• H. Toyokawa
  
• H. Ikeura-Sekiguchi, M. K. Koike, R. Kuroda, H. Ogawa, N. Sei, M. Tanaka, K. Y. Yamada, M. Y. Yasumoto
  AIST, Tsukuba, Ibaraki
• T. Nakajyo, F. Sakai, T. Y. Yanagida
  SHI, Tokyo

• J.-M. Lagniel
  

• K. C.D. Chan
  
• A. J. Jason, P. J. Turchi
  LANL, Los Alamos, New Mexico

For national security, it is important to detect the presence of Special Nuclear Materials (SNM), especially Highly-Enriched Uranium (HEU). Generally used methods for such detection include interrogation by photons and neutrons. For example, photofission in HEU can be initiated with 14-MeV photons. The resulting delayed neutrons and photons from the fission fragments are clear signatures of the presence of HEU. One can generate high-energy photons using electron accelerators via various mechanisms. In this paper, we will describe two of them, namely electron bremsstrahlung and Compton-backscattered photons. We focus on these two mechanisms because they cover a wide range of accelerator requirements. Electron bremsstrahlung can be generated using a compact low-energy electron linac while the generation of Compton-backscattered photons requires a high-energy electron accelerator of a few hundred MeV. We review these two options, describe their accelerator requirements, and compare their relative merits.

• M. Lonza
  
• D. Bulfone, V. Forchi', G. Gaio
  ELETTRA, Basovizza, Trieste

• T. Takahashi
  
• M. Izawa, S. Sakanaka, K. Umemori
  KEK, Ibaraki
• H. Suzuki, J. Watanabe
  Toshiba, Yokohama

• H.-S. Kang
  
• J. Choi, K. M. Ha, E.-H. Lee, W. W. Lee, I. S. Park
  PAL, Pohang, Kyungbuk

• N. P. Di Monte
  

The P0 Feedback System is a new design at the APS with the main intent to stabilize a single bunch in order to operate at a higher accumulated charge. The algorithm for this project required a high-speed DSP solution for a single channel that would make adjustments on a turn-by-turn basis. An FPGA solution was selected that not only met the requirements of the project, but far exceeded the requirements. By using a single FPGA, we were able to adjust up to 324 bunches on two separate channels with a total computational time of ~6x10⁹ multiply-accumulate operations per second. The IOC is a Coldfire CPU tightly coupled to the FPGA, providing a dedicated control and monitoring of the system through EPICS process variables. One of the benefits of this configuration is having a four-channel scope in the FPGA that can be monitored on a continuous basis.

• S. Marks
  
• K. Kennedy, D. W. Plate, D. Schlueter, M. S. Zisman
  LBNL, Berkeley, California

The positron and electron damping rings for the ILC (International Linear Collider) will contain long straight sections consisting of twenty wiggler/quadrupole pairs. The wigglers will be based upon the CESR-C superconducting design* . There are a number of challenges associated with the design of the wiggler straight vacuum system, in particular, the absorption of photon power generated by the wigglers. This paper will present the overall conceptual design of the wiggler straight vacuum system developed for the ILC RDR. Particular emphasis will be placed on photon power load calculations and the absorber design.

* A. Mihailichenko, Optimized Wiggler Magnet for CESR, Proceedings of PAC2001, Chicago, Il, June 18-22, 2001

• P. Chen
  
• M. Lundquist, R. Yi, D. Yu
  DULY Research Inc., Rancho Palos Verdes, California

High-gradient electron guns can suppress space-charge induced transverse emittance growth when the electron beam is still in the low-energy injection stage. A synchronizable, high-voltage pulser can be used to power up a high-gradient gun. We propose to build a 200 kV pulser using a special trigger that utilizes a laser-photocathode sub-system. A laser trigger beam will first energize a spark gap, and then provide a second trigger signal from a photocathode using its leftover energy, to further close the gap. This system will not only raise the utilization efficiency of the laser beam energy, but also enhance the reliability of the trigger circuit. Our preliminary analysis shows that the proposed system will significantly improve the performance of the laser trigger pulse with the jitter on the order of hundreds of picoseconds. It is expected that the pulser can be used in the applications of high gradient guns as well as in other devices that need high precision trigger such as short pulse lasers, streak cameras, impulse radiating antennas, etc.

