Comparison of Kα x-ray source from different metal targets using Sub-mJ kilohertz femto-second laser pulses

Summary form only given. We have developed an efficient Cu Kalpha X-ray source produced by a commercial kilohertz fs laser system. The source has a high X-ray conversion efficiency of 4x10^-5 into Cu Kalpha line emission at 8.05 keV. The microplasma X-ray source is produced by focusing 260 muJ laser pulses of 130 fs (FWHM) on a moving Cu-wire target. The source has a size of < 10 mum as measured by a knife edge technique and is expected to have a short temporal duration on the order of a picosecond. Recently we have extended the operation of the source to new wavelengths by using steel wire and silver coated copper wire targets. The Fe and Ag Kalpha line emission is at 6.4 keV and 22.2 keV respectively. The emission energy and spectra at these new photon energies has been characterized using three different detector systems which include a filtered PIN diode detector, pulse height spectrometer using a CdTe detector along with multichannel analyzer and a single hit CCD camera used in pulse height analysis mode. The conversion efficiencies and spectra will be presented at these new wavelengths and compared to scaling laws for expected conversion efficiency from the energetic laser-produced electrons into X-rays. An average X-ray photon flux of > 109 ph/sr/s is achieved and the emission provides sufficient spatial coherence and intensity for applications such as phase contrast imaging of biological samples or testing of X-ray microscope components. It is expected that this compact source can be developed into a durable low cost operating system for time resolved pulse probe experiments, phase contrast imaging of biological specimens and testing of X-ray optics.