phase sample at the ambient condition a prior art sampling process is shown by the line u201c rac u201d line u201c ra u201d indicates the over pressuring of the sample above the reservoir pressure however depending on the kind of sample collected this process may or may not result in a single phase sample therefore point u201c c u201d could be in the two phase region the present invention is represented by the line u201c rpmn u201d the sample is cooled while entering the reservoir tube 34 at reservoir pressure line u201c rp u201d such cooling reduces the overall sample shrinkage due to temperature reduction during the retrieval further the sample is presurized above the hydrostatic wellbore pressure by the extraction pump 19 line u201c pm u201d the sample pressure is maintained during the retrieval by the high pressure nitrogen trapped in the intermediate chamber 62 line u201c mn u201d an alternative embodiment of the invention might substitute a eutectic compound or material for the vacuum space 40 in the vacuum jacket 32 a eutectic salt for example may be selected to absorb the geothermal wellbore heat for a solid to liquid phase change below but near the bottomhole temperature as the extracted formation sample captured in the.