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Survey of electric field shear driven by radio frequency waves in tokamak plasmas

Description: The stabilization of plasma turbulence by sheared poloidal rotation is thought to explain enhanced confinement in tokamak plasmas. One method proposed for controlling sheared flow is the use of externally driven radio-frequency (RF) waves. A number of calculations and some experiments have suggested that a modest amount of power in the ion cyclotron range of frequencies (ICRF) can drive the needed flows. Previous calculations have relied on incompressible fluid models which balance RF forces in the poloidal direction against neoclassical viscosity. But the incompressible assumption is not always valid, particularly for ion Bernstein waves (IBW). Also, since the IBW is a kinetic wave by nature, a fully consistent model should include kinetic effects. In this paper, RF driven flows are calculated from both compressible fluid and kinetic points of view.
Date: November 1, 1998
Creator: Jaeger, E.F.; Berry, L.A. & Batchelor, D.B.
Partner: UNT Libraries Government Documents Department

Inhibition of the current-driven ion wave instability by electron trapping in the FM-1 spherator

Description: An experimental analysis is made of the scattering of microwaves by the density fluctuations due to the current-driven ion wave instability in a toroidal plasma confinement device, the FM-1 spherator. It is found that the instability exists in the collisional regime and it is inhibited (i.e., quenched by two orders in magnitude) in the trapped-electron (i.e., banana) regime. The inhibition occurs when the electron collision frequency is about equal to the electron bounce frequency between mirror trapping. (auth)
Date: October 1, 1975
Creator: Arunasalam, V.; Okabayaski, M.; Hawryluk, R.J. & Suckewer, S.
Partner: UNT Libraries Government Documents Department

Role of plasma edge in the direct launch Ion Bernstein Wave experiment in TFTR

Description: Two types of direct IBW launching, EPW {R_arrow} IBW and CESICW {R_arrow} IBW are investigated using two numerical codes, Full Hot Plasma Ray-Tracing Code and SEMAL Full Wave Slab Code, for the TFTR direct launch IBW experimental parameters. The measured density profiles (by microwave reflectometry) in TFTR appear to be satisfactory for IBW launching while the observed stored energy rise compared to the expected value (ray tracing + TRANSP) indicates only up to 50% of launched power is reaching the plasma core. Possible causes of IBW inefficiency are also discussed.
Date: June 1, 1997
Creator: Ono, M.; Cesario, R. & Bush, C.E.
Partner: UNT Libraries Government Documents Department

Enhanced loss of fast ions during mode conversion ion Bernstein wave heating in TFTR

Description: A strong interaction of fast ions with ion Bernstein waves has been observed in TFTR. It results in a large increase in the fast ion loss rate, and heats the lost particles to several MeV. The lost ions are observed at the passing/trapped boundary and appear to be either DD fusion produced tritons or accelerated D neutral beam ions. Under some conditions, enhanced loss of DT alpha particles is also seen. The losses provide experimental support for some of the elements required for alpha energy channeling.
Date: December 1, 1995
Creator: Darrow, D.S.; Majeski, R.; Fisch, N.J.; Heeter, R.F.; Herrmann, H.W.; Herrmann, M.C. et al.
Partner: UNT Libraries Government Documents Department

Alpha particle losses from Tokamak Fusion Test Reactor deuterium-tritium plasmas

Description: Because alpha particle losses can have a significant influence on tokamak reactor viability, the loss of deuterium-tritium alpha particles from the Tokamak Fusion Test Reactor (TFTR) has been measured under a wide range of conditions. In TFTR, first orbit loss and stochastic toroidal field ripple diffusion are always present. Other losses can arise due to magnetohydrodynamic instabilities or due to waves in the ion cyclotron range of frequencies. No alpha particle losses have yet been seen due to collective instabilities driven by alphas. Ion Bernstein waves can drive large losses of fast ions from TFTR, and details of those losses support one element of the alpha energy channeling scenario.
Date: January 1, 1996
Creator: Darrow, D.S.; Zweben, S.J. & Batha, S.
Partner: UNT Libraries Government Documents Department

