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Tune-shift with amplitude due to nonlinear kinematic effect

Description: Tracking studies of the Muon Collider 50 on 50 GeV col-lider ring [1] show that the on-momentum dynamic aper-ture is limited to around 10{sigma} even with the chromaticity sextupoles turned off. Numerical results from the normal form algorithm show that the tune-shift with amplitude is surprisingly large. Both analytical and numerical results are presented to show that nonlinear kinematic effect originated from the large angles of particles in the interaction region is responsible for the large tune-shift which in turn limits the dynamic aperture. Acomparative study of the LHC collider ring is also presented to demonstrate the difference between the two machines.
Date: May 10, 1999
Creator: Wan, W.
Partner: UNT Libraries Government Documents Department

Generating Ultrashort Coherent Soft X-ray Radiation in Storage Rings Using Angular-modulated Electron Beams

Description: A technique is proposed to generate ultrashort coherent soft x-ray radiation in storage rings using angular-modulated electron beams. In the scheme a laser operating in the TEM01 mode is first used to modulate the angular distribution of the electron beam in an undulator. After passing through a special beam line with non-zero transfer matrix element R{sub 54}, the angular modulation is converted to density modulation which contains considerable higher harmonic contents of the laser. It is found that the harmonic number can be one or two orders of magnitude higher than the standard coherent harmonic generation method which relies on beam energy modulation. The technique has the potential of generating femtosecond coherent soft x-ray radiation directly from an infrared seed laser and may open new research opportunities for ultrafast sciences in storage rings.
Date: August 23, 2010
Creator: Xiang, D.; /SLAC; Wan, W. & /LBL, Berkeley
Partner: UNT Libraries Government Documents Department

Fixed field circular accelerator designs

Description: The rapid rate and cycle time required to efficiently accelerate muons precludes conventional circular accelerators. Recirculating linacs provide one option, but the separate return arcs per acceleration pass may prove costly. Recent work on muon acceleration schemes has concentrated on designing fixed-field circular accelerators whose strong superconducting fields can sustain a factor of 4 increase in energy from injection to extraction. A 4 to 16 GeV fixed-field circular accelerator has been designed which allows large orbit excursions and the tune to vary as a function of momentum. Acceleration is .6 GeV per turn so the entire cycle consists of only 20 turns. In addition, a 16 to 64 GeV fixed-field circular accelerator has been designed which is more in keeping with the traditional Fixed Field Alternating Gradient machines. In this work the two machine designs are described.
Date: January 6, 2000
Creator: Johnstone, C.; Wan, W. & Garren, A.
Partner: UNT Libraries Government Documents Department

Effect of the beam-beam interactions on the dynamic aperture and amplitude growth in the LHC

Description: The dynamic aperture at collision energy is determined pri-marily by the nonlinear fields of the IR quadrupoles but is also influenced by the beam-beam interactions. We revisit the choice of the crossing angle that maximizes the dynamic aperture with an accurate modeling of the long-range inter-actions and use of the present values of the IR quadrupole field harmonics. A separate but related issue we address is the amplitude growth of particles in the beam halo due to the long-range interactions.
Date: June 17, 1999
Creator: Johnstone, C.; Wan, W.; Gelfand, N. & Sen, T.
Partner: UNT Libraries Government Documents Department

Lattice design for a 50 on 50-GeV muon collider

Description: Two modes are being considered for a 50 on 50-GeV muon collider: one being a high-luminosity ring with broad momentum acceptance (dp/p of {approximately} 0.12%, rms) and the other lower luminosity with narrow momentum acceptance (dp/p of {approximately} 0.003%, rms). To reach the design luminosities, the value of beta at collision in the two rings must be 4 cm and 14 cm, respectively. In addition, the bunch length must be held comparable to the value of the collision beta to avoid luminosity dilution due to the hour-glass effect. To assist the rf system in preventing the bunch from spreading in time, the constraint of isochronicity is also imposed on the lattice. Finally, the circumference must be kept as small as possible to minimize luminosity degradation due to muon decay. Two lattice designs will be presented which meet all of these conditions. Furthermore, the lattice designs have been successfully merged into one physical ring with mutual components; the only difference being a short chicane required to match dispersion and floor coordinates from one lattice into the other.
Date: January 6, 2000
Creator: Johnstone, C.; Wan, W. & Garren, A.
Partner: UNT Libraries Government Documents Department