• T. Quast
  
• A. Firsov, K. Holldack
  BESSY GmbH, Berlin
• S. Khan
  Uni HH, Hamburg
• R. Mitzner
  Universität Muenster, Physikalisches Institut, Muenster

• G. Gatti
  
• L. Cultrera, F. Tazzioli
  INFN/LNF, Frascati (Roma)
• J. Moody, P. Musumeci
  UCLA, Los Angeles, California
• A. Perrone
  INFN-Lecce, Lecce

• G. Gatti
  
• A. M. Cook, J. B. Rosenzweig, R. Tikhoplav
  UCLA, Los Angeles, California

• Y. Kobayashi
  
• S. Asaoka, W. X. Cheng, K. Haga, K. Harada, T. Honda, T. Ieiri, S. Isagawa, M. Izawa, T. Kageyama, T. Kasuga, M. Kikuchi, K. Kudo, H. Maezawa, A. Mishina, T. Mitsuhashi, T. Miyajima, H. Miyauchi, S. Nagahashi, T. T. Nakamura, H. Nakanishi, T. Nogami, T. Obina, K. Oide, M. Ono, T. Ozaki, C. O. Pak, H. Sakai, Y. Sakamoto, S. Sakanaka, H. Sasaki, Y. Sato, T. Shioya, M. Tadano, T. Takahashi, S. Takasaki, Y. Tanimoto, M. Tejima, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, S. Yamamoto, Ma. Yoshida, S. I. Yoshimoto
  KEK, Ibaraki

• H. Toyokawa
  
• R. Kuroda
  AIST, Tsukuba, Ibaraki
• H. Ohgaki
  Kyoto IAE, Kyoto

• T. Gowa
  
• H. Hayano, J. Urakawa
  KEK, Ibaraki
• Y. Kamiya, A. Masuda, R. Moriyama, K. Sakaue, M. Washio
  RISE, Tokyo
• S. Kashiwagi
  ISIR, Osaka
• R. Kuroda
  AIST, Tsukuba, Ibaraki
• K. U. Ushida
  RIKEN, Saitama

At Waseda University, we have succeeded in generating soft X-rays based on laser Compton scattering. The energies are within "Water Window" part (250~500eV) where the X-ray absorption coefficient of water is much less than that of constituent elements of living body such as carbon, hydrogen and nitrogen. For this reason, it is expected to apply to a bio-microscope with which we can observe living cells without dehydration. To improve the generation system, we remodeled our collision chamber and adopted 3-pass flash lamp amplifier system. With these modifications, we achieved high S/N ratio. The photon number detected by MCP was 278/pulse, tenfold increase of that in last year. Moreover, we succeeded in generating soft X-rays stably for more than 10 hours. Now we are planning to measure two-dimensional distribution of the X-rays by CCD. In this conference, experimental results and future plans will be reported.

• K. Sakaue
  
• S. Araki, M. K. Fukuda, Y. Higashi, Y. Honda, T. Taniguchi, N. Terunuma, J. Urakawa
  KEK, Ibaraki
• N. Sasao, H. Yokoyama
  Kyoto University, Kyoto
• M. Takano
  Tsukuba-shi, Ibaraki-ken
• M. Washio
  RISE, Tokyo

• R. Kuroda
  
• T. Gowa, Y. Kamiya, A. Masuda, R. Moriyama, K. Sakaue, M. Washio
  RISE, Tokyo
• S. Kashiwagi
  ISIR, Osaka
• M. K. Koike, H. Ogawa, N. Sei, H. Toyokawa, K. Y. Yamada, M. Y. Yasumoto
  AIST, Tsukuba, Ibaraki
• T. Nakajyo, F. Sakai, T. Y. Yanagida
  SHI, Tokyo

• C.-S. Hwang
  
• C.-H. Chang, M.-H. Huang, P. H. Lin
  NSRRC, Hsinchu

• C.-S. Hwang
  

• M. Borland
  
• G. Decker, A. Nassiri, M. White
  ANL, Argonne, Illinois

The Advanced Photon Source (APS) is a 7-GeV storage ring light source that has been in operation for over a decade. In order to make revolutionary improvements in the performance of the existing APS ring, we are exploring the addition of a 7-GeV energy recovery linac (ERL) to the APS complex. In this paper, we show the possible configuration of such a system, taking into account details of the APS site and the requirement that stored beam capability be preserved. We exhibit a possible configuration for the single-pass, 7-GeV linac. We discuss optical solutions for transport from 10 MeV to 7 GeV and back, including a large turn-around arc that would support 48 additional user beamlines. Tracking results are shown that include incoherent and coherent synchrotron radiation, resulting in predictions of the beamline performance.

• 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.

