The dynamics of supported polymer films were studied by probing the surface height fluctuations as a function of lateral length scale using x-ray photon correlation spectroscopy. Measurements were performed on polystyrene (PS) films of thicknesses varying from 84 to 333 nm at temperatures above the PS glass transition temperature. Within a range of wave vectors spanning 10(-3) to 10(-2) nm(-1), good agreement is found between the measured surface dynamics and the theory of overdamped thermal capillary waves on thin films. Quantitatively, the data can be accounted for using the viscosity of bulk PS.

Volume recombination within the Alcator C-Mod [I.H. Hutchinson et al., Phys. Plasmas 1 1511 (1994)] divertor plasma is measured and found to be a significant fraction of the total ion sink under detached divertor conditions. The recombination occurs in regions where Te ~1 eV and ne ~ 101 m-3 . Measurements of the spatial distribution of the recombination are presented. The determinations of the recombination rates are made by measuring the DO Balmer spectrum and by using a collisional radiative model describing the level populations, ionization and recombination of Do. The concept of 'recombinations per Balmer series photon' is developed to simplify the determinations. Measurements of the opacity of Lyo emission are presented. It is observed that up to 50% of the Lyo emission is trapped, indicating that Ly, is strongly trapped in some cases. The effects of Ly,, trapping on the 'recombinations per photon' curves are calculated and considered in the recombination rate determinations. Observations indicating the presence of Molecular Activated Recombination are discussed.+ Also at I.V. Kurchatov Institute of Atomic Energy, Moscow, Russian Federation

Significant recombination of the majority ion species has been observed in the divertor region of Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] under detached conditions. This determination is made by analysis of the visible spectrum from the divertor, in particular the Balmer series line emission and the observed recombination continuum, including an apparent recombination edge at ∼375 nm. The analysis shows that the electron temperature in the recombining plasma is 0.8–1.5 eV. The measured volume recombination rate is comparable to the rate of ion collection at the divertor plates. The dominant recombination mechanism is three-body recombination into excited states (e+e+D+⇒D0+e), although radiative recombination (e+D+⇒D0+hν) contributes ∼5% to the total rate. Analysis of the Balmer series line intensities (from nupper=3 through 10) shows that the upper levels of these transitions are populated primarily by recombination. Thus the brightnesses of the Balmer series (and Lyman series) are directly related to the recombination rate.