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Preliminary Study on Emittance Growth in the LHEC Recirculating Linac

Description: In this paper, we estimate the emittance growth in the LHeC recirculating Linac, the lattice design of which is presented in another paper of IPAC10 proceedings. The possible sources for emittance growth included here are: energy spread from RF acceleration in the SRF (superconducting RF) linac together with large chromatic effects from the lattice, and synchrotron radiation (SR) fluctuations in the recirculating arcs. 6-D multi-particle tracking is launched to calculate the emittance from the statistical point of view. The simulation results are also compared with a theoretical estimation.
Date: May 20, 2011
Creator: Sun, Yi-Peng; Adolphsen, Chris; /SLAC; Zimmermann, Frank & /CERN
Partner: UNT Libraries Government Documents Department

Progress on a Vlasov Treatment of Coherent Synchrotron Radiation From Arbitrary Planar Orbits

Description: We report on our progress in the development of a fully self-consistent Vlasov treatment of coherent synchrotron radiation (CSR) effects on particle bunches traveling on arbitrary planar orbits. First we outline our Vlasov approach and the approximation we are currently studying. Then we discuss recent numerical results for a benchmark model studied extensively with codes by several authors.
Date: February 10, 2006
Creator: Bassi, G.; Ellison, J.A.; U., /New Mexico; Warnock, R.L. & /SLAC
Partner: UNT Libraries Government Documents Department

Comparison of 2 mrad and 14/20 mrad Crossing Angle Extraction Lines

Description: A study of the beam distributions in the 2 mrad and 14/20 mrad extraction lines are presented. Beam losses, energy losses due to synchrotron radiation and spin diffusion are shown. Synchrotron radiation distributions generated by the beam as it traverses the extraction lines are studied.
Date: July 17, 2006
Creator: Moffeit, Ken; Maruyama, Takashi; Nosochkov, Yuri; Seryi, Andrei; Wood, Mike & /SLAC
Partner: UNT Libraries Government Documents Department

First Operation of the Abort Gap Monitor for LHC

Description: The Large Hadron Collider (LHC) beam-dump system relies on extraction kickers that need 3 microseconds to rise to their nominal field. Since particles transiting the kickers during the rise will not be dumped properly, the proton population in this interval must always remain below quench and damage limits. A specific monitor to measure the particle population of this gap has been designed based on the detection of synchrotron radiation using a gated photomultiplier. Since the quench and damage limits change with the beam energy, the acceptable population in the abort gap and the settings of the monitor must adapt accordingly. This paper presents the design of the monitor, the calibration procedure and the detector performance with beam.
Date: July 6, 2012
Creator: Lefevre, Thibaut; /CERN; Bart Pedersen, Stephane; /CERN; Boccardi, Andrea; /CERN et al.
Partner: UNT Libraries Government Documents Department

CSR in the SuperKEKB Damping Ring

Description: Coherent synchrotron radiation (CSR) is generated when a bunched beam traverses a dipole magnet or a wiggler/undulator. It can degrade the beam quality in both storage rings and linacs through enhancing the beam energy spread and lengthening the bunch length, even cause single-bunch microwave instabilities. Using several methods, CSR impedances in the positron damping ring (DR) of the SuperKEKB which is under design were calculated. From the impedances due to CSR, resistive wall and various vacuum components, quasi-Green function wake potentials were constructed and used in simulations of Particle-In-Cell (PIC) tracking. We present the CSR related results in this paper.
Date: July 6, 2012
Creator: Zhou, Demin; /KEK, Tsukuba; Abe, Tetsuo; /KEK, Tsukuba; Ikeda, Hitomi; /KEK, Tsukuba et al.
Partner: UNT Libraries Government Documents Department

Designs for a Linac-Ring LHeC

Description: We consider three scenarios for the recirculating electron linear accelerator (RLA) of a linac-ring type electron-proton collider based on the LHC (LHeC): (i) a pulsed linac with a final beam energy of 60 GeV ['p-60'], (ii) a higher luminosity configuration with two cw linacs and energy-recovery (ERL) also at 60 GeV ['erl'], and (iii) a high energy option using a pulsed linac with 140-GeV final energy ['p-140']. We discuss parameters, synchrotron radiation, footprints, and performance for the three scenarios.
Date: June 21, 2012
Creator: Zimmermann, Frank; /CERN; Bruning, Oliver; /CERN; Ciapala, Edmond; /CERN et al.
Partner: UNT Libraries Government Documents Department

