The proton Zeeman spin-lattice relaxation time T1 and the proton dipolar spin-lattice relaxation time T1D of a chiral compound p-decyloxybenzylidene p′-amino-2-methyl butyl cinnamate are studied as a function of temperature and sample rotation in a magnetic field at 30 MHz. In addition, proton T1 is measured in the smetic A, ferroelectric smectic C* and H* phase at 15.1 and 45.5 MHz. The spin relaxation mechanisms for the proton T1 and T1D in the smectic A and C* phase are ‘‘diffusion-induced’’ orientational order director fluctuations and molecular self-diffusion. In contrast with the achiral compound TBBA, the T1 angular dependence in the smectic C* and C phase are different, while the T1D angular dependence appears to be similar in these smectic phases.

We describe experiments on the launching of drift waves in the UMIST Quadrupole GOLUX, presenting the general principles of successful launching and showing how these are applied to launch both the unstable drift waves which occur spontaneously in the device, and other stable modes representing different branches of the drift wave dispersion relation. In each case the measured dispersion curves are presented and compared with theory. All the waves appear to be spatially damped, including those known to be unstable; we propose that this is due to systematic error in the detection system. The results suggest that only if the measured decay constant exceeds about 8 m −1 can we be certain that the waves are actually damped. This is the case at low frequencies, where the dissipation is due to ion Landau damping, and again at high wavenumbers where no suitable dissipative process has been discovered. We conjecture that the effect is due to radiative damping, associated with the breakdown of the one-dimensional propagation assumed in the theory.

We present a theoretical and experimental study of the launching impedance Z L , which describes the effectiveness of drift wave launching into the plasma in the quadrupole GOLUX. The theory, valid only for damped modes, incorporates the plasma response function (the inverse of the dielectric function) and measurements of the impedance can, therefore, lead to an experimental test of theoretical forms for this function. Using a lock-in amplifier technique, Z L has been measured for four different branches of the drift wave dispersion curve, two expected to be linearly stable and damped and two believed to be linearly unstable but in practice apparently damped. For the stable modes theory and experiment agree within a factor of two, as good as can be expected given experimental error and approximations in the theory. For the unstable mode, a well defined value of Z L is obtained, but it exceeds the theoretical estimate by two orders of magnitude. Using a different technique we have been able to detect growth of the unstable mode after launching, provided the launched amplitude is sufficiently small; this explains the failure of the theory. It appears, however, that in most cases the wave launched into the plasma is already saturated and does not grow further. We propose that the launched wave amplitude is limited by the power available from the external circuit, and on this basis we have derived an upper limit for the impedance.

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