Ion Beams in Multi-Species Plasma

Argon and xenon ion velocity distribution functions are measured in Ar-He, Ar-Xe, and Xe-He expanding helicon plasmas to determine if ion beam velocity is enhanced by the presence of lighter ions. Contrary to observations in mixed gas sheath experiments, we find that adding a lighter ion does not increase the ion beam speed. The predominant effect is a reduction of ion beam velocity consistent with increased drag arising from increased gas pressure under all conditions: constant total gas pressure, equal plasma densities of different ions, and very different plasma densities of different ions. These results suggest that the physics responsible for the acceleration of multiple ion species in simple sheaths is not responsible for the ion acceleration observed in expanding helicon plasmas

Breastfeeding resources for mothers of preterm infants in Canadian neonatal intensive care units (NICUs): An environmental scan

Supportive breastfeeding resources are needed in neonatal intensive care units (NICUs) to effectively promote breastfeeding among mothers of preterm infants, yet researchers have not examined the existence of such support in a Canadian context. The purpose of this study was to determine, using an environmental scan, the types and frequencies of breastfeeding resources available to mothers of preterm infants in Canadian NICUs. Semi-structured interviews were conducted with 33 key informants from 29 level 3 NICUs across Canada. Six categories of resources were identified via content analysis: breastfeeding-friendly layout, breastfeeding support personnel, breastfeeding education for mothers, breast pump-related resources, coordination of post-discharge breastfeeding support, and breastfeeding-related policies. Several resources were reported by informants to exist in a high proportion of NICUs, such as privacy measures and breast pump availability, whereas other resources were reported in lower frequencies, such as the presence of peer counsellors and breastfeeding-related policies

Confocal Laser Induced Fluorescence with Comparable Spatial Localization to the Conventional Method

We present measurements of ion velocity distributions obtained by laser induced fluorescence (LIF) using a single viewport in an argon plasma. A patent pending design, which we refer to as the confocal fluorescence telescope, combines large objective lenses with a large central obscuration and a spatial filter to achieve high spatial localization along the laser injection direction. Models of the injection and collection optics of the two assemblies are used to provide a theoretical estimate of the spatial localization of the confocal arrangement, which is taken to be the full width at half maximum of the spatial optical response. The new design achieves approximately 1.4 mm localization at a focal length of 148.7 mm, improving on previously published designs by an order of magnitude and approaching the localization achieved by the conventional method. The confocal method, however, does so without requiring a pair of separated, perpendicular optical paths. The confocal technique therefore eases the two window access requirement of the conventional method, extending the application of LIF to experiments where conventional LIF measurements have been impossible or difficult, or where multiple viewports are scarce

Effect of ion cyclotron parametric turbulence on the generation of edge suprathermal ions during ion cyclotron plasma heating

The effect of parametric ion cyclotron turbulence on the heating of cold and suprathermal ions in the edge of a tokamak plasma during injection of high rf power in the ion cyclotron resonance frequency (ICRF) range is studied. The maximum turbulent heating rates for cold edge ions and suprathermal edge ions are calculated analytically for ion cyclotron turbulence driven by rf heating at the plasma edge. It is demonstrated that the maximum turbulent ion-heating rate for suprathermal ions is insufficient to explain the observed heating of edge ions. Therefore, the excitation of ion cyclotron turbulence by rf heating systems in the plasma edge is unlikely to be responsible for the experimentally observed large population of suprathermal ions in the edge of tokamak plasmas