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Suppression of Secondary Electron Emission using Triangular Grooved Surface in the ILC Dipole and Wiggler Magnets

Description: The development of an electron cloud in the vacuum chambers of high intensity positron and proton storage rings may limit machine performance. The suppression of electrons in a magnet is a challenge for the positron damping ring of the International Linear Collider (ILC) as well as the Large Hadron Collider. Simulation show that grooved surfaces can significantly reduce the electron yield in a magnet. Some of the secondary electrons emitted from the grooved surface return to the surface within … more
Date: July 6, 2007
Creator: Wang, L.; Bane, K.; Chen, C.; Himel, T.; Munro, M.; Pivi, M. et al.
Partner: UNT Libraries Government Documents Department
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Direct Measurement of the Transverse Wakefields of Tapered Collimators

Description: We report on a recent set of measurements of the transverse wakefields from longitudinally-tapered collimators. The measurements were performed with a low-emittance 1.19 GeV beam in the SLAC linac by inserting a collimator aperture into the beam path and reconstructing the vertical deflection of the beam as a function of the vertical position of the aperture. Each collimator in the experiment was designed to present a relatively large transverse impedance and to minimize the impedance from othe… more
Date: January 9, 2007
Creator: Tenenbaum, P.; Bane, K. L. F.; Eriksson, L.; Irwin, J.; Jobe, R. K.; McCormick, D. et al.
Partner: UNT Libraries Government Documents Department
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Suppression of Secondary Emission in a Magnetic Field Using a Sawtooth and Isosceles Triangle Surface

Description: The effect of surface roughness on the secondary electron emission from a sawtooth and isosceles triangle surface in a magnetic field under electron bombardment is investigated using a Monte-Carlo method. Some of the secondary electrons emitted from the surface return to the surface within their first few gyrations, resulting in a low effective secondary electron yield. Both sawtooth and isosceles triangle surface in magnetic field can significantly reduce the secondary emission yield below the… more
Date: September 26, 2006
Creator: Wang, L.; Raubenheimer, T.O. & Stupakov, G.
Partner: UNT Libraries Government Documents Department
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Luminosity Loss due to Beam Distortion and the Beam-Beam Instability

Description: In a linear collider, sources of emittance dilution such as transverse wakefields or dispersive errors will couple the vertical phase space to the longitudinal position within the beam (the so-called ''banana effect''). When the Intersection Point (IP) disruption parameter is large, these beam distortions will be amplified by a single bunch kink instability which will lead to luminosity loss. We study this phenomena both analytically using linear theory and via numerical simulation. In particul… more
Date: June 30, 2005
Creator: Wu, Juhao; Raubenheimer, T. O.; Chao, A. W.; Seryi, A. & Sramek, C. K.
Partner: UNT Libraries Government Documents Department
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Electron-Cloud Effects in Transport Lines of a Normal Conducting Linear Collider

Description: In the transport lines of a normal conducting linear collider, the long positron bunch train can generate an electron cloud which can then amplify intra-train offsets. This is a transient effect which is similar to the electron-cloud driven coupled bunch instabilities in a positron storage ring. In this paper, we study this phenomenon analytically. Some criteria on the critical cloud density with respect to given collider parameters are discussed.
Date: June 15, 2005
Creator: Wu, Juhao; Raubenheimer, T. O.; Pivi, M. T. F. & Seryi, A.
Partner: UNT Libraries Government Documents Department
open access

Suppressing Electron Cloud in Future Linear Colliders

Description: Any accelerator circulating positively charged beams can suffer from a build-up of an electron cloud (EC) in the beam pipe. The cloud develops through ionization of residual gases, synchrotron radiation and secondary electron emission and, when severe, can cause instability, emittance blow-up or loss of the circulating beam. The electron cloud is potentially a luminosity limiting effect for both the Large Hadron Collider (LHC) and the International Linear Collider (ILC). For the ILC positron da… more
Date: May 27, 2005
Creator: Pivi, M; Kirby, R. E.; Raubenheimer, T. O. & Le Pimpec, F.
Partner: UNT Libraries Government Documents Department
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Ion Effects in the Electron Damping Ring of the International Linear Collider

Description: Ion-induced beam instabilities and tune shifts are critical issues for the electron damping ring of the International Linear Collider (ILC). To avoid conventional ion trapping, a long gap is introduced in the electron beam by omitting a number of successive bunches out of a long train. However, the beam can still suffer from the fast ion instability, driven by ions that last only for a single passage of the electron bunches. Our study shows that the ion effects can be significantly mitigated by… more
Date: July 17, 2006
Creator: Wang, L.; Raubenheimer, T. & Wolski, A.
Partner: UNT Libraries Government Documents Department
open access

