High-power pulsed lasers

The ideas that led to the successful construction and operation of large multibeam fusion lasers at the Lawrence Livermore Laboratory are reviewed. These lasers are based on the use of Nd:glass laser materials. However, most of the concepts are applicable to any laser being designed for fusion experimentation. This report is a summary of lectures given by the author at the 20th Scottish University Summer School in Physics, on Laser Plasma Interaction. This report includes basic concepts of the laser plasma system, a discussion of lasers that are useful for short-pulse, high-power operation, laser design constraints, optical diagnostics, and system organization

Summary of the status of lasers for inertial confinement fusion

Laser systems designed for plasma research are operating in many laboratories throughout the world. The laser performance itself has become reasonably consistant from laboratory to laboratory and the focusing properties of the laser beams are understood. The plasma physics data, obtained with these systems, also appears to be reasonably self-consistant and is of great interest for inertial fusion applications. These lasers are commonly providing output powers of 0.5 > 2 TW, and power densities on target of 10/sup 13/-10-/sup 16/ W/cm/sup 2/, pulse durations on the order of 100 psec to 3 nsec, wavelengths between 0.5 ..mu.. and 10 ..mu.., and focal spot sizes of 100 ..mu.. or larger where focal spot edge effects are becoming less dominant. In addition, spurious target responses due to such behavior as pre-pulses, self-focusing, or imprecise focal spot measurement are being observed less often. The technical problems of large multi-beam systems, performing at the 10 TW level, have been overcome and these systems (e.g. the Shiva and Helios lasers) are providing high density compression data with ablative targets. The next step in laser design, the 100 to 300 kJ systems, are under construction and 1 MJ lasers are being contemplated

Speech Articulator and User Gesture Measurements Using Micropower, Interferometric EM-Sensore

Very low power, GHz frequency, ''radar-like'' sensors can measure a variety of motions produced by a human user of machine interface devices. These data can be obtained ''at a distance'' and can measure ''hidden'' structures. Measurements range from acoustic induced 10-micron amplitude vibrations of vocal tract tissues, to few centimeter human speech articulator motions, to meter-class motions of the head, hands, or entire body. These EM sensors measure ''fringe motions' as reflected EM waves are mixed with a local (homodyne) reference wave. These data, when processed using models of the system being measured, provide real time states of interface positions vs. time. An example is speech articulator positions vs. time in the user's body. This information appears to be useful for a surprisingly wide range of applications ranging from speech coding and recognition, speaker or object identification, noise cancellation, hand or head motions for cursor direction, and other applications

Energy absorption by laser fusion targets determined by ion calorimetry

The absorbed energy determined by the ion calorimeters was used as a basis for computations of the target behavior. Both neutron yield and x-ray spectra thus obtained were in agreement with the measured values within the precision of both calculations and experiments. Some results are described. (MOW

Research with high-power short-wavelength lasers

Three important high-temperature, high-density experiments were conducted recently using the 10-TW, short-wavelength Novette laser system at the Lawrence Livermore National Laboratory. These experiments demonstrated successful solutions to problems that arose during previous experiments with long wavelength lasers (lambda greater than or equal to 1..mu..m) in which inertial confinement fusion (ICF), x-ray laser, and other high-temperature physics concepts were being tested. The demonstrations were: (1) large-scale plasmas (typical dimensions of up to 1000 laser wavelengths) were produced in which potentially deleterious laser-plasma instabilities were collisionally damped. (2) Deuterium-tritium fuel was imploded to a density of 20 g/cm/sup 3/ and a pressure of 10/sup 10/ atm. (3) A 700-fold amplification of soft x rays by stimulated emission at 206 and 209 A (62 eV) from Se/sup +24/ ions was observed in a laser-generated plasma. Isoelectronic scaling to 155 A (87 eV) in Y/sup +29/ was also demonstrated