• R. Xiang, A. Arnold, H. Büttig, D. Janssen, M. Justus, U. Lehnert, P. Michel, P. Murcek, A. Schamlott, Ch. Schneider, R. Schurig, F. Staufenbiel, J. Teichert
  FZD, Dresden
• T. Kamps, J. Rudolph, M. Schenk
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
• G. Klemz, I. Will
  MBI, Berlin

As the first superconducting rf photo-injector (SRF gun) in practice, the FZD 3+1/2 cell SRF gun is successfully connected to the superconducting linac ELBE. This setting will improve the beam quality for ELBE users. It is the first example for an accelerator facility fully based on superconducting RF technology. For high average power FEL and ERL sources, the combination of SRF linac and SRF gun provides a new chance to produce beams of high average current and low emittance with relative low power consumption. The main parameters achieved from the present SRF gun are the final electron energy of 3 MeV, 16 μA average current, and rms transverse normalized emittances of 3 mm mrad at 77 pC bunch charge. A modified 3+1/2 cell niobium cavity has been fabricated and tested, which will increase the rf gradient in the gun and thus better the beam parameters further. In this paper the status of the integration of the SRF gun with the ELBE linac will be presented, and the latest results of the beam experiments will be discussed.

• S. Lal, K.K. Pant
  RRCAT, Indore (M.P.)
• S. Krishnagopal
  BARC, Mumbai

Four and eight cell Plane Wave Transformer (PWT) linac structures have been developed as part of the injector development for the Compact Ultrafast Terahertz Free Electron Laser (CUTE-FEL) at RRCAT. In this paper, we discuss the tuning of resonant frequency and waveguide-cavity coupling coefficient for these structures, and compare results obtained from cold tests with those predicted by RF simulations. We also compare energy gain and RF properties of these structures, determined from transient and steady state behavior of the structure during recent high power tests, with those predicted by cold tests.

• S. Lal, B. Biswas, S. Chouksey, S.K. Gupta, U. Kale, M. Khursheed, A. Kumar, V. Kumar, P. Nerpagar, K.K. Pant, A. Patel, V. Prasad, A.K. Sarkar
  RRCAT, Indore (M.P.)
• S. Krishnagopal
  BARC, Mumbai

The injector system for the Compact Ultrafast Terahertz Free Electron Laser (CUTE-FEL) consists of a 1 ns, 90 kV pulsed thermionic electron gun, a 476 MHz sub-harmonic prebuncher, and a standing wave, S-band Plane Wave Transformer (PWT) linac capable of accelerating beam to 10 MeV. Beam from this injector will be transported to the entrance of the undulator through a beam transport line, with the required diagnostic elements, that has been designed, developed and commissioned. The control system and the low and high power microwave lines have also been commissioned. In this paper, we discuss salient features of the injector system and results from recent commissioning trials of the injector.

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

The production of Cs2Te photoemissive films used as laser driven electron sources in the high brightness photoinjectors at FLASH and PITZ, is a well established activity at INFN Milano since the '90s. Our total production is of more than 100 photocathodes, with an average QE of 8% (@ 254 nm) for fresh films and an operative lifetime that increased up to some months at FLASH. In the last two years, we have improved the standard diagnostic used during the cathode growth to better understand the material properties of the films. This activity is motivated by the need to improve the photocathode properties, mainly the energy distribution of the photoemitted electrons that influences the thermal emittance. The multiwavelengths diagnostic, i.e. the on-line measurements of the photocurrent and reflectivity from the film during its growth in the 239 nm ~ 436 nm range, has been deeply applied on several cathodes and the potentiality of this technique are discussed in this paper.

• H. Hanaki, T. Asaka, H. Ego, H. Kimura, T. Kobayashi, S. Suzuki, M. Yamaga
  JASRI/SPring-8, Hyogo-ken
• T. Fukui, T. Inagaki, N. Kumagai, Y. Otake, T. Shintake, K. Togawa
  RIKEN/SPring-8, Hyogo

The injector of the 8 GeV linac generates an electron beam of 1 nC, accelerates it up to 30 MeV, and compresses its bunch length down to 20 ps. Even slight RF instability in its multi-stage bunching section fluctuates the bunch width and the peak current of an electron beam and it accordingly results in unstable laser oscillation in the undulator section. The acceptable instabilities of the RF fields in the cavities, which permit 10% rms variation of the peak beam current, are only about 0.01% rms in amplitude and 120 fs rms in phase according to beam simulation. The long-term RF variations can be compensated by feedback control of the RF amplitude and phase, the short-term or pulse-to-pulse variations, however, have to be reduced as much as possible by improving RF equipment such as amplifiers. Thus we have carefully designed and manufactured the RF cavities, amplifiers and control systems, giving the highest priority to the stabilization of the short-term variations. Components of the injector will be completed by the end of the April 2010, and the injector will be perfected in the summer 2010. We will present the performance of the completed devices in the conference.

• H. Zen
  UVSOR, Okazaki
• M. A. Bakr, K. Higashimura, T. Kii, R. Kinjo, K. Masuda, K. Nagasaki, H. Ohgaki
  Kyoto IAE, Kyoto
• H. Zen
  Sokendai - Okazaki, Okazaki, Aichi

Thermionic RF guns are compact, economical and high brightness electron sources. However, when the guns are used for a driver linac of oscillator-type Free Electron Lasers (FELs), which requires moderate bunch charge (several tens pico-coulomb) and long macro-pulse duration (several micro-seconds), the guns have been suffered from the back-bombardment effect*. The effect induces beam current increment in a macro-pulse. And consequently the current increment leads to decrement of beam energy during a macro-pulse and significantly limits the beam macro-pulse duration after some bending magnets. Our group found a new energy compensation scheme called as cavity detuning** and the method was introduced to compensate the beam energy decrement in the thermionic RF gun used for KU-FEL***. In this presentation, we will introduce the principle of the method and experimental results. Detailed analysis of the method will be also presented.