Scraping beam halo in {mu} {sup +} {mu} {sup minus} colliders

Description: Beam halo scraping schemes have been explored in the 50 x 50 GeV and 2 x 2 TeV {mu}{sup +}{mu}{sup -} colliders using both absorbers and electrostatic deflectors. Utility sections have been specially designed into the rings for scraping. Results of realistic STRUCT- MARS Monte-Carlo simulations show that for the low-energy machine a scheme with a 5 m long steel absorber suppresses losses in the interaction region by three orders of magnitude. The same scraping efficiency at 2 TeV is achieved only by complete extraction of beam halo from the machine. The effect of beam-induced power dissipation in the collider superconducting magnets and detector backgrounds is shown both for the first few turns after injection and for the rest of the cycle.
Date: January 1, 1998
Creator: Drozhdin, A.; Mokhov, N.; Johnstone, C.; Wan, W. & Garren, A.
Partner: UNT Libraries Government Documents Department

Initial lattice studies for the Berkeley Femtosecond X-ray Light Source

Description: We present lattice studies for a proposed femtosecond synchrotron radiation X-ray source based on a recirculating accelerator. After a general description, we cover specific aspects of the lattice that are relevant to this type of machine and show preliminary results of particle tracking and briefly describe a new code developed for a comprehensive particle tracking in recirculating accelerators.
Date: May 30, 2002
Creator: Zholents, A.; Reichel, I.; Robin, D.; Tanabe, J.; Wan, W.; Forest, E. et al.
Partner: UNT Libraries Government Documents Department

Broadband Single-Shot Electron Spectrometer for GeV-Class Laser Plasma Based Accelerators

Description: Laser-plasma-based accelerators can provide electrons over a broad energy range and/or with large momentum spread. The electron beam energy distribution can be controlled via accurate control of laser and plasma properties, and beams with energies ranging from'0.5 to 1000 MeV have been observed. Measuring these energy distributions in a single shot requires the use of a diagnostic with large momentum acceptance and, ideally, sufficient resolution to accurately measure energy spread in the case of narrow energy spread. Such a broadband single-shot electron magnetic spectrometer for GeV-class laser-plasma-based accelerators has been developed at Lawrence Berkeley National Laboratory. A detailed description of the hardware and the design concept is presented, as well as a performance evaluation of the spectrometer. The spectrometer covered electron beam energies raging from 0.01 to 1.1 GeV in a single shot, and enabled the simultaneous measurement of the laser properties at the exit of the accelerator through the use of a sufficiently large pole gap. Based on measured field maps and 3rd-order transport analysis, a few percent-level resolution and determination of the absolute energy were achieved over the entire energy range. Laser-plasma-based accelerator experiments demonstrated the capability of the spectrometer as a diagnostic and its suitability for such a broadband electron source.
Date: May 1, 2008
Creator: Nakamura, K.; Wan, W.; Ybarrolaza, N.; Syversrud, D.; Wallig, J. & Leemans, W.P.
Partner: UNT Libraries Government Documents Department

US-LHC IR magnet error analysis and compensation

Description: This paper studies the impact of the insertion-region (IR) magnet field errors on LHC collision performance. Compensation schemes including magnet orientation optimization, body-end compensation, tuning shims, and local nonlinear correction are shown to be highly effective.
Date: August 1, 1998
Creator: Wei, J.; Ptitsin, V.; Pilat, F.; Tepikian, S.; Gelfand, N.; Wan, W. et al.
Partner: UNT Libraries Government Documents Department

