description fig2 is a cross sectional view of a high pressure xenon ionization detector having an annular space the chemical element xenon xe atomic number 54 is the fifth member of the family of noble gases group viii in the periodic table of elements xenon however exists in various isotopes namely xe 124 xe 126 xe 128 xe 129 xe 130 xe 131 xe 132 xe 134 and xe 136 all isotopes of xenon will behave the same way in the present invention in one embodiment of the invention naturally occurring xenon removed from the atmosphere having the following composition is utilized ______________________________________xe sup l24 0 096 xe sup l30 4 l xe sup l26 0 090 xe sup l3l 2l 2 xe sup l28 l 92 xe sup l32 26 9 xe sup l29 26 4 xe sup 134 l0 4 xe sup 136 8 9 ______________________________________ the high pressure xenon used in the present invention may be liquid gas or a mixture thereof xenon at or near its critical point has to have a sufficiently high density required for a high efficiency of detection of nuclear radiation e g gamma rays accordingly xenon at 0 u00b0 to 30 u00b0 c preferably 16 u00b0 to 22 u00b0 c and 50 to 70 atmospheres preferably 55 to 65 atmospheres can be used for the present invention the present invention can be used to detect and measure ionizing radiation from for example alpha beta or gamma rays x rays neutrinos mesons protons and heavy ions.