Resistive-wall Wake Effect in the Beam Delivery System

Description: General formulae for resistive-wall induced beam dilution are presented and then applied to the final beam delivery system of linear colliders. Criteria for the design of final beam delivery systems are discussed.
Date: June 2, 2005
Creator: Delayen, J. R.; Wu, Juhao; Raubenheimer, T. O. & Wang, Jiunn-Ming
Partner: UNT Libraries Government Documents Department
open access

Luminosity Optimization With Offset, Crossing Angle, and Distortion

Description: In a linear collider, sources of beam jitter due to kicker noise, quadrupole vibration and long-range transverse wakefields will lead to beam offsets and tilts at the Intersection Point (IP). In addition, sources of emittance dilution such as short-range transverse wakefields or dispersive errors will lead to internal beam distortions. When the IP disruption parameter is large, these beam imperfections will be amplified by a single bunch kink instability which will lead to luminosity loss. In t… more
Date: June 15, 2005
Creator: Wu, Juhao & Raubenheimer, T. O.
Partner: UNT Libraries Government Documents Department
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A Test Facility for the International Linear Collider at SLAC End Station A, for Prototypes of Beam Delivery and IR Components

Description: The SLAC Linac can deliver damped bunches with ILC parameters for bunch charge and bunch length to End Station A. A 10Hz beam at 28.5 GeV energy can be delivered there, parasitic with PEP-II operation. We plan to use this facility to test prototype components of the Beam Delivery System and Interaction Region. We discuss our plans for this ILC Test Facility and preparations for carrying out experiments related to collimator wakefields and energy spectrometers. We also plan an interaction region… more
Date: May 23, 2005
Creator: Woods, M.; Erickson, R.; Frisch, J.; Hast, C.; Jobe, R. K.; Keller, L. et al.
Partner: UNT Libraries Government Documents Department
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Optimization of the X-Band Structure for the JLC/NLC

Description: In this paper, we present design considerations to address the high gradient, wakefields, and RF efficiency issues for the JLC/NLC structures. We will present the rationale for the choices of phase advance, structure length, structure aperture, and other design aspects in the optimization of the structure. We will study the impact of parameter choices for the JLC/NLC beam environment and discuss approaches being taken for an optimal JLC/NLC structure design.
Date: June 21, 2006
Creator: Li, Z.; Adolphsen, C.; Burke, D. L.; Dolgashev, V.; Jones, R. M.; Miller, R. H. et al.
Partner: UNT Libraries Government Documents Department
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Measurements of Intra-Beam Scattering at Low Emittance in the Advanced Light Source

Description: The beam emittance at the interaction point of linear colliders is expected to be strongly influenced by the emittance of the beams extracted from the damping rings. Intra-beam scattering (IBS) potentially limits the minimum emittance of low-energy storage rings, and this effect strongly influences the choice of energy of damping rings [1]. Theoretical analysis suggests that the NLC damping rings will experience modest emittance growth at 1.98 GeV, however there is little experimental data of I… more
Date: March 13, 2006
Creator: Byrd, J.; Corlett, J.; Nishimura, H.; Robin, D.; De Santis, S.; Steier, C. et al.
Partner: UNT Libraries Government Documents Department
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Multi-Stage Bunch Compressors for the International Linear Collider

Description: We present bunch compressor designs for the International Linear Collider (ILC) which achieve a reduction in RMS bunch length from 6 mm to 0.3 mm via multiple stages of compression, with stages of acceleration inserted between the stages of compression. The key advantage of multi-stage compression is that the maximum RMS energy spread is reduced to approximately 1%, compared to over 3% for a single-stage design. Analytic and simulation studies of the multi-stage bunch compressors are presented,… more
Date: May 27, 2005
Creator: Tenenbaum, P.; Raubenheimer, T. O. & Wolski, A.
Partner: UNT Libraries Government Documents Department
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500 MW X-BAND RF SYSTEM OF A 0.25 GEV ELECTRON LINAC FOR ADVANCED COMPTON SCATTERING SOURCE APPLICATION

Description: A Mono-Energetic Gamma-Ray (MEGa-Ray) Compton scattering light source is being developed at LLNL in collaboration with SLAC National Accelerator Laboratory. The electron beam for the Compton scattering interaction will be generated by a X-band RF gun and a X-band LINAC at the frequency of 11.424 GHz. High power RF in excess of 500 MW is needed to accelerate the electrons to energy of 250 MeV or greater for the interaction. Two high power klystron amplifiers, each capable of generating 50 MW, 1.… more
Date: May 12, 2010
Creator: Chu, T S; Anderson, S G; Gibson, D J; Hartemann, F V; Marsh, R A; Siders, C et al.
Partner: UNT Libraries Government Documents Department
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FACET Emittance Growth