• R. J. Dejus
  
• I. Vasserman
  ANL, Argonne, Illinois

Two full-length 2.4-m-long undulators, with period lengths 2.3 cm and 2.7 cm, were recently installed in tandem in the 5.6-m-long straight on the storage ring in sector 14. One part of the user research program requires that both undulators be tuned to 12.0 keV and the x-ray intensity maximized. The total intensity is sensitive to the phasing between the undulators, so the distance between the devices must be optimized and the ends tuned appropriately. Because of the different period lengths, the gaps and K values of the undulators will be different: 10.6-mm gap and a K value of 1.17 for the shorter-period device and 15.7-mm gap and a K value of 0.93 for the longer-period device. A special shield was designed and installed between the devices to eliminate interference. Results of magnetic measurements, tuning, and computer simulations of the spectral performance are presented.

• W. Guo
  
• M. Borland, K. C. Harkay, C.-X. Wang, B. X. Yang
  ANL, Argonne, Illinois

• E. Trakhtenberg
  
• T. Barsz, P. K. Den Hartog, G. S. Lawrence, E. R. Moog, S. Sasaki, I. Vasserman, M. White
  ANL, Argonne, Illinois
• T. Becker, S. Dufresne, W. Kummerle, R. Schuermann
  Metalex Manufacturing, Cincinnati, Ohio
• G. Goldfarb, N. Lagonsky, S. Lagonsky, S. Sorsher
  Hi-Tech Manufacturing, Schiller Park, Illinois

Design and construction of the undulators for the Linac Coherent Light Source (LCLS) is the responsibility of Argonne National Laboratory. A prototype undulator* was constructed in-house and was extensively tested. The device was tunable to well within the LCLS requirements and was stable over a period of several years. Experience constructing the prototype undulator led us to conclude that with appropriate engineering design and detailed assembly procedures, precision undulators can be constructed by qualified vendors without previous undulator-construction experience. Our detailed technological knowledge and experience were transferred to the successful bidders who have produced outstanding undulators. Our production concept for the 40 3.4 m long, fixed-gap, planar-hybrid undulators with a 30 mm period is presented. Manufacturing, quality assurance, and acceptance testing details are also presented.

*LCLS Prototype Undulator Report, Argonne National Laboratory Report ANL/APS/TB-48, January 2004, R. Dejus, Editor.

• B. X. Yang
  
• E. M. Dufresne, E. C. Landahl, A. H. Lumpkin
  ANL, Argonne, Illinois

A short x-ray pulse source based on the crab cavity scheme proposed by Zholents* is being developed at the Advanced Photon Source (APS). Photon diagnostics that visualizes the electron bunches with transverse momentum chirp and verifies the performance of the short x-ray pulse is required. We present a design study for the imaging diagnostics inside and outside of the crab cavity zone, utilizing both x-ray and visible synchrotron radiation. Several design options of monochromatic and polychromatic x-ray optics will be explored for their compatibility with the short-pulse source. The diagnostics outside of the crab cavity zone will be used to map out stable operation parameters of the storage ring with crab cavities, and to perform single-bunch single-pass imaging of the chirped bunch, which facilitates the tuning of the crab cavity rf phase and amplitude so the performance of the short pulse source can be optimized while other users around the ring will not be disturbed.

* A. Zholents et al., NIM A 425, 385 (1999).

• 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

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.

• H. Nishimura
  
• R. J. Donahue, R. M. Duarte, D. Robin, F. Sannibale, C. Steier, W. Wan
  LBNL, Berkeley, California

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.

• D. J. Gibson
  
• S. G. Anderson, C. P.J. Barty, S. M. Betts, F. V. Hartemann, I. Jovanovic, D. P. McNabb, M. J. Messerly, J. A. Pruet, M. Shverdin, C. Siders, A. M. Tremaine
  LLNL, Livermore, California

Thomson-Scattering based systems offer a path to high-brightness high-energy (> 1 MeV) x-ray & gamma-ray sources due to their favorable scaling with electron energy. LLNL is currently engaged in an effort to optimize such a device, dubbed the "Thomson-Radiated Extreme X-Ray" (T-REX) source, targeting up to 680 keV photon energy. Such a system requires precise design of the interaction between a high-intensity laser pulse and a high-brightness electron beam. Presented here are the optimal design parameters for such an interaction, including factors such as the collision angle, focal spot size, optimal bunch charge and laser intensity, pulse duration, and laser beam path. These parameters were chosen based on extensive modelling using PARMELA and in-house, well-benchmarked scattering simulation codes. Also discussed are early experimental results from the newly commissioned system.