Bunch Length Measurements With Laser/SR Cross-Correlation

Description: By operating SPEAR3 in low-{alpha} mode the storage ring can generate synchrotron radiation pulses of order 1ps. Applications include pump-probe x-ray science and the production of THz radiation in the CSR regime. Measurements of the bunch length are difficult, however, because the light intensity is low and streak cameras typically provide resolution of only a few ps. Tests are now underway to resolve the short bunch length using cross-correlation between a 60-fs Ti:Sapphire laser and the visible SR beam in a BBO crystal. In this paper we report on the experimental setup, preliminary measurements and prospects for further improvement.
Date: July 6, 2012
Creator: Miller, Timothy; /Stanford U., Phys. Dept.; Daranciang, Dan; /Stanford U., Phys. Dept.; Lindenberg, Aaron; /Stanford U., Phys. Dept. et al.
Partner: UNT Libraries Government Documents Department

Absolute Bunch Length Measurements at the ALS by Incoherent Synchrotron Radiation Fluctuation Analysis

Description: By analyzing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and tested a simple scheme based on this principle that allows for the absolute measurement of the bunch length. A description of the method and the experimental results are presented.
Date: January 24, 2008
Creator: Filippetto, D.; /Frascati; Sannibale, F.; Zolotorev, Max Samuil; /LBL, Berkeley; Stupakov, G.V. et al.
Partner: UNT Libraries Government Documents Department

SPEAR3 Accelerator Physics Update

Description: The SPEAR3 storage ring at Stanford Synchrotron Radiation Laboratory has been delivering photon beams for three years. We will give an overview of recent and ongoing accelerator physics activities, including 500 mA fills, work toward top-off injection, long-term orbit stability characterization and improvement, fast orbit feedback, new chicane optics, low alpha optics & short bunches, low emittance optics, and MATLAB software. The accelerator physics group has a strong program to characterize and improve SPEAR3 performance
Date: November 2, 2007
Creator: Safranek, James A.; Corbett, W.Jeff; Gierman, S.; Hettel, R.O.; Huang, X.; Nosochkov, Yuri et al.
Partner: UNT Libraries Government Documents Department

ILC Extraction Line for 14 mrad Crossing Angle

Description: The earlier studies of the ILC extraction line for 20 mrad and 2 mrad crossing angle options [1]-[5] showed that the 20 mrad design has an advantage of a simpler beamline and lower extraction beam loss because of the independent incoming and extraction optics. However, the large 20 mrad crossing angle requires the use of a crab cavity correction, increases synchrotron radiation emittance growth in the solenoid, and increases photon backscattering from the forward calorimeter of the detector. To reduce these effects, an attempt has been made to minimize the crossing angle while keeping the extraction and incoming lines separate. A new quadrupole scheme near the interaction point has been proposed which allows a reduction of the crossing angle to 14 mrad [6]. The optics design and results of tracking and background simulations for the 14 mrad extraction line are presented.
Date: December 8, 2005
Creator: Nosochkov, Y.; Markiewicz, T.; Maruyama, T.; Seryi, A.; /SLAC; Parker, B. et al.
Partner: UNT Libraries Government Documents Department

HOM Sensitivity in the PEP-II HER Vacuum Chamber

Description: Synchrotron radiation is the main source of vacuum chamber heating in the PEP-II storage ring collider. This heating is reduced substantially as lattice energy is lowered. Energy scans over {Upsilon} energy states were performed by varying the high energy ring (HER) lattice energy at constant gap voltage and frequency. We observed unexpected temperature rise at particular locations when HER lattice energy was lowered from 8.6 GeV ({Upsilon}(3S)) to 8.0 GeV ({Upsilon}(2S)) while most other temperatures decreased. Bunch length measurements reveal a shorter bunch at the lower energy. The shortened bunch overheated a beam position monitoring electrode causing a vacuum breach. We explain the unexpected heating as a consequence of increased higher order mode (HOM) power generated by a shortened bunch. In this case, temperature rise helps to identify HOM sources and HOM sensitive vacuum chamber elements. Reduction of gap voltage helps to reduce this unexpected heating.
Date: February 10, 2010
Creator: Weathersby, Stephen; Novokhatski, Alexander; Sullivan, Mike & /SLAC
Partner: UNT Libraries Government Documents Department

