sub e/) from the same point in the plasma and the measurements are continuous in time. Measurements can be made qu… more

Date: June 1, 1980

Creator: Hickok, R. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Profile correction to electron temperature and enhancement factor in soft x-ray pulse-height-analysis measurements in tokamaks

Because soft x-ray pulse-height-analysis (PHA) spectra contain chordal information, the electron temperature and the radiation intensity (enhancement factor) measurements do not represent the local values. Assuming that the profile Ansatz for the electron temperature and density is of the form n/sub eo/(1-(ra)/sup 2/)/sup ..cap alpha../ and kT/sub eo/(1--(ra)/sup 2/)/sup ..beta../, we obtain the correction factors for the electron temperature and the enhancement factor as a function of the prof… more

Date: April 1, 1988

Creator: Sesnic, S.; Diesso, M.; Hill, K.; Holland, A. & Pohl, F.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Transport inhibition due to flow-driven ion turbulence at the shock behind the critical surface

Using a fine-zoned spherical hydrodynamic code, we examine the effects of reduced thermal conductivity at the ion acoustic shock behind the ponderomotive force-steepened profile. Narrow, high density peaks, and shock heated ions are found.

Date: January 1, 1980

Creator: Mayer, F. J.; Mitrovich, D.; Powers, L. V. & Speziale, T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Alfven wave stability in D-III-D

Within the framework of the global Alfven eigenmode theory in a cylindrical background plasma, I examine the excitation of global Alfven eigenmodes by intense neutral beam injection in the D III-D tokamak operating at General Atomics. I have considered two separate sets of experimental conditions, a low power'' set of cases using 10MW of hydrogen beams, and a high power'' shot of 20MW of deuterium beams. My results are particularly sensitive to the background density profile. For parabolic back… more

Date: September 1, 1989

Creator: Campbell, R.B. (Lawrence Livermore National Lab., CA (USA)) & Samec, T.K. (TRW, Inc., Redondo Beach, CA (USA))

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Comparisons of the structure, stability and electron distribution of nitrobenzenes and nitro-sym-triazines

Nitrobenzenes are a well known class of stable organic compounds. Nitro-sym-triazines are not known, although other substituted triazines are very well known. To investigate what properties the nitrotriazines might have, should they be synthesized, we performed molecular orbital calculations for nitrotriazine (NTZ), dinitrotriazine (DNTZ), and trinitrotriazine (TNTZ). Nitrobenzenes with analogous nitrogroup substitution were also studied to provide a check on the calculations. In particular, ni… more

Date: January 1, 1986

Creator: Ritchie, J.P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Design and operation of the multipulse Thomson scattering diagnostic on DIII-D

This paper describes the design and operation of a 40 spatial channel Thomson scattering system that uses multiple 20 Hz Nd:YAG lasers to measure the electron temperature and density profiles periodically throughout an entire plasma discharge. As many as eight lasers may be fired alternately for an average measurement frequency of 160 Hz, or they may be fired in rapid succession (< 10 kHz), producing a burst of pulses for measuring transient events. The high spatial resolution (1.3 cm) and wide… more

Date: March 1, 1992

Creator: Carlstrom, T. N.; Campbell, G. L.; DeBoo, J. C.; Evanko, R.; Greenfield, C. M.; Haskovec, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Sources of hot electrons in laser-plasma interaction with emphasis on Raman and turbulence absorption

Heating targets with high power lasers results in a sizable fraction of the absorbed energy going into electrons of temperature much greater than thermal which can pre-heat the pellet core and accelerate fast ion blowoff which results in poor momentum transfer and hence poor compression efficiency. The present emphasis is to build lasers of higher frequency, ..omega../sub 0/, which at the same W/cm/sup 2/ results in more absorption into cooler electrons. Two physical reasons are that the laser … more

Date: April 6, 1982

Creator: Estabrook, K.; Kruer, W. L.; Phillion, D. W.; Turner, R. E. & Campbell, E. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electron energy distributions, vibrational population distributions, and negative-ion concentrations in hydrogen discharges