• J. Bisognano
  
• R. A. Bosch, M. A. Green, H. Hoechst, K. Jacobs, K. J. Kleman, R. A. Legg, R. Reininger, R. Wehlitz
  UW-Madison/SRC, Madison, Wisconsin
• J. Chen, W. Graves, F. X. Kaertner, J. Kim, D. E. Moncton
  MIT, Cambridge, Massachusetts

The University of Wisconsin-Madison and its partners are developing a design for an FEL operating in the UV to soft x-ray range that will be proposed as a new multidisciplinary user facility. Key features of this facility include seeded, fully coherent output with tunable photon energy and polarization over the range 5 eV to 1240 eV, and simultaneous, independent operation of multiple beamlines. The different beamlines will support a wide range of science from femto-chemistry requiring ultrashort pulses with kHz repetition rates to photoemission and spectroscopy requiring high average flux and narrow bandwidth at MHz rates. The facility will take advantage of the flexibility, stability, and high average pulse rates available from a CW superconducting linac driven by a photoinjector. This unique facility is expected to enable new science through ultra-high resolution in the time and frequency domains, as well as coherent imaging and nano-fabrication. This project is being developed through collaboration between the UW Synchrotron Radiation Center and MIT. We present an overview of the facility, including the motivating science, and its laser, accelerator, and experimental systems.

• J. A. Safranek
  
• W. J. Corbett, S. M. Gierman, R. O. Hettel, X. Huang, J. J. Sebek, A. Terebilo
  SLAC, Menlo Park, California

• M. G. Fedurin
  
• P. Mortazavi, J. B. Murphy, G. Rakowsky
  BNL, Upton, Long Island, New York

• W. Guo
  
• G. L. Carr, S. Krinsky, J. Rose
  BNL, Upton, Long Island, New York

A notable feature of the proposed National Synchrotron Light Source II is that the vertical emittance is close to the diffraction limit of 1 Angstrom. With such a small emittance, the brightness is strongly affected by the longitudinal parameters, such as the momentum spread. Various effects are discussed and tolerances on the longitudinal parameters will be given. The lower level RF feedback system will be designed based on these tolerances.

• K. Jensen
  
• D. W. Feldman, P. G. O'Shea
  UMD, College Park, Maryland
• N. A. Moody
  LANL, Los Alamos, New Mexico
• J. J. Petillo
  SAIC, Burlington, Massachusetts

A recently developed model* of the emittance and brightness of a photocathode based on the evaluation of the moments of the electron emission distribution function admits an analytical solution for the zero-field and zero-temperature asymptotic model. Here, the model has been extended to account for the critical modifications of temperature and field dependence, which are tied to material issues with the cathode. Temperature impacts the nature of scattering within the photoemitter material and therefore affects quantum efficiency significantly. Field changes the emission probability at the surface barrier, and is particularly important for low work function coatings, as occur for the cesiated surfaces characteristic of our controlled porosity dispenser photocathodes. Extensions of the theoretical models shall be given, followed by an analysis of their comparison with numerical simulations of the intrinsic emittance and brightness of a photocathode. The methodology is designed to facilitate the development of photoemission models into comprehensive particle-in-cell (PIC) codes to address issues otherwise not readily treated, e.g., variation in surface coverage and topology.

* K. L. Jensen, P. G. O'Shea, D. W. Feldman, and N. A. Moody, Applied Physics Letters 89, 224103 (2006).

• Y.-C. Chae
  

The Impedance Database is a standardized 3D computation of the wake potential generated by a high-intensity beam. The database concept is described and compared to analytical and model-based approaches. The talk will address the computational challenges introduced by tapers, collimators, and very short bunches. Finally, single-bunch instabilities are predicted through tracking and compared to measurements at the Advanced Photon Source and other accelerators.

• H. Burkhardt
  
• I. V. Agapov, G. A. Blair
  Royal Holloway, University of London, Surrey
• F. Jackson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• A. Latina, L. Neukermans, D. Schulte
  CERN, Geneva

Halo simulations and estimates are important for the design of future linear accelerators. We present simulations performed for the ILC and CLIC and compare these with semi-analytical estimates and other simulations.

• A. E. Grelick
  
• A. R. Cours, N. P. Di Monte, A. Nassiri, T. Smith, G. J. Waldschmidt
  ANL, Argonne, Illinois

The Phase I Advanced Photon Source Deflecting Cavity System for producing short X-ray pulses uses one multi-cell, S-band cavity to apply a deflecting voltage to the stored electron beam ahead of an undulator that supports a beamline utilizing short picosecond X-rays. Two additional multi-cell cavities are then used to cancel out the perturbation and redirect the electron beam along the path of its nominal orbit. The pulsed rf system driving the deflecting cavities is described. Design tradeoffs are discussed with emphasis on topology considerations and digital control loops making use of sampling technology in a manner consistent with the present state of the art.

