Estimated viscosity, surface tension, and density of liquid DT from the triple point to 25 K

Abstract

The literature data for the saturated viscosity, liquid-vapor surface tension, and density of liquid hydrogen is reviewed for the temperature range 14-25 K. Extrapolations are made to estimate the corresponding values for DT and Tj. Solution mixing data is considered to estimate values for the solution eD2-DT-eT2-Estimated values at the 1:1 D-T triple point at 19.75 K are: viscosity, 550 X I0~7 Pa's; sur face tension, 4.23 X I0" 3 N/m: and density, 225 kg/m 3 . These derived values are used to illustrate, via Currently, laser fusion is of great interest as a possible means of producing power. The current tar gets are hollow glass microspheres filled with DT gas. 1-3 Future targets for higher energy lasers will be solid shells of DT. When very high-energy lasers (per haps 10 s J) are available, the targets may be liquid or solid drops of DT. 4 This use of DT will require infor mation about its cryogenic properties. Thus, we tire embarking on a program to experimentally measure those physical properties of DT (near the triple point) which would be most affected by the presence of tritium. We are also reviewing a number of physical properties of hydrogen in order to extrapolate to the values for DT, Two such studies have already been published 5 ** as part of this program.Cryogenic laser targets will probably be created from liquid droplets. Hence, the liquid viscosity, sur face tension, and density on the phase boundary near the triple point are of considerable interest. We review here the literature data, which is almost all on H2, simplified equations, some basic properties of liquid DT droplets, which may eventually be used as targets in laser-induced hydrogen fusion experiments. Slow creation of individual drops and the liquid jet method are considered. The combination of low liquid den* sfty with law surface tension will allow formation of hundreds of ixm-diamcicr droplets with little prob lem. The viscosity is sufficient to damp out oscilla tions on a millisecond time scale.HD, and D2, and thou estimate DT and T2 values.The actual laser fuel will be the litres-component solution of eDj-DT-eT-, with a 1; I atomic D:T ratio. We have estimated the relative amounts of these three components by extrapolation of 0.1-Pa thermody namic gas calculations. 8 ' 7 These predict the approxi mate proportions in the range 19-25 K of 30 mole % Di, 40 mole % DT, and 30 mole % T2. The triple point should occur at about 19.75 K, and we have assigned an extrapolated value of 40.20 7c DT at this temperature. We assume that the percent of DT in creases linearly with temperature to 41.04 % at 25 K. It should be emphasized, however, that no measure ments or calculations have actually been made for this chemical equilibrium tn the liquid state.We feel that the properties of viscosity, surface tension, and density will probably not be affected by the presence of the tritium beta particles and the resultant radiation damage. Hence, estimating these properties for the liquid state seems feasible.