Optical pumping experiments in the XUV regime

The construction of the Tesla Test Facility at DESY, a short pulse tunable soft X-ray free electron laser (FEL) source based on the self-amplified spontaneous emission (SASE) process, will provide a major advance in the capability for dense plasma-related and warm dense matter research. This source will provide 1013 photons in a 200 fs duration pulse that is tunable from ∼6 to 100 nm . Laser-based plasma spectroscopic techniques have been used with great success to determine the line shapes of atomic transitions in plasmas, study the population kinetics of atomic systems embedded in plasmas, and look at the redistribution of radiation. However, the possibilities for optical lasers end for plasmas with n e ⩾10 22 cm −3 as light propagation is severely altered by the plasma. Since an XUV-FEL will not have this limitation the entire field of high density plasma kinetics in laser produced plasma will then be available to study with the tunable source. Thus, one will be able to use these X-ray sources to pump individual transitions creating enhanced population in the excited states that can be easily monitored. We show two case studies illuminating different aspects of plasma spectroscopy.