• V. A. Dolgashev
  
• M. Borland, G. J. Waldschmidt
  ANL, Argonne, Illinois

• L. Deacon, G. A. Blair, S. T. Boogert, A. Bosco, L. Corner, L. Deacon, N. Delerue, F. Gannaway, D. F. Howell, V. Karataev, M. Newman, A. Reichold, R. Senanayake, R. Walczak
  JAI, Egham, Surrey
• A. Aryshev, H. Hayano, K. Kubo, N. Terunuma, J. Urakawa
  KEK, Ibaraki
• G. E. Boorman
  Royal Holloway, University of London, Surrey
• B. Foster
  OXFORDphysics, Oxford, Oxon

The ATF extraction line laser-wire (LW) aims to achieve a micron-scale laser spot size and to verify that micron-scale beam profile measurements can be performed at the International Linear Collider beam delivery system. Recent upgrades to the LW system are presented together with recent results including the first use of the LW as a beam diagnostic tool.

• T. Russo
  
• S. Bellavia, D. M. Gassner, P. Thieberger, D. Trbojevic, T. Tsang
  BNL, Upton, Long Island, New York

A hydrogen jet polarimeter was developed for the RHIC accelerator to improve the process of measuring polarization. Particle beams intersecting with gas molecules can produce light by the process known as luminescence. This light can then be focused, collected, and processed giving important information such as size, position, emittance, motion, and other parameters. The RHIC hydrogen jet polarimeter was modified in 2005 with specialized optics, vacuum windows, light transport, and camera system making it possible to monitor the luminescence produced by polarized protons intersecting the hydrogen beam. This paper will describe the configuration and preliminary measurements taken using the RHIC hydrogen jet polarimeter as a luminescence monitor.

• F. Sannibale
  
• D. Filippetto
  INFN/LNF, Frascati (Roma)
• G. V. Stupakov
  SLAC, Menlo Park, California
• M. S. Zolotorev
  LBNL, Berkeley, California

By analysing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and tested a simple scheme based on this principle that allows for the absolute measurement of the bunch length. A description of the method and the experimental results are presented.

• O. Dadoun
  
• P. Bambade
  LAL, Orsay

• A. Ushakov
  
• S. Riemann, A. Schaelicke
  DESY Zeuthen, Zeuthen

A positron source based on a helical undulator system is planned to be used for the future International Linear Collider (ILC). Depending on the accelerator design it will be possible to get polarized positrons at the interaction point. A source performance with high positron yield and high polarization is the aim of our design studies. We focus on the optimization of target and capture section using several simulation codes. FLUKA is a suitable tool to calculate the positron yield, heat deposition, neutron generation and induced activity of source parts. The ASTRA code is used to calculate positron capture efficiency into the optical matching device. The new release of Geant4 includes the spin dependence of all QED processes and allows to perform a helicity-dependent tracking of particles through target and capture section. Starting with a cross-check, the synergy of these three codes allowed to specify the the parameters of a polarized positron source.

• L. Auditore, L. Auditore, R. C. Barna, D. De Pasquale, D. Loria, A. Trifiro, M. Trimarchi
  Universita di Messina, Messina
• U. Emanuele, A. Italiano
  INFN - Gruppo Messina, S. Agata, Messina

• D. Sertore
  
• P. Michelato, L. Monaco, C. Pagani
  INFN/LASA, Segrate (MI)

Based on our experience on photocathode production, we present in this paper the results of the application of different optical diagnostic techniques on fresh and used photocathodes. These techniques allow to study effects like non uniformity, cathode aging, etc. In particular, photocathode optical parameters and QE characterization, both done at different wavelengths, give fundamentals information for the construction of a model of the photoemission process to be applied to Cs2Te photocathodes. These studies are useful for further improving key cathode features, such as its robustness and lifetime as well as to study and control the photocathodes thermal emittance.

• A. Ferrari
  

Strong beam-beam effects at the interaction point of a high-energy e⁺e^- linear collider such as CLIC lead to an emittance growth for the outgoing beams, as well as to the production of beamstrahlung photons and e⁺e^- coherent pairs. We present a conceptual design of the post-collision line for CLIC at 3 TeV, which separates the various components of the outgoing beam in a vertical magnetic chicane and then transports them to their respective dump.

