Harold T. Evensen

Measurements of ion temperature fluctuations in the Tokamak Fusion Test Reactor

First of a kind measurements of high-frequency ion temperature microturbulence in fusion-grade plasmas have been made in TFTR. The ion temperature fluctuations and carbon density fluctuations were found to have spectra similar to those of the ion density fluctuations across the plasma radius. The ratio of the relative fluctuation levels, (/T)/(/n), is 2 ? 0.5 from r/a = 0.59 to r/a = 0.99. The fact that this ratio is greater than unity is consistent with the general expectations of ion temperature gradient driven turbulence theory and suggests that ion drift modes dominate trapped electron modes in the turbulent spectrum. The temperature fluctuation spectra were found to exhibit a narrow transition region between distinctive edge and core turbulent modes, as has been seen with ion density fluctuations. The ratio of the relative fluctuation levels is greater than unity across this transition, which suggests that, despite the different modes present, the underlying instability is driven by the ion temperature gradient.

Automated fluid mixing in glass capillaries

A fast method and compact device for mixing sub-microliter fluid samples contained in glass capillaries is presented. The fluid is rapidly moved back and forth by air volume displacement driven by a piezo-ceramic actuator. Rapid mixing of different fluids is achieved via diffusion between the main fluid volume in the capillary and the thin fluid film it deposits on the capillary wall through its motion. Bubbles in the fluid are processed out of the capillary by use of an asymmetric velocity profile. A simple analysis model is used to optimize the design of the device and to elucidate the mechanisms involved in mixing. The mixing time is found to be inversely proportional to the fraction of the fluid volume that is left in the film layer for each cycle, which is determined by the wetting properties and the viscosity. The mixing time is therefore controlled by the dead-air volume of the system, the fluid volume, the capillary size, and the displacement limits of the piezo-ceramic actuator, in addition to the intrinsic properties of the fluid being mixed. The device described can mix two 1 μl water solutions in under 3 s. The possible shear breakage of DNA in solution is investigated, and λ-DNA is found to remain intact at aggressive mixing parameters. No evidence of aerosol contamination in polymerase chain reaction reactions was found to date.

ACAPELLA-1K: a biomechatronic fluid handling system for genome analysis that processes 1000 samples in 8 hours

An automated biomechatronic submicroliter fluid handling system for processing deoxyribonucleic acid (DNA) has been developed in the Genomation Laboratory, Department of Electrical Engineering, University of Washington, Seattle. This first generation system, ACAPELLA-1K, can process 1000 samples in 8 h in preparation for DNA sequencing using sample volumes ten times smaller than current state-of-the art manual and automated instrumentation. The system is based upon a proof-of-concept system that was developed by the Genomation Laboratory. The ACAPELLA-1K is the first integration of modules for fluid aspiration, dispensing, mixing, transport, and thermal processing that have been designed and developed with corporate partners Orca Photonic Systems, Inc., Redmond, WA, and Engineering Arts, Mercer Island, WA. These modules, comprising piezoceramic actuators, pneumatic pumps, linear mechanisms, thermal controllers, optical sensors, electronics, computer control, and software, are described in detail. Processing statistics are presented and successful experimental results are presented.