An important upgrade of UV holographic interferometry is now in use. Many hundreds of laser fusion-type target plasmas have been probed at KMS Fusion, Inc. using the holographic technique. The data obtained with this diagnostic include high-resolution images and plasma electron density distributions at various probe times. The diagnostic system now produces a sequence of four interferograms of an evolving plasma. The times of the 20-ps pulses in the sequence are fully adjustable and known within 10 ps. The experiments to which this diagnostic has been adapted will be described along with details of problems and their solutions. Selected sets of recent interferograms of plasmas produced by irradiation of thin foils will be presented along with their inversions.
Temporal pulse splitting has been observed at an aperture 8 m from a passively mode-locked Nd : YAG laser oscillator. A theoretical model using the published value of the nonlinear refractive index n2 of YAG shows the splitting mechanism.
Current laser-fusion theory dictates the need for relatively short laser pulses that are shaped in time to implode optimally a fuel pellet. The laser pulse width and shape should be varied to match different types and sizes of targets. For current experiments, pulse widths as short as 100 psec are desirable, which eliminates the choice of relatively slow electrooptic shutters to shape the pulse, since they are limited to rise times and pulse widths longer than several hundred picoseconds. The device described here can generate a wide variety of pulse shapes and widths by stacking a set of 30-psec mode-locked pulses. This versatile pulse stacker currently shapes the pulses for the KMS Fusion neodymium-doped-glass laser system that has produced over 500 neutron-yielding shots since 1 May 1974 by heating and compressing deuterium or deuterium-tritium fuel inside hollow glass spherical targets.
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