Physicists at Rice University, Texas have created the first laser cooled neutral plasma, to open up the possibility of simulating super-dense stars.
The findings involve new techniques for laser cooling plasma clouds to temperatures about 50 times colder than deep space, creating the first laser cooled neutral plasma.
The lead scientist Tom Killian, professor of physics and astronomy at Rice, said: “We don’t know the practical payoff yet, but every time physicists have laser cooled a new kind of thing, it has opened a whole world of possibilities. Nobody predicted that laser cooling atoms and ions would lead to the world’s most accurate clocks or breakthroughs in quantum computing. We do this because it’s a frontier.”
Studying strongly coupled plasmas
Plasma is one of the four fundamental states of matter, an electrically conductive mix of ions and electrons. Unlike solids, liquids and gases, common in our everyday life, plasma tends to occur in very hot places such as the surface of the sun or a lightning bolt.
Explaining the difficulty of studying strongly coupled plasmas , Killian commented: “In strongly coupled plasmas, there is more energy in the electrical interactions between particles than in the kinetic energy of their random motion. We mostly focus on the ions, which feel each other, and rearrange themselves in response to their neighbours’ positions. That’s what strong coupling means.”
Killian added: “We can’t study strongly coupled plasmas in places where they naturally occur. Laser cooling neutral plasmas allows us to make strongly coupled plasmas in a lab, so that we can study their properties”.
By studying the laser cooled neutral plasma, the team hopes to answer fundamental questions about how matter behaves under extreme high density or low temperature conditions.
Will this pave the way to simulating super-dense stars?
“We are just at the beginning of exploring the implications of strong coupling in ultracold plasmas,” Killian said. “For example, it changes the way that heat and ions diffuse through the plasma. We can study those processes now. I hope this will improve our models of exotic, strongly coupled astrophysical plasmas, but I am sure we will also make discoveries that we haven’t dreamt of yet. This is the way science works.