• H. Aksakal
  
• A. K. Ciftci, Z. Nergiz
  Ankara University, Faculty of Sciences, Tandogan/Ankara
• D. Schulte, F. Zimmermann
  CERN, Geneva

• A. F. Hartin
  

Incoherent background pair production processes are studied with respect to full polarizations of all states. Real initial photon polarizations are obtained via a QED calculation of the beamstrahlung process. Virtual photon polarizations are related to the electric field of the colliding bunches at the point of pair production. An explicit expression for the virtual photon polarization vector is developed and found to have no circular polarization component. Pair polarization states are highly dependent on initial state circular polarization and are consequently produced almost unpolarized. The Breit-Wheeler cross-section with full polarizations is calculated and coded into the CAIN pair generator program. Numerical evaluations of the ILC operating in the seven proposed collider parameter sets shows that there are 10-20% less low energy pairs than previously thought. Collider luminosity as calculated by CAIN remains the same.

• I. Konkashbaev
  
• P. F. Fisher, A. Hassanein
  ANL, Argonne, Illinois
• N. V. Mokhov
  Fermilab, Batavia, Illinois

• W. Liu
  
• W. Gai, K.-J. Kim
  ANL, Argonne, Illinois

• W. D. Zacherl
  
• E. R. Colby, C. Mcguinness
  SLAC, Menlo Park, California
• T. Plettner
  Stanford University, Stanford, Califormia

The E163 laser acceleration experiments conducted at SLAC have stringent requirements on the temporal properties of two regeneratively amplified, 800nm, Spitfire laser systems. To determine the magnitude and cause of timing instabilities between the two Ti:Sapphire amplifiers, we pass the two beams through a cross-correlator and focus the combined beam onto a Hamamatsu G1117 photodiode. The photodiode has a bandgap such that single photon processes are suppressed and only the second order, two-photon process produces an observable response. The response is proportional to the square of the intensity. The diode is also useful as a diagnostic to determine the optimal configuration of the compression cavity.

Yoshihiro Takagi et al, 'Multiple- and Single-shot autocorrelator based on two-photon conductivity in semiconductors.' Optics Letters, Vol. 17, No. 9, May 1, 1992.

• I. Pogorelsky
  
• V. Yakimenko
  BNL, Upton, Long Island, New York

Compton interaction point incorporated into a high-average-power laser cavity is the key element of the Polarized Positron Source (PPS) concept proposed for ILC [1]. According to this proposal, circularly polarized gamma rays are produced in Compton backscattering from a 6 GeV linac e-beam inside a CO2 laser amplifier cavity. Intra-cavity positioning of the interaction point allows multiple laser recycling to match the electron bunch train format. We conducted experimental tests of multi-pulse operation of such active Compton cavity upon injection of a picosecond CO2 laser beam. Together with earlier demonstration of a high x-ray yield via the e-beam/CO2-laser backscattering, these new results show a viability of the entire PPS concept and closely prototype the laser source requirements for ILC.

[1] V. Yakimenko and I. V. Pogorelsky, Phys. Rev. ST Accel. Beams 9, 091001 (2006)

• A. Bacci
  
• V. Petrillo
  Universita' degli Studi di Milano, Milano
• A. R. Rossi, L. Serafini
  INFN-Milano, Milano

• M. Borland
  
• L. Emery, V. Sajaev
  ANL, Argonne, Illinois

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).

• W. R. Flavell
  

* e.g. J Andruszkow et al., Phys. Rev. Lett., 85, 3825, (2000).**e.g. G. R. Neil et al., Phys. Rev. Lett. 84, 662, (2000).*** e.g. H Wabnitz et al., Nature, 420, 467, (2002), T Laarmann et al., Phys. Rev. Lett., 95, 063402 (2005)

• S. Sakanaka
  
• T. Mitsuhashi, T. Obina
  KEK, Ibaraki

* S. Sakanaka, T. Mitsuhashi, and T. Obina, Phys. Rev. ST Accel. Beams 8, 042801 (2005).

• Y. Suetsugu
  
• H. Hisamatsu, K.-I. Kanazawa, K. Shibata
  KEK, Ibaraki

* Y. Suetsugu et al., NIM-PR-A, Vol.556 (2006) 399.

• D. Xiang
  
• W.-H. Huang
  TUB, Beijing

* Dao Xiang and Wen-Hui Huang, Nucl. Instr. and Meth. in Phys. Res. B, 254 (2007) 165.** Dao Xiang and Wen-Hui Huang, Nucl. Instr. and Meth. in Phys. Res. A, 570 (2007) 357.*** Dao Xiang and Wen-Hui Huang, Phys. Rev. ST-AB, 10 (2007) 012801.

