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

Paper VT-WeM6
Photon Stimulated Desorption from Aluminum and Electroplated Copper Chambers

Wednesday, November 15, 2006, 9:40 am, Room 2000

Session: Electron, Photon and Ion-beam Induced Desorption and Their Effects on the Dynamics of Accelerators
Presenter: J. Gómez-Goñi, Universidad Politécnica de Madrid, Spain
Correspondent: Click to Email
Photon stimulated desorption (PSD) from aluminum and copper electroplated vacuum chambers have been obtained using synchrotron radiation of critical energies ranging from 12.4 to 280 eV. We first compared different cleaning methods on electroplated copper, including bakeout, pre bakeout (bakeout in situ, venting and pumping) and glow discharge with argon and 10% oxygen. As expected, in situ bakeout gave the best results, followed by glow discharge, which was quite effective removing desorbed gases. After this experiment, we compared two chambers manufactured with different copper electroplating methods measuring initial yields differing by factors between 1 and 3. During dose accumulation, the cleaning effect was more clearly seen in one of them, especially for hydrogen. Initial desorption yields were also measured for an aluminum chamber, before and after bakeout. We obtained that initial yields were almost linear with critical energy in this range. The difference between baked and unbaked aluminum was mainly due to water yield which was greatly reduced after bakeout. For aluminum we obtained that photoelectron production yield was linear with critical energy and specific pressure rise was also linear with photoelectron yield. Combining both facts we obtained that photoelectron stimulated yields were independent of critical energy for both baked and unbaked aluminum. This relation suggested a process where photoelectrons are responsible for the desorption of molecules.