Texas Petawatt laser helps create laboratory conditions like those in a white dwarf star atmosphere

Laboratory measurements of white dwarf star-like conditions can help with determining the mass of those stars observed by telescopes. Roycroft et al. demonstrate a method to achieve temperatures and densities in the laboratory similar to those found in the atmosphere and envelope of a white dwarf star.

Using a short pulse, ultrahigh intensity laser, the researchers created a proton beam that near-instantaneously heated a carbon nanofoam to 10,000-12,000K. They then measured the cooling temperature of the foam as it expanded over time and used computer simulations to model the results in comparison to existing experimental data.

“This is the first time that isochoric heating of carbon nanofoams has been done with the Texas Petawatt laser,” said author Rebecca Roycroft. This process cannot easily be done with conventional accelerators, because their proton pulses are usually too long, and the material expands while heating.

White dwarf mass is critical to understanding important cosmological questions, including stellar physics in extreme conditions and the chemical distribution of material in our galaxy. The researchers’ work showed that white dwarf star-like conditions can be achieved at the Texas Petawatt laser.

“The next steps for this project are to match DQ white dwarf envelope conditions by increasing the temperature of the heated carbon foam to more than 100,000 K,” said Roycroft. To measure the relationship between temperature and density of the heated foam, they will combine temperature measurements with an expansion measurement that would come from time dependent X-ray images.

The isochoric heating platform developed could be used on any other material for which equation of state information at relatively low temperatures and high density is needed.

Source: “Experiments and simulations of isochorically heated warm dense carbon foam at the Texas Petawatt Laser,” by R. Roycroft, P. A. Bradley, E. McCary, B. Bowers, H. Smith, G. M. Dyer, B. J. Albright, S. Blouin, P. Hakel, H. J. Quevedo, E. L. Vold, L. Yin, and B. M. Hegelich, Matter and Radiation at Extremes (2020). The article can be accessed at https://doi.org/10.1063/5.0026595 .