Scientists cooled a plasma with a laser

A group of physicists from the university of flight has developed a cooling technology of photoyoneized neutral plasma strontium.

In order to avoid the difficulties associated with the high temperature of such an aggregate state, the researchers used a neutral plasma created by photoionization of ultra-cooled atomic gas. After 135 cooling microseconds, there was a decrease in the temperature of the ions almost four times, to 50 MK.

The technology operates through the scattering rate dependent and the pulse exchange rate between almost resonant photons and ions, molecules or atoms. Immediately after the formation of plasma, counter-polarized bundles were illuminated by forming a one-dimensional optical flow for laser cooling along its direction. The peak intensity of the single beam reached 100 MW / cm2. Reducing the cooling efficiency caused by coherent consideration of states and arising from this magnetic-induced transparent sections was minimized due to the rapidly changing plasma clashes rates.

Experimental scheme. Cooling (408 nm) and repulsing (1092 and 1033 nm) lasers were used in counter configurations with indicated polarization. Light 422 nm for LIF was formed with a slit for lighting the central plasma cut.

Cooling was effective only in the central region and in areas for which the expansion rate along the axis of the laser remained less or comparable to the speed capture range for a noticeable time. However, due to the high frequency of plasma clashes, the effect spread in all directions.

According to physicists, in addition to lowering the temperature, the technology allows you to create sufficiently sharp speed gradients and measure the shear viscosity. The same optical forces also slow down the expansion of the plasma, opening the way to its retention and other manipulations.

Experiments and classical hot plasma are successfully promoted. At the Chinese experimental superconducting tokamak, the temperature increase was able to achieve