IRFP: High energy ion interactions in warm dense matter

Chen Sophia N, Fremont CA

Investigators

Abstract

1064468 Chen The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four-month research fellowship by Dr. Sophia N. Chen to work with Dr. Julien Fuchs Lee at Ecole Polytechnique in Palaiseau, France. Current high intensity short pulse lasers have now made possible investigations into the properties of warm dense matter (WDM) regime. This is a notoriously difficult area to study since it lies at the junction between condensed matter, dense plasma and nuclear physics, which covers a wide panel of research topics including, high-pressure physics, applied material studies, astrophysics, geophysics, inertial fusion as well as many industrial applications. Plasmas in this state have density ranging from the solid density up to 10 times greater and temperature that vary from 0.1 to 100 eV. Laboratory studies of the properties of this transient state are doubly challenging: first, there is tremendous difficulty in producing homogeneous samples of WDM which exist long enough to be probed over picosecond time-scales, and second, in regards to theory and model, such matter is partially correlated and degenerate which renders numerical modeling a tremendous challenge. This therefore naturally points to the need for experimental data to benchmark current codes. Now, with these new techniques of employing short-pulse high-power lasers to create WDM, it opens up numerous topics which can now be studied. This project, through experiments and modeling, will answer some basic questions. First, since present stopping models are dependent on the effective charge state Z* of the projectile, how does the modification of Z* depend on the characteristics of the plasma that it passes through? Which current theoretical model closely predicts this interactions and over which conditions? Second, what foundational platform would need to be developed to study ion stopping power in plasmas to bridge cold stopping to hot plasma stopping data? This program is being carried out with two laboratories in France, namely LULI (Laboratoire pour l'Utilisation des Lasers Intenses at Ecole Polytechnique) and CELIA (Centre Lasers Intenses et Applications at Université de Bordeaux). LULI houses unique experimental capability available there, namely their flexible high-power, multi-beams laser user facility. With this system, the multiple laser beams will allow matter to be heated to several eV temperatures at solid density (i.e. WDM plasmas), create a broadband ion beam up to tens of MeV, and provide short duration probe beams for diagnostics. Diagnostics fielded fall into two categories: those that measure the characteristics of the ion beams and those that provide information of the plasma conditions that the ion beam had passed through. With the PIC and QMD codes which have been adapted to simulating short pulse laser-plasma interactions developed at CELIA, the experimental effort will be grounded in theory. Most importantly on a broader scale, this approach will aid in verifying and validating simulations that are currently being developed both in the US and in Europe. Also, this research will compliment and develop platforms for studying WDM at X-FELs, accelerators, and HiPER (the European laser fusion project), all of which will ultimately prepare experiments at the National Ignition Facility (NIF).