During the first year of operation, the TCV tokamak has produced a large variety of plasma shapes and magnetic configurations, with 1 . O B J1.46T, I <800kA, ~S2.05, -0.7G%0.7. A new shape control algorithm, Eased on a finite element reconstruction of the plasma current in real time, has been implemented. Vertical growth rates of 800 sec-', corresponding to a stability margin f=l.IS, have been stabilized. Ohmic H-modes, with energy confinement times reaching 8 h s , normalized beta (p ,aB/I> of 1.9 and z P R 8 9 -P of 2.4 have been obtained in singlenuB X-point deuterium discharges with the ion grad B drift towards the X-point. Limiter H-modes with maximum line averaged electron densities of 1 . 7~1 0~~m -~ have been observed in D-shaped plasmas with 360kASIp&00kA.

Confinement in TCV electron cyclotron heated discharges was studied as a function of plasma shape, i.e. as a function of elongation, 1.1 < κ < 2.15, and triangularity, −0.65 ≤ δ ≤ 0.55. The electron energy confinement time was found to increase with elongation, owing in part to the increase of plasma current with elongation. The beneficial effect of negative triangularities was most effective at low power and tended to decrease at the higher powers used. The large variety of sawtooth types observed in TCV for different power deposition locations, from on-axis to the q = 1 region, was simulated with a model that included local power deposition, a growing m/n = 1 island (convection and reconnection), plasma rotation and finite heat diffusivity across flux surfaces. Furthermore, a model with local magnetic shear reproduced the experimental observation that the sawtooth period is at a maximum when the heating is close to the q = 1 surface.

On many tokamaks the reconstruction of the magnetic field structure in the plasma is supported by polarimetric measurements. Recent proposed and realized methods are based on a far-infrared laser beam with a rotating polarization ellipse. The same instrument usually performs as an interferometer measuring the line integrated plasma density. It has been shown that the rotating polarization ellipse disturbs the interferometric measurements. A method based on the principle of a rotating polarization in which the interferometric measurement is unaffected is proposed. Bench test results are presented which show the feasibility of this method.

Combined interferometer and polarimeter systems, using a single detecting element per line of sight, are susceptible to perturbation of the interferometric phase when modulation of the polarization vector is applied. This issue has been investigated extensively for the case of a rotating elliptically polarized probing beam, demonstrating that here a perturbation is inevitable. In this article the analogy between this analysis and earlier work is pointed out, and the underlying physics discussed. It will be demonstrated that schemes have been proposed in which the perturbation has been avoided or kept well within acceptable limits.

Electrophysiological evidence for the critical band phenomenon in humans using event-related potentials has been sought for many years with conflicting results. Components Na and Pa of the middle-latency response (MLR) and wave V of the auditory brain-stem response (ABR) were simultaneously recorded in response to a two-tone complex varying in bandwidth from 76 Hz to 1012 Hz, centered at 2 kHz, and presented at an overall level of 85 dB SPL, in ten normal female subjects. Only the amplitude of Na showed an abrupt increase as bandwidth changed from 268 to 330 Hz, yielding an estimate of critical bandwidth in good agreement with previous behavioral estimates.