• K. Oide
  
• T. Abe, K. Akai, M. Akemoto, A. Akiyama, A. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J. W. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, S. Hiramatsu, H. Hisamatsu, H. Honma, K. Hosoyama, T. Ieiri, N. Iida, H. Ikeda, M. Ikeda, S. Isagawa, H. Ishii, A. Kabe, E. Kadokura, T. Kageyama, K. Kakihara, E. Kako, S. Kamada, T. Kamitani, K.-I. Kanazawa, H. Katagiri, S. Kato, T. Kawamoto, S. Kazakov, M. Kikuchi, E. Kikutani, K. Kitagawa, H. Koiso, Y. Kojima, K. Komada, T. Kubo, K. Kudo, N. K. Kudo, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, S. Michizono, K. Mikawa, T. Mimashi, S. Mitsunobu, K. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T. T. Nakamura, H. Nakanishi, K. Nakao, S. Ninomiya, Y. Ogawa, K. Ohmi, Y. Ohnishi, S. Ohsawa, Y. Ohsawa, N. Ohuchi, M. Ono, T. Ozaki, K. Saito, H. Sakai, Y. Sakamoto, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, T. Sueno, M. Suetake, Y. Suetsugu, R. Sugahara, T. Sugimura, T. Suwada, O. Tajima, S. Takano, S. Takasaki, T. Takenaka, Y. Takeuchi, M. Tawada, M. Tejima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, Ma. Yoshida, M. Yoshida, S. I. Yoshimoto, K. Yoshino
  KEK, Ibaraki
• E. Perevedentsev, D. N. Shatilov
  BINP SB RAS, Novosibirsk

Work presented on behalf of the KEKB Accelerator Group.

• M. E. Biagini
  
• D. Alesini, D. Babusci, R. Boni, M. Boscolo, F. Bossi, B. Buonomo, A. Clozza, G. O. Delle Monache, T. Demma, G. Di Pirro, A. Drago, A. Gallo, S. Guiducci, C. Ligi, F. Marcellini, G. Mazzitelli, C. Milardi, F. Murtas, L. Pellegrino, M. A. Preger, L. Quintieri, P. Raimondi, R. Ricci, U. Rotundo, C. Sanelli, G. Sensolini, M. Serio, F. Sgamma, B. Spataro, A. Stecchi, A. Stella, S. Tomassini, C. Vaccarezza, M. Zobov
  INFN/LNF, Frascati (Roma)
• S. Bettoni
  CERN, Geneva
• I. Koop, E. Levichev, P. A. Piminov, D. N. Shatilov, V. V. Smaluk
  BINP SB RAS, Novosibirsk
• K. Ohmi
  KEK, Ibaraki

*DAPHNE Upgrade Team, "DAPHNE Upgrade for Siddharta run", DAPHNE Tech. Note G-68, LNF-INFN, Dec. 2006

• J. Rossbach
  

• R. J. Steinhagen
  
• A. Boccardi, M. Gasior, O. R. Jones, K. K. Kasinski
  CERN, Geneva

• M. Guinchard
  
• K. Artoos, A. Catinaccio, K. Kershaw, A. Onnela
  CERN, Geneva

• F. Z. Hsiao
  
• S.-H. Chang, W.-S. Chiou, H. C. Li, H. H. Tsai
  NSRRC, Hsinchu

• J. W. Staples
  
• J. M. Byrd, R. B. Wilcox
  LBNL, Berkeley, California

Long-term phase drifts of less than a femtosecond per hour have been demonstrated in a 2 km length of single-mode optical fiber, stabilized interferometrically at 1530 nm. Recent improvements include a wide-band phase detector that reduces the possibility of fringe jumping due to fast external perturbations of the fiber and locking of the master CW laser wavelength to a molecular absorption line. Mode-locked lasers may be synchronized using two wavelengths of the comb, multiplexed over one fiber, each wavelength individually interferometrically stabilized.

• C. H. Rivetta
  
• R. Akre, P. Cutino, J. C. Frisch, K. D. Kotturi
  SLAC, Menlo Park, California

The LCLC RF gun requires a water cooling thermal system to tune the resonance frequency of the cavity to 2856.03MHz. The RF system operates in pulsed mode with bursts of 2.5usec at a repetition rate of 30-120Hz. The thermal system operates in combination with the low-level RF system to set the operation point of the cavity. The Low-Level RF system controls the magnitude and phase of the cavity voltage and define slow signals to the thermal system. The thermal system operates by pre-heating / pre-cooling the water and mixing both channels to achieve the optimal temperature to control the cavity resonant frequency. The tune control of the RF gun include two systems with different dynamics. The dynamics of the thermal system is slow while the RF system is fast. Additionally, different actuators in the system present limits that introduce non-linearities to be taking into account during the start up process . Combining these characteristics, a controller is designed for the resulting hybrid system that allows convergence in large for all the operation conditions and achieve the performance in the magnitude and phase of the cavity voltage required around the operation point.

• V. P. Yakovlev
  
• J. L. Hirshfield
  Omega-P, Inc., New Haven, Connecticut
• A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• S. Kazakov
  KEK, Ibaraki
• E. Nenasheva
  Ceramics Ltd., St. Petersburg
• S. V. Shchelkunov
  Columbia University, New York

Fast, electrically-controlled ferroelectric RF vector modulators are under development for different accelerator applications in the frequency range 0.4 - 1.3 GHz. The exact design of a vector modulator depends on the electrical parameters of particular ferroelectric material to be used, namely its dielectric constant, loss tangent and tunability. The exact values of these parameters were unknown in this frequency domain for low loss BST material that is planned to be used. A special two-disc test cavity has been designed and built that allows direct measurements of these parameters for large (100 mm in diameter) ferroelectric rings that are to be used in vector modulators. The results of measurements are presented.

• V. P. Yakovlev
  
• J. L. Hirshfield
  Omega-P, Inc., New Haven, Connecticut
• A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• S. Kazakov
  KEK, Ibaraki
• E. Nenasheva
  Ceramics Ltd., St. Petersburg

A fast, electrically-controlled phase shifter is described with parameters suitable for operation with the SC acceleration structure of the electron cooling system of Relativistic Heavy Ion Collider (RHIC) at BNL. The phase shifter is a key element of the external RF vector modulator that is capable of fast tuning of the cavities against microphonics, Lorentz force and beam instabilities in a way that can possibly lead to an order of magnitude reduction in the required RF power. The phase shifter is based on a shortened low-impendence coaxial line with ferroelectric rings. The dielectric constant of the ferroelectric rings is altered by applying a 4.2 kV voltage that provides an RF phase shift from 0 to 180 deg.

