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Measurement of emitted power in the divertor region in PBX

Description: In strongly indented PBX plasmas, radiated power profiles are calculated by combining data obtained from two bolometer arrays in order to study poloidal asymmetries arising from plasma indentation and characterize emission from the divertor region. A compact, 15-channel bolometer array that views the plasma tangentially along the midplane complements a 19-channel array that scans the plasma vertically in a poloidal plane. Assuming that radiated power density is constant along a magnetic flux su… more
Date: September 1, 1986
Creator: Paul, S. F.; Fonck, R. J. & Schmidt, G. L.
Partner: UNT Libraries Government Documents Department
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Operation of a tangential bolometer on the PBX tokamak

Description: A compact 15-channel bolometer array that views plasma emission tangentially across the midplane has been installed on the PBX tokamak to supplement a 19-channel poloidal array which views the plasma perpendicular to the toroidal direction. By comparing measurements from these arrays, poloidal asymmetries in the emission profile can be assessed. The detector array consists of 15 discrete 2-mm x 2-mm Thinistors, a mixed semiconductor material whose temperature coefficient of resistance is relati… more
Date: April 1, 1987
Creator: Paul, S. F.; Fonck, R. J. & Schmidt, G. L.
Partner: UNT Libraries Government Documents Department
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Neutral beam emission spectroscopy diagnostic for measurement of density fluctuations on the TFTR tokamak

Description: A multi-channel diagnostic for measuring low amplitude, long wavelength (k{sub {perpendicular}{rho}i} < 0.5) density fluctuations along the outer half of the plasma has been installed on TFTR. It is based on observing fluctuations in the H{sub {alpha}} fluorescence of a neutral heating beam due to collisional excitation from the plasma and impurity ions. Both radial and poloidal correlation lengths as short as 2--3 cm can be determined, with the spatial resolution limited primarily by the width… more
Date: June 1, 1990
Creator: Paul, S.F. & Fonck, R.J.
Partner: UNT Libraries Government Documents Department
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Impurity behavior in PBX L- and H-mode plasmas

Description: Intrinsic impurity behavior and transport properties in neutral-beam-heated L- and H-mode PBX tokamak plasmas were studied with a variety of impurity diagnostics. Central impurity accumulation was most often observed in H-mode discharges and sometimes resulted in a thermal collapse due to high central metallic radiation (-- 1.5 W/cm/sup 3/). The accumulation was evident from peaked Z/sub eff/ and radiated power profiles and further substantiated from specific VUV and X-ray spectroscopy measurem… more
Date: August 1, 1988
Creator: Ida, K.; Fonck, R. J.; Sesnic, S.; Hulse, R. A.; LeBlanc, B. & Paul, S. F.
Partner: UNT Libraries Government Documents Department
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Local carbon diffusion coefficient measurement in the S-1 spheromak

Description: The local carbon diffusion coefficient was measured in the S - 1 spheromak by detecting the radial spread of injected carbon impurity. The radial impurity density profile is determined by the balance of ionization and diffusion. Using measured local electron temperature T/sub e/ and density n/sub e/, the ionization rate is determined from which the particle diffusion coefficient is inferred. The results found in this work are consistent with Bohm diffusion. The absolute magnitude of D/sub /perp… more
Date: October 1, 1988
Creator: Mayo, R.M.; Levinton, F.M.; Meyerhofer, D.D.; Chu, T.K.; Paul, S.F. & Yamada, M.
Partner: UNT Libraries Government Documents Department
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A High-Speed Optical Diagnostic that uses Interference Filters to Measure Doppler Shifts

Description: A high-speed, non-invasive velocity diagnostic has been developed for measuring plasma rotation. The Doppler shift is determined by employing two detectors that view line emission from the identical volume of plasma. Each detector views through an interference filter having a passband that varies linearly with wavelength. One detector views the plasma through a filter whose passband has a negative slope and the second detector views through one with a positive slope. Because each channel views … more
Date: August 9, 2004
Creator: Paul, S.F.; Cates, C.; Mauel, M.; Maurer, D.; Navratil, G. & Shilov, M.
Partner: UNT Libraries Government Documents Department
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Confinement of Pure Ion Plasma in a Cylindrical Current Sheet

Description: A novel method for containing a pure ion plasma at thermonuclear densities and temperatures has been modeled. The method combines the confinement properties of a Penning-Malmberg trap and some aspects of the magnetic field geometry of a pulsed theta-pinch. A conventional Penning trap can confine a uniform-density plasma of about 5x1011 cm-3 with a 30-Tesla magnetic field. However, if the axial field is ramped, a much higher local ion density can be obtained. Starting with a 107 cm-3 trapped deu… more
Date: December 10, 1999
Creator: Phillips, C.K.; Chao, E.H.; Davidson, R.C. & Paul, S.F.
Partner: UNT Libraries Government Documents Department
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Direct numerical solution of Poisson`s equation in cylindrical (r, z) coordinates

