PROTON MICROBEAM INDUCED DAMAGES IN GLASSES - CA AND NA DISTRIBUTION MODIFICATION

Nowadays, nuclear microprobes are commonly used in Earth Sciences as a n analytical tool to detect a large number of trace elements in geolog ical samples. However, radiation damages induced in natural glasses du ring an analysis by ionization are not completely controlled. Some dif ficulties remain in defining the appropriate analytical conditions wit hout modifying the alkaline distribution in the matrix. Our approach c onsists of using a synthetic glass to quantify these modifications. Wi th a 2 MeV proton microbeam, the Na and Ca signal evolution has been f ollowed as a function of the deposited charge. Na and Ca distribution maps in and around the beam impact evidence a complex remobilization o f 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 re alized for increasing depth layers. A similar behavior of alkaline ele ments has been found within complex natural glasses.