Excitation of large-{kappa}{sub {theta}} ion-Bernstein waves in tokamaks

Description: The mode-converted ion-Bernstein wave excited in tokamaks is shown to exhibit certain very interesting behavior, including the attainment of very small poloidal phase velocities, the reversal of poloidal direction, and up-down asymmetries in propagation and damping. Because of these effects, this wave holds promise for channeling {alpha}-particle power to ions, something that would make a tokamak fusion reactor far more attractive than presently envisioned.
Date: September 1, 1994
Creator: Valeo, E. J. & Fisch, N. J.
Partner: UNT Libraries Government Documents Department

Global gyrokinetic simulation of tokamak transport

Description: A kinetic simulation code based on the gyrokinetic ion dynamics in global general metric (including a tokamak with circular or noncircular cross-section) has been developed. This gyrokinetic simulation is capable of examining the global and semi-global driftwave structures and their associated transport in a tokamak plasma. The authors investigate the property of the ion temperature gradient (ITG) or {eta}{sub i}({eta}{sub i} {equivalent_to} {partial_derivative}{ell}nT{sub i}/{partial_derivative}{ell}n n{sub i}) driven drift waves in a tokamak plasma. The emergent semi-global drift wave modes give rise to thermal transport characterized by the Bohm scaling.
Date: October 1, 1998
Creator: Furnish, G.; Horton, W.; Kishimoto, Y.; LeBrun, M.J. & Tajima, T.
Partner: UNT Libraries Government Documents Department

Fundamental studies of fusion plasmas. Final report, May 1, 1993--December 14, 1997

Description: In the course of this grant, Lodestar has collaborated with the TFTR ICRF team to carry out an extensive investigation of rf-edge physics relevant to the understanding and operation of the TFTR fast wave (FW) and ion Bernstein wave (IBW) antennas. Their FW work covered four main areas: rf sheath geometry on TFTR, ICRF convective cells and edge profile modifications, impurity production, and plasma glow and Fermi acceleration. Their IBW work, carried out over the last two years, was in support of the IBW transport barrier and poloidal flow generation experiments. A theoretical survey of rf-edge physics expected to be critical for these antennas was carried out. While the physics that was known to be important for FW systems was considered (especially sheath power dissipation, edge density modifications, and impurities), additional physics enters for IBW waves because of the shorter wavelength, slower group velocity, larger electric fields and the different polarization. In particular, ponderomotive forces, while normally negligible in the FW context, can be substantial for the IBW, but the jitter excursion distance of an electron is too large for validity of the usual theory. A new model for the resulting electron heating and density expulsion was developed. A new model of antenna coupling to the electron plasma wave, mode transformation to the IBW, and the effect of reflected waves at the lower hybrid layer was also developed.
Date: December 15, 1997
Creator: Myra, J.R.
Partner: UNT Libraries Government Documents Department

Alpha power channeling with two waves

Description: The complete channeling of energy from alpha particles is likely to be realized only through the excitation of a variety of waves, rather than by one wave alone. While one wave constrains more firmly the direction of the energy transfer, the necessary wave characteristics are far more easily achieved through a combination of waves, even at the expense of less restrictive motion of the {alpha}-particles.
Date: September 1, 1995
Creator: Fisch, N.J. & Herrmann, M.C.
Partner: UNT Libraries Government Documents Department

Calculation of Moments from Measurements by the Los Alamos Magnetospheric Plasma Analyzer

Description: The various steps involved in computing the moments (density, velocity, and temperature) of the ion and electron distributions measured with the Los Alamos Magnetospheric Plasma Analyzer (MPA) are described. The assumptions, constants, and algorithms contained in the FORTRAN code are presented, as well as the output parameters produced by the code.
Date: May 1, 1999
Creator: Thomsen, M. F.; Noveroske, E.; Borovsky, J. E. & McComas, D. J.
Partner: UNT Libraries Government Documents Department