Description: A direct solver method is developed for solving Poisson`s equation numerically for the electrostatic potential {phi}(r,z) in a cylindrical region (r < R{sub wall}, 0 < z < L). The method assumes the charge density {rho}(r,z) and wall potential {phi}(r = R{sub wall}, z) are specified, and {partial_derivative}{phi}/{partial_derivative}z = 0 at the axial boundaries (z = 0, L).
Date: July 22, 1997
Creator: Chao, E.H.; Paul, S.F.; Davidson, R.C. & Fine, K.S.
Partner: UNT Libraries Government Documents Department
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Accounting of the Power Balance for Neutral-beam-heated H-Mode Plasmas in NSTX

Description: A survey of the dependence of power balance on input power, shape, and plasma current was conducted for neutral-beam-heated plasmas in the National Spherical Torus Experiment (NSTX). Measurements of heat to the divertor strike plates and divertor and core radiation were taken over a wide range of plasma conditions. The different conditions were obtained by inducing a L-mode to H-mode transition, changing the divertor configuration [lower single null (LSN) vs. double-null (DND)] and conducting a… more
Date: August 9, 2004
Creator: Paul, S. F.; Maingi, R.; Soukhanovskii, V.; Kaye, S. M. & Kugel, H.
Partner: UNT Libraries Government Documents Department
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Impurity behavior during ion-Bernstein wave heating in PBX-M

Description: Ion-Bernstein-wave heating (IBWH) has been tested in several tokamaks. In some cases the results have been quite positive, producing temperature increases and also improving both energy and particle confinement times, whereas in others, no distinctive changes were observed. Most recently, IBWH has been utilized in the Princeton Beta Experiment-Modified (PBX-M) where the long-range goal is the achievement of operation in the second stable region by current and pressure profile control. Investiga… more
Date: September 1, 1994
Creator: Isler, R. C.; Post-Zwicker, A. P.; Paul, S. F.; Tighe, W.; Ono, M.; LeBlanc, B. P. et al.
Partner: UNT Libraries Government Documents Department
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The relationship between turbulence measurements and transport in different heating regimes in TFTR

Description: The scaling of broad band density fluctuations in the confinement zone of TFTR measured by microwave scattering, beam emission spectroscopy (BES), and reflectometry show a relationship between these fluctuations and energy transport measured from power balance calculations. In L-mode plasmas scattering and BES indicates that the density fluctuation level, {delta}n{sup 2}, in the confinement zone for 0.2 < k{perpendicular}ps < 1.0 depends qualitatively on P{sub aux} and I{sub p} in a way that is… more
Date: October 1, 1992
Creator: Bretz, N. L.; Mazzucato, E.; Nazikian, R.; Paul, S. F.; Hammett, G.; Rewoldt, G. et al.
Partner: UNT Libraries Government Documents Department
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The relationship between turbulence measurements and transport in different heating regimes in TFTR

Description: The scaling of broad band density fluctuations in the confinement zone of TFTR measured by microwave scattering, beam emission spectroscopy (BES), and reflectometry show a relationship between these fluctuations and energy transport measured from power balance calculations. In L-mode plasmas scattering and BES indicates that the density fluctuation level, [delta]n[sup 2], in the confinement zone for 0.2 < k[perpendicular]ps < 1.0 depends qualitatively on P[sub aux] and I[sub p] in a way that is… more
Date: January 1, 1992
Creator: Bretz, N. L.; Mazzucato, E.; Nazikian, R.; Paul, S. F.; Hammett, G.; Rewoldt, G. et al.
Partner: UNT Libraries Government Documents Department
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Excitation of toroidal Alfven eigenmodes in TFTR

Description: Deuterium neutral beams with energies up to 110 keV were injected into TFTR (Tokamak Fusion Test Reactor) plasmas at low magnetic field such that the beam injection velocities were comparable to the Alfven velocity. Excitation of toroidal Alfven eigenmodes was observed by Mirnov coils and beam emission spectroscopy. 10 refs., 4 figs.
Date: March 1, 1991
Creator: Wong, K. L.; Fonck, R. J.; Paul, S. F.; Roberts, D. R.; Fredrickson, E. D.; Nazikian, R. et al.
Partner: UNT Libraries Government Documents Department
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Confinement Studies of Auxiliary Heated NSTX Plasmas

Description: The confinement of auxiliary heated NSTX discharges is discussed. The energy confinement time in plasmas with either L-mode or H-mode edges is enhanced over the values given by the ITER97L and ITER98Pby(2) scalings, being up to 2-3 times L-mode and 1.5 times H-mode. TRANSP calculations based on the kinetic profile measurements reproduce the magnetics-based determination of stored energy and the measured neutron production rate. Power balance calculations reveal that, in a high power neutral bea… more
Date: May 6, 2003
Creator: LeBlanc, B. P.; Bell, M. G.; Bell, R. E.; Bitter, M. L.; Bourdelle, C.; Gates, D. A. et al.
Partner: UNT Libraries Government Documents Department
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Transport in Auxiliary Heated NSTX Discharges

Description: The NSTX spherical torus (ST) provides a unique platform to investigate magnetic confinement in auxiliary-heated plasmas at low aspect ratio. Auxiliary power is routinely coupled to ohmically heated plasmas by deuterium neutral-beam injection (NBI) and by high-harmonic fast waves (HHFW) launch. While theory predicts both techniques to preferentially heat electrons, experiment reveals the electron temperature is greater than the ion temperature during HHFW, but the electron temperature is less t… more
Date: July 10, 2003
Creator: LeBlanc, B. P.; Bell, M. G.; Bell, R. E.; Bitte, M. L.; Bourdelle, C.; Gates, D. A. et al.
Partner: UNT Libraries Government Documents Department

Plasma-Material Interface Development for Future Spherical Tokamak-based Devices in NSTX.

