New Spectroscopic Features Radiated from Low-Atomic-Number Z-Pinch Plasmas

Since great advances in late 60s, x-ray plasma spectroscopy continues to prove itself as an invaluable resource in studying astrophysical and laboratory high-temperature plasmas. With the recent progress in technologies of producing High-Energy-Density (HED) plasmas that can radiate new spectroscopic features which are not currently properly modeled and well understood, it became even more apparent. For example, about two decades ago x-ray spectra of multiply charged hollow ions (such as exotic ions without K shell) were observed using the femtosecond laser produced plasmas. These very complex quasi-continuous x-ray spectra included a new type of satellite lines that were identified as being emitted from the autoionizing states of hollow ions and their location were predicted with the reasonable precision by the atomic structure codes. However, their relatively high intensity continues to be a challenge to understand. More recently, charge exchange in nonhomogeneous plasma and collisions by non-Maxwellian (hot) electrons were considered as possible explanations of such features from hollow ions in HED plasmas. Despite the recent progress in studying these new hollow ion spectroscopic features produced by laser-produced plasmas, there is a very limited number of papers of their observation and identification in Z-pinch plasmas, which is the focus of this presentation. We present radiative characteristics of K-shell low-atomic-number Z-pinches produced at university-scale pulsed power generators (see, for example, [1]–[2]). Then, we highlight new spectroscopic features from hollow ions as well as their identification and modeling. Lastly, the future work is discussed.