Experimental Characterization of the Transverse Phase Space of a 60-MeV Electron Beam Through a Compressor Chicane

Description: Space charge and coherent synchrotron radiation may deteriorate electron beam quality when the beam passes through a magnetic bunch compressor. This paper presents the transverse phase-space tomographic measurements for a compressed beam at 60 MeV, around which energy the first stage of magnetic bunch compression takes place in most advanced linacs. Transverse phase-space bifurcation of a compressed beam is observed at that energy, but the degree of the space charge-induced bifurcation is appreciably lower than the one observed at 12 MeV.
Date: February 12, 2007
Creator: Zhou, F.; Kabel, A.; Rosenzweig, J.; Agustsson, R.; Andonian, G.; Cline, D. et al.
Partner: UNT Libraries Government Documents Department

Effect of Centrifugal Transverse Wakefield for Microbunch in Bend

Description: We calculate centrifugal force for a short bunch in vacuum moving in a circular orbit and estimate the emittance growth of the beam in a bend due to this force. Many of the basic features of the coherent synchrotron radiation (CSR) of short bunches and its effect on beam dynamics in accelerators are now well established. The effect is usually described in terms of the longitudinal force, or wakefield, that causes the energy loss in the beam, and also redistributes the energy between the particles by accelerating the head and decelerating the tail of the bunch. Coherent radiation becomes most important for short bunches and high currents. More subtle features of CSR such as transition effect due to the entrance to and exit from the bend, CSR force in the undulator, and shielding due to the close metallic boundaries have been also studied. Much less is known about the transverse force in a short bunch moving on a circular orbit. The problem has been treated in several papers beginning from R. Talman's work, who pointed out that the centrifugal force of a rotating bunch can result in a noticeable tune shift of betatron oscillations. Later, an important correction to the Talman paper has been added, where it was shown that due to the energy variation in the bunch, the effect of the transverse force proportional to R{sup -1} is canceled, and the residual effect is of the order of R{sup -2}, that is much smaller than originally predicted. Recently, however, Derbenev and Shiltsev found the centrifugal force of the order of R{sup -1} that differs from Talman's result by a logarithmic factor only. Taking into account the existing controversy in the literature, in this paper, we consider the transverse force in a bunch based on simple physical arguments, starting from ...
Date: March 22, 2006
Creator: Stupakov, G. V.
Partner: UNT Libraries Government Documents Department

Study of Bunch Instabilities By the Nonlinear Vlasov-Fokker-Planck Equation

Description: Instabilities of the bunch form in storage rings may be induced through the wake field arising from corrugations in the vacuum chamber, or from the wake and precursor fields due to coherent synchrotron radiation (CSR). For over forty years the linearized Vlasov equation has been applied to calculate the threshold in current for an instability, and the initial growth rate. Increasing interest in nonlinear aspects of the motion has led to numerical solutions of the nonlinear Vlasov equation, augmented with Fokker-Planck terms to describe incoherent synchrotron radiation in the case of electron storage rings. This opens the door to much deeper studies of coherent instabilities, revealing a rich variety of nonlinear phenomena. Recent work on this topic by the author and collaborators is reviewed.
Date: July 11, 2006
Creator: Warnock, Robert L.
Partner: UNT Libraries Government Documents Department

Interaction-Region Design Options for a Linac-Ring LHeC

Description: The interaction-region design for a linac-ring electron-proton collider based on the LHC ('LR-LHeC') poses numerous challenges related to collision scheme, synchrotron radiation, aperture, magnet technology, and optics. We report a first assessment and various options.
Date: June 21, 2012
Creator: Zimmermann, Frank; /CERN; Bettoni, Simona; /CERN; Bruning, Oliver; /CERN et al.
Partner: UNT Libraries Government Documents Department