* C.B. McKee et al., NIM, A296, pp. 716-719, 1990.
** H. Zen et al., IEEE Trans. of Nucl. Sci., vol. 56, No. 3, pp. 1487-1491
*** T. Yamazaki et al., Proc. of 23rd FEL Conf., pp. II-13-14, 2002.

• S. Kashiwagi, K. Furuhashi, G. Isoyama, R. Kato, M. Morio, N. Sugimoto, Y. Terasawa
  ISIR, Osaka
• H. Hayano, H. Sugiyama, T. Takatomi, J. Urakawa
  KEK, Ibaraki
• H. Iijima, M. Kuriki
  HU/AdSM, Higashi-Hiroshima

We conduct research on Free Electron Laser (FEL) in the infrared region and pulse radiolysis for radiation chemistry using the 40 MeV, 1.3 GHz L-band linac of Osaka University. At present, the L-band linac is equipped with a thermionic electron gun. It can accelerate a high-intensity single-bunch beam with charge up to 91 nC but the normalized emittance is large. In order to advance the research, we have begun development of a photocathode RF gun for the L-band electron linac in collaboration with KEK and Hiroshima University. We start the basic design of the RF gun cavity for the L-band linac at ISIR, Osaka University, based on the 1.5 cells, which is a normal conducting photocathode RF gun. A material of the cathode should be Cs2Te, which has the high quantum efficiency of a few percents, to produce a beam with high charge up to 30 nC/bunch. We improve the cooling system of the cavity for high duty operation to suppress the thermal deformation due to the heat load of input rf power. The simulation study has been also performed for the L-band linac at ISIR with a high charge electron beam. In this conference, we describe the details of the L-band photocathode RF gun development.

• F. Hinode, H. Hama, M. Kawai, F. Miyahara, T. Muto, K. Nanbu, H. Oohara, Y. Tanaka
  Tohoku University, School of Scinece, Sendai
• S. Kashiwagi
  Tohoku University, Research Center for Electron Photon Science, Sendai

A test accelerator for the coherent terahertz source (t-ACTS) has been under development at Laboratory of Nuclear Science, Tohoku University*. Intense coherent terahertz radiation will be generated by the very short electron bunch less than 100 fs using a thermionic RF gun (ITC RF-gun). ITC RF-gun is designed to have two cells uncoupled with each other, so that it can be operated at various combinations of different rf-power level and phase difference so as to optimize the longitudinal phase space distribution of the electron beam for bunch compression**. The gun employs single-crystal LaB6 cathode with small diameter of 1.8 mm to obtain a very small initial emittance with sufficiently high current density. The RF gun has been already manufactured and the measurement of RF characteristics is now in progress. We will present the results of low-power measurement and also discuss the effect of the cathode misalignment on the beam parameters such as transverse emittance and longitudinal phase space distribution.

* H. Hama et al., New J. Phys. 8 (2006) 292.
** H. Hama et al., Nucl. Instr. and Meth., A 528, (2004) 371.

• X.H. Liu, C.-X. Tang
  TUB, Beijing

In this paper, we present the preliminary structure design and optimization of a C-band photocathode RF gun for a compact electron diffraction facility. It will work at 5.712GHz. A dual coupler and elliptical iris between half-cell and full-cell are adopt in this gun for lower emittance and larger mode separation. A detailed 3D simulation of the C-band RF gun with coupler is performed. This paper likewise presents the beam dynamics parameters and analysis of this gun.

• Y.J. Pei
  USTC/NSRL, Hefei, Anhui

Recently, great attention has been paid to short electron pulses because of requirement for FEL project. Our aim is a 0.2nC, 5ps, 2MeV electron bunch with a normalized emittance less than 10 mm mrad without compensation coil. To create such beams, an External Cathode Independently Tunable Cells RF gun (EC-ITCRF Gun) was advanced, which consists of two independent cavities and a diode gun. The RF power and its phase fed to the two cavities can be independently adjustable. The paper described simulating results of the beam dynamic in the gun and a test facility. After RF power exercising a week, the electric field in the cavities surface was reached 100MV/m and dark current was disappearance. Main parameters measured are as following: energy is of 1.98MeV, pulse bean current of 20A, beam width of 5ps and energy spread of 0.5% so on. Keyword: EC-ITC RF Gun, emittance, energy spread, external cathode

• J.H. Hong, M.S. Chae, I.S. Ko, S.-I. Moon, Y.W. Parc
  POSTECH, Pohang, Kyungbuk
• C. Kim, S.J. Park
  PAL, Pohang, Kyungbuk

A Brookhaven National Laboratory (BNL) type S-band photocathode RF gun is used at Pohang Accelerator Laboratory (PAL) to produce femtosecond tera hertz (fs-THz) radiation. In order to upgrade the fs-THz Facility at PAL, we need to develop the performance of the RF gun. The requirements for new RF gun are following: 1 nC beam charge, 60 Hz repetition frequency and 1 mm mrad normalized rms transverse emittance. A dual feed photocathode RF gun is designed satisfy these requirements. Two additional pumping ports are used to remove the field asymmetry. A large radius and short length of the iris increases the mode separation. The coupling scheme is changed to make the fabrication simpler. The RF gun structure had been modeled using 3D field solver to provide the desired RF parameters and to obtain the field profile. In this paper the new RF gun design and the cold test results will be presented.

• C.H. Gough, S. Ivkovic, F. Le Pimpec, M. Paraliev
  PSI, Villigen

As part of the SwissFEL project at Paul Scherrer Institute, an electron gun test stand has been built and operated. The goal is to achieve an exceptionally low emittance beam with a charge of 200pC for XFEL application. The electron gun consists of a High Gradient (HG) pulsed diode followed by an RF acceleration structure. The diode has an adjustable gap and the cathode is pulsed at up to 500 kV. The electrons were extracted either from a near-flat cathode surface or a dedicated photo-source recessed in a hollow cathode surface. For the diode electrtodes, many metals, geometries and surface treatments were studied for their HG and photo emission suitability. Polished metal electrodes, single tips, field emitter arrays and electrodes coated with different Diamond Like Carbon (DLC) types were tested. In particular, we found that DLC coating had useful properties. Surface electric fields over 250MV/m (350 ~ 400kV, in pulsed mode) with negligible parasitic electron emission were achieved; when UV laser illumination was applied to DLC electrodes, it was possible to extract electron bunches of over 60pC at gradients up to 150MV/m.