Harmonic cascade FEL designs for LUX

Description: LUX is a design concept for an ultrafast X-ray science facility, based on an electron beam accelerated to GeV energies in are circulating linac. Included in the design are short duration (200 fs or shorter FWHM) light sources using multiple stages of higher harmonic generation, seeded by a 200-250 nm laser of similar duration. This laser modulates the energy of a group of electrons within the electron bunch; this section of the electron bunch then produces radiation at a higher harmonic after entering a second, differently tuned undulator. Repeated stages in a cascade yield increasing photon energies up to 1 keV. Most of the undulators in the cascade operate in the low-gain FEL regime. Harmonic cascades have been designed for each pass of the recirculating linac up to a final electron beam energy of 3.1 GeV. For a given cascade, the photon energy can be selected over a wide range by varying the seed laser frequency and the field strength in the undulators. We present simulation results using the codes GENESIS and GINGER, as well as the results of analytical models which predict FEL performance. We discuss lattice considerations pertinent for harmonic cascade FELs, as well as sensitivity studies and requirements on the electron beam.
Date: July 16, 2004
Creator: Penn, G.; Reinsch, M.; Wurtele, J.; Corlett, J.N.; Fawley, W.M.; Zholents, A. et al.
Partner: UNT Libraries Government Documents Department

An Ultra-Bright Pulsed Electron Beam With Low Longitudinal Emittance

Description: Most existing electron sources extract electrons from conductors. Since the actual temperature inside the conductor is much less than the Fermi temperature of the conduction electrons, the electron degeneracy {delta}{sub f} is close to 1, the maximum allowed by the Pauli exclusion principle. However, during extraction several factors conspire together to reduce {delta}{sub f} many orders of magnitude, limiting the achieved values to {approx} 10{sup -5}. A new concept is described for building a novel electron source designed to produce a pulsed beam with {delta}{sub f} {approx} 2 10{sup -3} and longitudinal emittance four orders of magnitude smaller than currently achieved values. This high brightness, low longitudinal emittance regime enables a wide range of novel applications that utilize angstrom-scale spatial resolution and eV-scale energy resolution. The current state of a proof-of-principle experiment conducted at LBNL is also described.
Date: February 10, 2006
Creator: Zolotorev, M.; Commins, E.D.; Denes, P.; Hussain, Z.; Lebedev, G.V.; Lidia, S.M. et al.
Partner: UNT Libraries Government Documents Department

CIRCE: A dedicated storage ring for coherent THz synchrotron radiation

Description: We present the concepts for an electron storage ring dedicated to and optimized for the production of stable coherent synchrotron radiation (CSR) over the far-infrared terahertz wavelength range from 200 mm to about one cm. CIRCE (Coherent InfraRed CEnter) will be a 66 m circumference ring located on top of the ALS booster synchrotron shielding tunnel and using the existing ALS injector. This location provides enough floor space for both the CIRCE ring, its required shielding, and numerous beamlines. We briefly outline a model for CSR emission in which a static bunch distortion induced by the synchrotron radiation field is used to significantly extend the stable CSR emission towards higher frequencies. This model has been verified with experimental CSR results. We present the calculated CIRCE photon flux where a gain of 6-9 orders of magnitude is shown compared to existing far-IR sources. Additionally, the particular design of the dipole vacuum chamber has been optimized to allow an excellent transmission of these far-infrared wavelengths. We believe that the CIRCE source can be constructed for a modest cost.
Date: August 12, 2003
Creator: Byrd, J.M.; Martin, Michael C.; McKinney, W.R.; Munson, D.V.; Nishimura, H.; Robin, D.S. et al.
Partner: UNT Libraries Government Documents Department

Progress on PEEM3 - An Aberration Corrected X-Ray PhotoemissionElectron Microscope at the ALS

Description: A new ultrahigh-resolution photoemission electron microscope called PEEM3 is being developed and built at the Advanced Light Source (ALS). An electron mirror combined with a much-simplified magnetic dipole separator is to be used to provide simultaneous correction of spherical and chromatic aberrations. It is installed on an elliptically polarized undulator (EPU) beamline, and will be operated with very high spatial resolution and high flux to study the composition, structure, electric and magnetic properties of complex materials. The instrument has been designed and is described. The instrumental hardware is being deployed in 2 phases. The first phase is the deployment of a standard PEEM type microscope consisting of the standard linear array of electrostatic electron lenses. The second phase will be the installation of the aberration corrected upgrade to improve resolution and throughput. This paper describes progress as the instrument enters the commissioning part of the first phase.
Date: May 20, 2006
Creator: MacDowell, Alastair A.; Feng, J.; DeMello, A.; Doran, A.; Duarte,R.; Forest, E. et al.
Partner: UNT Libraries Government Documents Department

