Proton microbeam induced damages in glasses: Ca and Na distribution modification

Nowadays, nuclear microprobes are commonly used in Earth Sciences as an analytical tool to detect a large number of trace elements in geological samples. However, radiation damages induced in natural glasses during an analysis by ionization are not completely controlled. Some difficulties remain in defining the appropriate analytical conditions without modifying the alkaline distribution in the matrix. Our approach consists of using a synthetic glass to quantify these modifications. With a 2 MeV proton microbeam, the Na and Ca signal evolution has been followed as a function of the deposited charge. Na and Ca distribution maps in and around the beam impact evidence a complex remobilization of both elements. The use of three different proton energies (1.32 MeV, 2 MeV and 3 MeV) permits the Na and Ca distribution profiles to be realized for increasing depth layers. A similar behavior of alkaline elements has been found within complex natural glasses.