THE IONIC ENTRAPMENT AND THERMAL DESORPTION OF INERT GASES IN TUNGSTEN FOR KINETIC ENERGIES OF 40 EV TO 5 KEV

Abstract

A clean polycrystalline tungsten wire was bombarded with monoenergetic ions of neon, argon, krypton, and xenon in the energy range 40 ev to 5 kev. The gas trapped in the tungsten was desorbed by then heating the wire to 2400 °K at 66 °K/second. Ion sticking probabilities determined from the quantities of gas desorbed ranged from ~0.6 for all gases at 3 kev to <10−5 at ion energies (ev) ~4 times the ion atomic number. From the variation of the desorption rates with temperature, six activation energies of thermal desorption were found which were not dependent on the ion or its incident energy. The lowest four (33 to 63 kcal/mole) are believed to be associated with gas trapped within a few atom layers of the metal surface, and the highest (102 kcal/mole) with normal impurity diffusion in the bulk tungsten.