| Paper |
Title |
Page |
| MOPLS021 |
Beam Pipe Desorption Rate in RHIC
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583 |
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- H. Huang, W. Fischer, P. He, H.-C. Hseuh, U. Iriso, V. Ptitsyn, D. Trbojevic, J. Wei, S.Y. Zhang
BNL, Upton, Long Island, New York
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Increase of beam intensity in RHIC has caused several decades of pressure rises in the warm sections during operation. This has been a major factor limiting the RHIC luminosity. About 250 meters of NEG coated beam pipes have been installed in many warm sections to ameliorate this problem. Beam ion induced desorption is one possible cause of pressure rises. A series beam studies in RHIC has been dedicated to estimate the desorption rate of various beam pipes (regular and NEG coated) at various warm sections. Correctors were used to generate local beam losses and consequently local pressure rises. The experiment results are presented and analyzed in this paper.
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| MOPCH132 |
Coupled Maps for Electron and Ion Clouds
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354 |
| |
- U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- S. Peggs
BNL, Upton, Long Island, New York
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Contemporary electron cloud models and simulations reproduce second order phase transitions, in which electron clouds grow smoothly beyond a threshold from "off" to "on". In contrast, some locations in the Relativistic Heavy Ion Collider (RHIC) exhibit first order phase transition behaviour, in which electron cloud related outgassing rates turn "on" or "off" precipitously. This paper presents a global framework with a high level of abstraction in which additional physics can be introduced in order to reproduce first (and second) order phase transitions. It does so by introducing maps that model the bunch-to-bunch evolution of coupled electron and ion clouds. This results in simulations that run several orders of magnitude faster, reproduce first order phase transitions, and show hysteresis effects. Coupled maps also suggest that additional dynamical phases (like period doubling, or chaos) could be observed.
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| MOPCH133 |
An Analytic Calculation of the Electron Cloud Linear Map Coefficient
|
357 |
| |
- U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- S. Peggs
BNL, Upton, Long Island, New York
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The evolution of the electron density during multibunch electron cloud formation can often be reproduced using a bunch-to-bunch iterative map formalism. The coefficients that parameterize the map function are readily obtained by fitting to results from compute-intensive electron cloud simulations. This paper derives an analytic expression for the linear map coefficient that governs weak cloud behaviour from first principles. Good agreement is found when analytical results are compared with linear coefficient values obtained from numerical simulations. This analysis is useful in predicting thresholds beyond which electron cloud formation occurs, and thus in determining safety regions in parameter space where an accelerator can be operated without creating electron clouds. The formalism explicitly shows that the multipacting resonance condition is not a sine qua non for electron cloud formation.
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| MOPCH134 |
Electron-impact Desorption at the RHIC Beam Pipes
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360 |
| |
- U. Iriso, U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- W. Fischer
BNL, Upton, Long Island, New York
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The electron induced molecular desorption coefficient of a material provides the number 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.
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| MOPCH134 |
Electron-impact Desorption at the RHIC Beam Pipes
|
360 |
| |
- U. Iriso, U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- W. Fischer
BNL, Upton, Long Island, New York
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The electron induced molecular desorption coefficient of a material provides the number 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.
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| MOPCH135 |
Benchmarking Electron Cloud Data with Computer Simulation Codes
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363 |
| |
- U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- G. Rumolo
CERN, Geneva
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Saturated electron flux and time decay of the electron cloud are experimentally inferred 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.
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| THPLS056 |
Synchrotron Radiation Monitors at ALBA
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3410 |
| |
- U. Iriso
CELLS, Bellaterra (Cerdanyola del Vallès)
- F. Pérez
ALBA, Bellaterra
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ALBA is a 3 GeV, low emittance third generation synchrotron light source that is in the construction phase in Cerdanyola, Spain. Synchrotron Radiation Monitors (SRM) are one of the most useful, non-destructive tools to easily obtain information of three important parameters for a synchrotron user: beam position, beam dimensions and beam stability. These monitors diagnose beam performance using the radiation produced when the beam traverses a bending magnet. An extensive usage of SRM, based on the visible part of the spectrum, is planned in the ALBA synchrotron: Linac, Booster, Transfer Lines and the Storage Ring. The latter will be equipped as well with an SRM based on the x-ray part of the spectrum, using the PinHole technique in order to accurately measure the low beam size and emittance. This paper describes the different SRM designs for the ALBA light source.
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| THPLS057 |
Injector Design for ALBA
|
3413 |
| |
- M. Pont, G. Benedetti, D. Einfeld, A. Falone, U. Iriso, M.L. Lopes, M. Muñoz
CELLS, Bellaterra (Cerdanyola del Vallès)
- E. Al-Dmour, F. Pérez
ALBA, Bellaterra
- W. Joho
PSI, Villigen
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The storage ring ALBA is a 3rd generation synchrotron light source under construction in Barcelona (Spain). The facility is based on a 3.0 GeV storage ring of 268.8 m circumference with a beam emittance under 5 nm.rad. Top-up operation is foreseen from the start. The injector complex for ALBA will consist of a 100 MeV linac and a full energy booster. The linac will be a turn-key system which has already been ordered to the industry and delivery is expected in the second half of 2007. The full energy booster will be placed in the same tunnel as the storage ring and will have a circumference of 249.6 m. The lattice of the booster is a modified FODO lattice providing an emittance as low as 9 nm.rad. The magnet system comprises 40 combined magnets and 60 quadrupoles. Chromaticity correction relies on the sextupole component built-in the combined magnets and the quadrupoles. In this paper a description of the booster design including the present status of the different components will be given.
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