Description: FACET, the Facility for Advanced Accelerator and Experimental Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study beam driven plasma wakefield acceleration. The FACET beamline consists of a chicane and final focus system to compress the 23 GeV, 3.2 nC electron bunches to {approx}20 {micro}m long and {approx}10 {micro}m wide. Simulations of the FACET beamline indicate the short-duration and large, 1.5% rms energy spread beams may suffer a factor of four e… more
Date: April 5, 2011
Creator: Frederico, J.; Hogan, M. J.; Nosochkov, Y.; Litos, M. D. & Raubenheimer, T.
Partner: UNT Libraries Government Documents Department
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ADVANCED X-BAND TEST ACCELERATOR FOR HIGH BRIGHTNESS ELECTRON AND GAMMA RAY BEAMS

Description: In support of Compton scattering gamma-ray source efforts at LLNL, a multi-bunch test stand is being developed to investigate accelerator optimization for future upgrades. This test stand will enable work to explore the science and technology paths required to boost the current 10 Hz monoenergetic gamma-ray (MEGa-Ray) technology to an effective repetition rate exceeding 1 kHz, potentially increasing the average gamma-ray brightness by two orders of magnitude. Multiple bunches must be of exceedi… more
Date: May 12, 2010
Creator: Marsh, R A; Anderson, S G; Barty, C P; Chu, T S; Ebbers, C A; Gibson, D J et al.
Partner: UNT Libraries Government Documents Department
open access

Suppression of Beam-Ion Instability in Electron Rings with Multi-Bunch Train Beam Fillings

Description: The ion-caused beam instability in the future light sources and electron damping rings can be serious due to the high beam current and ultra-small emittance of picometer level. One simple and effective mitigation of the instability is a multi-bunch train beam filling pattern which can significantly reduce the ion density near the beam, and therefore reduce the instability growth rate up to two orders of magnitude. The suppression is more effective for high intensity beams with low emittance. Th… more
Date: August 18, 2011
Creator: Wang, L.; Cai, Y.; Raubenheimer, T. O. & Fukuma, H.
Partner: UNT Libraries Government Documents Department
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Beam Dynamics Study of X-Band Linac Driven X-Ray FELS

Description: Several linac driven X-ray Free Electron Lasers (XFELs) are being developed to provide high brightness photon beams with very short, tunable wavelengths. In this paper, three XFEL configurations are proposed that achieve LCLS-like performance using X-band linac drivers. These linacs are more versatile, efficient and compact than ones using S-band or C-band rf technology. For each of the designs, the overall accelerator layout and the shaping of the bunch longitudinal phase space are described b… more
Date: December 13, 2011
Creator: Adolphsen, C.; Limborg-Deprey, C.; Raubenheimer, T. O.; Wu, J. & Sun, Y.
Partner: UNT Libraries Government Documents Department
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Observation of Beam ION Instability in Spear3

Description: Weak vertical coupled bunch instability with oscillation amplitude at {mu}m level has been observed in SPEAR3. The instability becomes stronger when there is a vacuum pressure rise by partially turning off vacuum pumps and it becomes weaker when the vertical beam emittance is increased by turning off the skew quadrupole magnets. These confirmed that the instability was driven by ions in the vacuum. The threshold of the beam ion instability when running with a single bunch train is just under 20… more
Date: December 14, 2011
Creator: Teytelman, D.; Cai, Y.; Corbett, W. J.; Raubenheimer, T. O.; Safranek, J. A.; Schmerge, J. F. et al.
Partner: UNT Libraries Government Documents Department
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Evidence of High Harmonics from Echo-Enabled Harmonic Generation for Seeding X-ray Free Electron Lasers

Description: Echo-enabled harmonic generation free electron lasers hold great promise for the generation of fully coherent radiation in x-ray wavelengths. Here we report the first evidence of high harmonics from the echo-enabled harmonic generation technique in the realistic scenario where the laser energy modulation is comparable to the beam slice energy spread. In this experiment, coherent radiation at the seventh harmonic of the second seed laser is generated when the energy modulation amplitude is about… more
Date: November 20, 2011
Creator: Xiang, D.; Colby, E.; Dunning, M.; Gilevich, S.; Hast, C.; Jobe, K. et al.
Partner: UNT Libraries Government Documents Department
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