Feedback-controlled optimization of soft-X-ray radiation from femtosecond laser-produced plasmas

Using feedback-controlled optimizing algorithms the X-ray yield of a femtosecond laser-produced plasma with photon energies of more than 150 eV was maximized. This scheme has the advantage that even without any detailed knowledge of the complex laser plasma interaction the X-ray radiation in a certain wavelength range can be optimized. The parameters varied by the control procedure are the delay between a pre- and a main pulse, the energy splitting between the two pulses, and the position of the focusing lens. The algorithms investigated are a simplex downhill, a simulated annealing, and an evolutionary strategy code, respectively. Compared to the X-ray yield of only the main pulse the yield after optimizing was a factor of 27 higher, clearly showing the feasability of the procedure.