High-sensitivity interferometric measurements of gas density distributions from a PRS nozzle synchronized with a heterodyne interferometer

Summary form only given. Gas distributions are important for modeling z-pinch implosions. This paper reports new measurements of a 3.5 cm diameter argon gas puff nozzle used on the Saturn generator at Sandia National Laboratories, Albuquerque, NM. A 532 nm high-sensitivity interferometer makes time-dependent, line-integrated gas density measurements at a series of chordal locations that are then Abel inverted to obtain the radial gas density distribution. The measurements are synchronized using a double-pass heterodyne interferometer. The high-sensitivity line of sight is parallel to the x axis and at one axial distance, z, from the nozzle exit. The displacement,y, from the nozzle axis is moved to scan the (x,y) cross section. This scan was taken at three values of z (0.1 cm, 1 cm, 2 cm). The heterodyne line of sight is perpendicular to the high sensitivity line of sight, along the nozzle diameter and moves with the nozzle at a fixed position 0.1 cm from the end of the nozzle. The phase shift is found from the heterodyne signal using the times of the zero-crossings. All the shots are then synchronized using the heterodyne phase shift. The density distribution was determined at 500 μs, the time of interest. This method is an improvement over previous measurements which used a breakdown pin and accounted for mechanical jitter by averaging over a 100 μs period.