• J.W. McKenzie, B.L. Militsyn
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

The injector for the UK's New Light Source project is required to deliver low emittance 200 pC electron bunches at a repetition rate of up to 1 MHz. Initial design of a photoinjector based around a 1' cell L-band superconducting RF gun able to meet these requirements is presented, including beam dynamic simulations of the injector up to the end of the first linac module.

• J.W. McKenzie, B.L. Militsyn
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

The injector for the UK's New Light Source project is required to deliver low emittance 200 pC electron bunches at a repetition rate of up to 1 MHz. A possible solution to these requirements is an injector based around a normal conducting VHF RF gun. The injector design and results of beam dynamics simulations are presented for cases with and without an independent buncher cavity.

• N. Chanlek, R.M. Jones
  UMAN, Manchester
• J.D. Herbert, L.B. Jones, K.J. Middleman, B.L. Militsyn
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

Gallium Arsenide (GaAs) photocathodes have in recent year been widely used and have become the focus for use in modern accelerators and light sources such as the Accelerators and Lasers in Combined Experiments (ALICE) and the International Linear Collider (ILC). Once activated to a Negative Electron Affinity (NEA) state and illuminated by a laser, these materials can be used as a high-brightness source of both polarised and un-polarised electrons. This work presents an effective preparation procedure including heat cleaning, atomic hydrogen cleaning and the activation process for NEA GaAs photocathode. The stability of quantum efficiency (QE) and lifetime of NEA GaAs photocathode have been studied in the load-lock and photocathode preparation system for the ALICE photo- electron gun which has a base pressure in the order of 10^-11 mbar. These studies are also supported with experimental evidence from surface science techniques such as Photoelectron Spectroscopy (XPS) and Low Energy Electron Diffraction (LEED) to demonstrate the processes at the atomic level.

• R. Sah, A. Dudas, M.L. Neubauer
  Muons, Inc, Batavia
• M. Poelker, K.E.L. Surles-Law
  JLAB, Newport News, Virginia

Many user facilities such as synchrotron radiation light sources and free electron lasers require accelerating structures that support electric fields of 10-100 MV/m, especially at the start of the accelerator chain where ceramic insulators are used for very high gradient DC guns. These insulators are difficult to manufacture, require long commissioning times, and often exhibit poor reliability. Two technical approaches to solving this problem will be investigated. Firstly, inverted ceramics offer solutions for reduced gradients between the electrodes and ground. An inverted design will be presented for 350 kV, with maximum gradients in the range of 5-10 MV/m. Secondly, novel ceramic manufacturing processes will be studied, in order to protect triple junction locations from emission, by applying a coating with a bulk resistivity. The processes for creating this coating will be optimized to provide protection as well as be used to coat a ceramic with an appropriate gradient in bulk resistivity from the vacuum side to the air side of an HV standoff ceramic cylinder. Example insulator designs are being computer modelled, and insulator samples are being manufactured and tested

• A. Fukasawa, J.B. Rosenzweig, D. Schiller
  UCLA, Los Angeles, California
• D. Alesini, L. Ficcadenti, B. Spataro
  INFN/LNF, Frascati (Roma)
• L. Faillace, L. Palumbo
  Rome University La Sapienza, Roma

A unique SW/TW hybrid photoinjector are being developed under the collaboration of UCLA, LNF/INFN, and University of Rome. It can produce 240-fs (rms) bunch with 500 pC at 21 MeV. The bunch distribution has a strong spike (54 fs FWHM) and the peak current is over 2kA. As the bunch form factor at 1 THz is 0.43, it can produce coherent radiation at 1 THz. We are considering three types of way to generate it; coherent Cherenkov radiation (CCR), superradiant FEL, and coherent transition/edge radiation (CTR/CER). CCR used hollow dielectric with the outer surface metallic-coated. OOPIC simulation showed 21 MW of the peak power (5 mJ) at 1 THz. For FEL and CTR/CER simulation, QUINDI, which was written at UCLA to solve the Lienard-Wiechert potential, was used to calculate the radiation properties. In the contrast to CCR, their spectra were broad and their pulse lengths were short. They will be useful for fast pumping.

• F. Zhou, C. Adolphsen, Y.T. Ding, Z. Li, A.E. Vlieks
  SLAC, Menlo Park, California

SLAC is studying the feasibility of using an X-band RF photocathode gun to produce low emittance bunches for applications such as an MeV gamma source (in collaboration with LLNL) and an injector for a compact FEL. Systematic beam dynamics study are being done for a 5.5 cell X-band gun followed by several 53 cm long high-gradient X-band accelerator structures. A fully 3D program, ImpactT*, is used to track particles taking into account space charge forces, short-range longitudinal and transverse wakefields and the 3D rf fields in the structures, including the quadrupole component of the couplers. The effect of misalignments of the various elements (drive-laser, gun, solenoid and accelerator structures) are being evaluated. This paper presents these results and estimates of the expected bunch emittance versus bunch charge and cathode gradient.

*Ji Qiang, LBNL-62326, January 25, 2007.

