We report the results of experiments on lowtemperature alkali plasmas in strong magnetic fields and their interpretation in terms of collisional drift modes, in which diffusion over the transverse wavelength, resulting from ionion collisions, ' plays an important role.

A detailed comparison between the observed and expected loss of alpha-like MeV fusion products in TFTR is presented. The D-D fusion products (mainly the 1 MeV triton) were measured with an 2-D imaging scintillation detector. The expected first-orbit loss was calculated with a simple Lorentz orbit code. In almost all cases the measured loss was consistent with the expected first-orbit loss model. Exceptions are noted for small major radius plasmas and during strong MHD activity.

We report the results of experiments on lowtemperature alkali plasmas in strong magnetic fields and their interpretation in terms of collisional drift modes, in which diffusion over the transverse wavelength, resulting from ionion collisions, 1 plays an important role.Collisional drift modes 2 arise in the presence of a density gradient perpendicular to the magnetic field and result from the combined effects of ion inertia, 3 electron-ion collisions, and mean electron kinetic energy along the magnetic-field lines. 4 Our experiments determine frequencies, amplitudes, and azimuthal mode numbers of steadystate drift waves as functions of magnetic field strength and ion density. Their interpretation is based on a theory which includes the effects of ion-ion collisions on the ion motion. Although the observed relative wave amplitudes are not small, the linearized approximation is expected and found to predict correctly frequencies and the abrupt appearance of certain modes as functions of the various physical parameters (density, magnetic field, temperature, and ion mass).The principal experimental results are the consistent observations of single-mode steadystate oscillations, which we have identified as drift modes, and, at certain critical values of the magnetic-field strength, sudden changes of both the azimuthal mode number and frequency 5 of the oscillations. We have explained these results by a theory, which predicts abrupt stabilization of a particular mode with decreasing magnetic field as a result of increased diffusion over the transverse wavelength 1 due to ion-ion collisions. 6 This type of diffusion, in fact, suppresses the instability when the ion gyroradius reaches a critical size relative to the transverse wavelength of the mode.