Physicists have developed a groundbreaking method to study the ultrafast transformation of solid copper into a blazing-hot plasma state, unlocking new insights into the inner workings of giant planets and fusion fuel cores.
Picosecond Plasma Transformation
Some 200,000 degrees Fahrenheit and a few trillionths of a second from now, a solid piece could be entirely ionized in a state of dense plasma. The phenomenon of this rapid transformation, termed ‘warm dense matter,’ has intrigued physicists for decades.
Hiroshi Sawada, associate professor at the University of Nevada, Reno and an international team of collaborators recently discovered a new way to track how plasmas progress in real time. By using pulses of X-rays emitted by the world’s most powerful X-ray Free Electron Laser (XFEL) facility, in Japan, they can now ‘see’ these changes as copper warms, melts and finally vaporizes on this almost unimaginably fast time scale.
This advance in experimental methods led to a new–and surprising– finding by the researchers. What they found was not the classical plasma, as expected, but that copper had been transformed into warm dense matter (WDM)—a new state made of nearly continuous light ions held together by strongly coupled localized electrons—offering a new regime of interacting with ultra-dense plasmas.
Five Years, 12 Labs and 3.5 Tons of Liquid Magical Metal Baby — Unleashing High-Density Plasmas
This versatility for probing the evolution of heat in such high-density plasmas is transformative to many scientific disciplines. It can be applied to variety of areas, ranging from astrophysics and inertial fusion energy research to quantum physics in atomic scale.
Here a high-powered laser pulse roasts the copper (the ‘pump’), before a second X-ray pulse shooting out of a separate laser is used to record what happens in the material (the ‘probe’). Through carefully tuning the delay between the two laser pulses, the team followed the temperature and ionization evolution in copper with time.
The level of precision and temporal resolution in this process is truly astounding, especially given that the entire transformation happens within just a few picoseconds (a time scale so small that we can hardly wrap our heads around it). But inside this tiny window, the copper goes through a violent change as its heat fronts zip along almost at light speed
The sheer number of surprising results that emerged from their preliminary experiments left the researchers in disbelief, underscoring the necessity to collect and cross-check data meticulously when probing such rarefied high-density plasma states.
Conclusion
This represents a major discovery in high-density plasmas because the work marks the first use of ultrashort pulse laser to observe the dynamics of plasma formation within copper, and may be applicable to many other materials as well. By deciphering such exotic physical states, the researchers have revealed a way to explore new frontiers in many fields, from astrophysics and fusion energy science, with possible applications to determine the foundational nature of the universe. While the limits of this new technique are still being explored by the scientific community, this approach is poised to become a novel method for unlocking cosmic riddles.