• A. Grassellino
  
• J. K. Keung, F. M. Newcomer
  University of Pennsylvania, Philadelphia, Pennsylvania
• N. Lockyer
  TRIUMF, Vancouver

• P. He
  
• M. Anerella, S. Aydin, G. Ganetis, M. Harrison, A. K. Jain, B. Parker
  BNL, Upton, Long Island, New York

The conceptual design of compact superconducting magnets for the International Linear Collider final focus is presently under development at BNL. A primary concern in using superconducting quadrupoles is the potential for inducing additional vibrations from cryogenic operation. We have employed a Laser Doppler Vibrometer system to measure the vibrations at resolutions ~1 nm (at frequencies above ~8 Hz) in a spare RHIC quadrupole coldmass under cryogenic conditions. Some preliminary results of these studies were presented at the Nanobeam 2005 workshop*. These results were limited in resolution due to a rather large motion of the laser head itself. As a first step towards improving the measurement quality, an actively stabilized isolation table was used to reduce the motion of the laser holder. The improved set-up will be described, and vibration spectra measured at cryogenic temperatures, both with and without helium flow, will be presented.

*A. Jain, et al., Nanobeam 2005, Kyoto, Japan, Oct.17-21, 2005; paper WG2d-05; available at http://wwwal.kuicr.kyoto-u.ac.jp/NanoBM .

• M. Bai
  
• L. Ahrens, I. G. Alekseev, J. G. Alessi, J. Beebe-Wang, M. Blaskiewicz, A. Bravar, J. M. Brennan, K. A. Brown, D. Bruno, G. Bunce, J. J. Butler, P. Cameron, R. Connolly, T. D'Ottavio, J. DeLong, K. A. Drees, W. Fischer, G. Ganetis, C. J. Gardner, J. Glenn, T. Hayes, H.-C. Hseuh, H. Huang, P. Ingrassia, J. S. Laster, R. C. Lee, A. U. Luccio, Y. Luo, W. W. MacKay, Y. Makdisi, G. J. Marr, A. Marusic, G. T. McIntyre, R. J. Michnoff, C. Montag, J. Morris, P. Oddo, B. Oerter, J. Piacentino, F. C. Pilat, V. Ptitsyn, T. Roser, T. Satogata, K. Smith, S. Tepikian, D. Trbojevic, N. Tsoupas, J. E. Tuozzolo, M. Wilinski, A. Zaltsman, A. Zelenski, K. Zeno, S. Y. Zhang
  BNL, Upton, Long Island, New York
• D. Svirida
  ITEP, Moscow

The Relativistic Heavy Ion Collider~(RHIC) as the first high energy polarized proton collider was designed to provide polarized proton collisions at a maximum beam energy of 250GeV. It has been providing collisions at a beam energy of 100GeV since 2001. Equipped with two full Siberian snakes in each ring, polarization is preserved during the acceleration from injection to 100GeV with careful control of the betatron tunes and the vertical orbit distortions. However, the intrinsic spin resonances beyond 100GeV are about a factor of two stronger than those below 100GeV making it important to examine the impact of these strong intrinsic spin resonances on polarization survival and the tolerance for vertical orbit distortions. Polarized protons were accelerated to the record energy of 250GeV in RHIC with a polarization of 45\% measured at top energy in 2006. The polarization measurement as a function of beam energy also shows some polarization loss around 136GeV, the first strong intrinsic resonance above 100GeV. This paper presents the results and discusses the sensitivity of the polarization survival to orbit distortions.

• H. Huang
  
• L. Ahrens, M. Bai, K. A. Brown, C. J. Gardner, J. Glenn, F. Lin, A. U. Luccio, W. W. MacKay, T. Roser, S. Tepikian, N. Tsoupas, K. Yip, K. Zeno
  BNL, Upton, Long Island, New York

Dual partial snake scheme has provided polarized proton beams with 1.5*10¹¹ intensity and 65% polarization for RHIC spin program. To overcome the residual polarization loss due to horizontal resonances in the AGS, a new string of quadrupoles have been added. The horizontal tune can now be set in the spin tune gap generated by the two partial snakes, such that horizontal resonances are avoided. This paper presents the accelerator setup and preliminary results.

• B. Nash
  

• G. Franchetti
  

• T.-T. Yang
  
• C.-S. Fann, K. T. Hsu, S. Y. Hsu, J.-Y. Hwang, W. K. Lau, A. P. Lee, C. C. Liang, K.-K. Lin, K.-B. Liu, Y.-C. Liu, H. M. Shih, M.-S. Yeh
  NSRRC, Hsinchu

• G. J. Portmann
  
• K. M. Baptiste, W. Barry, J. Julian, S. Kwiatkowski, L. Low, D. W. Plate, D. Robin
  LBNL, Berkeley, California

Typically storage ring light sources operate with the maximum number of bunches as possible with a gap for ion clearing. By evenly distributing the beam current the overall beam lifetime is maximized. The Advanced Light Source (ALS) has 2 nanoseconds between the bunches and typically operates with 276 bunches out of a possible 328. For experimenters doing timing experiment this bunch separation is too small and would prefer to see only one or two bunches in the ring. In order to provide more flexible operations and substantially increase the amount of operating time for time-of-flight experimenters, it is being proposed to kick one bunch on a different vertical closed orbit. By spatially separating the light from this bunch from the main bunch train in the beamline, one could potentially have single bunch operation all year round. By putting this bunch in the middle of the ion clearing gap the required bandwidth of the kicker magnets is reduced. Using one kicker magnet running at the ring repetition rate (1.5 MHz), this bunch could be permanently put on a different closed orbit. Using multiple kicker magnets, this bunch could be locally offset at an arbitrary frequency.

• Y. Hao
  
• L.-H. Yu
  BNL, Upton, Long Island, New York

Quiet start scheme is broadly utilized in Self Amplified Spontaneous Radiation (SASE) FEL simulations, which is proven to be correct and efficient. Nevertheless, due to the existing of energy modulation effect and the dispersion section, the High Gain Harmonic Generation (HGHG) FEL simulation will not be improved by the traditional quiet start method. A new approach is presented to largely decrease the macro-particles per slice that can be implemented in both time-independent and time-dependent simulation, accordingly expedites the HGHG FEL simulation especially high order harmonic cascade case and makes the multi-parameter scanning be possible.

