Electron Heating Via Mode Converted Ion Bernstein Waves in the Alcator C-mod Tokamak PDF Download
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Author: Paul Bonoli
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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Author: Paul Bonoli
Publisher:
ISBN:
Category :
Languages : en
Pages : 42
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Author: Yijun Lin
Publisher:
ISBN:
Category :
Languages : en
Pages : 52
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Localized direct electron heating by mode-converted ion cyclotron range of frequencies (ICRF) waves in D(H) tokamak plasmas has been clearly observed for the first time in Alcator C-Mod. Both on- and off-axis (high field side) mode conversion electron heating (MCEH) have been observed. The MCEH profile was obtained from a break in slope analysis of electron temperature signals in the presence of rf (radio frequency) shut-off. The temperature was measured by a 32-channel high spatial resolution (7 mm) 2nd harmonic heterodyne electron cyclotron emission (ECE) system. The experimental profiles were compared with the predictions from a toroidal full-wave ICRF code TORIC. Using the hydrogen concentration measured by a high-resolution optical spectrometer, TORIC predictions were shown qualitatively in agreement with the experimental results for both on- and off-axis MC cases. From the simulations, the electron heating from mode converted ion cyclotron wave (ICW) and ion Bernstein wave (IBW) is examined.
Author: Abhay Ram
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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Author: Eric Alan Nelson-Melby
Publisher:
ISBN:
Category :
Languages : en
Pages : 352
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(Cont.) The PCI system in C-Mod measures line-integrated density fluctuations using a CO2 laser which passes vertically through the plasma. The density fluctuation pattern is an inherently 3-dimensional structure, so the full-wave code TORIC has been used to interpret the one-dimensional measurements, which have some unexpected features, such as multiple peaks and troughs in amplitude. Strong IBW signal was often observed to the low-field side of the mode conversion layer. The importance of the parallel electric field for these IBW density fluctuation measurements is identified. IBW wavenumbers from 5 to 12 cm-1 have been detected, which is within the range of the code results.
Author: A.K. RAM
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Yijun Lin
Publisher:
ISBN:
Category :
Languages : en
Pages : 32
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Mode conversion (MC) of long wavelength fast electromagnetic (magnetosonic) waves into shorter wavelength electrostatic (ion-Bernstein, or IBW) or the electromagnetic (ion cyclotron, or ICW) waves is of great interest in laboratory, magnetic fusion and space physics experiments. Such processes are particularly important in multi-ion species plasmas. In this paper we report recent results from high power ion cyclotron heating experiments in the Alcator C-Mod tokamak where mode converted waves near the 3He-H hybrid layer have been detected by means of Phase Contrast Imaging (PCI) in H(3He-D) plasmas [E. Nelson-Melby et al, Phys. Rev. Lett. 90, 155004 (2003)]. The measured k-spectrum and spatial location are in agreement with the theoretical predictions[F.W. Perkins, Nucl. Fusion 17, 1197 (1977)] who showed that in a sheared magnetic field, mode-conversion of the magnetosonic wave into ICW may dominate over IBW for appropriate ion species (i.e. D-T, or equivalently, H-3He). Recent modeling with full wave codes, as well as solving the hot plasma dispersion equation in the presence of sheared magnetic fields, verifies the interpretation of such a mode conversion process. Thus, the geometry of the magnetic field, as well as the particular ion species mix, influences the physics of mode conversion processes. In this talk, we also present recent results on the study of mode conversion electron heating (MCEH) in D(H) plasmas [Y. Lin et al., Plasma Phys. Control. Fusion 45 (6), 1013 (2003)]. By comparing the experimentally measured MCEH profile with modeling, the study shows that the MC ICW may make a significant contribution to the direct electron heating when the D-H hybrid layer is off-axis on the high field side. Preliminary results of mode conversion plasma flow drive experiments are also reported.
Author: Y. Nakamura
Publisher: Nova Publishers
ISBN: 9781594544866
Category : Science
Languages : en
Pages : 294
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Nuclear fusion is a process in which two nuclei join, forming a larger nucleus and releasing or absorbing energy. With some exceptions, nuclei lighter than iron release energy when they fuse, while heavier nuclei absorb energy; this is because iron has the largest binding energy. Nuclear fusion of light elements is the energy source which causes stars to shine and hydrogen bombs to explode. Nuclear fusion of heavy elements is part of the process that triggers supernovae. Nuclear fusion as an energy source has several advantages: It is vast, new source of energy; Fuels are plentiful; Inherently safe since any malfunction results in a rapid shutdown; No atmospheric pollution leading to acid rain or "greenhouse" effect; Radioactivity of the reactor structure, caused by the neutrons, decays rapidly and can be minimised by careful selection of low-activation materials. Provision for geological time-span disposal is not needed. This book brings together leading research in this field which will play a major role in the 21st century.
Author: John D. Moody
Publisher:
ISBN:
Category :
Languages : en
Pages : 20
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Author: Abhay Ram
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
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The high beta operating regime of spherical tokamaks (ST), such as in NSTX and MAST, make them attractive fusion devices. To attain the high beta's there is a need to heat and to drive currents in ST plasmas. While ST plasmas are overdense to conventional electron cyclotron (EC) waves, electron Bernstein waves (EBW) offer an attractive possibility both for heating and for driving plasma currents. EBWs, which have no density limits, can propagate into the plasma core for frequencies above the electron cyclotron frequency fce [A.K. Ram and S.D. Schultz, Phys. Plasmas, 7, 4084 (2000)]. Since EBWs are not vacuum modes, they are excited inside the plasma by mode conversion of the traditional X and O modes. From ray tracing analysis we find that EBWs are strongly absorbed by electrons in the region where the wave frequency matches the Doppler broadened electron cyclotron resonance frequency or its harmonics [A.K. Ram and S.D. Schultz, Phys. Plasmas, 7, 4084 (2000)]. The strong and localized absorption implies that thermal emission of EBWs can occur for frequencies corresponding to the local Doppler-shifted electron cyclotron frequency. This emission then converts, at the UHR, to the X and O modes which are then observed in the vacuum region.
Author: Francis W. Perkins
Publisher:
ISBN:
Category :
Languages : en
Pages : 74
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