The secondary electron yield of TiZr and TiZrV non-evaporable getter thin film coatings

Abstract

The secondary electron yield (SEY) of two different non-evaporable getter (NEG) samples has been measured`as received' and after thermal treatment. The investigated NEGs are TiZr and TiZrV thin ®lm coatings of 1 mm thickness, which are sputter deposited onto copper substrates. The maximum SEY d max of the air exposed TiZr and TiZrV coating decreases from above 2.0 to below 1.1 during a 2 h heat treatment at 250 and 2008C, respectively.Saturating an activated TiZrV surface under vacuum with the gases typically present in ultra-high vacuum systems increases d max by about 0.1. Changes in elemental surface composition during the applied heat treatments were monitored by Auger electron spectroscopy (AES). After activation carbon, oxygen and chlorine were detected on the NEG surfaces. The potential of AES for detecting the surface modi®cations which cause the reduction of SE emission during the applied heat treatments is critically discussed. #

Experimental observations of in situ secondary electron yield reduction in the PEP-II particle accelerator beam line

“…where is the relativistic coefficient, c the speed of light, m the electron mass, Z the charge, h the Planck constant, M and C are constants depending on the molecules, and the Note that an electron dose of ~1 mC/mm 2 is sufficient to considerably decrease the SEY on most surfaces in a laboratory set-up system [24].…”

Secondary electron yield and groove chamber tests in PEP-II

“…Typically, a peak SEY value range is δmax~1.5-2.2 for as-received technical vacuum chamber materials, and for aluminum δmax>2.3. The SEY of technical surfaces has been measured in the past for example at SLAC [3,4], at CERN [5,6] at KEK [7,8] and in other laboratories [9][10][11][12][13].…”

“…The electron conditioning or bombardment reduces the surface SEY to low values [3][4][5][6][7][8]. Nevertheless, an electron cloud is still observed in several existing storage rings.…”

Artifacts in Secondary Electron Emission Yield Measurements

“…TiN continues to be used widely today to coat beam chambers (particularly Al) and high-rf field components. Other coatings have been evaluated and found successful as well, e.g., Cr 2 O 3 for ceramics [3] and TiZrV non-evaporable getter for metals [4].…”