Atomic and Nuclear Physics

Biography

Biography: Alla S Safronova

Abstract

Tungsten (W, Za=74) is now considered one of the best candidate materials for fusion reactors: it carries away heat efficiently, has the high melting point, low sputtering yield and tritium retention. Th e ability to melt during the transient events and large Z are among critical issues for tungsten application in fusion reactor and should be investigated in detail. Recently, W divertor was implemented in the ITER project and it became possible that W plasmas can reach the reactor core and then attain very high temperatures. Hence, tungsten might radiate a very broad spectrum from a few times ionized up to more than sixty times ionized, which is very challenging for the interpretation and comprehensive analysis. In this talk, we consider dielectronic recombination as a very important atomic process in laboratory and astrophysical plasmas and present the calculations of relativistic energy levels, radiative probabilities and autoionization rates of W in a very broad range of ionization stages from Yb-like W4+ to Cu-like W45+ to such very high ionization stages as Li-like W71+ [1-3]. 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: 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 muti-MA but also 1 MA university-scale pulsed power generators are able to produce multiply-ionized high-Za plasma [4-5], which is illustrated in this talk for W Z-pinches. In particular, x-ray spectra from 1 to 10 Å from W wire loads are presented and analyzed. Future work relevant to both atomic and nuclear physics is discussed. Th is research was supported by National Nuclear Security Administration under DoE grants DE-NA0003047 and DE-NA0002945.