• A. France
  
• O. Delferriere, M. Desmons, O. Piquet
  CEA, Gif-sur-Yvette

• G. Stancari
  

On behalf of the Fermilab E835 Collaboration

• M. Zobov
  
• P. Raimondi
  INFN/LNF, Frascati (Roma)
• D. N. Shatilov
  BINP SB RAS, Novosibirsk

• Y. Funakoshi
  

• H. Koiso
  
• T. Abe, T. A. Agoh, K. Akai, M. Akemoto, A. Akiyama, A. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J. W. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, S. Hiramatsu, H. Hisamatsu, H. Honma, T. Honma, K. Hosoyama, T. Ieiri, N. Iida, H. Ikeda, M. Ikeda, S. Inagaki, S. Isagawa, H. Ishii, A. Kabe, E. Kadokura, T. Kageyama, K. Kakihara, E. Kako, S. Kamada, T. Kamitani, K.-I. Kanazawa, H. Katagiri, S. Kato, T. Kawamoto, S. Kazakov, M. Kikuchi, E. Kikutani, K. Kitagawa, Y. Kojima, I. Komada, T. Kubo, K. Kudo, N. K. Kudo, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, S. Michizono, K. Mikawa, T. Mimashi, S. Mitsunobu, K. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T. T. Nakamura, H. Nakanishi, K. Nakao, S. Ninomiya, Y. Ogawa, K. Ohmi, Y. Ohnishi, S. Ohsawa, Y. Ohsawa, N. Ohuchi, K. Oide, M. Ono, T. Ozaki, K. Saito, H. Sakai, Y. Sakamoto, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, T. Sueno, M. Suetake, Y. Suetsugu, R. Sugahara, T. Sugimura, T. Suwada, O. Tajima, S. Takano, S. Takasaki, T. Takenaka, Y. Takeuchi, M. Tawada, M. Tejima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, Ma. Yoshida, M. Yoshida, S. I. Yoshimoto, K. Yoshino
  KEK, Ibaraki
• E. Perevedentsev
  BINP SB RAS, Novosibirsk

For the KEKB Accelerator Group.

• K. Ohmi
  
• M. E. Biagini, P. Raimondi, M. Zobov
  INFN/LNF, Frascati (Roma)
• Y. Funakoshi
  KEK, Ibaraki

• A. Gomez Alonso
  
• R. Schmidt
  CERN, Geneva

• C. M. Warsop
  
• D. J. Adams, B. G. Pine
  STFC/RAL/ISIS, Chilton, Didcot, Oxon

• T. Sen
  
• J. A. Johnstone
  Fermilab, Batavia, Illinois

• V. D. Shiltsev
  
• T. Kroyer, R. de Maria
  CERN, Geneva

• L. Zhao
  
• B. Cluggish, J. S. Kim
  Far-Tech, Inc., San Diego, California

To model ECRIS, GEM is being extended to 2D by adding radial dimension. The electron distribution function (EDF) is calculated on each magnetic flux surface using a bounce-averaged Fokker-Planck code with 2D ECR heating (ECRH) modeling. The ion fluid model is also being extended to 2D by adding collisional radial transport terms. All species in ECRIS are balanced by keeping the neutrality in each cell and the plasma potential is calculated by maintaining the ambipolarity globally. The graphical user interface (GUI) and parallel computing ability of GEM make it an easy-to-use tool for ECRIS research. Numerical results and comparisons with experimental data will be presented.

• M. Bai
  
• A. U. Luccio, Y. Makdisi, P. H. Pile, T. Roser
  BNL, Upton, Long Island, New York

Full spin flip in the presence of full Siberian snake has been achieved by using an rf dipole or solenoid as spin flipper at IUCF and COSY. This technique requires one to change the snake configuration to move the spin tune away from half integer. However, this is not practical for an operational high energy polarized proton collider like RHIC where beam lifetime is sensitive to small betatron tune change. An new technique of achieving full spin flip with the spin tune staying at half integer is proposed. This paper presents the design of RHIC spin flipper along with simulation results.

• M. Bai
  
• P. Cameron, H. Huang, A. U. Luccio, V. Ptitsyn, T. Roser, S. Tepikian
  BNL, Upton, Long Island, New York

Snake depolarizing resonances due to the imperfect cancellation of the accumulated perturbations on the spin precession between snakes were observed at the Relativistic Heavy Ion Collider~(RHIC). During the RHIC 2005 and 2006 polarized proton runs, we mapped out the spectrum of odd order snake resonance at Q_y=7/10. Here, Q_y is the beam vertical betatron tune. We also studied the beam polarization after crossing the 7/10th resonance as a function of resonance crossing rate. This paper reports the measured resonance spectrum as well as the results of resonance crossing.

The work was performed under the US Department of Energy Contract No. DE-AC02-98CH1-886, and with support of RIKEN(Japan) and RenaissanceTechnologies C orp.(USA)

• C. Montag
  
• M. Bai, J. Beebe-Wang, M. Blaskiewicz, R. Calaga, W. Fischer, A. K. Jain, Y. Luo, N. Malitsky, T. Roser, S. Tepikian
  BNL, Upton, Long Island, New York

To achieve the RHIC polarized proton enhanced luminosity goal of 150*10³⁰ cm^-2 sec^-1 on average in stores at 250 GeV, the luminosity needs to be increased by a factor of 3 compared to what was achieved in 2006. Since the number of bunches is already at its maximum of 111, limited by the injection kickers and the experiments' time resolution, the luminosity can only be increased by either increasing the bunch intensity and/or reducing the beam emittance. This leads to a larger beam-beam tuneshift parameter. Operation during 2006 has shown that the beam-beam interaction is already dominating the luminosity lifetime. To overcome this limitation, a near-integer working point is under study. We will present recent results of these studies.

• S. Banna
  
• V. Berezovsky, L. Schachter
  Technion, Haifa

Franck and Hertz in 1914 were the first to demonstrate that free electrons can be decelerated by mercury atoms in discrete energy quanta. In 1930 Latyscheff and Leipunsky have demonstrated the inverse effect namely; free electrons can be accelerated by energy stored in the mercury atoms (collision of the second kind). It was only in 1958 that Townes has used multiple collisions between photons and excited atoms to amplify radiation (MASER & LASER). In 1995 Schachter suggested to use excited atoms for coherently accelerate particles. The results of a proof-of-principle experiment (2006) demonstrating the PASER scheme are reported here. Performed at the BNL-ATF, the essence of the experiment is to inject a 45MeV density modulated beam into an excited CO2 gas mixture. Resonance is insured by having the beam bunched by its interaction with a high-power CO2 laser pulse within a wiggler. The electrons experienced 0.15% relative change in their kinetic energy, in less than 40cm long interaction region. The experimental results indicate that a fraction of these electrons have gained 200keV each, implying that such an electron has undergone 2,000,000 collisions of the second kind.

