Neutron-induced Cavitation Tension Metastable Pressure Thresholds of Liquid Mixtures

Radiation-induced cavitation or nucleation for liquids in metastable states allows one to utilize this phenomenon for nuclear particle detection. Indeed, Glaser (1958) received the Nobel Prize for his work on the bubble chamber wherein bubbles are formed in a thermally superheated liquid when nuclear particles strike the metastable fluid. This realization has resulted in the development of so-called superheated droplet detectors (SDDs) (Apfel, 1979, Ing, 1997). However, SDDs require the fluid-state to be thermally-superheated and the intrinsic efficiency for detection from such systems inherently suffers due to the need for spatial separation of superheated droplets in host liquids by factors of ~ 1,000. A more interesting and useful means for detection of radiation that we have studied and developed (Lapinskas et al. (2006); Smagacz et al. (2006); Xu et al. (2006); Taleyarkhan et al. (2006)) relies on liquids in “tensioned” metastable states allowing room temperature operation. In such a system the entire tensioned volume is sensitive. Therefore, such a system will have intrinsic efficiencies higher than those of SDDs by a factor of ~ 1,000. It has been known, although not widely appreciated, for some time, that liquids, like solids, can indeed be put under negative pressure (below perfect vacuum). Although surprising at first, this was confirmed via elegant experiments reported in Science (Scholander et al., 1965). Since Glaser’s discovery, sporadic efforts were also attempted to examine radiation-induced cavitation in tensioned liquids (Greenspan et al., 1967; Lieberman, 1958). These earlier efforts employed large, complex and/or expensive apparatus. More recently, this technique was successfully employed for attaining supercompression and thermonuclear fusion states in deuterated liquids (Forringer et al., 2006; Taleyarkhan et al., 2002, 2004, 2006; Lahey et al., 2005; Nigmatulin et al., 2005; Xu et al, 2005). Radiation-induced cavitation or nucleation involves several distinctive physical phenomena including radiation type, linear-energy transfer rate, probability of interaction on nuclear and atomic scales, physical properties of the target molecules, etc. A given liquid has unique properties that are useful in detection. However, this may not necessarily attain all of the desired characteristics (e.g., volatility, safety, sensitivity, etc.). All known past studies have been conducted with single molecule liquids. Studies with mixtures of molecules could offer a huge leap in possible combination of key parameters determining the Tensioned metastable fluids provide a powerful means for low-cost, efficient detection of a wide range of nuclear particles with spectroscopic capabilities. Past work in this field has relied on one-component liquids. Pure liquids may provide very good detection capability in some aspects, such as low thresholds or large radiation interaction cross sections, but it is rare to find a liquid that is a perfect candidate on both counts. It was hypothesized that liquid mixtures could offer optimal benefits and present more options for advancement. However, not much is known about radiation-induced thermal-hydraulics involving destabilization of mixtures of tensioned metastable fluids. This paper presents results of experiments that assess key thermophysical properties of liquid mixtures governing fast neutron radiation-induced cavitation in liquid mixtures. Experiments were conducted by placing liquid mixtures of various proportions in tension metastable states using Purdue’s centrifugally-tensioned metastable fluid detector (CTMFD) apparatus. Liquids chosen for this study covered a good representation of both thermal and fast neutron interaction cross sections, a range of cavitation onset thresholds and a range of thermophysical properties. Experiments were devised to measure the effective liquid mixture viscosity and surface tension. Neutron-induced tension metastability thresholds were found to vary non-linearly with mixture concentration; these thresholds varied linearly with surface tension and inversely with mixture vapor pressure (on a semi-log scale), and no visible trend with mixture viscosity nor with latent heat of vaporization.