• E. Wang, I. Ben-Zvi, A. Burrill, J. Kewisch, T. Rao, Q. Wu
  BNL, Upton, Long Island, New York
• D. Holmes
  AES, Medford, NY
• E. Wang
  PKU/IHIP, Beijing

RF electron guns with strained super lattice GaAs cathodes can produce higher brightness and lower emittance polarized electron beams, due to the higher field gradient at the cathode surface compared with DC guns. The vacuum in the gun must be better than 10^-11 torr to obtain a sufficient cathode life time with high quantum efficiency (QE). Such high vacuum cannot be obtained easily in a normal conducting RF gun. We report on an experiment with a superconducting RF (SRF) gun, which can maintain a vacuum of nearly 10^-12 torr because of cryo-pumping at the temperature of 4.2K . The GaAs cathode was activated by Cs'O treatment with a QE of 3% and exhibits a long lifetime in a preparation chamber. This cathode will be used in a 1.3 GHz - cell SRF gun to measure the destruction of the QE by ion and electron back-bombardment.

• E. Wang, I. Ben-Zvi, A. Burrill, J. Kewisch, T. Rao, Q. Wu
  BNL, Upton, Long Island, New York
• D. Holmes
  AES, Medford, NY
• E. Wang
  PKU/IHIP, Beijing

Superconducting RF (SRF) electron guns deliver higher brightness beams than DC guns because the field gradient at the cathode is higher. SRF guns with metal cathodes have been successfully tested. For the production of polarized electrons a Gallium-Arsenide (GaAs) cathode must be used, and an experiment to test this type of cathode is under way at BNL. Since the cathode will be normal conducting, the primary concern is cathode-driven heat load. We present measurements of the electric resistance of GaAs at cryogenic temperatures, a prediction of the heat load, and verification by measuring the quality factor of the gun with and without the cathode.

• E. Meier, G. LeBlanc
  ASCo, Clayton, Victoria
• S. Biedron
  ELETTRA, Basovizza
• M.J. Morgan
  Monash University, Faculty of Science, Victoria

We report the development of an artificial intelligent system for the optimisation of electron beam parameters at the Australian Synchrotron Linac. The system is based on state of the art developments in Artificial Intelligence techniques for video games and is adapted here to beam parameters optimisation problems. It consists of a genetically evolved neural network that mimics an operator's decisions to perform an optimisation task when no prior knowledge other than constraints on the actuators is available. The system's decisions are based on the actuators positions, the past performance of close points in the search space and the probability of reaching a better performance in the local region of the search space.

• O. Dressler, M.V. Hartrott
  Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Elektronen-Speicherring BESSY II, Berlin
• N. Hauge
  Danfysik A/S, Jyllinge

The pre-accelerator microtron supplies an electron beam at 10⁵ MeV for the Metrology Light Source (MLS) of the Physikalisch-Technische Bundesanstalt (PTB) in Berlin. The beam is delivered via the transfer line to the injection septum and then into the storage ring. This septum magnet has its stainless steel vacuum beam pipe placed inside a laminated silicon iron magnet core. Hence, the pulsed magnetic field (half sine) used for the beam deflection must propagate through the thin metallic beam pipe. During the commissioning of the injection process, it became apparent that the calculated nominal pulse current for this energy and geometry had to be increased by 30 % to achieve proper beam transfer and accumulation. Two problems were apparent. Firstly, the injected beam trajectory had to be set at an angle away from the main beam axis. Secondly, the beam transfer from the septum entrance to exit was disturbed. As a first measure, the septum current pulse length was extended from 35 to 10⁷ μs. Further on, the septum magnet was insulated from the transfer line beam pipe by a ceramic brake. This paper reports on measurements of pulsed magnetic fields inside the septum magnet.

* Commissioning and Operation of the Metrology Light Source, J. Feikes et al., BESSY, Berlin, Germany; R. Klein, G. Ulm, Physikalisch-Technische Bundesanstalt, Berlin, Germany; EPAC08, Genoa, Italy.

• M. Migliorati
  Rome University La Sapienza, Roma
• M. Ferrario, C. Vaccarezza
  INFN/LNF, Frascati (Roma)
• C. Ronsivalle
  ENEA C.R. Frascati, Frascati (Roma)
• M. Venturini
  LBNL, Berkeley, California

Velocity bunching (or RF compression) represents a promising technique complementary to magnetic compression to achieve the high peak current required in the linac drivers for FELs. Here we report on recent progress aimed at characterizing the RF compression from the point of view of the microbunching instability. We emphasize the development of a linear theory for the gain function of the instability and its validation against macroparticle simulations that represents a useful tool in the evaluation of the compression schemes for FEL sources.

• C. Vaccarezza, E. Chiadroni, M. Ferrario
  INFN/LNF, Frascati (Roma)
• G. Dattoli, L. Giannessi, M. Quattromini, C. Ronsivalle
  ENEA C.R. Frascati, Frascati (Roma)
• M. Migliorati
  Rome University La Sapienza, Roma
• M. Venturini
  LBNL, Berkeley, California

The effects of microbunching instability for the SPARX accelerator have been analyzed by means of different numerical simulation codes and analytical approach. The laser heater counteracting action has been also addressed in order to optimize the parameters of the compression system, either hybrid RF plus magnetic chicane or only magnetic, and possibly enhance the FEL performance.

• M. A. Bakr, Y.W. Choi, T. Kii, R. Kinjo, K. Masuda, H. Ohgaki, T. Sonobe, M. Takasaki, S. Ueda, K. Yoshida
  Kyoto IAE, Kyoto
• H. Zen
  UVSOR, Okazaki

RF gun has been chosen as injector for Kyoto University free electron laser because it can potentially produce an electron beam with high energy, small emittance, moreover inexpensive and compact configuration in comparison with other injectors. As for the RF gun cathode, thermionic cathode is simpler, easier to treat and reliable than photocathode. On the other hand, backbombardment electrons make cathode surface temperature and current density increase within the macropulse, as a result, beam energy and macropulse duration decrease, which means, it is difficult to generate stable FEL. The heating property of cathode not only depends on physical properties of the cathode material such as work function, but also backbombardment electrons energy. We investigated the heating property of six hexaboride materials against the backbombarding electrons by numerical calculation of the range and stopping power. In this investigation, the emission property of the cathode was also taken into account, since high electron emission is required for generation of high brightness electron beam. The results will be discussed.

