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Laser irradiation of solid targets has been demonstrated to produce an extremely intense source of soft x rays. Conversion efficiencies of greater than 10% emission of over 1 keV radiation into 2π sr have been demonstrated with subjoule 1.06 μ laser pulses. This high conversion efficiency is achieved by using subnanosecond pulse lengths, tight focusing, and shaped pulses. A laser capable of producing the requisite high quality laser pulses at 100 Hz repetition rates has been constructed using newly developed slab techniques to maintain good beam quality at high average powers. A windowless target chamber has been designed to mate to x-ray stepper/aligners which are now being built. The present laser will permit average x-ray intensities of 2 mW/cm2 to be realized behind current (boron nitride) x-ray masks with negligible penumbral effects. This is an order of magnitude higher than possible with conventional electron beam impact sources and, with the present or upgraded laser system, should assist the commercialization of x-ray steppers.
Hoffman et al. (Tue,) studied this question.