Thomas Weber

The sheared -flow -stabilized Z pinch concept has been studied extensively and is able to produce fusionrelevant plasma parameters along with neutron production over several microseconds. We present here elevated electron temperature results spatially and temporally coincident with the plasma neutron source. An optical Thomson scattering apparatus designed for the FuZE device measures temperatures in the range of 1 -3 keV on the axis of the device, 20 cm downstream of the nose cone. The 17 -fiber system measures the radial profiles of the electron temperature. Scanning the laser time with respect to the neutron pulse time over a series of discharges allows the reconstruction of the T e temporal response, confirming that the electron temperature peaks simultaneously with the neutron output, as well as the pinch current and inductive voltage generated within the plasma. Comparison to spectroscopic ion temperature measurements suggests a plasma in thermal equilibrium. The elevated T e confirms the presence of a plasma assembled on axis, and indicates limited radiative losses, demonstrating a basis for scaling this device toward net gain fusion conditions.

The evolution of plasma parameters over confinement timescales is a key consideration for any confinement concept, especially the relatively short-lived Field Reversed Configuration (FRC). While it is challenging to model dynamic systems far from equilibrium, it is often possible to model the evolution and decay of FRCs through a progression of quasi-equilibrium states using simple analytic and phenomenological models. This approach can elucidate historically observed trends in decaying FRCs and be used to predict plasma parameters throughout slowly-varying dynamic processes, such as adiabatic expansion/compression. Limitations of this method are also discussed and several example cases are presented.

For the first time, a diagnostic for extreme ultraviolet (EUV) spectroscopy was fielded on a sheared-flow-stabilized (SFS) fusion Z-pinch experiment (FuZE-Q). The spectrometer collected time-gated plasma emission spectra in the 5-40 nm wavelength (30-250 eV) range for impurity identification, radiative power studies, and for plasma temperature and density measurements. The implementation of the diagnostic included fast (−10-ns risetime) pulsed high voltage electronics and a multi-stage differential pumping system that allowed the vacuum-coupled spectrometer to collect 3-independently-timed spectra per FuZE-Q shot while also protecting sensitive internal components. Analysis of line emission identified oxygen (0-III, O-IV, O-V, and O-VI), peaking in intensity shortly after maximum current (>500 kA). This work provides a foundation for future high energy spectroscopy experiments on SFS Z-pinch devices.

A colloidal quantum dot loaded polymer coated onto the surface of a sample pre-coated with epoxy was found to linearly change photoluminescence intensity around a 611.5 nm peak while under tensile strain. This peak was the epoxy's photoluminescence emission wavelength while the wavelengths around it were attributed to the colloidal quantum dot loaded polymer. From the spectra emitted from both the epoxy and the colloidal quantum dot loaded polymer, an empirical relation was made to calculate the changes in photoluminescence intensity between them. A calibration was then devised to create an optical stress-strain curve. The relationship found between both the optical and mechanical stress-strain curves indicated that this measurement technique followed the sample towards failure in the plastic region better than when only measuring from a colloidal quantum dot loaded polymer peak. For the first time, the results demonstrated here show that an epoxy's photoluminescence emission peak utilized in tandem with colloidal quantum dot loaded polymer can be used for strain sensing. Potential applications that could benefit from this finding would be: quality control, strain gauge for systems, and materials science.