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Robin, D.

Paper Title Page
MPPE074 Commissioning of a Locally Isochronous Lattice at ALS 3922
 
  • W. Wan, W.E. Byrne, H. Nishimura, G.J. Portmann, D. Robin, F. Sannibale, A. Zholents
    LBNL, Berkeley, California
 
  Funding: Work supported by the Director, Office of Energy Research, Office of Basic Energy Science, Material Sciences Division, U.S. Department of Energy, under Contract No. DE-AC03-76SF00098.

With the advance of ultrafast science, manipulating electron beam at the sub-micron and nanometer scale has been actively pursued. A special lattice of the ALS storage ring was conceived to studythe sub-micron longitudinal structure of the beam. It contains sections that are isochronous to the firstorder. Due to the practical constraints of the accelerator, sextupoles have to be off and the dispersion at the injection point is 60 cm, which make commissioning a highly nontrivial task. After a few months of tuning, we have been able to store at 30 mA of beam at the life time of 2 hours. After a brief introduction to the motivation of the experiment and the design of the lattice, the process and more detailed results of the commissioning will be presented. Future plan will also be discussed.

 
TPAT001 An Ultra-Bright Pulsed Electron Beam with Low Longitudinal Emittance 770
 
  • M.S. Zolotorev, E. D. Commins, P. Denes, Z. Hussain, G.V. Lebedev, S.M. Lidia, D. Robin, F. Sannibale, R.W. Schoenlein, R. A. Vogel, W. Wan
    LBNL, Berkeley, California
  • S.A. Heifets
    SLAC, Menlo Park, California
 
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

We describe a novel scheme for an electron source in the 10 - 100 eV range with the capability of approaching the brightness quantum-limit and of lowering the effective temperature of the electrons orders of magnitude with respect to existing sources. Such a device can open the way for a wide range of novel applications that utilize angstrom-scale spatial resolution and ?eV-scale energy resolution. Possible examples include electron microscopy, electron holography, and investigations of dynamics on a picosecond time scale using pump-probe techniques. In this paper we describe the concepts for such a source including a complete and consistent set of parameters for the construction of a real device based on the presented scheme.

 
WOAC008 Measuring and Understanding the Momentum Aperture in a Storage Ring 645
 
  • C. Steier, D. Robin
    LBNL, Berkeley, California
  • W. Decking
    DESY, Hamburg
  • J. Laskar
    IMCCE, Paris
  • L.S.N. Nadolski
    SOLEIL, Gif-sur-Yvette
  • Y.K. Wu
    DU/FEL, Durham, North Carolina
 
  Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-AC03-76SF00098.

The momentum aperture of a storage ring is a very important parameter that strongly influences the performance, especially the beam lifetime. For the special case of synchrotron light sources with small emittance like the Advanced Light Source (ALS), the momentum aperture depends strongly on the transverse dynamics. It is very sensitive to machine conditions such as the tunes, chromaticities, lattice symmetry, and spurious coupling, since depending on those conditions the Touschek scattered particles explore different resonance regions in the phase space. In light sources, the momentum aperture usually also depends strongly on the vertical physical aperture. Applying frequency analysis techniques in simulations and for turn-by-turn orbit measurement data provides a very powerful tool to measure and understand limitations of the dynamic momentum aperture. The techniques presented are applicable to other light sources, as well as damping rings and many types of colliders.

 
RPAE061 Beam Loss Simulation Studies for ALS Top-Off Operation 3532
 
  • H. Nishimura, R.J. Donahue, D. Robin, C. Steier
    LBNL, Berkeley, California
 
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

The ALS is planning to operate with top-off injection at higher beam currents and smaller vertical beam size. As part of a radiation safety study for top-off, we carried out two kinds of tracking studies: (1) to confirm that the injected beam cannot go into users’ photon beam lines, and (2) to control the location of beam dump when the storage ring RF is tripped. (1) is done by tracking electrons from a photon beam line to the injection sector inversely by including the magnetic field profiles, varying the field strength with geometric aperture limits to conclude that it is impossible. (2) is done by tracking an electron with radiation in the 6-dim space for different combinations of vertical scrapers for the realistic lattice with errors.

 
RPAE065 Generation of Picosecond X-Ray Pulses in the ALS Using RF Orbit Deflection 3659
 
  • D. Robin, J.M. Byrd, P. Fischer, P.A. Heimann, D.H. Kim, S. Kwiatkowski, D. Li, F. Sannibale, C. Steier, W. Wan, W. Wittmer, A. Zholents
    LBNL, Berkeley, California
 
  Funding: This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Sciences Division of the U.S. Department of Energy, under Contract No. DE-AC03-76SF00098.