• A. V. Burov
  
• V. A. Lebedev
  Fermilab, Batavia, Illinois

The more beam is cooled, the less stable it is. In the Recycler Ring, antiprotons are cooled both with stochastic and electron cooling. To stabilize it against the resistive wall instability, a digital damper is successfully used. Digital dampers can be described as linear operators with explicit time dependence, and that makes a principle difference with analogous dampers. Theoretical description of the digital dampers is presented. Electron cooling makes possible a two-beam instability of the cooled beam with the electron beam. Special features of this instability are described, and the remedy is discussed.

• R. Amirikas
  
• A. Bertolini, W. Bialowons
  DESY, Hamburg

In this presentation, we will report on a comprehensive vibration measurement program of a superconducting accelerating module designed for the European X-ray Free Electron Laser (XFEL), currently planned at DESY, at room temperature. This module is a type III, high gradient module which is also the basis of module design for the International Linear Collider (ILC). We will discuss stability within the vessel, for example, cold mass vs. He Gas Return Pipe (GRP), as well as stability along the length of the module. Results of this study may be used for the design of future XFEL/ILC module prototypes.

• T. Higo
  
• F. Furuta, Y. Higashi, T. Saeki, K. Saito, M. Satoh, H. Yamaoka
  KEK, Ibaraki

• A. Schnase
  
• S. Anami, E. Ezura, K. Hara, K. Hasegawa, C. Ohmori, A. Takagi, M. Toda, M. Yoshii
  KEK, Ibaraki
• M. Nomura, F. Tamura, M. Yamamoto
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

* C. Ohmori at. al, "High Field-Gradient Cavity for J-PARC 3 GeV RCS", PAC 2004

• Y. Iwashita
  
• H. Fujisawa, M. Ichikawa, Y. Tajima
  Kyoto ICR, Uji, Kyoto

• X. D. He
  
• S. Dong, Y. J. Pei, C.-F. Wu
  USTC/NSRL, Hefei, Anhui

We have developed the mathod to determine the permittivity and permeability of Kanthal alloy available. The alloy is coated on the inside walls of disk-loaded cavities,which is used for the collinear load. The collinear load absorbs the remaining rf-power over the last cells of the section while still accelerating the beam. Based on the experimental results of the permittivity and permeability,the computation study of the constant power-loss collinear load has been made by Microwave Studio. The design data about the S-band collinear load are present.

• C.-F. Wu
  
• S. Dong, X. D. He, H. Lin, L. Wang
  USTC/NSRL, Hefei, Anhui

Some model cavities have been further developed and investigated for a X-band (f=9.37GHz) hybrid dielectric-iris-loaded accelerating structure based on the calculated results about the effect of the dimension tolerance on the RF properties. The dispersion curve fitted by using the measurement value is consistent with the one calculated. The r/Q values of the dipole modes have been calculated by the Mafia code. The theoretical results show that the r/Q values of dipole modes for the new accelerating structure are lower than those for the iris-load accelerating structure.

• P. M. Sekalski
  
• J. W. Jalmuzna, A. Napieralski
  TUL-DMCS, Lodz
• L. Lilje, K. P. Przygoda, S. Simrock
  DESY, Hamburg
• R. P. Paparella
  INFN/LASA, Segrate (MI)

The SC cavities need a fast tuning system, which is able to adjust the shape during the pulse operation. The first attempts were focused on the compensation of the repetitive and periodic distortion. The algorithms were implemented in Matlab and allow compensating only the Lorentz force detuning. However, the previous solution was too slow to be able to compensate the microphonics. The paper presents recent development in the field. The previously worked out algorithms are implemented in the FPGA-based control system. The SIMCON board is used, which allows to perform parallel, deeply pipelined calculation. The new approach allows integrating the algorithm dedicated for cavity shape control with the LLRF system used for vector sum control. Moreover, the new algorithm for on-line detuning calculation which base on the electromechanical model of the cavity is presented. The system is tested with Module Test Stand (MTS) at DESY with the high gradient cavities (37 MV/m). The active elements are the NOLIAC's and PI's multilayer, low voltage piezostacks. The paper will present the first results from these measurements.

• K. R. Kim
  
• Y.-S. Cho, H.-J. Kwon
  KAERI, Daejon
• W. H. Hwang, H. S. Kim, H.-G. Kim, S. J. Kwon, J. Park, J. C. Yoon
  PAL, Pohang, Kyungbuk

The temperature-controlled cooling water system was designed to obtain the resonance frequency stabilization of the normal conducting drift tube linac (DTL) for the PEFP 100 MeV proton accelerator. The primary sizing of individual closed-loop low conductivity cooling water pumping skids for each DTL system was conducted with a simulation of thermo-hydraulic network model. The temperature control schemes incorporating the process dynamic model of heat exchangers were examined to regulate the input water temperatures into the DTL during the steady state operation. The closed water circuits to achieve system performance and stability for low and full duty operation modes were discussed, and numerical results were also presented.

• J. Norem
  
• A. Bross, A. Moretti, Z. Qian
  Fermilab, Batavia, Illinois
• D. Huang, Y. Torun
  IIT, Chicago, Illinois
• D. Li, M. S. Zisman
  LBNL, Berkeley, California
• R. A. Rimmer
  Jefferson Lab, Newport News, Virginia

The MuCool Experiment has been continuing to take data with 805 and 201 MHz cavities in the MuCool Test Area. The system uses rf power sources from the Fermilab Linac. Although the experimental program is primarily aimed at the Muon Ionization Cooling Experiment (MICE), we have been studying the dependence of rf limits on frequency, cavity material, high magnetic fields, gas pressure, coatings, etc. with the general aim of understanding the basic mechanisms involved. The 201 MHz cavity, essentially a prototype for the MICE experiment, was made using cleaning techniques similar to those employed for superconducting cavities and operates at its design field with very little conditioning.

• J. Branlard
  
• G. I. Cancelo, R. H. Carcagno, B. Chase, H. Edwards, R. P. Fliller, B. M. Hanna, E. R. Harms, A. Hocker, T. W. Koeth, M. J. Kucera, A. Makulski, U. Mavric, M. McGee, A. H. Paytyan, Y. M. Pischalnikov, P. S. Prieto, R. Rechenmacher, J. Reid, K. R. Treptow, N. G. Wilcer, T. J. Zmuda
  Fermilab, Batavia, Illinois

As part of the research and development towards the International Linear Collider (ILC), several test facilities have been developed at Fermilab. This paper presents the latest LLRF results obtained with Capture Cavity II at these test facilities. The main focus will be on controls and RF operations using the SIMCON based LLRF system. Details about hardware upgrades and overall system performance will be also explained. Finally, design considerations and objectives for the future test facility at the New Muon Laboratory (NML) will be presented.

