Laser Generated X-Ray Studies Relevant to Compression Diagnostics and Nuclear Level Excitation

Abstract

This paper is divided into two sections. In Section A, absorption spectroscopy has been used to diagnose the conditions in the pusher of laser imploded targets. Absorption lines are produced when continuum radiation from the hot central compressed gas passes out through the colder surrounding pusher. They can be used to determine both the temperature and the ρΔR product of the pusher around peak compression. Applications of this work to the diagnosis of future, high compression implosions is discussed. Section B describes the characterization of x-ray spectra obtained on OMEGA for resonantly pumping nuclear transitions. Total emitted energy on the 8.4 keV resonance line of Cu⁺²⁷ could be sufficient for resonantly pumping the 8.4099 keV Ml transition in ¹⁶⁹TM from the (1/2)+ ground level to the (3/2)+ excited level, with a lifetime of 3.9 nsec. We will measure such nuclear excitation by the 3.9 nsec decay of internal conversion electrons. Results from a praseodymium (Z = 59) target show a spectrally dense x-ray spectrum over an interval of about 1 keV around 8.4 keV, from transitions involving excitation of n = 2 shell electrons. Spectrally dense bands of successively higher Z targets can be used to maximize the chance of resonant pumping of unknown nuclear levels.