We consider the negative ion concentrations in hydrogen discharges caused by electron excitation and dissociative attachment processes. The principal formation and destruction processes are discussed for electron densities in the range 10/sup 8/ to 10/sup 13/ electrons cm/sup -3/. Expressions are developed for calculating the high energy portion of the electron energy distribution in the discharge; using these energy distributions the electron excitation rates are evaluated. At low densities, t… more

Date: June 28, 1982

Creator: Hiskes, J.R. & Karo, A.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Atomic processes in plasmas under ultra-intense laser irradiation

Lasers delivering subpicosecond pulses with energies of a fraction of a Joule have made it possible to generate irradiance levels approaching 10{sup 20} W/cm{sup 2}. We presently operate two such systems, a KrF based excimer laser capable of producing a few 10{sup 17} W/cm{sup 2} at 248 nm with a repetition rate of 3--5 Hz and a XeCl based excimer laser capable of producing mid 10{sup 19} W/cm{sup 2} at 308 nm and 1 Hz. We will discuss some experimental results and the theory and modeling of th… more

Date: November 1, 1989

Creator: Schappert, G. T.; Casperson, D. E.; Cobble, J. A.; Comly, J. C.; Jones, L. A.; Kyrala, G. A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Study of electron density and pressure profile behavior in a tokamak plasma

Simultaneous determinations of local electron density and magnetic flux surface in a tokamak plasma have been made feasible with multichannel interferometry using a new asymmetric Abel inversion method. This new method takes advantage of interferometry by measuring the electron density profile as a function of time. The derived electron density parameters, such as the total number of electrons, peak density, and the profile shape factor, have been extremely useful in tokamak plasma experiments.… more

Date: November 1, 1989

Creator: Park, H.K.; Goldston, R.J. & Taylor, G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Analysis of electron transport in the plasma of thermionic converters

Electron transport coefficients of a gaseous ensemble are expressed analytically as function of density, and are expressed analytically as function of temperature up to an unknown function which has to be evaluated for each specific electron-neutral atom cross section. In order to complete the analytical temperature dependence one may introduce a polynomial expansion of the function or one may derive the temperature dependence of a set of coefficients, numbering thirteen for a third approximati… more

Date: March 1, 1980

Creator: Stoenescu, M.L. & Heinicke, P.H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Simultaneously time- and space-resolved spectroscopic characterization of laser-produced plasmas

The CHROMA laser facility at KMS Fusion has been used to irradiate a variety of microdot targets. These include aluminum dots and mixed bromine dots doped with K-shell (magnesium) emitters. Simultaneously time- and space-resolved K-shell and L-shell spectra have been measured and compared to dynamic model predictions. The electron density profiles are measured using holographic interferometry. Temperatures, densities, and ionization distributions are determined using K-shell and L-shell spectra… more

Date: March 3, 1988

Creator: Charatis, G.; Young, B. K. F.; Busch, G. E.; Cerjan, C. J.; Goldstein, W. H.; Osterheld, A. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The effect of limiter conditioning on the Tokamak Fusion Test Reactor edge plasma

Measurements by moveable Langmuir probes and edge spectroscopy diagnostics have documented the conditioning effect of low density helium-initiated discharge sequences on the Tokamak Fusion Test Reactor (TFTR) edge plasma. Langmuir probe measurements show in general that the edge electron density n{sub e} decreases by less than a factor of 2 while the edge electron temperature T{sub e} doubles. Radial profiles to the plasma boundary show that the density scrape-off length increases somewhat whil… more

Date: July 1, 1991

Creator: Kilpatrick, S. J.; Manos, D. M.; Nyberg, I.; Ramsey, A. T.; Stratton, B. C.; Timberlake, J. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Confirmation of radiation pressure effects in laser--plasma interactions

Interferometric data resolved in 1..mu..m and 15 psec confirms the dominant role of radiation pressure during high intensity laser-plasma interactions. Specifically observed manifestations include electron density profiles steepened to 1 ..mu..m scale length, clearly defined upper and lower density shelves, and small and large scale deformation of transverse isodensity surfaces.

