Electron density measurements in a single wafer etch reactor

By using microwaves, abs. values of electron densities were obtained in a modified single wafer etch reactor. By using CF4 as the etch gas electron densities were found in the range of 2 * 1014 to 5 * 1016 m-3 at pressures of 5 * 10-2 - 0.5 torr and powers of 5 * 10-2 - 1 W/cm2. The decay time of the electron d. was also measured and is 1.7 - 7 msec. [on SciFinder (R)

The desorption of condensed noble gases and gas mixtures from cryogenic surfaces

In accelerators, operating at liquid-helium temperature, cold surfaces are exposed to intense synchrotron radiation and bombardment by energetic electrons and ions. Molecular desorption yield and secondary electron yield can strongly influence the performance of the accelerator. In order to predict the gas density during the operation, the knowledge of electron-induced desorption yields of condensed gases and of its variation with the gas coverage is necessary. Desorption yields under electron impact of various noble gases and gas mixtures condensed on a copper surface cooled at 4.2 K have been measured

Secondary Electron Yield on Cryogenic Surfaces as a Function of Physisorbed Gases

Electron cloud is a serious limitation for the operation of particle accelerators with intense positively charged beams. It occurs if the secondary electron yield (SEY) of the beam-pipe surface is sufficiently high to induce an electron multiplication. At low surface temperatures, the SEY is strongly influenced by the nature of the physisorbed gases and by the corresponding surface coverage. These conditions occur in many accelerators operating with superconducting magnets and cold vacuum sections such as the LHC and RHIC. In this work, we investigated the variation of the SEY of copper, aluminium and electro-polished copper as a function of physisorbed N2, CO, CO2, CH4, Kr, C2H6 at cryogenic temperatures. The conditioning by electron bombardment of the surface after the physisorption of H2O on electro polished copper will also be presented. The results of the various gases are compared in order to find a rationale for the behaviour of the secondary electrons for the various adsorbates

REACTIONS OF DOUBLY CHARGED IONS WITH VARIOUS NEUTRALS

Recent investigations of reactions of doubly charged ions /1-5/ have shown that they occur in most of the cases via single incharge transfer and that they obey a curve crossing model, developed by Landau, Zener and Stueckelberg (see Ref. 1). Spears et al. /1/, who have applied this model to reactions of Mg++ and ca++ could show, that the reactions are fast, when there is a curve crossing between the potential curve of the reactants and the coulomb repulsion curve of the products (Fig. 1) at an internuclear distance of a few Å

THE INFLUENCE OF ION VIBRATIONAL EXCITATION ON ION MOLECULE REACTIONS

The mean kinetic energy KEion of ions drifting in a buffer gas under the influence of an electric field is well represented by the Wannier equation /1/ KEion =3/2 kT + vd2/2 (mi + mb), where vd is the drift velocity of the ions and mi and mm are the ion and masses respectively