We observed, with an x-ray apparatus, the keyhole formed during the interaction of a pulsed Nd–YAG laser beam with a metallic target of a Ti–6Al–4V titanium alloy. We noted that the keyhole formation is not instantaneous and that it grows linearly during the duration of the interaction. We highlighted that its depth, at the end of the laser pulse, is practically equal to the melting-zone depth in the material. Finally, we showed from the results of these tests that a quick estimation of the melting depth can be made simply from the ratio of the power densities used with a reference test.

This work presents the highlights of high-voltage, positive-polarity experiments on the ASTERIX generator characterizing the rod-pinch diode at up to 6 MV as a source for high-resolution, flash radiography. The paper reviews experimental results and analyses including conversion of ASTERIX to positive polarity, rod-pinch electrical and radiation characteristics, comparisons to numerical simulation, and composite rod-pinch performance. A minimum LANL source diameter of 1.32 mm with a dose of 23.7 rad(air) at 1 m was achieved at a peak voltage of 5.9 MV, leading to a radiographic figure-of-merit of 13.6 rad(Si)/mm2. The results demonstrate the utility of the rod pinch for high-power pulsed radiography at up to 6 M V .

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distributions from on-and off-axis rolled-edgemeasurements are contrasted with those from standardconfiguration loads.[5] Composite-rod-pinch loads on Asterix consisting of hollow-aluminum tubes supporting either 1-cm-long, 1-mm-diam blunt-end or tapered gold slugs, or 1.5-to 2-mm-diam gold spheres are characterized. Composite-slug loads have slightly-lower doses than the 1.6-or 2-mmdiam standard rod pinches reported elsewhere and smaller spot sizes, leading to higher measured radiographic figures-of-merit (FOM). The FOM for the gold-sphere loads is substantially-smaller than for the slug loads.