Droplet evolution in expanding flow of warm dense matter

Abstract

We propose a simple, self-consistent kinetic model for the evolution of a mixture of droplets and vapor expanding adiabatically in vacuum after rapid, almost isochoric heating. We study the evolution of the two-phase fluid at intermediate times between the molecular and the hydrodynamic scales, focussing on out-of-equilibrium and surface effects. We use the Van der Waals equation of state as a test-bed to implement our model and study the phenomenology of the upcoming NDCXII ion heating experiments at LBNL. We find an approximate expression for the temperature difference between the droplets and the expanding gas and we check it with numerical calculations. The formula provides a useful criterion to distinguish the thermalized and non-thermalized regimes of expansion. In the thermalized case, the liquid fraction grows in a proportion that we estimate analytically, whereas, in case of too rapid expansion, a strict limit for the evaporation of droplets is derived. The range of experimental situations is discussed.

Quantum-enhanced measurements without entanglement

“…These Bose-Einstein condensates have been studied both at finite size and in the thermodynamic limit focusing on mathematical structures and general properties (Beau and Zagrebnov, 2010;van den Berg, 1983;van den Berg and Lewis, 1982;van den Berg et al, 1986a,b;Casimir, 1968;van Druten and Ketterle, 1982;Girardeau, 1960Girardeau, , 1965Ketterle and van Druten, 1982;Krueger, 1968;Mullin, 1997;Mullin and Sakhel, 2012;Rehr, 1970;Zobay and Garraway, 2004), in connection with liquid helium in thin films (Douglass et al, 1964;Goble and Trainor, 1965, 1966, 1967Khorana and Douglass, 1965;Mills, 1964;Osborne, 1949), magnetic flux of superconducting rings (Sonin, 1969), and gravito-optical traps (Wallis, 1996). Experimental realizations of effective low dimensional Bose-Einstein condensates with trapped atoms have been reported in (van Amerongen, 2008;van Amerongen et al, 2008;Armijo et al, 2011;Bouchoule et al, 2011;Esteve et al, 2006;Görlitz et al, 2001;Greiner et al, 2001). I µ,µ in these Bose-Einstein condensate phases is superextensive and interpolates between the scaling above the critical temperature and I µ,µ = O β 2 N 2 for a standard Bose-Einstein condensate only consisting of the ground state.…”

Numerical research on the ion-beam-driven hydrodynamic motion of fissile targets for nuclear safety studies

“…In this paper, in a similar manner to previous studies (Barnard et al, 2007;Armijo & Barnard, 2011), we propose a simple, safe, and inexpensive experimental setup, where a small amount of fissile sample is almost homogeneously and instantaneously heated by an intense short-pulsed medium-energy heavy-ion beam. For precise assessment of high-pressure EOS of fissile materials, subsequent hydrodynamic motion is examined in detail.…”

Long-lived nonthermal states realized by atom losses in one-dimensional quasicondensates

“…Experimentally, we prepare clouds of 87 Rb atoms by radio-frequency evaporation in our atom-chip experiment, as described in [26], and we record a set of density profiles taken under the same experimental conditions. The longitudinal trapping frequency is 6.2 Hz, while the transverse confinement is 1.9 kHz.…”

“…Since the local density approximation is well fulfilled longitudinally, the equilibrium profile can be computed using the equation of state for longitudinally homogeneous gases, ρ(µ, T ), where µ is the chemical potential. Using the well-established modified Yang-Yang equation of state [26,27], where the effective 1D coupling constant is g = 2 ω ⊥ a, the experimental density profile is fitted for a temperature T pr = 140 nK (see Fig. 4).…”

“…We also extract atom-number fluctuations δN 2 in each pixel from the same dataset, giving an independent temperature measurement. Since ∆ is both much smaller than the cloud size and much larger than the healing length, the physics of homogeneous gases is locally probed and thermodynamics predicts δN 2 = k B T ∆∂ρ/∂µ [26]. In Fig.…”