Ultra-high vacuum noble gas purification. Purification methods

Our planet, during its accretion 4.56 billion years ago, trapped rare gases from the solar nebula. These, of primitive composition (little or poorly known, ³ He/ ⁴ He > ≈ 10 ^–4 , ⁴⁰ Ar/ ³⁶ Ar ≈ 10 ^–4 ) then differentiated at both elemental and isotopic levels following crust formation, mantle outgassing and differentiation. Noble gases are currently present in all three of the Earth's major reservoirs, namely the atmosphere, crust and mantle, and their compositions are constantly evolving as a result :

• interactions between these reservoirs (subduction zones, volcanism, etc.);

• exhaust losses in space ;

• nuclear reactions.

These compositions have a :

• radiogenic, generated by fission and decay reactions certain isotopes ( ⁴ He, ⁴⁰ Ar, ¹²⁹ Xe, ¹³⁶ Xe) from radionuclides ( ²³⁵ - ²³⁸ U, ²³² Th, ⁴⁰ K, ¹²⁹ I, ²⁴⁴ Pu, etc.);

• nucleogenic, produced as a result of reactions between the nuclei of certain elements ( ⁶ Li, ¹⁷ - ¹⁸ O, ²⁴ - ²⁵ Mg, ³⁵ - ³⁷ Cl, etc.) and neutrons or α particles ( ⁴ He) of rare gas isotopes ( ³ He, ²⁰ - ²¹ - ²² Ne, ³⁶ Ar, ³⁸ Ar, etc.) ;

• cosmogenic, the result of interaction between target elements (O, Mg, Si, Al, Fe, Ca, Rb, Sr, Te, Ba, La, etc.) with cosmic radiation (spallation reaction) and...