Ion Bernstein wave heating (IBWH) utilizes the ion Bernstein wave (IBW), a hot plasma wave, to carry the radio frequency (rf) power to heat the tokamak reactor core. Earlier wave accessibility studies have shown that this finite‐Larmor‐radius (FLR) mode should penetrate into a hot dense reactor plasma core without significant attenuation. Moreover, the IBW’s low perpendicular phase velocity (ω/k⊥≊VTi≪Vα) greatly reduces the otherwise serious wave absorption by the 3.5 MeV fusion α particles. In addition, the property of IBW’s that k⊥ρi≊1 makes localized bulk ion heating possible at the ion cyclotron harmonic layers. Such bulk ion heating can prove useful in optimizing fusion reactivity.In another vein, with proper selection of parameters, IBW’s can be made subject to strong localized electron Landau damping near the major ion cyclotron harmonic resonance layers. This property can be useful, for example, for rf current drive in the reactor plasma core. IBW’s can be excited with loop antennas or with a lowe...

/pdf/ion-bernstein-wave-heating-research-4rvnqub6sa.pdf

Ion Bernstein wave heating research

The constitutive relation of a non-homogeneous plasma for h.f. waves in the ion cyclotron frequency domain is derived by integrating the Vlasov equation along the unperturbed particle orbits in the drift approximation. The integro-differential wave equations and the corresponding power balance equation in Tokamak geometry are obtained by expanding the h.f. current to second order in the ratio of the ion Larmor radius to the typical perpendicular wavelength; terms proportional to the much smaller ratio of Larmor radius to the length characterizing equilibrium gradients are neglected. This allows the author to cast the FLR wave equations into an explicitly vector form, and to identify clearly the physical meaning of each term. By specializing to a plane stratified model of the Tokamak, the author compared the complete set of FLR wave equations with a considerably simpler set previously derived by Swanson (1981) and by Colestock and Kashuba (1983), which has been extensively used for analytic and numerical studies of ICR heating. The author concludes that at least in the important scenario of a hydrogen minority in a deuterium plasma (and of pure first harmonic heating as a particular case), the use of the reduced set of equations is well justified, provided that finite Larmor radius contributions to electron absorption are taken into account.

Finite Larmor radius wave equations in Tokamak plasmas in the ion cyclotron frequency range

Nonlinear interactions of ion cyclotron range of frequency (ICRF) waves with fusion plasmas are reviewed. Although the linear theory of ICRF waves, including fast waves (FWs), high-harmonic fast waves and ion Bernstein waves (IBWs), is widely applicable, nonlinear effects can still be important, especially in the edge plasma or for novel core applications. Here the topics of flow drive, ponderomotive forces, radiofrequency (rf) sheaths, parametric decay and related interactions with the edge plasma are considered. Primary emphasis is placed on the basic underlying physics and tokamak applications. For FW antennas, the parallel electric field near launching structures is known to drive rf sheaths which can give rise to convective cells, interaction with plasma 'blobs', impurity production and edge power dissipation. In addition to sheaths, IBW waves in the edge plasma are subject to strong ponderomotive effects and parametric decay. In the core plasma, slow waves can sometimes induce nonlinear effects. Mechanisms by which these waves can influence the radial electric field and its shear are summarized and related to the general (reactive-ponderomotive and dissipative) force on a plasma from rf waves. Standard ICRF codes have begun to incorporate the nonlinear topics described here. Further progress in integrated simulation should allow new predictive modelling capabilities.

/pdf/nonlinear-icrf-plasma-interactions-4mjjju6omh.pdf

Nonlinear ICRF-plasma interactions

Ion Bernstein wave heating (IBWH) has been investigated on PLT with up to 650 kW of rf power coupled to the plasma, exceeding the ohmic power of 550 kW. Plasma antenna loading of 2 ..cap omega.. has been observed, resulting in 80 to 90% of the rf power being coupled to the plasma. An ion heating efficiency of ..delta..T/sub i/(0)n/sub e//P/sub rf/ = 6 x 10/sup 13/ eV cm/sup -3//kW, without high energy tail ions, has been observed up to the maximum rf power. The deuterium particle confinement during high power IBWH increases significantly (as much as 300%). Associated with it, a longer injected impurity confinement time, reduced drift wave turbulence activity, frequency shifts of drfit wave turbulence, and development of a large negative edge potential were observed. The energy confinement time, however, shows some degradation from the ohmic value, which can be attributed to the enhanced radiation loss observed during IBWH. The ion heating and energy confinement time are relatively independent of plasma current.

/pdf/effects-of-high-power-ion-bernstein-waves-on-a-tokamak-47veeevtpj.pdf

Effects of High-Power Ion Bernstein Waves on a Tokamak Plasma

We present high-resolution crystal spectroscopy measurements of the $n=3\ensuremath{\rightarrow}n=2$ $L$-shell x-ray transitions of neonlike W${}^{64+}$, which include seven electric-dipole--allowed transitions, two electric quadrupole transitions, and one magnetic quadrupole transition. The resulting wavelength data are compared to recent calculational results, allowing us to clearly distinguish between different theoretical approaches which need to take into account not only substantial electron correlations effects but also radiative contributions, which in case of the transition from the upper level ${(1{s}^{2}2{s}_{1/2}2{p}^{6}3{p}_{3/2})}_{J=1}$ to the closed-shell neonlike ground state exceeds 20 eV. Best agreement is found with calculations utilizing the relativistic multireference M\o{}ller-Plesset approach. In addition to the emission from W${}^{64+}$, we observed several inner-shell collisional satellite lines associated with oxygenlike W${}^{66+}$, fluorinelike W${}^{65+}$, sodiumlike W${}^{63+}$, and magnesiumlike W${}^{62+}$, which provide benchmarks for future calculations as well as for recent calculations using the relativistic many-body perturbation theory. The present measurements also provide accurate rest wavelengths for establishing the instrumental dispersion needed for future measurements of the core plasma motion in the ITER tokamak and show that the candidate W${}^{64+}$ line for such measurements remains well isolated from neighboring collisional satellite lines even when broadened by the expected high temperatures in this device.

/pdf/l-shell-x-ray-emission-from-neonlike-w-64-31jsv9i43z.pdf

L-shell x-ray emission from neonlike W 64+

A variety of RF experiments are being conducted on PLT in order to explore RF techniques which could improve Tokamak performance parameters. Of special importance are the studies of ion Bernstein wave (IBW) heating, lower hybrid MHD stabilization and electron heating, down-shifted electron cyclotron heating, and fast wave current drive. Ion Bernstein wave heating results at modest power indicate that the particle confinement time could be enhanced relative to that for fast wave heating in the ion cyclotron range of frequencies (ICRF) and neutral beam heating. At these power levels a conclusive determination of energy confinement scaling with power cannot yet be given. Central sawtooth and m=1 MHD stabilization is being obtained with centrally peaked lower hybrid (LH) current drive and the central electron temperature is peaking to values ( approximately 5 keV) well outside the bounds of 'profile consistency'. In this case the electron energy confinement is apparently increased relative to the ohmic value.

RF experiments on PLT

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Effects of High-Power Ion Bernstein Waves on a Tokamak Plasma

RF experiments on PLT