PBX-M ion Bernstein wave heating overview

Description: A high power ion Bernstein wave heating system has been introduced on PBX-M for heating and for controlling the plasma pressure profile in an effort to achieve the stable high beta ``second stability`` regime. The pressure profile can be controlled through local bulk ion heating as well as density profile control. In bean-shaped plasmas with plasma currents range from 180 kA to 250 kA, good ion heating up to the highest, applied rf power, ({approx}700 kW) has been observed. The observed broadening of the ion temperature profile is consistent with localized off-axis bulk ion heating as predicted by IBW ray tracing calculations. Application of IBW also resulted in a greatly modified density profile. The ability for IBW to change the density profile appears to be particularly attractive for controlling the bootstrap current profile for advanced tokamaks. Many important IBWH-related edge physics results were also obtained, including ponderomotive edge plasma modification and parametric instability onset conditions. The experimental plan for the next IBW run includes investigation of synergy with LHCD, attainment of high bootstrap current fraction discharges utilizing the IBW density profile control, and exploration of high beta plasma regimes.
Date: April 1, 1993
Creator: Ono, M.; Chu, T. K.; Hermann, H.; LeBlanc, B.; Tighe, W.; Bell, R. et al.
Partner: UNT Libraries Government Documents Department

Quasilinear analysis of absorption of ion Bernstein waves by electrons

Description: The effects induced on plasma electrons by an externally launched ion Bernstein wave (IBW), in the presence of a lower hybrid wave (LHW) in the current drive regime, are studied by analytical integration of the IBW ray-tracing equations along with the amplitude transport equation (Poynting theorem). The electric field amplitude parallel and perpendicular to the external magnetic field, the quasilinear diffusion coefficient, and the modified electron distribution function are analytically calculated in the case of IBW. The analytical calculation is compared to the numerical solution obtained by using a 2-D Fokker-Planck code for the distribution function, without any approximation for the collision operator. The synergy between the IBW and LHW can be accounted for, and the absorption of the IBW power when the electron distribution function presents a tail generated by the LHW in the current drive regime can be calculated.
Date: January 1, 1995
Creator: Cardinali, A.; Paoletti, F.; Bernabei, S. & Ono, M.
Partner: UNT Libraries Government Documents Department

Ion anisotropy driven waves in the earth`s magnetosheath and plasma depletion layer

Description: Recent studies of low frequency waves ({omega}{sub r} {le} {Omega}{sub p}, where {Omega}{sub p} is the proton gyrofrequency) observed by AMPTE/CCE in the plasma depletion layer and magnetosheath proper arereviewed. These waves are shown to be well identified with ion cyclotron and mirror mode waves. By statistically analyzing the transitions between the magnetopause and time intervals with ion cyclotron and mirror mode waves, it is established that the regions in which ion cyclotron waves occur are between the magnetopause and the regions where the mirror mode is observed. This result is shown to follow from the fact that the wave spectral properties are ordered with respect to the proton parallel beta, {beta}{sub {parallel}p}. The later result is predicted by linear Vlasov theory using a simple model for the magnetosheath and plasma depletion layer. Thus, the observed spectral type can be associated with relative distance from the magnetopause. The anisotropy-beta relation, A{sub p} {triple_bond} (T{perpendicular}/T{sub {parallel}}){sub p} {minus} 1 = 0.50{beta}{sub {parallel}p}{sup {minus}0.48} results from the fact that the waves pitch angle scatter the particles so that the plasma is near marginal stability, and is a fundamental constraint on the plasma.
Date: May 1, 1993
Creator: Denton, R. E.; Hudson, M. K.; Anderson, B. J.; Fuselier, S. A. & Gary, S. P.
Partner: UNT Libraries Government Documents Department

Absorption of ion Bernstein waves by impurity cyclotron harmonics

Description: This paper analyzes the damping of externally-launched ion Bernstein waves by absorption at the cyclotron harmonics of the impurity ions. The inclusion of the non-magnetic energy flux term reduces the damping rate by nearly two orders of magnitude from the previous calculation. Excessive impurity damping can be avoided by launching ion Bernstein waves at a frequency just below the second (or higher) cyclotron harmonic of hydrogen.
Date: May 1, 1982
Creator: Ono, M.
Partner: UNT Libraries Government Documents Department

