Beam-deflection technique for the measurement of electron density in laser-produced plasmas

Beam-deflection techniques have been shown to perform well for measurements in fluid flows and flames. Because of the growing interest in laser-produced plasmas, the authors have investigated the capability of beam-deflection techniques for plasma measurement. While other techniques including interferometry and schlieren techniques are well established for measuring electron density in laser-produced plasmas, they show that a beam-deflection technique is simple to implement and has advantages over current techniques. They describe a two-wavelength beam-deflection technique for temporally and spatially resolved electron density measurements in a laser-produced plasma. Deflection of a laser beam in a plasma or other system arises from gradients in the index of refraction. Measurement of beam deflections is quantitative in that the deflection angle is proportional to the integrated transverse gradient of the index of refraction. Techniques such as Abel inversion or tomography may be applied to such measurements to reconstruct spatially resolved values of the index of refraction. From measurements of the index of refraction at two wave-lengths, the electron density may be calculated