Abstracts Brochure - CERN

MOPCH — Poster Session 26-Jun-06 16:00 - 18:00
Electron-impact Desorption at the RHIC Beam Pipes
The electron induced molecular desorption
coefficient of a material provides the number U. Iriso, W. Fischer (BNL)
of molecules released when an electron hits
its surface. This coefficient changes as a function of the material, energy of the electrons, surface status, etc. In this
paper, this coefficient is inferred analyzing electron detector and pressure gauge signals during electron clouds at
the Relativistic Heavy Ion Collider (RHIC) beam pipes. The evolution of the electron-impact desorption coefficient
after weeks of electron bombardment is followed for both baked and unbaked stainless steel chambers, evaluating the
feasibility of the scrubbing effect. Measurements of an energy spectrum during multipacting conditions are shown,
and the final results are compared with laboratory simulations.
Benchmarking Electron Cloud Data with Computer Simulation Codes
Saturated electron flux and time decay of the
electron cloud are experimentally inferred U. Iriso (BNL) G. Rumolo (CERN)
using many electron detector datasets at the
Relativistic Heavy Ion Collider (RHIC). These results are compared with simulation results using two independent
electron cloud computer codes, CSEC and ECLOUD. Simulation results are obtained over a range of different values
for 1) the maximum Secondary Electron Yield (SEY), and 2) the electron reflection probability at zero energy. These
results are used to validate parameterization models of the SEY as a function of the electron energy.
An Overview of the Beijing Spallation Neutron Source Accelerators
The Beijing Spallation Neutron Source
(BSNS) is a newly approved high power ac- J. Wei (BNL) S.X. Fang, S. Fu (IHEP Beijing)
celerator project based on a H − linear accelerator
and a rapid cycling synchrotron. During the past year, several major revisions were made to the design including
the type of the front end, linac frequency, transport layout, ring lattice, and type of ring components. Possible upgrade
paths were also laid out: based on an extension of the warm linac, the ring injection energy and the beam current
could be raised doubling the beam power on target to reach 200 kW; an extension with a superconducting RF linac
of similar length could raise the beam power near 0.5 MW. Based on these considerations, research and development
activities are started. In this paper, we discuss the rationale of design revisions and summarize the recent work.
An Anti-symmetric Lattice for High Intensity Rapid-cycling Synchrotrons
Rapid cycling synchrotrons are used in many
high power facilities like spallation neutron
sources and proton drivers. In such accelerators,
beam collimation plays a crucial role in
J. Wei, S. Tepikian (BNL) S.X. Fang, Q. Qin, J. Tang, S. Wang (IHEP
Beijing)
reducing the uncontrolled beam loss. Furthermore, the injection and extraction section needs to reside in dispersionfree
region to avoid couplings; a significant amount of drift space is needed to house the RF accelerating cavities;
orbit, tune, and chromatic corrections are needed; long, uninterrupted straights are desired to ease injection tuning
and to raise collimation efficiency. Finally, the machine circumference needs to be small to reduce construction costs.
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