Plasma heating by externally launched ion Bernstein waves

Description: Externally launched ion Bernstein waves are shown to provide highly effective means for heating reactor plasmas. In a high density plasma (n/sub 0/ greater than or equal to 10/sup 14/cm/sup -3/), an ion Bernstein wave with a parallel index of refraction n/sub parallel/ = O (1) is mode-transformed into a high-density ion Bernstein wave with electron Landau damping several orders of magnitude smaller than that of the original ion Bernstein wave. Because of this reduced damping, an externally launched ion Bernstein wave with n/sub parallel/ less than or equal to 6 can penetrate to and deposit most of its wave power in the core of even a reactor-grade plasma (n/sub 0/= 3 x 10/sup 14/cm/sup -3/, T/sub eo/ = T/sub io/ = 7 keV, B/sub 0/ = 60 kG).
Date: October 1, 1979
Creator: Ono, M.
Partner: UNT Libraries Government Documents Department

Observation of the backward electrostatic ion cyclotron wave

Description: The backward branch of the electrostatic ion cyclotron wave has been observed, we believe, for the first time. The wave, which was driven by a phased antenna structure inserted in a neon plasma, exists in the parameter ranges 2T/sub i//m/sub i/ << (..omega../k/sub parallel/)/sup 2/ << 2T/sub e//m/sub e/, n..cap omega../sub i/ < ..omega.. < (n+1)..cap omega../sub i/, T/sub e/ greater than or equal to T/sub i/, and ..omega../sub pi/ > ..cap omega../sub i/. Double-tip probe interferomety data agree with the theoretical dispersion relation.
Date: December 1, 1984
Creator: Goree, J.; Ono, M. & Wong, K.L.
Partner: UNT Libraries Government Documents Department

Caviton collapse of SRS by SBS

Description: Particle simulations are performed to show that the ion waves resulting from Stimulated Brillouin Scatter (SBS) can trigger the collapse of the plasma waves excited by Stimulated Raman Scatter (SRS). We discuss the effect of this collapse mechanism on the hot-electron spectrum produced by the electrostatic waves. A fluid model for the coupling of the ion fluctuations to the plasma waves is formulated and we discuss the necessary condition on the SBS to induce collapse of the plasma waves produced by SRS.
Date: January 1, 1984
Creator: Aldrich, C.; Bezzerides, B.; DuBois, D.F. & Rose, H.
Partner: UNT Libraries Government Documents Department

Nonlinear ion-cyclotron waves in mirror machines. Paper IAEA-CN-38/S-1

Description: Experimental results on ion-cyclotron waves observed in the 2XIIB mirror machine are reviewed, and relevant theoretical work is discussed. The work reported generally substantiates the quasilinear diffusion model of mirror-plasma confinement, but also suggests alternatives. The end-loss current required by theory of the drift-cyclotron loss-cone (DCLC) instability agrees with measurements of this current. The experiment indicates that an increased ratio of plasma radius to ion gyroradius improves plasma confinement. However, measurements sometimes show a second ion-cyclotron mode, which is not the DCLC mode. Theoretical work on loss-cone instabilities has concentrated on linear, quasilinear, and fully nonlinear models of increased sophistication and experimental applicability.
Date: May 22, 1980
Creator: Cohen, B.I.; Smith, G.R. & Berk, H.L.
Partner: UNT Libraries Government Documents Department

Effect of noise on the standard mapping

Description: The effect of a small amount of noise on the standard mapping is considered. Whenever the standard mapping possesses accelerator models (where the action increases approximately linearly with time), the diffusion coefficient contains a term proportional to the reciprocal of the variance of the noise term. At large values of the stochasticity parameter, the accelerator modes exhibit a universal behavior. As a result the dependence of the diffusion coefficient on stochasticity parameter also shows some universal behavior.
Date: March 1, 1981
Creator: Karney, C.F.F.; Rechester, A.B. & White, R.B.
Partner: UNT Libraries Government Documents Department

