Dense plasma focus x-ray source for sub-micron lithography

A discharge driven, dense plasma focus in neon is under development at SRL for use as a point x-ray source for sub-micron lithography. This source is presently capable of delivering ∼ 13j/pulse of neon K-shell x-rays (8--14 angstrom) into 4π steradians with 2 kj of electrical energy stored in the capacitor bank charged to 9 kV at a pulse repetition rate of 2 Hz. The discharge is produced by a ≤4 kj, ≤12 kV, capacitor bank circuit, which has a fixed inductance of 12 nH and drives ≤450 kA currents into the DPF load, with ∼1.1 μs rise-times. X-rays are produced when a dense pinch of neon is formed along the axis of the DPF electrodes. A new rail-gap switched capacitor bank and DPF have been built, designed for continuous operation at 2 Hz and burst mode operation at 20 Hz. This paper will present measurements of the x-ray output at a repetition rate of 2 Hz using the new capacitor bank. It will also describe measurements of the spot size (0.3--0.8 mm) and the spectrum (8--14 angstrom) of the DPF source. The dependence of these parameters on the DPF head geometry, bank energy and operating pressure will be discussed. The x-ray output has been measured using filtered pin diodes, x-ray diodes, and absolutely calibrated x-ray crystal spectra. Results from the source operating at 2 Hz will be presented. A novel concept of a windowless beamline has also been developed. The results of preliminary experiments to test the concept will be discussed. At a pulse repetition rate of 20 Hz, this source should produce 200--400 W of x-ray power in the 8-14 angstrom wavelength band, with an input power of 40--60 kW