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Wan, W.

Paper Title Page
TUPMN111 A Low Emittance Lattice for the Advanced Light Source 1170
 
  • H. Nishimura, S. Marks, D. Robin, D. Schlueter, C. Steier, W. Wan
    LBNL, Berkeley, California
 
  Funding: Work supported by the U. S. Department of Energy under Contract No. DE-AC03-76SF00098

The possibility exists of achieving significantly lower emittances in an electron storage ring by increasing its horizontal betatron tune. However, existing magnet locations and strengths in a given ring may be inadequate to implement such an operational mode. For example, the ALS storage ring could lower its emittance to one third of the current value by increasing the horizontal tune from 14.25 to 16.25. However, this would come with the cost of large chromaticities that could not be corrected with our existing sextupole magnets. We discuss such operational issues and possible options in this paper.

 
TUPMN112 ALS Top-off Simulation Studies for Radiation Safety 1173
 
  • H. Nishimura, R. J. Donahue, R. M. Duarte, D. Robin, F. Sannibale, C. Steier, W. Wan
    LBNL, Berkeley, California
 
  Funding: Work supported by the U. S. Department of Energy under Contract No. DE-AC03-76SF00098

We plan to commission top-off injection at the Advanced Light Source in the near future. In order to guarantee radiation safety, we have been simulating the injection process to exclude the possibility of injected electrons traveling down the user's photon beam lines. As the final stage of our simulation study, we use photon beam line CAD drawings to define the beam line's aperture in the phase space which electrons must not enter. Then we virtually inject electrons from within these phase spaces backwards into the storage ring to prove that such electrons can never get back to the real injection point under any possible scenario. This paper summarizes such inverse tracking studies.

 
TUPMN116 Numerical Study of Coulomb Scattering Effects on Electron Beam from a Nano-tip 1185
 
  • J. Qiang, J. N. Corlett, S. M. Lidia, H. A. Padmore, W. Wan, A. Zholents, M. S. Zolotorev
    LBNL, Berkeley, California
  • A. Adelmann
    PSI, Villigen
 
  Funding: This work was supported by the U. S. Department of Energy under Contract no. DE-AC02-05CH11231.

Nano-tips with high acceleration gradient around the emission surface have been proposed to generate high brightness beams. However, due to the small size of the tip, the charge density near the tip is very high even for a small number of electrons. The Coulomb scattering near the tip can significantly degrade the beam quality and cause extra emittance growth and energy spread. In the paper, we present a numerical study of these effects using a direct relativistic N-body model. We found that emittance growth and energy spread, due to Coulomb scattering, can be significantly enhanced with respect to mean-field space-charge calculations in different parameter regimes.

 
TUPMN117 Exploring the Limits of the ALS Triple Bend Lattice 1188
 
  • D. Robin, W. Wan
    LBNL, Berkeley, California
 
  Funding: Work supported by the U. S. Department of Energy under Contract No. DE-AC03-76SF00098

The triple bend achromat cell of the ALS has been shown to be very flexible and compact. It has been operated in a low emittance mode and a low momentum compaction mode. In fact the lattice can be operated in a large range of different stable modes. Until recently most of these recently discovered modes had not been explored or even known about. Many of these modes have potentially attractive features as compared with the present operational mode. In this paper we take a step back and look at the general stability limits of the lattice. We employ a technique we call GLASS that allows us to rapidly scan and find all possible stable modes and then characterize their associated properties. In this paper we illustrate how the GLASS technique gives a global and comprehensive vision of the capabilities of the lattice.

 
TUPMS002 Successful Completion of the Femtosecond Slicing Upgrade at the ALS 1194
 
  • C. Steier, P. A. Heimann, S. Marks, D. Robin, R. W. Schoenlein, W. Wan
    LBNL, Berkeley, California
  • W. Wittmer
    SLAC, Menlo Park, California
 
  Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.

An upgraded femtosecond slicing facility has been commissioned successfully at the Advanced Light Source. In contrast to the original facility at the ALS which pioneered the concept, the new beamline uses an undulator (the first in-vacuum undulator at the ALS) as the radiator producing the user photon beam. To spatially separate the femtosecond slices in the radiator, a local vertical dispersion bump produced with 12 skew quadrupoles is used. The facility was successfully commissioned during the last 1.5 years and is now used in routine operation.

 
TUPMN109 A High Repetition Rate VUV-Soft X-Ray FEL Concept 1167
 
  • J. N. Corlett, J. M. Byrd, W. M. Fawley, M. Gullans, D. Li, S. M. Lidia, H. A. Padmore, G. Penn, I. V. Pogorelov, J. Qiang, D. Robin, F. Sannibale, J. W. Staples, C. Steier, M. Venturini, S. P. Virostek, W. Wan, R. P. Wells, R. B. Wilcox, J. S. Wurtele, A. Zholents
    LBNL, Berkeley, California
 
  Funding: This work was supported by the Director, Office of Science, High Energy Physics, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.

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, and wavelength; utilization of harmonics to attain shorter wavelengths; and precise synchronization of the x-ray pulse with 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 FELs, each producing high average brightness, tunable over the soft x-ray-VUV range, and each with individual performance characteristics determined by the configuration of the FEL SASE, enhanced-SASE (ESASE), seeded, self-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. FELs would be tailored to specific experimental needs, including production of ultrafast pulses even into the attosecond domain, and high temporal coherence (i.e. high resolving power) beams.

 
FRPMS022 Progress on Modeling of Ultrafast X-Ray Streak Cameras 3961
 
  • G. Huang, J. M. Byrd, J. Feng, J. Qiang, W. Wan
    LBNL, Berkeley, California
 
  Streak cameras continue to be useful tools for studying ultra phenomena on the sub-picosecond time scale and beyond. We have employed accelerator modeling tools to understand the key parts of the streak camera in order to improve the time resolution. This effort has resulted in an start-to-end model of the camera including a dedicated 3D modeling of time-dependent fields. This model has contributed to the recent achievement of 230 fsec (FWHM) resolution measured using 266 nm laserat the Advanced Light Source Streak Camera Laboratory. We will report on our model and its comparison with experiments. We also extrapolate the performance of this camera including several possible improvements.