Research On Technology For Preparing Gaseous Dense Samples And Equation Of State Of Hydrogen, Helium And Their Mixture

In this thesis, a new cryogenic target system is set up for preparing the dense gaseous samples on the two-stage light-gas gun. It includes three subsystems: the filling system of highly compressed gas, the liquid nitrogen cooling subsystem, and the thermo-couple measurement subsystem. It is successfully used to prepare dense helium, hydrogen, and their mixture samples. And also, valuable investigations are performed on the multi-shock compression experiments by two-stage light-gas gun. The important achievements in three aspects are summarized as follows.(1) The establishment of a cryogenic target system for preparing highly compressed gas is one of apparent technical achievements. It can increase the pressure of gas sample to 40MPa under low temperature of liquid nitrogen, and the initial density of the prepared denser gaseous samples are nearly 40 times as that of the similar sample used before. The difficulty of separation of different components is effectively overcome by directly compressing the mixing gas, which is a technical bottleneck of liquid mixture sample preparation. Two key technical problems are solved in the new system: (i) a hydraulic-pressure driven technique is adopted to compress gas samples of low pressures, and a miniature pump for increasing pressure is set up. It provides a low-price way for preparing dense gaseous sample, because no special made gas compressor is needed. The new system is especially useful for preparing rare gas of small quantity, and it can be widely used in laboratory. The reached maximum pressure is 40MPa with accuracy of 0. 02MPa;(ii) The gas leakage problem under the condition of low temperature of liquid nitrogen and high gas pressure is solved by combination of metal and glue seal technique. When preparing the mixture of hydrogen and helium, 30MPa only produced a neglected deformation on target under 79K.(2) Apparent achievement is made on measurement of multi-shock processes. PhotoMultiplier Tube (PMT) is used to measure the radiation history, and a whole multi-shock process is clearly recorded. In the similar experiments, at most the first, second, and third shocked processes was observed, but in our experiments the later higher order shocked processes up to at least 8th shock are also distinguished. The thermodynamic quantities of the multi-shocked states are determined based on the measured the lasting periods. Such a technical improvement makes it possible to investigate the equation of state of gaseous substances by multi-shock experiments.(3) By use of two-stage light-gas gun, the thermodynamic states of hydrogen-helium mixture at lOOGPa and 3000-5000K is firstly reached and actually measured in laboratory, and some EOS data of them is respectively obtained. They will be experimental proof for further improving the theoretical EOS model, and make it possible to study other physical and chemical properties at high pressures and temperatures.