• G. Feng, W. Fan, W.W. Gao, W. Li, L. Wang, S.C. Zhang
  USTC/NSRL, Hefei, Anhui

In order to obtain more straight sections for insertion devices and higher brilliance synchrotron radiation, an upgrade project of Hefei Light source (HLS) is undergoing. A new injection system has been designed to improve injection efficiency and keep the machine running stably. Four kickers will be used to generate a local injection bump. Effects of injection system to injecting beam and stored beam have been simulated considering errors. Finally, ELEGANT code was used to simulate the injection process with new designed bump system. The simulation results show that the injection efficiency would be higher than 99% and perturbation on stored beam would be small enough, which are benefit to full energy injection and top-up operation of HLS in the future.

• M. Gu, Z.H. Chen, B. Liu, L. Ouyang, R. Wang, Y. Wu, Q. Yuan
  SINAP, Shanghai

The injection system composed of four kickers and two septa in the SSRF have been built and operated. The commissioning shows that fine injecting efficiency and smaller disturbance are carried out. The septum magnets are eddy current designs with a sheet of magnetic screening material around the stored electron beam to reduce the leakage field. The beam tube with RF finger flanges at each end is added to keep the continuity of impedance for the circulating beam. The pulser excite the septum with 60μsecond waveform of half sine-wave and 8kA peak current. Four identical kicker magnets provide the symmetric bump in 10 meter long straight sections. The excitation waveform is a 3.8μsecond half sine pulse up to 7 kA peak. The emphasis was on achieving the best possible tracking in time of the magnet field waveforms so that the residual closed orbit disturbance is minimized for top-up injection. The performance of the injection system with these pulsed magnets are described.

• M. Znidarcic
  I-Tech, Solkan
• K.B. Scheidt
  ESRF, Grenoble

Initially, the Libera Brilliance Single Pass was intended for beam position monitoring at injector system for the FEL machines, this was afterwards followed by the idea of using it on transfer lines on the 3rd generation light sources. The device can be used on pickup buttons and on striplines. The measurement principles and results of Libera Brilliance Single Pass at ESRF, as beam-charge monitor and injection-efficiency monitor, are presented.

• J.C. Huang, C.-H. Chang, C.-S. Hwang, C.Y. Kuo, F.-Y. Lin, C.-S. Yang
  NSRRC, Hsinchu

Pulsed magnet system of Taiwan Photon source(TPS) requires a very low stray field to avoid parasitic magnetic field into the stored beam. The stray field from storage ring(SR) injection septum is required to be less than 0.2 Gauss. The most common method to protect parasitic magnetic field is to use high permeability and conductivity material, such as a Mu-metal. A 1.2 ms half-sine wave pulse of up to 8280A current peak are supply to a septum and would result in eddy current loss in magnet and conductor current diffusion during the rapid charging on magnet. Moreover, competition between eddy current loss and magnetic permeability would lead to a complex phenomena inside the mumetal shielding cabinet and shielding performance. In this study, the magnetic shielding performance of a shielding cabinet was examined in different shielding cabinet geometry and thickness. The results were calculated in Opera software and show that there is a significant suppression of SR septum stray field when round shielding cabinet is in use.

• K.L. Tsai, C.-T. Chen, Y.-S. Cheng, C.-S. Fann, K.T. Hsu, S.Y. Hsu, K.H. Hu, K.-K. Lin, C.Y. Wu
  NSRRC, Hsinchu
• Y.-C. Liu
  National Tsing-Hua University, Hsinchu

The test results of a dual one-turn coils configuration for Taiwan Light Source (TLS) booster extraction kicker is presented in this report. The achieved capability of the test unit demonstrates that the rise-time of the kicker current pulse has been improved for beam extraction optimization. This improved performance is mainly accomplished by reducing the load inductance effectively with a dual one-turn coils configuration. The measured result of rise-time variation versus the corresponding load inductance change is briefly discussed.

• P.H. Williams, D.J. Dunning, N. Thompson
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• D. Angal-Kalinin, J.K. Jones, P.H. Williams
  Cockcroft Institute, Warrington, Cheshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford
• J. Rowland
  Diamond, Oxfordshire

We present progress in the design of the recirculating linac option for the UK New Light Source. Improvements in all accelerator sections have been made such that the output meets the required specifications to drive the seeded NLS FELs. Full start-to-end simulations and tolerance studies are presented together with a comparison to the baseline, single pass linac design.

• D. Angal-Kalinin, P.H. Williams
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• D. Angal-Kalinin, F. Jackson, S.P. Jamison, J.K. Jones, B.D. Muratori, N. Thompson
  Cockcroft Institute, Warrington, Cheshire
• R. Bartolini, I.P.S. Martin
  JAI, Oxford

The design of free electron laser (FEL) driver needs careful beam transport design to pass very short bunches through the switchyard/spreader to switch the beam to different FEL lines. The spreader design which allows flexibility in operation has been adapted following the LBNL design*. In order to measure the slice properties of the bunches two beam diagnostics lines are proposed, a straight one for beam commissioning purposes and a branch of the spreader similar to the FEL lines to measure the adverse effects that may arise due to passing the short bunches through the kicker and septum magnets. As a part of machine protection, post linac collimation system collimates the halo particles in transverse and energy planes. The design of the collimation, beam spreader and beam diagnostics lines is discussed.

* Zholents A.A. et al, CBP Tech Note 401, 2009

• J.-L. Fernandez-Hernando, D. Angal-Kalinin
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

The proposed UK New Light Source project will need beam dump to absorb a bunch charge of 200 pC with the repetition rates starting from 1 KHz initially up to 1 MHz in the upgrade. We are exploring an option of a solid dump with a graphite core to absorb the beam power up to 450 kW for the upgrade option as this is the most challenging design. Since the beam dump design will also affect the building layout the choice of its design should be made at an early stage. Based on the feasibility studies of a solid dump, a decision not to go for more complex water dump can be taken. The post linac collimation section should protect the undulators from irradiation due to beam halo particles. This paper shows results and conclusions from simulations of the impact of the NLS beam on different solid beam dump solutions and the effect of the beam halo on the collimators.

