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Sajaev, V.

Paper Title Page
TUPMN091 Planned Use of Pulsed Crab Cavities for Short X-ray Pulse Generation at the Advanced Photon Source 1127
 
  • M. Borland, J. Carwardine, Y.-C. Chae, P. K. Den Hartog, L. Emery, K. C. Harkay, A. H. Lumpkin, A. Nassiri, V. Sajaev, N. Sereno, G. J. Waldschmidt, B. X. Yang
    ANL, Argonne, Illinois
  • V. A. Dolgashev
    SLAC, Menlo Park, California
 
  Funding: Work supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

In recent years, we have explored application to the Advanced Photon Source (APS) of Zholents'* crab-cavity-based scheme for production of short x-ray pulses. Work concentrated on using superconducting (SC) cavities in order to have a continuous stream of crabbed bunches and flexibility of operating modes. The challenges of the SC approach are related to the size, cost, and development time of the cavities and associated systems. A good case can be made for a pulsed system** using room-temperature cavities. APS has elected to pursue such a system in the near term, with the SC-based system planned for a later date. This paper describes the motivation for the pulsed system and gives an overview of the planned implementation and issues. Among these are overall configuration options and constraints, cavity design options, frequency choice, cavity design challenges, tolerances, instability issues, and diagnostics plans.

*A. Zholents et al., NIM A 425, 385 (1999).**P. Anfinrud, private communication.

 
TUPMN096 New Lattice Design for APS Storage Ring with Potential Tri-fold Increase of the Number of Insertion Devices 1139
 
  • V. Sajaev, M. Borland, A. Xiao
    ANL, Argonne, Illinois
 
  Funding: Work supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-06CH11357

APS has recently held a round of discussions on upgrade options for the APS storage ring. Several options were discussed that included both storage ring and energy-recovery linac options. Here we present a storage ring lattice that fits into the APS tunnel and has a number of significant improvements over the existing storage ring. The present APS lattice has 40-fold symmetry with each sector having one 5-m-long straight section for insertion device (ID) placement. Each sector also provides one beamline for radiation from the bending magnet. The upgrade lattice preserves locations of the existing insertion devices but provides for increased ID straight section length to accommodate 8-m-long insertion devices. This lattice also decreases emittance by a factor of two down to 1.6 nm rad. And last but not least, it provides two additional 2.1-m-long ID straight sections per sector with one of these straight sections being parallel to the existing bending magnet beamline. We also present dynamic aperture optimization, lifetime calculations, and other nonlinear-dynamics-related simulations.

 
THPAN089 Beam Dynamics, Performance, and Tolerances for Pulsed Crab Cavities at the Advanced Photon Source for Short X-ray Pulse Generation 3429
 
  • M. Borland, L. Emery, V. Sajaev
    ANL, Argonne, Illinois
 
  Funding: Work supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

The Advanced Photon Source (APS) has decided to implement a system using pulsed* crab cavities to produce short x-ray pulses using Zholents'** scheme. This paper describes beam dynamics issues related to implementation of this scheme in a single APS straight section. Modeling of the cavity is used to demonstrate that the deflection will be independent of transverse position in the cavity. Parameters and performance for a standard and lengthened APS straight section are shown. Finally, tolerances are discussed and obtained from tracking simulations.

* M. Borland et al., these proceedings.** A. Zholents et al., NIM A 425, 385 (1999).

 
THPAN096 A 1-nm Emittance Lattice for the Advanced Photon Source Storage Ring 3447
 
  • A. Xiao, M. Borland, V. Sajaev
    ANL, Argonne, Illinois
 
  Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

We present a triple-bend lattice design that uses the current APS tunnel. The new lattice has a 1 nm-rad effective emittance at 7 GeV. A forty-period symmetric optics is presented. For the benefit of some X-ray user experiments, an optics with four special straight sections of one-third the beam size of normal sections was investigated as well. The associated nonlinear optical difficulties are addressed and simulation results are presented.

 
FRPMN110 Transverse Multibunch Bursting Instability in the APS Storage Ring 4360
 
  • K. C. Harkay, V. Sajaev, B. X. Yang
    ANL, Argonne, Illinois
 
  Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

The horizontal bursting instability was first observed in a single bunch in the APS in 1998, soon after operation began. Above the instability threshold, the bursting is characterized by exponentially growing bunch centroid oscillations that saturate, then decay, repeating quasi-periodically. More recently, bursting was also observed with multiple bunches in both the horizontal and vertical planes, showing that this is not purely a single-bunch phenomenon. On the other hand, the multibunch instability threshold is strongly dependent on bunch spacing, and the dependence is markedly different for the two transverse planes. Depending on the bunch spacing, the bunch-to-bunch oscillations are sometimes coupled, sometimes not. In this paper, we discuss the threshold in terms of the chromaticity required to stabilize the beam. We present instability imaging data using a streak camera that shows the bunch-to-bunch oscillation phase, and turn-by-turn beam position histories that give the bursting time dependence for different bunch spacings. Finally, we discuss the machine impedance and measured tune shift with current.