An investigation of self-generated magnetic fields and electron emission in laser-produced plasmas
Case, Roger Salisbury
Schwirzke, Fred R.
Gurenther, Arthur H.
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An experimental study of magnetic signals from laserproduced plasmas has been performed. From 2 to 30 joules of laser energy impinged upon metallic and hydrocarbon targets in pulse lengths of from 4 to 80 nanoseconds, and at incident angles of 0° and 45°. Two magnetic signals were detected using inductive probes; one whose peak intensity is temporally coincident with, and whose rise time is a function of the incident laser pulse length; the second longerlasting and time-delayed from the arrival of the laser pulse on target. The first signal results from electrons emitted anisotropically from the laser-produced plasma. This emission current is limited by space charge effects, and is strongly dependent upon the ambient gas pressure over the range of 10~ 6 to 10 +1 Torr. The second magnetic signal arises from misaligned temperature and density gradients within the laser plasma. The dependencies of these signals on residual gas pressure, laser pulse length and shape, and spatial location have been evaluated.