• G.C. Pappas
  LBNL, Berkeley, California

For quadrupole or sextupole magnets, the field at the center is zero and will not disturb the stored beam, while the field away from the center increases in magnitude, giving a larger kick to the particles off axis. By pulsing such multipole magnets it is possible to improve the injection efficiency of the Advanced Light Source (ALS) in top off mode. The requirements for a multipole pole kicker injection scheme for ALS are to kick a 1.9 GeV beam by an angle of 10 mrad with a magnet of 1 meter length. Both quadrupole and sextupole magnets have been studied, as well as a dipole magnet with non-constant field magnitude across the center of the aperture. This paper describes the design and gives a comparison of each type of magnet as well as the modulators needed to drive them.

• W.J. Corbett, A.S. Fisher, X. Huang, J.A. Safranek, S. Westerman
  SLAC, Menlo Park, California
• W.X. Cheng
  BNL, Upton, Long Island, New York
• W.Y. Mok
  Life Imaging Technology, Palo Alto, California

As SPEAR3 moves closer to trickle-charge topup injection, the complex phase-space dynamics of the injected beam becomes increasingly important for capture efficiency and machine protection. In the horizontal plane the beam executes ~12mm betatron oscillations and begins to filament within 10's of turns. In the vertical plane the beam is more stable but a premium is placed on flat-orbit injection through the Lambertson septum and the correct optical match. Longitudinally, energy spread in the booster is converted to arrival-time dispersion by the strong R56 component in the transfer line. In this paper, we report on turn-by-turn imaging of the injected beam in both the transverse plane and in the longitudinal direction using a fast-gated ccd and streak camera, respectively.

• R.P. Fliller
  BNL, Upton, Long Island, New York

Injection into a ring requires that the injected beam be optimally matched to the storage ring lattice. For on axis injection this requires that the twiss functions of the transfer line match the twiss functions of the lattice. When injection off axis, as is done in light sources for top off injection, the goal is to use the minimum phase space area in the storage ring. A. Streun* has given an analytical method to compute the twiss functions for top off injection into the SLS where injection occurs at a beam waist. We have extended his theory to include cases where there is no beam waist. A simple analytical formula is not possible in this case, however we give an algorithm to compute the twiss parameters of the injected beam given the storage ring lattice. We also compute the twiss functions for a variety of cases for the NSLS-II storage ring.

* A. Streun. "SLS booster-to-ring transfer line optics for optimum injection effciency". Technical Note SLS-TME-TA-2002-0193. May 27, 2005.

• R.P. Fliller, R. Heese, S. Kowalski, J. Rose, T.V. Shaftan, G.M. Wang
  BNL, Upton, Long Island, New York

The National Synchrotron Light Source II (NSLS-II) is a state of the art 3 GeV third generation light source currently under construction at Brookhaven National Laboratory. The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster synchrotron. The injection system needs to deliver 7.5 nC in 80 - 150 bunches to the storage ring every minute to achieve current stability goals in the storage ring. This is a very stringent requirement that has not been demonstrated at an operating light source, though it should be achievable. To alleviate the charge requirement on the linac, we have designed a scheme to stack two bunch trains in the booster. In this paper we discuss this stacking scheme. The performance of the stacking scheme is studied in detail at injection and through a full booster ramp. We show the the ultimate performance of the stacking scheme is similar to a single bunch train in the booster if the linac emittance meets the requirements. Increasing the emittance of the linac beam degrades the performance, but still allows an overall increase of train charge vs. one bunch train.

• R.P. Fliller, W.R. Casey, R. Faussete, H. Fernandes, G. Ganetis, R. Heese, H.-C. Hseuh, P.K. Job, B.N. Kosciuk, R. Meier, D. Padrazo, I. Pinayev, J. Rose, T.V. Shaftan, O. Singh, J. Skaritka, C.J. Spataro, G.M. Wang
  BNL, Upton, Long Island, New York

The NSLS-II injection system consists of a 200 MeV linac and a 3 GeV booster synchrotron and associated transport lines. The transport lines need to transport the beam from the linac to the booster and from the booster to the storage ring in a way that provide high injection efficiency. In this paper we discuss progress on specifying and prototyping the NSLS-II transfer lines including diagnostics, magnet specifications, and safety systems. Commissioning plans are also discussed.

• T.V. Shaftan, A. Blednykh, Y. Kawashima, S. Krinsky, J. Rose, L.-H. Yu
  BNL, Upton, Long Island, New York

Booster extraction presents a number of problems that include strengths and waveforms of the pulsed magnets and design of the vacuum chamber. Instabilities in the booster extraction may compromise the extracted beam quality deteriorating value of high-performance injector design. Here we discuss requirements and tolerances for the extraction system components and methods of increasing its performance.

• P. Gouard, S. Champeaux
  CEA, Bruyeres le Chatel
• P. Liger, D. Morisseau
  GETINGE - La Calhene, Villebon sur Yvette

The original linac consists of an electron gun (45 kV, 6 A peak, 4 μs pulses @ 210 Hz) and 8 accelerating cells coupled with coupling cells in π/2 mode @ 3 GHz to provide for a 1 mA and 5 MeV beam. A loss of control of electron emission was experimentally observed due to anomalous heating of the cathode. We simulate the linac operation with the 2D1/2 MAGIC® electromagnetic PIC code to understand and suppress these phenomena. We show that electrons are accelerated back from the accelerating structure to the cathode. Their power is responsible for the unwanted cathode heating and emission control loss. To overcome these phenomena, a new design is proposed. A buncher cavity and a solenoid are inserted to improve the coupling between the electron beam and the accelerating cells.

