title: The simulator for icy world interiors: a 700 MPa pressure system for impulsive stimulated scattering and other optical measurements, with thermal control from -20 to 100 degrees C.
abstract: The simulator for icy world interiors (SIWI) was developed for sound velocity measurements in simulated extraterrestrial ocean materials by the method of impulsive stimulated scattering (ISS). The design and operation of SIWI are described. Optical measurements at low temperature in corrosive solution were enabled by enclosing sample fluid in a stoppered spectrophotometric cuvette. To maintain minimum optical density it was necessary to limit contact of the dioctyl sebacate hydraulic fluid with nitrile o-rings, which caused discoloring enhanced absorption of the 532 nm ISS probe pulses. Dilution of hydraulic fluid with kerosene in the amount of 5% by volume prevented clouding at high pressures and at low temperatures. Pure kerosene was found to attenuate the ISS signal, and so was deemed unsatisfactory at low temperatures where the lower thermal expansion of water leads to weaker density contrasts between heated and unheated regions in the sample fluid. When 50 cS silicone oil was used as a hydraulic medium, clouding was observed at pressures above 400 MPa when temperatures were raised above approximately 50 degrees C and lowered to less than approximately 10 degrees C. To our knowledge, such clouding has not been reported previously for dioctyl sebacate, nor for silicone at such low pressures.
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology, MS 183-401, 4800 Oak Grove Drive, Pasadena, California 91109, USA. svance@jpl.nasa.gov
authors.forename: Steve
authors.initials: S
authors.lastname: Vance
authors.forename: J Michael
authors.initials: JM
authors.lastname: Brown