a high energy photon source . a pair of plasma pinch electrodes are located in a vacuum chamber . the chamber contains a working gas which includes a noble buffer gas and an active gas chosen to provide a desired spectral line . a pulse power source provides electrical pulses at voltages high enough to create electrical discharges between the electrodes to produce very high temperature , high density plasma pinches in the working gas providing radiation at the spectral line of the active gas . a blast shield positioned just beyond the location of the high density pinch provides a physical barrier which confines the pinch limiting its axial elongation . a small port is provided in the blast shield that permits the radiation but not the plasma to pass through the shield . in a preferred embodiment a surface of the shield facing the plasma is dome - shaped .