• L. Haenichen, W.F.O. Müller, T. Weiland
  TEMF, TU Darmstadt, Darmstadt
• O. Boine-Frankenheim
  GSI, Darmstadt

Beam coupling impedances have been identified as an appropriate quantity to describe collective instabilities caused through beam-induced fields in heavy ion synchrotron accelerators such as the SIS-18 and the SIS-100 at the GSI facility. The impedance contributions caused by the multiple types of beamline components need to be determined to serve as input condition for later stability studies. This paper will discuss different approaches to calculate the Coupling Impedance contribution of ferrite devices, exploiting the abilities of both commercial codes such as CST STUDIO SUITE® and specific extensions of this code to address kicker related problems in particular. Before addressing actual beamline devices, benchmark problems with cylindrical and rectangular geometry will be simulated and the results will be compared with the corresponding analytical formulations.

• G. Pöplau, U. van Rienen
  Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock

Precise and fast 3D space-charge calculations for bunches of charged particles are still of growing importance in recent accelerator designs. Whereas an adaptive discretization of a bunch is often required for efficient space charge calculations in practice, such a technique is not implemented in many computer codes. For instance, the FFT Poisson solver that is often applied allows only an equidistant mesh. An adaptive discretization following the particle density distribution is implemented in the GPT tracking code (General Particle Tracer, Pulsar Physics) together with a multigrid Poisson solver. The disadvantage of this approach is that jumps in the distribution of particles are not taken into account and the hierarchical construction of meshes in multigrid can not be used. In this paper we present an approach to an adaptive discretization which is based on the multigrid technique. The goal is that the error estimator needed for the adaptive distribution of mesh lines can be calculated directly from the multigrid procedure. The algorithm will be investigated for several particle distributions and compared to that adaptive discretization method implemented in GPT.

• P. Jain
  Sokendai, Ibaraki
• H. Fukuma, K. Kanazawa, Y. Suetsugu
  KEK, Ibaraki

Electron Cloud (ECLOUD) deteriorates the performance of proton and positron storage rings. Therefore it is desirable to understand the ECLOUD buildup in a given machine. The data taken by Retarded Field Analyzer (RFA) with a multi channel plate showed that the signal had the peaks coinciding with the positron bunch pattern if a high voltage of -2kV is applied to the retarded grid*. This suggests that the cloud electrons get maximum kick near the positron bunch. A computer program has been developed to study the near bunch ECLOUD density at KEKB LER (Low Energy Ring). In simulations, secondary electron emission is modeled according to the Furman and Pivi's model**. In this paper we compare the simulation results of the ECLOUD buildup with the experiments performed in KEK under different beam-optics elements.

* K. Kanazawa et al., PAC05, 10⁵⁴.
** M. Furman and M. Pivi, PRST-AB, 5, 124404 (2002).

• H. Kawaguchi
  Muroran Institute of Technology, Department of Electrical and Electronic Engineering, Muroran
• T. Weiland
  TEMF, TU Darmstadt, Darmstadt

A Time Domain Boundary Element Method (TDBEM) has advantages of grid dispersion free property, treatment of electron bunch with curved trajectory, etc. in wake field analysis. On the other hand, the TDBEM has also serious problems of heavy calculation cost and large required memory which are main reasons why the TDBEM can not be widely used yet. For the large memory problem, moving window scheme was introduced into the TDBEM and it was shown that the TDBEM can be applied to very long accelerator structures*. This paper presents a new formulation of the TDBEM, an initial value problem formulation. To use the initial value problem formulation of the TDBEM, a new type of moving window scheme, which can be applied to curved trajectory or electron motion with smaller velocity than the speed of light, will be introduced.

* K.Fujita, H.Kawaguchi, R.Hampel, W.F.O.Muller, T.Weiland, S.Tomioka,"Time Domain Boundary Element Analysis of Wake Fields in Long Accelerator Structures,"IEEE Trans. Nucl. Sci.,55[5](2008),pp.2584-2591.

• S.V. Kutsaev
  MEPhI, Moscow

This paper introduces "Hellweg 2D" code, a special tool for electron dynamics simulation in waveguide accelerating structure. The underlying theory of this software is based on the numerical solutions of differential equations of particle motion. The effects considered in this code include beam loading, space charge forces, external focusing magnetic field. "Hellweg 2D" is capable to deal with multisectional accelerators. Along with a manual input of electrodynamical parameters of the cells, for disk-loaded structures they can be calculated automatically with a help of experimental data tables. In order to obtain the maximum capture in the buncher section, the optimizer of phase velocity and electric field strength functions is developed. The comparison of U-1-M buncher beam dynamics simulations via "Hellweg 2D" and experimental data is provided.

• B.S.C. Oswald, S. Tsujino
  PSI, Villigen
• P. Leidenberger
  IFH, Zurich

Laser induced field emission has become an enabling technology for building ultra-low emittance electron sources for particle accelerators, such as the x-ray free-electron laser (SwissFEL) under development at the Paul Scherrer Institut (PSI). One approach consists of a sharp pyramidal tip with lateral dimensions of a few nanometers, illuminated by a laser to increase the extracted electron current. Another approaches uses conventional cathodes. In both cases, there are structural details on the nanometer scale, that determine the interaction between the laser and the cathode and thus directly the quantum efficiency of the emitter. We use a 3-d full-wave finite element time domain electromagnetic approach* to understand the nano-optical interaction between structure and laser pulse. For example, the lightning rod effect of sharp tips enhances the electric field in the vicinity. Also, optical antenna concepts have been proposed to enhance the electric field at the field emitter's tip so that higher currents can be extracted. We use dispersive material models for the metals in the optical region of the electromagnetic spectrum.