• T. W. Koeth, T. W. Koeth
  Rutgers University, The State University of New Jersey, Piscataway, New Jersey
• J. Branlard, H. Edwards, R. P. Fliller, E. R. Harms, A. Hocker, M. McGee, Y. M. Pischalnikov, P. S. Prieto, J. Reid
  Fermilab, Batavia, Illinois

Valuable experience in operating and maintaining superconducting RF cavities in a horizontal test module has been gained with Capture Cavity II. We report on all facets of our experience to date.

• T. N. Khabiboulline
  
• I. G. Gonin, N. Solyak
  Fermilab, Batavia, Illinois

• M. McGee
  
• Y. M. Pischalnikov
  Fermilab, Batavia, Illinois

Operated by Universities Research Association, Inc., under Contract No. DE-AC02-76CH03000 with the U. S. Department of Energy#mcgee@fnal.gov

• Y. M. Pischalnikov
  
• J. Branlard, R. H. Carcagno, B. Chase, H. Edwards, A. Makulski, M. McGee, R. Nehring, D. F. Orris, V. Poloubotko, C. Sylvester, S. Tariq
  Fermilab, Batavia, Illinois

The technology for mechanically compensating Lorentz Force detuning in superconducting RF cavities has already been developed at DESY. One technique is based on commercial piezoelectric actuators and was successfully demonstrated on TESLA cavities*. Piezo actuators for fast tuners can operate in a frequency range up to several kHz; however, it is very important to maintain a constant preload force on the piezo stack in the range of 10 to 50% of its specified blocking force. Determining the preload force during cooldown, warm-up, or re-tuning of the cavity is difficult without instrumentation, and exceeding the specified range can permanently damage the piezo stack. A technique based on strain gauge technology for superconducting magnets has been applied to fast tuners for monitoring the preload on the piezoelectric assembly. This paper will address the design and testing of piezo actuator preload sensor technology. Results from measurements of preload sensors installed on the tuner of the DESY Capture Cavity II tested at Fermilab will be presented. These results include measurements during cooldown, warm-up, and cavity tuning along with dynamic Lorentz force compensation.

* M. Liepe et al," Dynamic Lorentz Force Compensation with a Fast Piezoelectric Tuner" PAC2001

• T. N. Khabiboulline
  
• C. A. Cooper, N. Dhanaraj, H. Edwards, M. Foley, E. R. Harms, D. V. Mitchell, A. M. Rowe, N. Solyak
  Fermilab, Batavia, Illinois
• W.-D. Moller
  DESY, Hamburg

• M. S. Prokop
  
• S. Kwon, S. Ruggles, P. A. Torrez
  LANL, Los Alamos, New Mexico

• J. Guo
  
• S. G. Tantawi
  SLAC, Menlo Park, California

• C. Hovater
  
• T. L. Allison, J. R. Delayen, J. Musson, T. E. Plawski
  Jefferson Lab, Newport News, Virginia

We have developed a digital process that emulates an analog oscillator and ultimately a self excited loop (SEL) for field control. The SEL, in its analog form, has been used for many years for accelerating cavity field control. In essence the SEL uses the cavity as a resonant circuit – much like a resonant ?tank? circuit is used to build an oscillator. An oscillating resonant circuit can be forced to oscillate at different, but close, frequencies to resonance by applying a phase shift in the feedback path. This allows the circuit to be phased locked to a master reference, which is crucial for multiple cavity accelerators. For phase and amplitude control the SEL must be forced to the master reference frequency, and feedback provided for in both dimensions. The novelty of this design is in the way digital signal processing (DSP) is structured to emulate an analog system. While the digital signal processing elements are not new, to our knowledge this is the first time that the digital SEL concept has been designed and demonstrated. This paper reports on the progress of the design and implementation of the digital SEL for field control of superconducting accelerating cavities.

• T. E. Plawski
  
• T. L. Allison, G. K. Davis, H. Dong, C. Hovater, K. King, J. Musson
  Jefferson Lab, Newport News, Virginia

The new digital LLRF system for the CEBAF 12GeV accelerator will perform a variety of tasks, beyond field control.* In this paper we present the superconducting cavity resonance control system designed to minimize RF power during gradient ramp and to minimize RF power during steady state operation. Based on the calculated detuning angle, which represents the difference between reference and cavity resonance frequency, the cavity length will be adjusted with a mechanical tuner. The tuner has two mechanical driving devices, a stepper motor and a piezo-tuner, to yield a combination of coarse and fine control. Although LLRF piezo processing speed can achieve 10 kHz bandwidth, only 10 Hz speed is needed for 12 GeV upgrade. There will be a number of additional functions within the LLRF system; heater controls to maintain cryomodule's heat load balance, ceramic window temperature monitoring, waveguide vacuum interlocks, ARC detector interlock and quench detection. The additional functions will be divided between the digital board, incorporating an Altera FPGA and an embedded EPICS IOC. This paper will also address hardware evolution and test results performed with different SC cavities.

*RF Control Requirements for the CEBAF Energy Upgrade Cavities, C. Hovater, J. Delayen, L. Merminga, T. Powers, C. Reece, Proceedings 2000 Linear Accelerator Conference, Monterey, CA , August 2000

• J. Haimson
  
• B. A. Ishii, B. L. Mecklenburg, G. A. Stowell
  HRC, Santa Clara, California

The gain of a high power TW relativistic klystron can be increased substantially with the use of a varying phase velocity, large beam aperture, lengthened output structure, designed for asynchronous interaction to control space charge fields and provide near-adiabatic bunch compression during the power extraction process. While this technique enables the replacement of a pulsed vacuum tube driver system with a small, inexpensive solid state RF source, lengthening the output circuit increases the number (and reduces the separation) of the longitudinal mode resonances in the TM01 operating band. Thus, the probability of exciting parasitic oscillations is increased, especially when the klystron is operated into a mismatched load or a high Q structure. The prevention of such oscillations, even when in close proximity to the operating frequency, using a technique that is unaffected by the phase or amplitude of reflected signals is described; and test results are presented of a solid state driven, 76dB gain 17GHz TW relativistic klystron, recently installed in the linac test facility at the MIT Plasma Science and Fusion Center.

• A. Bonatto
  
• R. Pakter, F. B. Rizzato
  IF-UFRGS, Porto Alegre

In the present analysis we study the self consistent propagation of nonlinear electromagnetic pulses in a one dimensional relativistic electron-ion plasma, from the perspective of nonlinear dynamics. We show how a series of Hamiltonian bifurcations give rise to the electric fields which are of relevance in the subject of particle acceleration. Nonlinear coupling of plasma waves and electromagnetic pulses triggers strong chaotic dynamics which may detrap the plasma wave from the electromagnetic pulse, leading to wave breaking. Connections with results of earlier analysis are discussed.