Optimizing ring-based CSR sources

Description: Coherent synchrotron radiation (CSR) is a fascinating phenomenon recently observed in electron storage rings and shows tremendous promise as a high power source of radiation at terahertz frequencies. However, because of the properties of the radiation and the electron beams needed to produce it, there are a number of interesting features of the storage ring that can be optimized for CSR. Furthermore, CSR has been observed in three distinct forms: as steady pulses from short bunches, bursts from growth of spontaneous modulations in high current bunches, and from micro modulations imposed on a bunch from laser slicing. These processes have their relative merits as sources and can be improved via the ring design. The terahertz (THz) and sub-THz region of the electromagnetic spectrum lies between the infrared and the microwave . This boundary region is beyond the normal reach of optical and electronic measurement techniques and sources associated with these better-known neighbors. Recent research has demonstrated a relatively high power source of THz radiation from electron storage rings: coherent synchrotron radiation (CSR). Besides offering high power, CSR enables broadband optical techniques to be extended to nearly the microwave region, and has inherently sub-picosecond pulses. As a result, new opportunities for scientific research and applications are enabled across a diverse array of disciplines: condensed matter physics, medicine, manufacturing, and space and defense industries. CSR will have a strong impact on THz imaging, spectroscopy, femtosecond dynamics, and driving novel non-linear processes. CSR is emitted by bunches of accelerated charged particles when the bunch length is shorter than the wavelength being emitted. When this criterion is met, all the particles emit in phase, and a single-cycle electromagnetic pulse results with an intensity proportional to the square of the number of particles in the bunch. It is this quadratic dependence that can produce colossal ...
Date: January 1, 2004
Creator: Byrd, J.M.; De Santis, S.; Hao, Z.; Martin, M.C.; Munson, D.V.; Li, D. et al.
Partner: UNT Libraries Government Documents Department

FEL Design Studies at LBNL: Activities and Plans

Description: LBNL staff are currently pursuing R&D for future x-ray FELs, and participate in two FEL construction projects. Our strategy is to address the most fundamental challenges, which are the cost-drivers and performance limitations of FEL facilities. An internally funded R&D program is aimed at investigating accelerator physics and technologies in three key areas: (1) Theoretical study, modeling, and experimental development of low emittance, high quantum efficiency cathodes; (2) Design studies of electron beam delivery systems, including emittance manipulations, high-resolution modeling of 6-D phase space, and low-emittance beam transport; and (3) Design studies of optical manipulations of electron beams for seeded and SASE FELs, providing short x-ray pulses of variable duration, synchronous with the seed and pump laser sources, and also long transform-limited pulses with a narrow bandwidth. Design studies of means for production of attosecond x-ray pulses at various wavelengths. We are collaborators in the FERMI{at}Elettra seeded FEL facility under construction at Sincrotrone Trieste, Italy, participating in accelerator design and FEL physics studies, and mechanical and electrical engineering. We are participating in the LCLS project at SLAC, implementing our design of stabilized timing and synchronization systems. Here we outline our long-term objectives, and current activities.
Date: March 1, 2007
Creator: Corlett, John N.; Fawley, W.; Lidia, S.; Padmore, H.; Penn, G.; Pogorelov, I. et al.
Partner: UNT Libraries Government Documents Department

Design Studies for a VUV--Soft X-ray Free-Electron Laser Array

Description: Several recent reports have identified the scientific requirements for a future soft X-ray light source [1, 2, 3, 4, 5], and a high-repetition-rate free-electron laser (FEL) facility responsive to them is being studied at Lawrence Berkeley National Laboratory (LBNL) [6]. The facility is based on a continuous-wave (CW) superconducting linear accelerator with beam supplied by a high-brightness, high-repetition-rate photocathode electron gun operating in CW mode, and on an array of FELs to which the accelerated beam is distributed, each operating at high repetition rate and with even pulse spacing. Dependent on the experimental requirements, the individualFELs may be configured for either self-amplified spontaneous emission (SASE), seeded highgain harmonic generation (HGHG), echo-enabled harmonic generation (EEHG), or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format ranging from sub-femtoseconds to hundreds of femtoseconds. This new light source would serve a broad community of scientists in many areas of research, similar to existing utilization of storage ring based light sources. To reduce technical risks and constructioncosts, accelerator research, development, and design studies at LBNL target the most critical components and systems of the facility. We are developing a high-repetition-rate low-emittance electron gun, high quantum efficiency photocathodes, and have embarked on design and optimization of the electron beam accelerator, FEL switchyard, and array of FELs. We continue our work on precision timing and synchronization systems critical for time-resolved experiments using pump-probe techniques.
Date: August 4, 2009
Creator: Corlett, J.; Baptiste, K.; Byrd, J.M.; Denes, P.; Falcone, R.; Kirz, J. et al.
Partner: UNT Libraries Government Documents Department

