• W. Gai, M. Borland, K.-J. Kim, W. Liu, A. Xiao
  ANL, Argonne
• J. Sheppard
  SLAC, Menlo Park, California

Funding: This work was supported by the US Department of Energy Office of Science under Contract No. DE-AC02-06CH11357.

The effect of ILC positron source’s helical undulator to the drive electron beam is of great interest. People have been looking into the effect of wakefield, quad misalignment and also the effect of radiation. In this paper we’ll report an emittance damping effect of the ILC positron source undulator to the drive electron beam and our QUAD-BPM error simulation results. For 100m RDR undulator, the emittance of drive electron beam will be damped down by about 1% instead of growing as the damping is stronger than quantum excitation for this RDR undulator with the RDR drive electron beam. Quad-BPM misalignment simulations show that a 20um rms misalignment error in a 250m long undulator beamline can cause about 5% emittance growth in drive electron beam. Taking into consider the damping effect of undulator, the net emittance growth will be smaller.

• A. Xiao, M. Borland
  ANL, Argonne

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

A high-brightness electron beam used for linac-based fourth-generation light sources such as X-ray free-electron lasers (FELs) and energy recovery linacs (ERLs) is often non-Gaussian distributed especially in the longitudinal direction. In order to study the intra-beam scattering effect (IBS) in such a beam, we added a slice analysis method to elegant. This paper explains this method and an application result to a possible ERL upgrade of the Advanced Photon Source.

• L. Emery, M. Borland, V. Sajaev, A. Xiao
  ANL, Argonne

Funding: This work was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CHlI357.

During an operating period in which a sextupole unknowingly connected with the wrong polarity resulted in reduced beam lifetime, a list of machine physics experiments and simulations were developed to identify possible gradient errors of one or more sextupole magnets. We tried tune dependence on orbit, response matrix measurements at different momenta, sector-wise chromaticity measurements, empirical search with sextupole harmonics, and guidance from tracking simulations. The practicality of each will be discussed.

• M. Borland, L. Emery, V. Sajaev, A. Xiao
  ANL, Argonne

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Optimization of dynamic and momentum aperture is one of the most challenging problems in storage ring design. For storage-ring-based x-ray sources, large dynamic aperture is sought primarily to obtain high injection efficiency, which is important in efficient operation but also in protecting components from radiation damage. X-ray sources require large momentum aperture in order to achieve workable Touschek lifetimes with low emittance beams. The most widely applied method of optimizing these apertures is to minimize the driving terms of various resonances. This approach is highly successful, but since it is based on perturbation theory, it is not guaranteed to give the best result. In addition, the user must somewhat arbitrarily assign weights to the various terms. We have developed several more direct methods of optimizing dynamic and momentum aperture. These have been successfully applied to operational and design problems related to the Advanced Photon Source and possible upgrades.