Sandia LabNews

Improving the Standard Solar Model

Sandia physicist Jim Bailey wins APS John Dawson award

By testing bits of iron at the temperature of the sun, Jim Bailey (1683) and his team have provided key data to improve the Standard Solar Model, widely used by astrophysicists to help model the behavior of stars.

 For this work, Jim will receive the American Physical Society’s annual John Dawson Award for excellence in plasma physics research.

Says Jim, “I am thrilled to receive the 2016 APS Dawson Award. It is an honor not only for me, but also for my multi-institutional team and the Pulsed Power Sciences Center at Sandia. I worked on this project for more than a decade and it is an extraordinary feeling to know that my peers believe it was time well spent.

He adds that “the achievement was clearly enabled by my talented Sandia teammates: Greg Rochau (1680), Taisuke Nagayama  and  Guillaume Loisel (both 1683), and Stephanie Hansen (1684). We benefited from consistently supportive management and the opportunity to perform experiments with the Sandia Z facility, one of the world’s preeminent scientific instruments.”

The exacting work measured iron’s capacity to hinder the migration of energy originating deep in the sun’s interior. Jim and his team were able to determine that iron’s ability to absorb X-ray radiation near the edge of the sun’s radiative zone was much greater than formerly surmised. The new, experimentally derived figures provided a dose of reality to the models of theoreticians.

“The exquisite measurements made by Jim and his colleagues have triggered enormous interest in the stellar and high energy density physics communities,” says Keith Matzen, director of Sandia’s Pulsed Power Center 1600. “These results, from data collected over years, show the growing importance of pulsed power as an experimental platform to study laboratory astrophysics.”

Says Mike Campbell, deputy director at the Laboratory for Laser Energetics at the University of Rochester, “While previous Dawson awards for this field have been awarded to work with lasers, this is the first for a pulsed power machine like Z.”

In the words of the society, the award was made “for extraordinarily thorough laboratory opacity measurements of plasmas at realistic stellar interior conditions that directly resolve outstanding questions about solar structure, identify new theoretical challenges, and propel a new generation of precision high energy density experiments of direct astrophysical relevance.”

John Dawson was among the first to realize that computers had become powerful enough to model clouds of particles that formerly had been the object of laboratory experiments. The simulation method has since spread to many areas of science and technology and is usually considered on an equal footing with experimental and theoretical techniques. However, the three techniques work best when used to check each other.

Jim will receive the award, consisting of a monetary stipend and certificate, at the APS Division of Plasma Physics meeting in San Jose, California, Oct. 31-Nov. 4.