Date: October 1, 1977

Creator: Attwood, D.T.; Sweeney, D.W.; Auerbach, J.M. & Lee, P.H.Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Surface areas by positron annihilation spectroscopy

Positron annihilation spectroscopy (PAS) is a technique for measuring the length of time that a positron exists after being injected into a specific material. Lifetime measurements have been used for studying defects in metals. These imperfections affect the localized electron densities which in turn influence the lifetime of the positron before annihilation occurs. Electron density differences are also associated with surfaces. This paper describes the PAS technique and shows a correlation bet… more

Date: January 1, 1985

Creator: Dale, J.M.; Rosseel, T.M.; Hulett, L.D.; Venkateswaran, K.; Jean, Y.C. & Fuller, E.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Recent Improvements in Thomson Scattering Data Analysis

A new profile analysis package for use with the Thomson scattering data on ISX-B has recently been implemented. The primary feature of this package is a weighted least squares fitting of temperature and density data to generate a representative curve, as opposed to the previous hand-fitting technique. The changes will automate the manner in which data are transmitted and manipulated, without affecting the calculational techniques previously used. The computer programs have also been used to est… more

Date: April 1, 1980

Creator: Tillack, M. S. & Lazarus, E. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Spectroscopic diagnostics of high temperature plasmas

A three-year research program for the development of novel XUV spectroscopic diagnostics for magnetically confined fusion plasmas is proposed. The new diagnostic system will use layered synthetic microstructures (LSM) coated, flat and curved surfaces as dispersive elements in spectrometers and narrow band XUV filter arrays. In the framework of the proposed program we will develop impurity monitors for poloidal and toroidal resolved measurements on PBX-M and Alcator C-Mod, imaging XUV spectromet… more

Date: January 1, 1990

Creator: Moos, W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Improved numerical grid generation techniques for the B2 edge plasma code

Techniques used to generate grids for edge fluid codes such as B2 from numerically computed equilibria are discussed. Fully orthogonal, numerically derived grids closely resembling analytically prescribed meshes can be obtained. But, the details of the poloidal field can vary, yielding significantly different plasma parameters in the simulations. The magnitude of these differences is consistent with the predictions of an analytic model of the scrape-off layer. Both numerical and analytic grids … more

Date: June 1, 1992

Creator: Stotler, D. P. & Coster, D. P.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Characterization of Open-Cycle Coal-Fired MHD Generators. Quarterly Technical Summary Report No. 3, January 1--March 31, 1977. [Negative Ion Formation, Electron/Slag Interaction, and Alkali/Slag Interaction]

The purpose of this contract effort is to understand how nonfuel components of coal will affect the electron and alkali seed chemistry in a high temperature coal combustion system like that envisioned for direct fired MHD generators. Three specific problems are being considered during this contract period. The first problem area is to characterize the formation of negative ions due to electron attachment processes in the combustion flow. While some stable negative ions may be formed from hydroc… more

Date: April 15, 1977

Creator: Kolb, C. E.; Yousefian, V.; Wormhoudt, J.; Martinez-Sanchez, M. & Kerrebrock, J. L.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Unusual bond paths in organolithium compounds

We have applied the topological method to a number of organolithium compounds. The wavefunctions were determined with GAUSSIAN-82 using 3-21G basis set and fully optimized geometries. Gradient paths were obtained using the RHODER package and critical points were located using EXTREME. These results indicate the unusual nature of organolithium compounds. The strange bond paths arise mainly from the ionic nature of the C-Li interaction. We suggest that the term ''bond path'' may best be suited fo… more

Date: January 1, 1986

Creator: Bachrach, S.M. & Ritchie, J.P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Sawtooth oscillations in the flux of runaway electrons to the PLT limiter

Increased fluxes of runaway electrons at the PLT limiter are observed in the few milliseconds following internal disruptions. These fluxes have an inverted (outside) sawtooth character. The time for the flux to reach a maximum after the disruption has been studied as a function of the plasma parameters for thousands of PLT discharges. One interpretation is that this delay represents the time for a perturbation to the runaway electron population to travel from the q = 1 region to the plasma boun… more

Date: March 1, 1982

Creator: Barnes, C.W. & Strachan, J.D.

Item Type: Report

Partner: UNT Libraries Government Documents Department