Browsing by Author "Castro, J."

Now showing 1 - 9 of 9
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    Creating and studying ion acoustic waves in ultracold neutral plasmas
    (2012) Killian, T.C.; McQuillen, P.; O'Neil, T.M.; Castro, J.; Rice Quantum Institute
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    Creating Non-Maxwellian Velocity Distributions in Ultracold Plasmas
    (arXiv, 2011) Castro, J.; Bannasch, G.; McQuillen, P.; Pohl, T.; Killian, T.C.; Rice Quantum Institute
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    Electron-Temperature Evolution in Expanding Ultracold Neutral Plasmas
    (2007-08-17) Gupta, P.; Laha, S.; Simien, C.E.; Gao, H.; Castro, J.; Killian, T.C.; Pohl, T.
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    Emergence of kinetic behavior in streaming ultracold neutral plasmas
    (AIP Publishing LLC, 2015) McQuillen, P.; Castro, J.; Bradshaw, S.J.; Killian, T.C.
    We create streaming ultracold neutral plasmas by tailoring the photoionizing laser beam that creates the plasma. By varying the electron temperature, we control the relative velocity of the streaming populations, and, in conjunction with variation of the plasma density, this controls the ion collisionality of the colliding streams. Laser-induced fluorescence is used to map the spatially resolved density and velocity distribution function for the ions. We identify the lack of local thermal equilibrium and distinct populations of interpenetrating, counter-streaming ions as signatures of kinetic behavior. Experimental data are compared with results from a one-dimensional, two-fluid numerical simulation.
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    Experimental Realization of an Exact Solution to the Vlasov Equations for an Expanding Plasma
    (2007-10-08) Laha, S.; Gupta, P.; Simien, C.E.; Gao, H.; Castro, J.; Pohl, T.; Killian, T.C.
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    Ion Acoustic Waves in Ultracold Neutral Plasmas
    (American Physical Society, 2010) Castro, J.; McQuillen, P.; Killian, T.C.; Rice Quantum Institute
    We photoionize laser-cooled atoms with a laser beam possessing spatially periodic intensity modulations to create ultracold neutral plasmas with controlled density perturbations. Laser-induced fluorescence imaging reveals that the density perturbations oscillate in space and time, and the dispersion relation of the oscillations matches that of ion acoustic waves, which are long-wavelength, electrostatic, density waves.
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    Ion holes in the hydrodynamic regime in ultracold neutral plasmas
    (American Institute of Physics, 2013) McQuillen, P.; Castro, J.; Strickler, T.; Bradshaw, S.J.; Killian, T.C.
    We describe the creation of localized density perturbations, or ion holes, in an ultracold neutral plasma in the hydrodynamic regime, and show that the holes propagate at the local ion acoustic wave speed. We also observe the process of hole splitting, which results from the formation of a density depletion initially at rest in the plasma. One-dimensional, two-fluid hydrodynamic simulations describe the results well. Measurements of the ion velocity distribution also show the effects of the ion hole and confirm the hydrodynamic conditions in the plasma.
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    Optical Probes of Ultracold Neutral Plasmas
    (2007) Laha, S.; Gao, H.; Castro, J.; Gupta, P.; Simien, C.E.; Killian, T.C.
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    Velocity Relaxation in a Strongly Coupled Plasma
    (American Physical Society, 2012) Bannasch, G.; Castro, J.; McQuillen, P.; Pohl, T.; Killian, T.C.; Rice Quantum Institute
    Collisional relaxation of Coulomb systems is studied in the strongly coupled regime. We use an optical pump-probe approach to manipulate and monitor the dynamics of ions in an ultracold neutral plasma, which allows direct measurement of relaxation rates in a regime where common Landau-Spitzer theory breaks down. Numerical simulations confirm the experimental results and display non-Markovian dynamics at early times.