• S. H. Kim
  
• M.-H. Cho, Y. M. Gil, S.-I. Moon, W. Namkung, H. R. Yang
  POSTECH, Pohang, Kyungbuk
• J. Jang, J.-S. Oh, S. J. Park
  PAL, Pohang, Kyungbuk

For a compact X-ray source, we designed a C-band standing-wave electron accelerator. It is capable of producing 4-MeV electron beams with 50-mA peak beam current. As an RF source, we use 5-GHz magnetron with duty factor of 0.08%. The accelerating structure is bi-periodic and on-axis coupled structure, operated with π/2-mode standing waves. Each cavity in the bunching and normal cell is designed by the MWS code and measured with aluminium prototype cavity. As per the dispersion relation derived from the measurement results, calibration factor obtained for the actual copper cavity.

• A. V. Tyukhtin
  
• S. N. Galyamin
  Saint-Petersburg State University, Saint-Petersburg

The possibility of using an active medium to amplify the generated wakefield of an electron beam and employing the amplified wakefield to accelerate a second beam has been recognized recently*. This acceleration scheme is one of several related methods referred to as the Particle Acceleration by Stimulated Emission of Radiation (PASER). However, only the case of an active medium with a single resonant frequency has been analyzed until now. In this paper we present the results of analytical and numerical studies of Cherenkov radiation (CR) in an active medium with two resonant frequencies. We show that this medium can amplify CR even in the case of a purely real refractive index. In contrast to a medium with a single resonant frequency the amplification effect takes place in the absence of metal boundaries but only for sufficiently strong restrictions on the parameters of the medium. The amplification can be effective even for a medium with a relatively small inversion. Examples of CR amplification are given for several active materials. The effect may be useful both for wakefield accelerators and Cherenkov detectors.

*L. Schachter, Phys. Rev., E, 62, 1252 (2000); N. V.Ivanov, A. V.Tyukhtin, Tech. Phys. Lett., 32, 449 (2006).

• D. J. Newsham
  
• S. A. Bogacz, Y.-C. Chao, Y. S. Derbenev
  Jefferson Lab, Newport News, Virginia
• R. P. Johnson, R. Sah
  Muons, Inc, Batavia

Parametric-resonance ionization cooling (PIC) is a muon-cooling technique that is useful for low-emittance muon colliders. This method requires a well-tuned focusing channel that is free of chromatic and spherical aberrations. In order to be of practical use in a muon collider, it also necessary that the focusing channel be as short as possible to minimize muon loss due to decay. G4Beamline numerical simulations are presented of a compact PIC focusing channel in which spherical aberrations are minimized by using design symmetry.

• I. Reichel
  

Designing a lattice with sufficient dynamic aperture for the ILC Damping Rings is very challenging as the lattice needs to provide a small equilibrium emittance and at the same time a large aperture for the injected beam including a large momentum acceptance. In addition outside constraints have forced layout changes in the damping ring. Some of the layout changes had an impact on the dynamic aperture. In order to better understand the changes in dynamic aperture, frequency maps are studied. Those studies can help in identifying the reason for the changed dynamic aperture and in finding a good location for the betatron tunes and determining an upper limit for the chromaticities. A summary of recent studies and suggestions improving the dynamic aperture by choosing a different tune are presented.

• M. A. Shapiro
  
• J. R. Sirigiri, R. J. Temkin
  MIT/PSFC, Cambridge, Massachusetts

We present the results of our recent research on 3D metal-wire lattices operating at microwave frequencies, with applications to advanced accelerator structures and radiation sources based on the Smith-Purcell effect. Bulk and surface electromagnetic waves supported by a diamond-like lattice are calculated using HFSS. The bulk modes are determined using primitive cell calculations. The surface mode is determined using the simulations of the stack of cells with the perfect-matching layer (PML) boundary.

• P. V. Avrakhov
  
• N. Solyak
  Fermilab, Batavia, Illinois

• P. Schoessow
  
• S. P. Antipov, M. E. Conde, W. Gai, J. G. Power
  ANL, Argonne, Illinois
• E. Bagryanskaya
  International Tomography Center, SB RAS, Novosibirsk
• V. Gorelik, A. Kovshik, A. V. Tyukhtin, N. Yevlampieva
  Saint-Petersburg State University, Saint-Petersburg
• A. Kanareykin
  Euclid TechLabs, LLC, Solon, Ohio
• L. Schachter
  Technion, Haifa

The PASER is a new method for particle acceleration, in which energy from an active medium is transferred to a charged particle beam. The effect is similar to the action of a maser or laser with the stimulated emission of radiation being produced by the virtual photons in the electromagnetic field of the beam. We are developing a demonstration PASER device operating at X-band, based on the availability of a new class of active materials that exhibit photoinduced electron spin polarization. We will report on the status of active material development and measurements, numerical simulations, and preparations for microwave PASER experiments at the Argonne Wakefield Accelerator facility.

• J. S. Berg
  
• S. R. Koscielniak
  TRIUMF, Vancouver
• S. Machida
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon
• A. G. Ruggiero
  BNL, Upton, Long Island, New York

EMMA is a 10 to 20 MeV electron ring designed to test our understanding of beam dynamics in a relativistic linear non-scaling fixed field alternating gradient accelerator (FFAG). This paper describes the design of the EMMA lattice. We begin with a description of the experimental goals that impact the lattice design. We then describe what motivated the choice for the basic lattice parameters, such as the type of cells, the number of cells, and the RF frequency. We next list the different configurations that we wish to operate the machine in so as to accomplish our experimental goals. Finally, we enumerate the detailed lattice parameters, showing how these parameters result from the various lattice configurations.

• I. Hofmann
  
• G. Franchetti
  GSI, Darmstadt

• A. Y. Molodozhentsev
  
• T. Koseki, M. Tomizawa
  KEK, Ibaraki

• A. Morita
  
• H. Koiso, Y. Ohnishi, K. Oide
  KEK, Ibaraki

• B. Qin
  
• M. Fan, Y. Q. Xiong, Y. Xu, J. Yang
  HUST, Wuhan

An intelligent magnet design, modelling and optimization method with the aid of beam dynamics analysis and three dimensional magnetic field calculation is introduced. The whole procedure is implemented in an integrated virtual prototyping environment built with python language. As a case study, the main magnet design of a 16MeV H^- compact cyclotron is illustrated. Both the field isochronism and transversal focusing of the beam can be fulfilled, and the mechanical analysis is performed to validate the feasibility in mechanics.

