Browsing by Author "Long, J.C."
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
Item Effect of an electric field on superfluid helium scintillation produced by $\alpha$-particle sources(American Physical Society, 2012) Ito, T.M.; Clayton, S.M.; Ramsey, J.; Karcz, M.; Liu, C.-Y.; Long, J.C.; Reddy, T.G.; Seidel, G.M.We report a study of the intensity and time dependence of scintillation produced by weak $\alpha$ -particle sources in super fluid helium in the presence of an electric field (0-45 kV/cm) in the temperature range of 0.2 to 1.1 K at the saturated vapor pressure. Both the prompt and the delayed components of the scintillation exhibit a reduction in intensity with the application of an electric field. The reduction in the intensity of the prompt component is well approximated by a linear dependence on the electric-field strength with a reduction of 15% at 45 kV/cm. When analyzed using the Kramers theory of columnar recombination, thiselectricfielddependence leads to the conclusion that roughly 40% of thescintillationresults from species formed from atoms originally promoted to excited states and 60% from excimers created by ionization and subsequent recombination with the charges initially having a cylindrical Gaussian distribution about the $\alpha$ track of 60 nm radius. The intensity of the delayed component of the scintillation has a stronger dependence on the electric field strength and on temperature. The implications of these data on the mechanisms affecting scintillation in liquid helium are discussed.Item Search for Lorentz violation in short-range gravity(American Physical Society, 2015) Long, J.C.; Kostelecký, V.A.A search for sidereal variations in the force between two planar tungsten oscillators separated by about 80 $\mu m$ sets the first experimental limits on Lorentz violation involving quadratic couplings of the Riemann curvature, consistent with no effect at the level of $10 ^{(-7)}$ $m^{(2)}$.