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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. #

A summary of the main results obtained so far from the electron cloud studies using strip detectors, pick-ups, COLDEX and a 100 MHz coaxial resonator will be presented. The spatial and energy distributions of the electrons in the cloud measured by the strip detectors will be detailed and compared to the results obtained with a conventional retarding field detector. The evidence of the scrubbing effect and of the NEG coatings as remedies to reduce the electron cloud activity will also be shown.In a second part, the improved hardware of the experiments will be presented together with the program of measurements foreseen for the 2003 SPS run.

An adequate dose of photoelectrons, accelerated by lowintensity proton bunches and hitting the LHC beam screen wall, will substantially reduce secondary emission and avoid the fast build-up of an electron cloud for the nominal LHC beam. The conditioning period of the liner surface can be considerably shortened thanks to secondary electrons, provided heat load and beam stability can be kept under control; for example this may be possible using a special proton beam, including satellite bunches with an intensity of 15-20% of the nominal bunch intensity and a spacing of one or two RF wavelengths. Based on recent measurements of secondary electron emission, on multipacting tests and simulation results, we discuss possible 'beam scrubbing' scenarios in the LHC and present an update of electron cloud effects.

Electron-stimulated desorption (ESD) of cryosorbed molecules on surfaces is a process of relevance to fields as varied as vacuum dynamics in accelerators and astrochemistry. While desorption from such molecular systems induced by keV electrons and fast ions has been extensively studied, the sub-keV electron regime is comparatively little known. We measured and quantified electron-stimulated desorption from molecular ice systems (layers of N2, CO, CO2, Ar, and H2O/D2O condensed at cryogenic temperatures) in the 150–2000 eV electron energy range. In this regime, stopping power is no longer sufficient to explain the electron energy dependence of ESD yields. We introduce the notion of desorption-relevant depth, which characterizes the transition between two energy deposition regimes near the surface. We then apply this notion to the different systems, showing how ESD in the sub-keV regime can, for example, reveal the differences in species diffusion in crystalline and porous amorphous CO2 ices.