• F. Schmidt
  
• I. V. Agapov
  DESY, Hamburg
• W. Herr, G. Kruk, M. Lamont
  CERN, Geneva

• F. Zimmermann
  
• M. Aiba, M. Chanel, U. Dorda, R. Garoby, J.-P. Koutchouk, M. Martini, E. Metral, Y. Papaphilippou, W. Scandale
  CERN, Geneva
• G. Franchetti
  GSI, Darmstadt
• V. D. Shiltsev
  Fermilab, Batavia, Illinois

• Y. Alexahin
  
• R. B. Palmer
  BNL, Upton, Long Island, New York
• K. Yonehara
  Fermilab, Batavia, Illinois

For muons with preferable for ionization cooling momentum <300MeV/c the longitudinal motion is naturally undamped. In order to provide the longitudinal damping a correlation between muon momentum and transverse position - described in terms of the dispersion function - should be introduced. In the present report we consider the possibility of dispersion generation in a periodic sequence of alternating solenoids (FOFO channel) by choosing the tune in the second passband (i.e. above half-integer per cell) and tilting the solenoids in adjacent cells in the opposite direction. Analytical estimates as well as simulation results for equilibrium emittances and cooling rates are presented.

• T. Sen
  
• H. J. Kim
  Fermilab, Batavia, Illinois

• F. Lin
  
• L. Ahrens, M. Bai, K. A. Brown, E. D. Courant, J. Glenn, H. Huang, A. U. Luccio, W. W. MacKay, T. Roser, N. Tsoupas
  BNL, Upton, Long Island, New York
• S.-Y. Lee
  IUCF, Bloomington, Indiana

Two partial helical dipole snakes were found to be able to overcome all imperfection and intrinsic spin resonances provided that the vertical betatron tunes were maintained in the spin tune gap near the integer 9. Recent vertical betatron tune scan showed that the two weak resonances at the beginning of the acceleration cycle may be the cause of polarization loss. This result has been confirmed by the vertical polarization profile measurement, and spin tracking simulations. Possible cure of the remaining beam polarization is discussed.

• J. F. DeFord
  
• B. Held
  STAR, Inc., Mequon, Wisconsin
• J. J. Petillo
  SAIC, Burlington, Massachusetts

Particle orbit errors in multipacting and dark current computations can arise from inadequate field representation, poor surface modeling, and from the integration algorithm used to advance the particles. Established fields-based adaptive mesh refinement (AMR) methods *,** selectively improve the field and surface representation over several iterations in finite-element codes but they are not optimized for particle tracking. In particular, field emission and secondary emission models require precise surface representations and highly accurate field representations near surfaces, and these requirements are not adequately addressed in standard AMR techniques. In this paper we report on extensions to existing AMR support in the Analyst software package for particle tracking, including adaptive improvement of near-surface and on-surface field representations, and control of element aspect ratios throughout successive iterations. We also discuss the merits of automated identification of important regions of the mesh based on field levels and orbit estimation to guide AMR in multipacting calculations, and multipacting results for a SRF cavity will be presented.

* G. Drago, et al., IEEE Trans. on Mag., 28, 1992, pp. 1743-1746.** D. K. Sun, et al., IEEE Trans. on Mag., 36, July 2000, pp. 1596-1599.

• H. Hahn
  
• L. R. Hammons, D. Naik
  BNL, Upton, Long Island, New York

An R&D facility for an Energy Recovery Linac (ERL) intended as part of the 'Electron-Cooling Xperiment' for RHIC is being constructed at this laboratory. The center piece of the project is the experimental 5-cell 703.75 MHz superconducting ECX cavity. Successful operation will depend on effective HOM suppression, and it is planned to achieve HOM damping exclusively with room temperature ferrite absorbers. A ferrite-lined pillbox model with dimensions reflecting the operational unit was assembled, and the cavity resonances and quality factors were determined from scattering coefficient measurements and were interpreted as surface impedance. Results from a 5-cell copper cavity with an attached ferrite absorber prototype are used for the prediction of the ECX cavity HOM damping. A rotational symmetric ferrite-lined pillbox was analyzed theoretically and compared with the simulation codesμWave Studio, GdfidL, and Superfish. Discrepancies of the resonance frequencies and Q-values were found, and steps to reach agreement are discussed.

• K. Fiuza
  
• R. Pakter, F. B. Rizzato
  IF-UFRGS, Porto Alegre

This paper analyzes the combined envelope-centroid dynamics of magnetically focused high-intensity charged beams surrounded by conducting walls. Similarly to the case were conducting walls are absent, we show that the envelope and centroid dynamics decouples from each other. Mismatched envelopes still decay into equilibrium with simultaneous emittance growth, but the centroid keeps oscillating with no appreciable energy loss. Some estimates are performed to analytically obtain some characteristics of halo formation seen in the full simulations.

• W. Simeoni
  

• A. Chance
  
• J. Payet
  CEA, Gif-sur-Yvette

The aim of the beta-beams is to produce highly energetic beams of pure electron neutrino and anti-neutrino, coming from beta-decays of the ¹⁸Ne¹⁰⁺ and ⁶He²⁺, both at γ=100, directed towards experimental halls situated in the Frejus tunnel. The high intensity ion beams are stored in a ring until the ions decay. The beta decay products have a magnetic rigidity different from the one of the parent ions and are differently deflected in the 6T superconducting dipoles. Consequently, all the injected ions are lost anywhere in the ring, generating a high level of irradiation. So, the dipole apertures need to be large enough to avoid the decay products hitting their walls, which may worsen the field quality. A study on its tolerances has been carried out. Since the decay ring has to accept the beam during a large number of turns, the chosen criteria is the size of the dynamic aperture that the multipolar defects in the dipoles may shrink. Tolerances on the systematic and random errors of these defects have been investigated. In order to relax the tolerances, a routine was written which enlarges automatically the dynamic aperture in presence of field errors.

• M. Takao
  
• M. Masaki, J. Schimizu, K. Soutome, S. Takano
  JASRI/SPring-8, Hyogo-ken

• A. Y. Molodozhentsev
  
• T. Koseki, M. Tomizawa
  KEK, Ibaraki
• S. Machida
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon

• K. Shibata
  
• H. Fukuma, S. Hiramatsu, Y. Suetsugu, M. Tejima, M. Tobiyama
  KEK, Ibaraki

• H. Hotchi
  
• S. Machida
  STFC/RAL/ASTeC, Chilton, Didcot, Oxon
• F. Noda
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

• Q. Luo
  
• H. He, P. Li, P. Lu, B. Sun, J. H. Wang
  USTC/NSRL, Hefei, Anhui

For the development of accelerators we require increasingly precise control of beam position. Cavity BPMs promise a much higher position resolution compared to other BPM types and manufacture of cavity BPMs is in general less complicated. The cavity BPM operating at S-band for HLS (Hefei Light Source) was designed. It consists of two cavities: a position cavity tuned to TM110 mode and a reference cavity tuned to TM010 mode. To suppress the monopole modes we use waveguides as pickups. Superheterodyne receivers are used in electronics for many cavity BPMs while we decide to use chip AD8302 produced by Analog Devices to process the signals. To simulate and calculate the electromagnetic field we use MAFIA.

