[en] The design of a flow cell that is applicable to pulse radiolysis/transient absorption experiments on supercritical water is described. The cell is designed to minimize dead volume and prevent the accumulation of radiolytic products. It is also necessary to minimize emission and absorption of sapphire windows from high energy electron beam irradiation. To obtain an optical throughput of f/4, the inner diameter is 6 mm, and distance between windows is 25 mm. The effective optical path length is 20 mm for irradiation from the side through a thin Hastelloy wall. Belleville spring washers were used to keep a constant force on the 3 mm sapphire windows, which were sealed to the Hastelloy body with copper gaskets. An application of this cell to measurements of solvated electrons in supercritical water is demonstrated. (c) 2000 American Institute of Physics

[en] We present experimental work exploring displacement and velocity interferometry as high spatial and temporal resolution diagnostics for measuring target preheat and the speed, planarity, and steadiness of a shock wave. A chirped pulse reflectometry experiment is also proposed as a frequency domain alternative for shock speed measurements. These techniques fill a need for high-precision diagnostics to derive accurate laboratory-based equation-of-state data at shock wave-driven pressures directly relevant to astrophysical systems. The performance of these optical laser probe techniques may exceed conventional passive techniques such as temporally streaked recording of optical emission upon shock breakout or side-on streaked X-ray radiography. Results from Nova laser and high-intensity ultrashort pulse experiments are presented. (c) 2000 The American Astronomical Society