Description: The divertor plasma-material interface (PMI) must be able to withstand steady-state heat fluxes up to 10 MW/m{sup 2} (a limit imposed by the present day divertor material and engineering constraints) with minimal material erosion, as well as to provide impurity control and ion density pumping capabilities. In spherical tokamaks (STs), the compact divertor geometry and the requirement of low core electron collisionality n*{sub e} at n{sub e} &lt; 0.5-0.7 n{sub G} (where n{sub G} is the Greenwald… more
Date: September 24, 2011
Creator: Soukhanovskii, V. A.; Battaglia, D.; Bell, M G.; Bell, R. E.; Diallo, A.; Gerhardt, S. et al.
Partner: UNT Libraries Government Documents Department
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Investigation of global Alfven instabilities in TFTR

Description: Toroidal Alfven Eigenmodes (TAE) were excited by the energetic neutral beam ions tangentially injected into TFTR plasmas at low magnetic field such that the injection velocities were comparable to the Alfven speed. The modes were identified by measurements from Mirnov coils and beam emission spectroscopy (BES). TAE modes appear in bursts whose repetition rate increases with beam power. The neutron emission rate exhibits sawtooth-like behavior and the crashes always coincide with TAE bursts. Thi… more
Date: January 1, 1992
Creator: Wong, K. L.; Paul, S. F.; Fredrickson, E. D.; Nazikian, R.; Park, H. K.; Bell, M. et al.
Partner: UNT Libraries Government Documents Department
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Beta-limiting MHD Instabilities in Improved-performance NSTX Spherical Torus Plasmas

Description: Global magnetohydrodynamic stability limits in the National Spherical Torus Experiment (NSTX) have increased significantly recently due to a combination of device and operational improvements. First, more routine H-mode operation with broadened pressure profiles allows access to higher normalized beta and lower internal inductance. Second, the correction of a poloidal field coil induced error-field has largely eliminated locked tearing modes during normal operation and increased the maximum ach… more
Date: May 29, 2003
Creator: Menard, J. E.; Bell, M. G.; Bell, R. E.; Kaye, E. D. Fredrickson D. A. Gates: S. M.; LeBlanc, B. P.; Maingi, R. et al.
Partner: UNT Libraries Government Documents Department
open access

Investigation of global Alfven instabilities in TFTR

Description: Toroidal Alfven Eigenmodes (TAE) were excited by the energetic neutral beam ions tangentially injected into TFTR plasmas at low magnetic field such that the injection velocities were comparable to the Alfven speed. The modes were identified by measurements from Mirnov coils and beam emission spectroscopy (BES). TAE modes appear in bursts whose repetition rate increases with beam power. The neutron emission rate exhibits sawtooth-like behavior and the crashes always coincide with TAE bursts. Thi… more
Date: January 1, 1992
Creator: Wong, K. L.; Paul, S. F.; Fredrickson, E. D.; Nazikian, R.; Park, H. K.; Bell, M. et al.
Partner: UNT Libraries Government Documents Department
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Excitation of high frequency pressure driven modes by non-axisymmetric equilibrium at high {beta}{sub pol} in PBX-M

Description: High-frequency pressure-driven modes have been observed in high-poloidal-{beta} discharges in the Princeton Beta Experiment-Modification (PBX-M). These modes are excited in a non-axisymmetric equilibrium characterized by a large, low frequency m{sub 1}=1/n{sub 1}=1 island, and they are capable of expelling fast ions. The modes reside on or very close to the q=1 surface, and have mode numbers with either m{sub h}=n{sub h} or (less probably) m{sub h}/n{sub h}=m{sub h}/(m{sub h}-1), with m{sub h} … more
Date: June 1, 1993
Creator: Sesnic, S.; Kaita, R.; Kaye, S.; Okabayashi, M.; Takahashi, H.; Bell, R. E. et al.
Partner: UNT Libraries Government Documents Department
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Limiter H-mode experiments on TFTR

Description: Limiter H-modes with centrally peaked density profiles have been obtained in TFTR using a highly conditioned graphite limiter. The transition to these centrally peaked H-modes takes place from the supershot to the H-mode rather than the usual L- to H-mode transition observed on other tokamaks. Bidirectional beam heating is required to induce the transition. Density peaking factors, n{sub e}(0)/<n{sub e}>, greater than 2.3 are obtained and at the same time the H-mode characteristics are similar … more
Date: May 1, 1991
Creator: Bush, C. E. (Oak Ridge National Lab., TN (USA)); Bretz, N. L.; Fredrickson, E. D.; McGuire, K. M.; Nazikian, R.; Park, H. K. et al.
Partner: UNT Libraries Government Documents Department
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