The effect of the microscopic structure of metal surfaces on their optical properties

Abstract

The non-inductive current drive from directional fast Alfvkn and electron cyclotron waves was measured in the DIII-D tokamak in order to demonstrate these forms of radiofrequency (RF) current drive and to compare the measured efficiencies with theoretical expectations. The fast wave frequency was 8 times the deuterium cyclotron frequency at the plasma centre, while the electron cyclotron wave was at twice the electron cyclotron frequency. Complete noninductive current drive was achieved using a combination of fast wave current drive (FWCD) and electron cyclotron current drive (ECCD) in discharges for which the total plasma current was inductively ramped down from 400 to 170 kA. For steady current discharges, an analysis of the loop voltage revealed up to 195 kA of non-inductive current (out of 310 kA) during combined electron cyclotron and fast wave injection, with a maximum of 110 kA of FWCD and 80 kA of ECCD achieved (not simultaneously). The peakedness of the current profile increased with RF current drive, indicating that the driven current was centrally localized. The FWCD efficiency increased linearly with the central electron temperature as expected; however, the FWCD was severely degraded in low current discharges owing to incomplete fast wave absorption.The measured FWCD agreed with the predictions of a ray tracing code only when a parasitic loss of 4% per pass was included in the modelling along with multiple pass absorption. Enhancement of the second harmonic ECCD efficiency by the toroidal electric field was observed experimentally. The measured ECCD was in good agreement with Fokker-Planck code predictions.

A Simple Derivation of the Surface Contribution to the Reflectivity of a Metal, and its Use in the Van der Waals Interaction

“…Quite a large number of papers have been published related to various aspects of the reflectance of a (layered) metal surface [l-121. Here we would like to mention some early work by Drude [ l ] , McIntyre and Aspnes [2] and Flores and Garcia-Moliner [3], further work by Brodski and Urbakh [4], Feibelman [5] and Mukhopadhyay and Lundqvist [6] and finally some recent work by Dasgupta and Bagchi [7], Barrera and Bagchi [8], Bagchi and Rajagopal [9], Bagchi, Earrera and Rajagopal [ 101 and Sipe [ 1 1,121 .…”

Bulk plasma waves in a randomly inhomogeneous conductor

“…The solution of this equation describes the contri bution made to the Green's function by both the plasma waves and the stochastic spread in the values of the randomly inhomogeneous parameter n 0 (r). This spread leads to an increase in the width Δν of the peak of the function (k, ν), which is known as the non (6) and (7); (3,4) ν m and Δν are determined using formulas (6) η η uniform (fluctuation, nondissipative) broadening. The dispersion relation for the averaged plasma waves has been obtained using the simplification of the integral equation (7), which provides a small violation of self consistency.…”

“…In these designations, from expres sion (3) for the spectrum of a plasma wave in a homo geneous electron gas (γ = 0), we obtain (4) where k is the wave vector, k = |k|; n 1 ∝ exp[i(kx -ωt)]. This dispersion relation in Fig.…”

“…); moreover, inhomogeneities can also be created artificially. In plasmonic gratings, there have been used surface plasma waves that are sensitive to random roughnesses of the surface of conductors (see, for example, [4,5]). Surface plasma waves do not interact with inhomogeneities in the bulk of conduc tors, but they are coupled with bulk plasma waves, which are sensitive to such inhomogeneities.…”

A plasma source based on the Penning ionization of caesium by photoexcited mercury

“…As the populations of both Hg(6 3 P 0 ) and Hg(6 3 P 1 ) increase, Penning ionization of caesium by reaction (4) begins to occur. This reaction has been previously studied experimentally (Brodskii et al 1970).…”