Status of the Super-B factory Design

Description: The SuperB international team continues to optimize the design of an electron-positron collider, which will allow the enhanced study of the origins of flavor physics. The project combines the best features of a linear collider (high single-collision luminosity) and a storage-ring collider (high repetition rate), bringing together all accelerator physics aspects to make a very high luminosity of 10{sup 36} cm{sup -2} sec{sup -1}. This asymmetric-energy collider with a polarized electron beam will produce hundreds of millions of B-mesons at the Y(4S) resonance. The present design is based on extremely low emittance beams colliding at a large Piwinski angle to allow very low {beta}{sub y} without the need for ultra short bunches. Use of crab-waist sextupoles will enhance the luminosity, suppressing dangerous resonances and allowing for a higher beam-beam parameter. The project has flexible beam parameters, improved dynamic aperture, and spin-rotators in the Low Energy Ring for longitudinal polarization of the electron beam at the Interaction Point. Optimized for best colliding-beam performance, the facility may also provide high-brightness photon beams for synchrotron radiation applications.
Date: May 18, 2012
Creator: Wittmer, W.; U., /Michigan State; Bertsche, K.; Chao, A.; Novokhatski, A.; Nosochkov, Y. et al.
Partner: UNT Libraries Government Documents Department

Parameters of a Super-B-Factory Design

Description: Parameters are being studied for a high luminosity e{sup +}e{sup -} collider operating at the Upsilon 4S that would deliver a luminosity in the range of 7 to 10 x 10{sup 35}/cm{sup 2}/s. Particle physics studies dictate that a much higher luminosity collider than the present B-Factory accelerators will be needed to answer future new key physics questions. The success of the present B-Factories, PEP-II and KEKB, in producing unprecedented luminosity with very short commissioning times has taught us about the accelerator physics of asymmetric e{sup +}e{sup -} colliders in a new parameter regime. Such a collider could produce an integrated luminosity of 10,000 fb{sup -1} (10 ab{sup -1}) in a running year. A Super-B-Factory [1-8] with 30 to 50 times the performance of the present PEP-II accelerator would incorporate a higher frequency RF system, lower impedance vacuum chambers, higher power synchrotron radiation absorbers, and stronger bunch-by-bunch feedback systems. The present injector based on the SLAC linac needs no improvements and is ready for the Super-B-Factory.
Date: March 3, 2006
Creator: Seeman, J.; Cai, Y.; Ecklund, S.; Fox, J.D.; Heifets, S.A.; Li, N. et al.
Partner: UNT Libraries Government Documents Department

Commissioning the SPEAR3 Diagnostic Beamlines

Description: SPEAR3 has two diagnostic beam lines: an x-ray pinhole camera and a visible/UV beam line. The pinhole camera images {approx}8 keV dipole synchrotron radiation (SR) incident on a phosphor screen. The visible beam line delivers conventional optical radiation to an array of cameras and diagnostic elements on a 1x3m optical bench. This paper briefly reviews the pinhole camera system while concentrating more on visible beam line power transmission calculations and streak camera data. Impedance estimates in the nominal optics and bunch length measurements in low-alpha optics are presented.
Date: June 5, 2007
Creator: Corbett, W.J.; Limborg-Deprey, C.; Mok, W.Y.; Ringwall, A. & /SLAC
Partner: UNT Libraries Government Documents Department

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 emittance growth from a combination of chromaticity, incoherent synchrotron radiation (ISR), and coherent synchrotron radiation (CSR). Emittance growth is directly correlated to head erosion in plasma wakefield acceleration and is a limiting factor in single stage performance. Studies of the geometric, CSR, and ISR components are presented. Numerical calculation of the rms emittance can be overwhelmed by long tails in the simulated phase space distributions; more useful definitions of emittance are given. A complete simulation of the beamline is presented as well, which agrees with design specifications.
Date: April 5, 2011
Creator: Frederico, J; Hogan, M.J.; Nosochkov, Y.; Litos, M.D.; Raubenheimer, T. & /SLAC
Partner: UNT Libraries Government Documents Department