A HIGH REPETITION RATE VUV-SOFT X-RAY FEL CONCEPT

Description: We report on design studies for a seeded FEL light source that is responsive to the scientific needs of the future. The FEL process increases radiation flux by several orders of magnitude above existing incoherent sources, and offers the additional enhancements attainable by optical manipulations of the electron beam: control of the temporal duration and bandwidth of the coherent output, reduced gain length in the FEL, utilization of harmonics to attain shorter wavelengths, and precise synchronization of the x-ray pulse with seed laser systems. We describe an FEL facility concept based on a high repetition rate RF photocathode gun, that would allow simultaneous operation of multiple independent FEL's, each producing high average brightness, tunable over the VUV-soft x-ray range, and each with individual performance characteristics determined by the configuration of the FEL. SASE, enhanced-SASE (ESASE), seeded, harmonic generation, and other configurations making use of optical manipulations of the electron beam may be employed, providing a wide range of photon beam properties to meet varied user demands.
Date: June 24, 2007
Creator: Corlett, J.; Byrd, J.; Fawley, W.M.; Gullans, M.; Li, D.; Lidia,S.M. et al.
Partner: UNT Libraries Government Documents Department

Preliminary results of the echo-seeding experiment at SLAC

Description: ECHO-7 is a proof-of-principle echo-enabled harmonic generation FEL experiment in the Next Linear Collider Test Accelerator (NLCTA) at SLAC. The experiment aims to generate coherent radiation at 318 nm and 227 nm, which are the 5th and 7th harmonic of the infrared seed laser. In this paper we present the preliminary results from the commissioning run of the completed experimental setup which started in April 2010.
Date: May 23, 2010
Creator: Xiang, D.; Colby, E.; Ding, Y.; Dunning, M.; Frederico, J.; Gilevich, S. et al.
Partner: UNT Libraries Government Documents Department

LUX - A recirculating linac-based ultrafast X-ray source

Description: We describe the design of a proposed source of ultra-fast synchrotron radiation x-ray pulses based on a recirculating superconducting linac, with an integrated array of ultrafast laser systems. The source produces x-ray pulses with duration of 10-50 fs at a 10 kHz repetition rate, with tunability from EUV to hard x-ray regimes, and optimized for the study of ultra-fast dynamics. A high-brightness rf photocathode provides electron bunches. An injector linac accelerates the beam to the 100 MeV range, and is followed by four passes through a 700 MeV recirculating linac. Ultrafast hard x-ray pulses are obtained by a combination of electron bunch manipulation, transverse temporal correlation of the electrons, and x-ray pulse compression. EUV and soft x-ray pulses as short as 10 fs are generated in a harmonic-cascade free electron laser scheme.
Date: August 1, 2003
Creator: Corlett, J. N.; Barletta, W. A.; DeSantis, S.; Doolittle, L.; Fawley, W. M.; Green, M. A. et al.
Partner: UNT Libraries Government Documents Department

LUX - A design study for a linac/laser-based ultrafast X-ray source

Description: A warm, relativistic fluid theory of a nonequilibrium, collisionless plasma is developed to analyze nonlinear plasma waves excited by intense drive beams. The maximum amplitude and wavelength are calculated for nonrelativistic plasma temperatures and arbitrary plasma wave phase velocities. The maximum amplitude is shown to increase in the presence of a laser field. These results set a limit to the achievable gradient in plasma-based accelerators.
Date: August 6, 2004
Creator: Corlett, J.N.; Barletta, W.A.; DeSantis, S.; Doolittle, L.; Fawley, W.M.; Heimann, P. et al.
Partner: UNT Libraries Government Documents Department

