Nonlocal heat transport in laser-produced aluminum plasmas

Abstract

The spatial and temporal evolutions of nonlocal heat transport in laser-produced aluminum plasmas are studied with the improvements of the Thomson scattering experiments and the kinetic Fokker–Planck simulations. The results are compared with the hydrodynamic simulations with the classical Spitzer–Härm theory. When another heater beam is used, the electron temperature decreases slowly and the temperature gradient becomes steep in the conduction zone. The nonlocal heat flux can be sustained at a high value with slow decrease for long time. The Fokker–Planck simulations considering electron-electron collisions can well describe the nonlocal heat transport process in laser-produced plasmas.

Measuring electron heat conduction in non-uniform laser-produced plasmas using imaging Thomson scattering

“…When the 1053 nm heater beam is added, the data show a clear electron temperature profile peaked near the turning surface for the 1053 nm light. It should be noted that the gradient in the electron temperatures measured for this case are steeper than the spacing in the time dependent Thomson scattering data collected by Yu et al, [12] demonstrating the importance of high resolution imaging Thomson scattering measurements. Figure 7 and figure 8 show the bulk plasma flow and relative electron drift with respect to the plasma as a function of distance from the target.…”

“…This information can be used to validate current nonlocal heat conduction models or develop better models for radiation hydrodynamics codes. Furthermore, comparisons of the electron temperature gradients measured in these experiments with recent experiments by Yu et al show the importance of high spatial resolution for temporallyresolved measurements [12]. Without measurements having sufficient spatial resolution and sampling rate, the inferred gradients may not be correct requiring more measurements meaning many more laser shots.…”

“…This approach was first implemented in the early 1990's in uniform gas generated plasmas, which are not the typical case for laser produced plasma experiments since there are no large gradients in these conditions [8][9][10]. More recent work has measured the time dependent electron temperatures in gradient dominated plasmas at different spatial locations relative to the target [11][12][13]. These type of experiments require a different laser shot for each spatial location needing several shots to build the spatial dependence.…”

Emergence of kinetic behavior in streaming ultracold neutral plasmas

“…This is often done to treat nonlocal transport in plasmas with low collisionality, in which particle and energy fluxes at a given location are affected by conditions in distant regions of the plasma, which represents an important and complex problem. Often, ad hoc schemes are used in which the flux is simply limited to a fraction of its free-streaming value [1,8,13,[52][53][54]. Data such as presented here can provide a measurement of fluxes and thermodynamic gradients with high temporal and spatial resolution.…”