A scheme is studied for producing ps length pulses of x-ray radiation from the Advanced Light Source (ALS) using two RF deflecting cavities. The cavities create vertical displacements of electrons correlated with their longitudinal position in the bunch. The two cavities separated by 180 degrees of vertical phase advance. This allows the vertical kick from one cavity to be compensated by the vertical kick of the other. The location of the cavities corresponds to the end of one straight section and the beginning of the following straight section. Halfway between the cavities a bending magnet source is located. The radiation from the bend can be compressed to ~1 ps in duration.

 
RPAE066 Terahertz Coherent Synchrotron Radiation from Femtosecond Laser Modulation of the Electron Beam at the Advanced Light Source 3682
 
  • J.M. Byrd, Z. Hao, M.C. Martin, D. Robin, F. Sannibale, R.W. Schoenlein, A. Zholents, M.S. Zolotorev
    LBNL, Berkeley, California
 
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

At the Advanced Light Source (ALS), the "femtoslicing" beamline is in operation since 1999 for the production of x-ray synchrotron radiation pulses with femtosecond duration. The mechanism used for generating the short x-ray pulses induces at the same time temporary structures in the electron bunch longitudinal distribution with very short characteristic length. Such structures emit intense coherent synchrotron radiation (CSR) in the terahertz frequency range. This CSR, whose measured intensity is routinely used as a diagnostics for the tune-up of the femtoslicing experiments, represents a potential source of terahertz radiation with very interesting features. Several measurements have been performed for its characterization and in this paper an updated description of the experimental results and of their interpretation is presented.

 
RPAE080 Diagnostic Systems Plan for the Advanced Light Source Top-Off Upgrade 4066
 
  • T. Scarvie, W. Barry, M.J. Chin, D. Robin, F. Sannibale, C. Steier
    LBNL, Berkeley, California
 
  Funding: This work was supported by the Director, Office of Energy Research, Office of Basic Energy Sciences, Materials Science Division, of the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

The Advanced Light Source (ALS) will soon be upgraded to enable top-off operation,* in which electrons are quasi-continuously injected to produce constant stored beam current. We will upgrade our injector from 1.5GeV to full-energy 1.9GeV, and top-off operation will also require more precise injector beam characterization and control than we are capable of using our current diagnostics system. Therefore, a diagnostics upgrade will be crucial for the success of top-off, and our plan for it is described in this paper. Among the improvements will be the integration of all existing beam current monitors along the accelerator chain into an injection efficiency monitoring application. New booster ring diagnostics will include a tune kick and monitoring system, updated beam position monitor electronics, and a new scraper. Two new synchrotron light monitors and a beam stop will be added to the booster-to-storage ring transfer line, and a dedicated bunch purity monitoring system will be installed in the storage ring. Together, these important diagnostic upgrades will enable smooth commissioning of the full energy injector and a quick transition to high quality top-off operation at the ALS.

*Please see the ALS Top-off Upgrade presentation at this conference.

 
RPAE082 The New Undulator Based fs-Slicing Beamline at the ALS 4096
 
  • C. Steier, D. Robin, F. Sannibale, R.W. Schoenlein, W. Wan, W. Wittmer, A. Zholents
    LBNL, Berkeley, California
 
  Funding: This work was supported by the U.S. Department of Energy, under Contract No. DE-AC03-76SF00098.

The existing Femtoslicing beamline at the ALS employs a femtosecond laser beam interacting resonantly with the electron beam in a wiggler (modulator). The induced energy spread over the femtosecond duration is converted to a transverse displacement by exploiting the storage ring dispersion. The displaced femtosecond pulse radiates and produces femtosecond synchrotron radiation. Up to now a regular bending magnet was used as radiator. To improve the flux, a significant upgrade was implemented, replacing the modulator, installing an in-vacuum undulator as new radiator, and installing a higher repeptition rate laser system. The new beamline will provide 100-200 fs long pulses of soft and hard x-rays with moderate flux and with a repetion rate of 10-40 kHz for experiments concerning ultrafast dynamics in solid state physics, chemistry and biology. To achieve the necessary spatial separation of the energy modulated slice from the rest of the bunch, a sizeable local vertical dispersion bump in the radiator is required. All accelerator physics aspects of the upgrade including challenging issues like the impact on the transverse single particle dynamics will be discussed together with initial results of the commissioning.