LUX - a recirculating linac-based facility for ultrafast X-ray science

Description: We present recent developments in design concepts for LUX - a source of ultra-short synchrotron radiation pulses based on a recirculating superconducting linac. The source produces high-flux x-ray pulses with duration of 100 fs or less at a 10 kHz repetition rate, optimized for the study of ultra-fast dynamics across many fields of science [1]. Cascaded harmonic generation in free-electron lasers (FEL's) produces coherent radiation in the VUV-soft x-ray regime, and a specialized technique is used to compress spontaneous emission for ultra-short-pulse photon production in the 1-10 keV range. High-brightness electron bunches of 2-3 mm-mrad emittance at 1 nC charge in 30 ps duration are produced in an rf photocathode gun and compressed to 3 ps duration following an injector linac, and recirculated three times through a 1 GeV main linac. In each return path, independently tunable harmonic cascades are inserted to produce seeded FEL radiation in selected photon energy ranges from approximately 20 eV with a single stage of harmonic generation, to 1 keV with a four-stage cascade. The lattice is designed to minimize emittance growth from effects such as coherent synchrotron radiation (CSR), and resistive wall wakefields. Timing jitter between pump lasers and x-ray pulses is minimized by use of a stable optical master oscillator, distributing timing signals over actively stabilized fiber-optic, phase-locking all lasers to the master oscillator, and generating all rf signals from the master oscillator. We describe technical developments including techniques for minimizing power dissipation in a high repetition rate rf photocathode gun, beam dynamics in two injector configurations, independently tunable beamlines for VUV and soft x-ray production by cascaded harmonic generation, a fast kicker design, timing systems for providing synchronization between experimental pump lasers and the x-ray pulse, and beamline design for maintaining nm-scale density modulation.
Date: June 29, 2004
Creator: Corlett, J.N.; Barletta, W.A.; DeSantis, S.; Doolittle, L.; Fawley, W.M.; Heimann, P. et al.
Partner: UNT Libraries Government Documents Department

An aberration corrected photoemission electron microscope at the advanced light source

Description: Design of a new aberration corrected Photoemission electron microscope PEEM3 at the Advanced Light Source is outlined. PEEM3 will be installed on an elliptically polarized undulator beamline and will be used for the study of complex materials at high spatial and spectral resolution. The critical components of PEEM3 are the electron mirror aberration corrector and aberration-free magnetic beam separator. The models to calculate the optical properties of the electron mirror are discussed. The goal of the PEEM3 project is to achieve the highest possible transmission of the system at resolutions comparable to our present PEEM2 system (50 nm) and to enable significantly higher resolution, albeit at the sacrifice of intensity. We have left open the possibility to add an energy filter at a later date, if it becomes necessary driven by scientific need to improve the resolution further.
Date: November 1, 2003
Creator: Feng, J.; MacDowell, A.A.; Duarte, R.; Doran, A.; Forest, E.; Kelez, N. et al.
Partner: UNT Libraries Government Documents Department

A recirculating linac-based facility for ultrafast X-ray science

Description: We present an updated design for a proposed source of ultra-fast synchrotron radiation pulses based on a recirculating superconducting linac, in particular the incorporation of EUV and soft x-ray production. The project has been named LUX - Linac-based Ultrafast X-ray facility. The source produces intense x-ray pulses with duration of 10-100 fs at a 10 kHz repetition rate, with synchronization of 10 s fs, optimized for the study of ultra-fast dynamics. The photon range covers the EUV to hard x-ray spectrum by use of seeded harmonic generation in undulators, and a specialized technique for ultra-short-pulse photon production in the 1-10 keV range. High-brightness rf photocathodes produce electron bunches which are optimized either for coherent emission in free-electron lasers, or to provide a large x/y emittance ration and small vertical emittance which allows for manipulation to produce short-pulse hard x-rays. An injector linac accelerates the beam to 120 MeV, and is followed by four passes through a 600-720 MeV recirculating linac. We outline the major technical components of the proposed facility.
Date: May 6, 2003
Creator: Corlett, J.N; Barletta, W.A.; DeSantis, S.; Doolittle, L.; Fawley, W.M.; Green, M.A. et al.
Partner: UNT Libraries Government Documents Department