Atomic and Nuclear Physics

Biography

Biography: Alla S Safronova

Abstract

Tungsten is a high atomic number, mass and density metal (W, Z=74, 183.84 amu and 19.3 g/cm3 respectively) that was extensively studied and has been found to have a lot of applications in atomic, nuclear and plasma physics, chemistry, biology as well as in industry, since its discovery in 1781. Tungsten is now considered one of the best candidate materials for fusion reactors: it carries heat away effi ciently, has the highest melting point of all metals and has low sputtering yield and tritium retention. In addition, recently a W divertor was implemented in the ITER (International Thermonuclear Experimental Reactor) project. Th e presence of heavy elements in the otherwise low-Z tokamak plasma may cause radiation losses that substantially infl uence the ignition of the plasma. Initially neutral, the W atoms can be collisionally ionized when moving to the hotter plasmas and it might become possible that W plasmas can reach the reactor core where they attain very high temperatures. Hence, tungsten will radiate a very broad spectrum from a few times ionized up to more than sixty times ionized, which is very challenging for the interpretation, modeling and comprehensive analysis. In this talk, we consider dielectronic recombination as a very important atomic process in laboratory and astrophysical plasmas and methods of calculations of W relativistic atomic data. In particular, we present the results of relativistic energy levels, radiative probabilities, autoionization rates and dielectronic satellite spectra of W in a very broad range of ionization stages from fi ve times ionized (Tm-like W5+) to forty fi ve times ionized (Cu-like W45+) to such very high ionization stages as seventy one times ionized (Li-like W71+) tungsten [1-6] (see Figure). A comparison between the results from various relativistic atomic structure codes and accuracy of atomic data is discussed. Another important application of tungsten is in z-pinch physics and ICF (Inertial Confi nement Fusion): wire arrays that consist of hundreds of micron- diameter W wires can be imploded at multi-MA currents and generate the highest radiation yield out of all other wire materials. Not only multi-MA but also 1 MA university-scale pulsed power generators are able to produce multiply-ionized high-Z plasma [7-8], which is illustrated in this talk for W z-pinches. Specifi cally, x-ray spectra from 1 to 10 Å from various W wire loads are presented and analyzed. Future work relevant to both atomic and nuclear physics is discussed. This research was supported by the National Nuclear Security Administration and the Office of Science of the U.S. Department of Energy.