AVS 53rd International Symposium
    Vacuum Technology Wednesday Sessions
       Session VT-WeM

Invited Paper VT-WeM1
New Understanding of Ion-Beam Induced Gas Desorption*

Wednesday, November 15, 2006, 8:00 am, Room 2000

Session: Electron, Photon and Ion-beam Induced Desorption and Their Effects on the Dynamics of Accelerators
Presenter: A.W. Molvik, Lawrence Livermore National Laboratory
Authors: A.W. Molvik, Lawrence Livermore National Laboratory
M. Kireeff Covo, Lawrence Livermore National Laboratory
F.M. Bieniosek, Lawrence Berkeley National Laboratory
P.A. Seidl, Lawrence Berkeley National Laboratory
Correspondent: Click to Email
Heavy-ion accelerator rings are frequently limited by gas-pressure rise, whereas proton rings are generally limited by electron clouds. We have shown that the desorption caused by high-energy ions is driven by the electronic component of ion slowing in matter, known as electronic sputtering to distinguish it from conventional or physical sputtering that is driven by nuclear scattering of ions in matter. A large body of literature exists on electronic sputtering, but does not include sputtering from metals that are clean except for one to a few monolayers of gas. We measured desorption by 70-1000 KeV potassium ions, for which the dominant ion energy loss transitions from nuclear stopping at 70 keV to electronic stopping above 250 keV. We found that gas desorption scaled with the electronic component, (dE/dx)@super n@ where 1