Control of energetic ion confinement by ion cyclotron range of frequency waves

Description: It is shown that ICRF waves can induce fast convective radial transport of energetic ions in a tokamak geometry without affecting the background ion transport. Spatially inhomogeneous ICRF waves with directional parallel wave vectors are needed; otherwise, a net parallel flow of the energetic ions has to be present. 8 refs.
Date: February 1, 1990
Creator: Chang, C.S. (New York Univ., NY (USA). Courant Inst. of Mathematical Sciences)
Partner: UNT Libraries Government Documents Department

Harmonic launching of ion Bernstein waves via mode transformation

Description: Ion Bernstein wave excitation and propagation via finite ion-Larmor-radium mode-transformation are investigated theoretically and experimentally. It is shown that in the ion cyclotron range of frequencies omega less than or equal to 4..cap omega../sub i/, with modest ion temperatures (T/sub i/ less than or equal to 10 eV), the finite-Larmor-radius effect removes the wave singularity at lower-hybrid resonance layer, enabling an externally initiated electron plasma wave to transform continuously into an ion Bernstein wave. In an ACT-1 hydrogen plasma (T/sub e/ approx. = 2.5 eV, T/sub i/ less than or equal to 2.0 eV), externally excited ion Bernstein waves have been observed for omega less than or equal to 2..cap omega../sub i/ as well as for omega less than or equal to 3..cap omega../sub i/. The finite ion-Larmor-radius mode transformation process resulting in strong ion Bernstein wave excitation has been experimentally verified. Detailed measurements of the wave dispersion relation and of the wave-packet trajectory show excellent agreement with theory. The dependence of the excited ion Bernstein wave on the antenna phasing, the plasma density, and on the neutral pressure (T/sub i/) is also investigated.
Date: June 1, 1982
Creator: Ono, M.; Wong, K.L. & Wurden, G.A.
Partner: UNT Libraries Government Documents Department

Externally launched ion Berstein wave in the ACT-1 toroidal device

Description: In a hydrogen plasma (T/sub e/ = 2.5 eV, T/sub i/ = 1.5 eV), excitation of ion Bernstein waves by an externally placed electrostatic antenna has been investigated for ..omega.. approx. = 2 ..cap omega../sub i/. Mode transformation of the electron plasma wave at ..omega.. approx. = ..omega../sub pi/ without observable reflection was observed, followed by strong excitation of the ion Bernstein wave. Detailed measurements of k/sub perpendicular to/(..omega..,k/sub parallel/) and of the wave packet trajectory show excellent agreement with theory.
Date: June 1, 1980
Creator: Ono, M. & Wong, K.L.
Partner: UNT Libraries Government Documents Department

Parasitic excitation of ion Bernstein waves from a Faraday shielded fast wave loop antenna

Description: Parasitic excitation of ion Bernstein waves is observed from a Faraday shielded fast wave loop antenna in the ion cyclotron frequency range. Local analysis of the Vlasov-Maxwell equations demonstrates the role of plasma density gradient in the coupling process. The effects of plasma density and of parallel wave number on the excitation process are investigated.
Date: December 1, 1984
Creator: Skiff, F.; Ono, M.; Colestock, P. & Wong, K.L.
Partner: UNT Libraries Government Documents Department

Parametric excitation of ion Bernstein waves by a fast wave antenna in the ion cyclotron frequency range

Description: Parametric excitation of ion Bernstein waves is observed with an ICRF fast wave induction loop antenna in the ion cyclotron frequency range (..omega../sub o/ approx. 2..cap omega../sub i/ - 4..cap omega../sub i/). Important features of the decay process are investigated and discussed.
Date: November 1, 1983
Creator: Skiff, F.; Ono, M. & Wong, K.L.
Partner: UNT Libraries Government Documents Department