Lattice Design for ERL Options at SLAC

Description: SLAC is investigating long-range options for building a high performance light source machine while reusing the existing linac and PEP-II tunnels. One previously studied option is the PEP-X low emittance storage ring. The alternative option is based on a superconducting Energy Recovery Linac (ERL) and the PEP-X design. The ERL advantages are the low beam emittance, short bunch length and small energy spread leading to better qualities of the X-ray beams. Two ERL configurations differed by the location of the linac have been studied. Details of the lattice design and the results of beam transport simulations with the coherent synchrotron radiation effects are presented.
Date: June 2, 2011
Creator: Nosochkov, Yuri; Cai, Yunhai; Huang, Xiaobiao; Wang, Min-Huey & /SLAC
Partner: UNT Libraries Government Documents Department

Development of a 2D Vlasov Solver for Longitudinal BeamDynamics in Single-Pass Systems

Description: Direct numerical methods for solving the Vlasov equation offer some advantages over macroparticle simulations, as they do not suffer from the numerical noise inherent in using a number of macroparticles smaller than the bunch population. Unfortunately these methods are more time-consuming and generally considered impractical in a full 6D phase space. However, in a lower-dimension phase space they may become attractive if the beam dynamics is sensitive to the presence of small charge-density fluctuations and a high resolution is needed. In this paper we present a 2D Vlasov solver for studying the longitudinal beam dynamics in single-pass systems of interest for X-FEL's, where characterization of the microbunching instability is of particular relevance. The solver includes a model to account for the smearing effect of a finite horizontal emittance on microbunching. We explore the effect of space charge and coherent synchrotron radiation (CSR). The numerical solutions are compared with results from linear theory and good agreement is found in the regime where linear theory applies.
Date: December 12, 2006
Creator: Venturini, M.; Warnock, R.; Zholents, A. & /SLAC
Partner: UNT Libraries Government Documents Department

Optimization and Modeling of the Accelerator for the FERMI @ Elettra FEL

Description: Design studies are in progress to use the existing FERMI{at}Elettra linear accelerator for a seeded harmonic cascade free-electron laser (FEL) facility [1]. This accelerator will be upgraded to 1.2 GeV and equipped with a low-emittance RF photocathode gun, laser heater, two bunch compressors, and a beam delivery system. We present an optimization study of all the components downstream of the gun, aimed at achieving the high peak current, low energy spread and low emittance electron beam necessary for the FEL. Various operational scenarios are discussed. Results of accelerator simulations including effects of space charge, coherent synchrotron radiation and wakefields are reported.
Date: September 30, 2005
Creator: Di Mitri, S.; Cornacchia, M.; Craievich, P.; Trieste, /Sincrotrone; Emma, P.; Huang, Z. et al.
Partner: UNT Libraries Government Documents Department

Recent SuperB Design Choices Improve Next-Generation e e___ B-Factory Collider

Description: The SuperB international team continues to optimize the design of an electron-positron collider, which will allow the enhanced study of the origins of flavor physics. The project combines the best features of a linear collider (high single-collision luminosity) and a storage-ring collider (high repetition rate), bringing together all accelerator physics aspects to make a very high luminosity of 10{sup 36} cm{sup -2} sec{sup -1}. This asymmetric-energy collider with a polarized electron beam will produce hundreds of millions of B-mesons at the {Upsilon}(4S) resonance. The present design is based on extremely low emittance beams colliding at a large Piwinski angle to allow very low {beta}*{sub y} without the need for ultra short bunches. Use of crab-waist sextupoles will enhance the luminosity, suppressing dangerous resonances and allowing for a higher beam-beam parameter. The project has flexible beam parameters, improved dynamic aperture, and spin-rotators in the Low Energy Ring for longitudinal polarization of the electron beam at the Interaction Point. Optimized for best colliding-beam performance, the facility may also provide high-brightness photon beams for synchrotron radiation applications.
Date: August 19, 2011
Creator: Wittmer, W.; Bertsche, K.; Chao, A.; Novokhatski, A.; Nosochkov, Y.; Seeman, J. et al.
Partner: UNT Libraries Government Documents Department

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 damping ring, the development of the electron cloud must be suppressed. This paper discusses the state-of-the-art of the ongoing SLAC and international R&D program to study potential remedies.
Date: May 27, 2005
Creator: Pivi, M; Kirby, R.E.; Raubenheimer, T.O.; /SLAC; Le Pimpec, F. & /PSI, Villigen
Partner: UNT Libraries Government Documents Department