• N. Sereno, M. Borland, H. W. Friedsam
  ANL, Argonne, Illinois

In the recent past, the Advanced Photon Source (APS) was asked by the U. S. Department of Energy to explore a revolutionary upgrade based on emerging energy recovery linac (ERL) technology. In an ERL, the energy of the 7-GeV, 100-mA beam is recovered after the beam passes through user beamlines by decelerating the beam back through the same superconducting linac cavities that accelerated it. The main constraint on this upgrade is that the existing APS beamlines not be disturbed. This requires that the APS storage ring be used as a single-pass transport line in the overall ERL beamline layout. A natural place to locate the ERL is inside the existing APS storage ring ‘‘infield'' area, which has unoccupied space south of the existing APS injector complex. Other important constraints include minimal disturbance of existing building structures and injector beamlines. The existing injector complex would be preserved so that existing operation can be continued through and even possibly beyond ERL commissioning. In this paper, we describe a layout that satisfies these constraints. We also estimate the amount of emittance increase the beam will experience before ring injection.

• 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

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.

• N. Sereno, M. Borland
  ANL, Argonne, Illinois

In recent years, we have explored various upgrade options for the Advanced Photon Source (APS) storage ring that would provide the user community higher brightness. Increased brightness would be accomplished by reducing the emittance of the storage ring as well as increasing the stored beam current from 100 mA to 200 mA. Two upgrade lattices were developed that reduce the effective beam emittance to 1 nm from the present 2.7 nm. These lattices have reduced dynamic aperture compared to the present ring lattice, which may require a reduced emittance booster to minimize injection losses. This paper describes injection tracking simulations that explore how high the booster emittance can be and still have no losses at injection for the 1-nm ring upgrade lattices. An alternative booster lattice is presented with reduced emittance compared to the present booster lattice (65 nm). The proposed low-emittance booster lattice would add pole-face windings to the existing booster dipoles and hence would not require replacement of the existing booster magnets.

• R. M. Lill, L. H. Morrison, W. E. Norum, N. Sereno, G. J. Waldschmidt, D. R. Walters
  ANL, Argonne, Illinois
• S. Smith, T. Straumann
  SLAC, Menlo Park, California

In this paper we present the design of the beam position monitor (BPM) system for the LCLS undulator, which features a high resolution X-band cavity BPM. Each BPM has a TM010 monopole reference cavity and a TM110 dipole cavity designed to operate at a center frequency of 11.384 GHz. The signal processing electronics features a low-noise single-stage three-channel heterodyne receiver that has selectable gain and a phase locking local oscillator. We will discuss the system specifications, design, and prototype test results.

• A. H. Lumpkin, W. Berg, N. Sereno, B. X. Yang, C. Yao
  ANL, Argonne, Illinois
• D. W. Rule
  NSWC, West Bethesda, Maryland

We have investigated the angular distribution patterns (far-field focus) of optical transition radiation (OTR) and optical diffraction radiation (ODR) generated by 7-GeV electron beams passing through and near an Al metal plane, respectively. The 70-μrad opening angles of the OTR patterns provide calibration factors for the system. Effects of the upstream quadrupole focusing strength on the patterns as well as polarization effects were observed. The OTR data are compared to an existing OTR single-foil model, while ODR profile results are compared to expressions for single-edge diffraction. ODR was studied with impact parameters of about 1.25 mm, close to the gamma λ?bar value of 1.4 mm for 628-nm radiation. We expect angle-pointing information along the x axis parallel to the mirror edge is available from the single-lobe ODR data as well as divergence information at the sub-100-μrad level. Experimental and model results will be presented.