• A. V. Tyukhtin
  
• S. P. Antipov
  ANL, Argonne, Illinois
• A. Kanareykin, P. Schoessow
  Euclid TechLabs, LLC, Solon, Ohio

Cherenkov radiation (CR) is extensively used for detection of charged particles. The prompt nature of the radiation is one major advantage for diagnostics that measure temporal properties of the beam. However, low signal levels and small angles of radiation with respect to the particle trajectory present limitations on the use of traditional detector media. Using modern artificial metamaterials as Cherenkov radiators can provide essential advantages. As a rule metamaterials are characterized by strong dispersion and anisotropy that can be engineered to the requirements of the detector. We present theoretical and numerical analyses of CR in bulk anisotropic and dispersive media and in waveguides. The properties exhibited by these materials (large angles of radiation, two maxima in the angular distributions, etc.) allow the design of detectors with unusual characteristics, like a detector that registers almost all moving particles, and simultaneously only particles with velocity exceeding a predetermined threshold. We consider the case of a material that is approximately equivalent to an isotropic left-handed medium that also presents advantages as a Cherenkov medium.

• F. Roncarolo
  
• R. Appleby, R. M. Jones
  UMAN, Manchester

* Cox, Brian et al., "FP420 : An R&D Proposal to Investigate the Feasibility of Installing Proton Tagging Detectors in the 420 m Region of the LHC", CERN-LHCC-2005-025

• Y. Alexahin
  

To avoid multiple head-on collisions the proton and antiproton beams in the Tevatron move along separate helical orbits created by 7 horizontal and 8 vertical electrostatic separators. Still the residual long-range beam-beam interactions can adversely affect particle motion at all stages from injection to collision. With increased intensity of the beams it became necessary to modify the orbits in order to mitigate the beam-beam effect on both antiprotons and protons. This report summarizes the work done on optimization of the Tevatron helical orbits, outlines the applied criteria and presents the achieved results.

• P. Snopok
  
• M. Berz
  MSU, East Lansing, Michigan
• C. Johnstone
  Fermilab, Batavia, Illinois

• A. Valishev
  
• G. Annala, V. A. Lebedev, R. S. Moore
  Fermilab, Batavia, Illinois

• J. Qiang
  
• W. Fischer
  BNL, Upton, Long Island, New York
• T. Sen
  Fermilab, Batavia, Illinois

Long-range beam-beam interactions can cause significant degrade of beam quality and lifetime in high energy ring colliders. At RHIC, a series of experiments were carried out to study these effects. In this paper, we report on numerical simulation of the long-range beam-beam interactions at RHIC using a parallel strong-strong particle-in-cell code, BeamBeam3D. The simulation includes nonlinearities from both the beam-beam interactions and the arc sextupoles. We observed significant emittance growth for beam separation below 4 σs under nominal tunes. A scan study in tune space shows strong emittance growth around 7th order resonance. Including the tune modulation due to chromaticity and synchrotron motion shows larger emittance growth than the case without the tune modulation.

• C. L. Bohn
  
• E. W. Nissen
  Northern Illinois University, DeKalb, Illinois

We undertake a study of particle dynamics in a model fixed-field alternating-gradient (FFAG) synchrotron in which space-charge plays a central role. The space-charge force corresponds to a Gaussian charge distribution in both transverse dimensions. The betatron-tune is linearly ramped through resonance. This ramping alone can cause particles to enter orbits that have chaotic motion.. We found that space-charge can lead to spreading of the available tunes which can either increase or decrease the effects of resonance. By applying recently developed techniques to measure complexity in the orbital dynamics, we also determine whether chaoticity can arise in particle trajectories and subsequently influence resonance crossings. Furthermore, we can see that the chaoticity changes drastically in the area around a resonance crossing.

• W. D. Zacherl
  
• I. Blumenfeld, M. J. Hogan, R. Ischebeck
  SLAC, Menlo Park, California
• C. E. Clayton, P. Muggli, M. Zhou
  UCLA, Los Angeles, California

A typical diagnostic used to determine the bunch length of ultra-short electron bunches is the autocorrelation of coherent transition radiation. This technique can produce artificially short bunch length results due to the attenuation of low frequency radiation if corrections for the material properties of the Michelson interferometer and detector response are not made. Measurements were taken using FTIR spectroscopy to determine the absorption spectrum of various materials and the response of a Molectron P1-45 pyroelectric detector. The material absorption data will be presented and limitations on the detector calibration discussed.

• Y. Luo
  
• M. Bai, J. Bengtsson, R. Calaga, W. Fischer, N. Malitsky, F. C. Pilat, T. Satogata
  BNL, Upton, Long Island, New York

To further improve the polarized proton (pp) run collision luminosity in the Relativistic Heavy Ion Collider, correction of the horizontal two-third resonance is desirable to increase the available tune space. The third resonance driving term (RTD) is measured with the turn-by-turn (TBT) beam position monitor (BPM) data with AC dipole excitation. A first order RTD response matrix based on the optics model is used to on-line compensate the third resonance driving term h30000 while keeping other first order RTDs and first order chromaticities unchanged. The results of beam experiment and simulation correction are presented and discussed.

• Y. Luo
  
• M. Bai, J. Beebe-Wang, W. Fischer, A. K. Jain, C. Montag, T. Roser, S. Tepikian, D. Trbojevic
  BNL, Upton, Long Island, New York

To further improve the the polarized proton (pp) luminosity in the Relativistic Heavy Ion Collider, the beta functions at the two interaction points (IPs) will be reduced from 1.0 m to 0.9m in 2007. In addition, it is planned to increase the bunch intensity from 1.5*10¹¹ to 2.0*10¹¹. To accommodate these changes, the nonlinear chromaticities and the third resonance driving term should be corrected. In 2007, the number of the arc sextupole power supplies will be doubled from 12 to 24, which allows nonlinear chromaticity correction. With the updated field errors in the interaction regions (IRs), detailed dynamic aperture studies are carried out to optimize the nonlinear correction schemes, and increase the available tune space in collision.