AVS 45th International Symposium
    Vacuum Technology Division Monday Sessions
       Session VT-MoP

Paper VT-MoP6
Measurement of Secondary Electron Yields of Copper Materials and the Surface Analysis

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Vacuum Technology Poster Session
Presenter: S. Kato, KEK, Japan
Authors: S. Kato, KEK, Japan
K. Kanazawa, KEK, Japan
N. Kitano, Tokyo Denki University, Japan
N. Matsuda, Tokyo Denki University, Japan
Correspondent: Click to Email
Photoelectron instability is one of serious problems in a positron storage ring of colliding accelerators such as PEP-II and KEKB where a current of a couple of amps is stored. It occurs in a manner that the positron beam interferes with an enormous amount of secondary electrons emitted from surfaces of vacuum pipes bombarded by a large amount of photoelectrons due to synchrotron radiation. This instability considerably disturbs beam operation. In this study, secondary electron yields from copper materials where some surface treatment techniques were performed were measured to make a comparison with other materials. Target samples were prepared by three different chemical polishing techniques using a) a water solution of sulfuric acid and hydrogen peroxide, b) a water solution of citric acid and c) a) and subsequent b). These samples were treated in the same condition as the extruded copper chambers for KEKB electron-positron collider. The secondary electron yields were measured at a typical condition of a kinetic energy ranging from 0.1 keV to 2.0 keV at a normal incident and a sample temperature of 23 ° C. The residual gas pressure of the sample chamber was less than 2x10@super -7@ Pa during the measurements. In order to avoid electron beam induced contamination at the sample surface from the residual gas even so, a total dose of electrons for a measurement was limited to be 1x10@super 12@ electrons/cm@super 2@ by use of a pulsed beam. Characterization of those surfaces was also done by Auger electron spectroscopy with argon ion sputter etching. This gives information about depth profiles of atomic compositions in an altered surface layer due to the treatment discussing the interrelation between the secondary electron yields and the surface atomic compositions. The lowest maximum yield of secondary electrons of 1.05 was observed at the surface treated as (a) where the oxidized layer was found to be the most stable against a long exposure to air in contrast to the surface treated as (b).