• M. T. Price
  
• K. Balewski, Eckhard. Elsen, V. Gharibyan, H.-C. Lewin, F. Poirier, S. Schreiber, N. J. Walker, K. Wittenburg
  DESY, Hamburg
• G. A. Blair, S. T. Boogert, G. E. Boorman, A. Bosco, S. Malton
  Royal Holloway, University of London, Surrey
• T. Kamps
  BESSY GmbH, Berlin

The current PETRA II Laser-Wire system, being developed for the ILC and PETRA III, uses a piezo-driven mirror to scan laser light across an electron bunch. This paper reports on the recently installed electron-beam finding system, presenting recent horizontal and vertical profile scans with corresponding studies.

• Y.-C. Chae
  
• Y. Wang
  ANL, Argonne, Illinois

The first Impedance Database* constructed at the Advanced Photon Source was successfully used in reproducing the main characteristics of single-bunch instabilities observed in the storage ring. However, the finite bandwidth of the corresponding impedance model was limited to 25 GHz, which happens to be the resolution limit of the density modulation observed in the microwave instability simulation. In order to resolve simulation results never verified in the experiments, we decided to extend the calculated bandwidth of impedance to 50 GHz by recalculating the wake potentials excited by a shorter bunch. Since low-order electromagnetic code requires 20-40 grid points per wavelength, reducing the bunch length required a large number of grids for the 3D structure. We used bunch lengths of 1- and 2-mm in the Gaussian distribution in the Impedance Database II project. For the large-scale computation we used the 3D electromagnetic code GdfidL ** for wake potential calculation at the cluster equipped with 240 GB of memory. The resultant wake potential excited by the short bunch together with application to the storage ring for collective effects is presented in the paper.

* Y.-C. Chae, "The Impedance Database and Its Application to the APS Storage Ring" Proc. 2003 PAC, p. 3017.** http://www.gdfidl.de

• Y.-C. Chae
  
• V. A. Dolgashev
  SLAC, Menlo Park, California
• G. J. Waldschmidt
  ANL, Argonne, Illinois

In recent years we have explored the application to the Advanced Photon Source (APS) of Zholents' crab-cavity-based scheme for production of short x-ray pulses. As a near-term project, the APS has elected to pursue a pulsed system using room-temperature cavities*. The cavity design has been optimized to heavily damp parasitic modes while maintaining large shunt impedance for the deflecting dipole mode**. We evaluated a system consisting of three crab cavities as an impedance source and determined their effect on the single- and multi-bunch instabilities. In the single-bunch instability we used the APS impedance model as the reference system in order to predict the overall performance of the ring when the crab cavities are installed in the future. For multi-bunch instabilities we used a realistic fill pattern, including hybrid-fill, and tracked multiple bunches where each bunch was treated as soft in distribution. To verify the electrical design, the realistic wake potential of the 3D structure was calculated using GdfidL and this wake potential was used in the multi-bunch simulations.

* M. Borland et al., "Planned Use of Pulsed Crab Cavities at the APS for Short X-ray Pulse Generation," these proceedings.** V. Dolgashev et al., "RF Design of Normal Conducting Deflecting Structures for the APS," these proceedings.

• G. Decker
  
• P. K. Den Hartog, O. Singh
  ANL, Argonne, Illinois
• G. Rosenbaum
  UGA, Athens, Georgia

Long-term pointing stability at synchrotron light sources using conventional rf-based particle beam position monitoring is limited by the mechanical stability of the pickup electrode assembly. Photoemission-based photon beam position monitors for insertion device beams suffer from stray radiation backgrounds and other gap-dependent systematic errors. To achieve the goal of 500-nanoradian peak-to-peak pointing stability over a one-week period, the development of a photon beam position detector sensitive only to hard x-rays (> several keV) using copper x-ray fluorescence has been initiated. Initial results and future plans are presented.

• L. Emery
  

The short-pulse X-ray project at the Advanced Photon Source (APS) uses three room-temperature nine-cell 2.815 GHz deflecting-mode cavities in a straight section. Undamped, these cavities' higher-order and lower-order resonator modes will cause multi-bunch instabilities in longitudinal and transverse planes for any bunch pattern of a 1'000mA store. Damping of these modes must be part of the design of the cavities. We report calculations of instability growth rates and tracking simulations that were essential in specifying the rf design of the damping structures. We used various operating bunch patterns and scanned levels of damping of the cavities. Because one of the operating bunch patterns is not symmetric, we used a normal mode analysis * implemented in the APS code clinchor. Our calculation included random sampling of resonator frequencies in a reasonable range. We found that staggering of frequencies is only effective for modes that could not be heavily damped.

