| Paper | Title | Page |
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| TUPP027 | Electron Energy Dependence of Scrubbing Efficiency to Mitigate E-cloud Formation in Accelerators | 1592 |
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Recently built and planned accelerators, base their ability to reach design parameters, on the capability to reduce Secondary Electron Yield (SEY) during commissioning, hence mitigating the potentially detrimental effects of e-cloud driven machine limitations. This SEY reduction (called "scrubbing"), is due to the fact that the electrons of the cloud, hit the vacuum chamber wall, modifying its surface properties and reducing its SEY. This minimise any disturbing effects of the e-cloud to the beam. "Scrubbing" has been studied only as a function of impinging electron dose. In reality SEY modifications are only studied by bombarding surfaces with 300-500 eV electrons, but no scrubbing dependence on the bombarding electron energy has ever been discussed. The actual energy of the electrons of the cloud hitting the wall in real accelerators has never been measured accurately, while simulations predict very low electron energies (<50 eV). For this reason and given the peculiar behaviour observed for low energy electrons*, we decided to study this dependence accurately. Here we present some preliminary results discussing eventual implications to machine commissioning procedures.
*R. Cimino et al. Phys. Rev. Lett 93, 14801 (2004). |
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| TUPP036 | "Scrubbing" Process of Cu Surfaces Induced by Electron Bombardment | 1619 |
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| Energy distribution curves of electrons emitted from accelerator used metal surfaces have been measured for electron irradiation with a primary energy from 20 to 400 eV. We separated the contributions of reflected, rediffused and true-secondary electrons out from the spectra and observed significant differences in their incidence angle dependence. These results provide crucial information on the electron cloud formation in particle accelerators and may shed light on the involved physical mechanisms | ||
| WEPD045 | Hydrogen Cryosorption on Multi Walled Carbon Nanotubes | 2515 |
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| We present a Temperature Programmed Desorption (TPD) study on H2 adsorption on multiwalled carbon nanotubes (MWNT) at very low pressure (< 10-6 Torr) and temperature (12-30 K). Our results show a hydrogen take up limit in the range of 10-8 mol per gram depending on the adsorption temperature. We compare the MWNT cryosorption capacity with that of commonly used activated carbon and discuss the possibility of employing MWNT as cryosorber in large particle accelerators. |