* K. Thompson and R. Ruth, PAC 1989

• W. E. Norum
  
• B. X. Yang
  ANL, Argonne, Illinois

Bunch purity is an important source quality factor for the magnetic resonance experiments at the Advanced Photon Source. Conventional bunch-purity monitors utilizing time-to-amplitude converters are subject to dead time. We present a novel design based on a single field-programmable gate array (FPGA) that continuously processes pulses at the full speed of the detector and front-end electronics. The FPGA provides 7778 single-channel analyzers (six per RF bucket). The starting time and width of each single-channel analyzer window can be set to a resolution of 178 ps. A detector pulse arriving inside the window of a single-channel analyzer is recorded in an associated 32-bit counter. The analyzer makes no contribution to the system dead time. Two channels for each RF bucket count pulses originating from the electrons in the bucket. The other four channels on the early and late side of the bucket provide estimates of the background. A single-chip microcontroller attached to the FPGA acts as an EPICS IOC to make the information in the FPGA available to the EPICS clients.

• S. E. Shoaf
  

A real-time image analysis system was developed for beam imaging diagnostics. An Apple Power Mac G5 with an Active Silicon LFG frame grabber were used to capture video images that were processed and analyzed. Software routines were created to utilize vector processing hardware to reduce the time to process images as compared to conventional methods. These improvements allow for more advanced image processing diagnostics to be performed in real time.

• X. Sun
  
• O. Singh
  ANL, Argonne, Illinois

The Advanced Photon Source storage ring employs a real-time orbit correction system to reduce orbit motion up to 50 Hz. This system uses up to 142 narrow-band rf beam position monitors (Nbbpms) in a correction algorithm by sampling at a frequency of 1.53 kHz. Several Nbbpms exhibit aliasing errors in orbit measurements, rendering these Nbbpms unusable in real-time orbit feedback. The aliasing errors are caused by beating effects of the internal sampling clocks with various other processing clocks residing within the BPM electronics. A programmable external clock has been employed to move the aliasing errors out of the active frequency band of the real-time feedback system (RTFB) and rms beam motion calculation. This paper discusses the process of tuning and provides test results.

• C. Yao
  
• A. H. Lumpkin
  ANL, Argonne, Illinois
• D. W. Rule
  NSWC, West Bethesda, Maryland

Interest in nonintercepting (NI) beam size monitoring for top-up operations at the Advanced Photon Source (APS) motivated our investigations of optical diffraction radiation (ODR) techniques. We have reported our experiment results earlier. In particular, we wanted to monitor the beam size in the booster-to-storage ring (BTS) transport line using near-field ODR. An analytical model was numerically evaluated for the APS BTS beam size cases. In addition, the simulations show that near-field ODR profiles have sensitivity to beam size in the 20- to 50-μm region, which are relevant to X-ray FELs and the international linear collider (ILC). The simulation indicates that the orthogonal polarization component is close to a Gaussian distribution and more sensitive to beam size variations, and therefore is more suitable for beam size measurement. Under some circumstances the parallel polarization component shows a non-Gaussian distribution that is also beam size dependent. This report describes the simulation method, the results, and the comparison with experiment results.

• T. J. Maxwell
  
• C. L. Bohn, D. Mihalcea, P. Piot
  Northern Illinois University, DeKalb, Illinois

Electrons impinging on a thin metallic foil are seen to deliver small bursts of transition radiation (TR) as they cross the boundary from one medium to the next. A popular diagnostic application is found for compact electron bunches. In this case they will emit radiation more or less coherently with an N-squared enhancement of the intensity on wavelengths comparable to the bunch size, generating coherent transition radiation (CTR). Several detailed analytical descriptions have been proposed for describing the resulting spectral distribution, often making different simplifying assumptions. Given that bunches tenths of millimeters long can generate measurable spectra into the millimeter range, concern may arise as to weak diffraction effects produced by optical interference devices containing elements with dimensions in the centimeter range. The work presented here is a report on an upcoming graduate thesis exploring these effects as they apply to the Fermilab/NICADD photoinjector laboratory using a minimal C++ code that implements the methods of virtual quanta and vector diffraction theory.

• C. Sun
  
• Y. K. Wu
  FEL/Duke University, Durham, North Carolina