*Benedikt Oswald and Patrick Leidenberger, Journal of Computational and Theoretical Nanoscience, Vol 6(3), 2009, pp. 784-794. doi 10.1166/jctn.2009.1109

• H. Guo
  PSI-LRF, Villigen, PSI
• A. Adelmann, A. Falone, C. Kraus, B.S.C. Oswald
  PSI, Villigen
• P. Arbenz
  ETH, Zurich

The X-ray Free Electron Laser (SwissFEL) under development at the Paul Scherrer Institut (PSI) will employ a special type of a deflecting cavity, LOLA*, for beam diagnostics. Since this cavity's design breaks the symmetry, a complete 3-dimensional eigenmodal analysis is indispensable. The 3-dimensional eigenmodal solver femaxx employs the finite element method and has been developed in a collaboration between PSI and the Swiss Federal Institute of Technology Zurich (ETH). The femaxx code uses the graphical frontend program heronion for the application of boundary conditions, including symmetry, and generates a tetrahedral mesh. We use femaxx to analyze the existing LOLA cavity design**, compute electromagnetic eigenmodes with their corresponding eigenfrequencies, and associated performance figures. Since these are large computational problems femaxx has been optimized for distributed memory parallel compute clusters. For the further usage in the beam dynamics code OPAL we sample the eigenmodal fields on a 3-dimensional Cartesian grid.

* A. Falone, et al: RF deflector for bunch length measurement at low energy at PSI. Proceedings of PAC2009.
** P. Arbenz et al., Parallel Computing, 32: 157-165 (2006).

• C. Lingwood, G. Burt, K. Gunn
  Cockcroft Institute, Lancaster University, Lancaster
• J.D.A. Smith
  Tech-X, Boulder, Colorado

The design of RF cavities is a multivariate multi-objective problem. Manual optimisation is poorly suited to this class of investigation, and the use of numerical methods results in a non-differentiable problem. Thus the only reliable optimisation algorithms employ heuristic methods. Using an evolutionary algorithm guided by Pareto ranking methods, a crab cavity design can be optimised for transverse voltage (V_T) while maintaining acceptable surface fields and the correct operating frequency. Evolutionary algorithms are an example of a parallel meta-heuristic search technique inspired by natural evolution. They allow complex, epistatic (non-linear) and multimodal (multiple optima and/or sub-optima) optimization problems to be efficiently explored. Using the concept of domination the solutions can be ordered into Pareto fronts. The first of which contains a set of cavity designs for which no one objective (e.g. the transverse voltage) can be improved without decrementing other objectives.

• J. Molson, R.J. Barlow, H.L. Owen, A.M. Toader
  UMAN, Manchester
• J. Molson
  Cockcroft Institute, Warrington, Cheshire

MERLIN is a highly abstracted particle tracking code written in C++ that provides many unique features, and is simple to extend and modify. We have investigated the addition of high order wakefields to this tracking code and their effects on bunches, particularly with regard to collimation systems for both hadron and lepton accelerators. Updates have also been made to increase the code base compatibility with current compilers, and speed enhancements have been made to the code via the addition of multi-threading to allow cluster operation on the grid. In addition, this allows for simulations with large numbers of particles to take place. Instructions for downloading the new code base are given.

• Y. Giboudot, R. Nilavalan
  Brunel University, Middlesex
• T.R. Edgecock
  STFC/RAL, Chilton, Didcot, Oxon
• A. Wolski
  The University of Liverpool, Liverpool

The Non Scaling Fixed Field Alternating Gradient EMMA has a compact linear lattice. Effect of Fringe Field on the beam has to be studied carefully. A numerical magnetic field map is generated by magnet measurements or magnet design softwares. We developed a technique that produces from the numerical field map, a dynamical map for a particle travelling in the entire EMMA cell for a reference energy without acceleration. Since the beam dynamics change with energy, a set of maps have been produce with different reference energies between 10 and 20MeV. For each reference energy, simulated tune and time of flight (TOF) have been compared with results in Zgoubi - tracking directly through numerical field map. The range of validity of a single map has been investigated by tracking particle with large energy deviation. From that, a sensible acceleration scheme has been implemented.

yoel.giboudot@stfc.ac.uk

• J. Resta-López, J. Dale
  JAI, Oxford
• B. Dalena, D. Schulte, J. Snuverink, F. Stulle, R. Tomás
  CERN, Geneva
• A. Latina
  Fermilab, Batavia

We present the current status of the beam tracking simulations of the Compact Linear Collider (CLIC) from the exit of the damping ring to the interaction point, including the ring to main linac (RTML) section, main linac, beam delivery system (BDS) and beam-beam interactions. This model introduces realistic alignment survey errors, dynamic imperfections and also the possibility to study collective effects in the main linac and the BDS. Special emphasis is put on low emittance transport and beam stabilization studies, applying beam based alignment methods and feedback systems. The aim is to perform realistic integrated simulations to obtain reliable luminosity predictions.

• S. Molloy, S.T. Boogert
  Royal Holloway, University of London, Surrey

Serpentine is a Python library, written for the purpose of simulating charged particle accelerators. It has been written to allow for the simulation of both rings and single-shot machines in a light-weight way (i.e. without requiring significant computational resources for typical calculations, such as the determination of transfer matrices, or matching of Twiss parameters), and has been structured to be highly modular (i.e. allowing extension of the simulations to include effects not already included in the base installation). Through the use of the Universal Accelerator Parser (UAP), Serpentine has no need for a new lattice representation, and allows access to any lattice format understood by UAP. The operation of this code on several complex accelerator designs is demonstrated.

• M. Min, P.F. Fischer
  ANL, Argonne

NekCEM is a high-performance parallel code for simulating wakefields based on high-order discretizations*,**. We will present performance of NekCEM code at large count of processors. A newly developed communication kernel for NekCEM enables simulations on 10K-100K processors. We will demonstrate scalablity analysis for P>10K, depending on the number of grid points per processor for wakepotential simulations with a 9-cell TESLA cavity.

* Spectral element discontinuous Galerkin (SEDG) simulations with a moving window, Proc. PAC09
** SEDG simulations for bunched beam in accelerating structures, Proc. PAC07

• T.J. Roberts
  Muons, Inc, Batavia
• D.M. Kaplan
  Illinois Institute of Technology, Chicago, Illinois

There are dozens of programs for designing and modeling accelerator systems, most of which have their own language for describing the system. This means a designer must spend considerable time learning the languages of different programs and converting system descriptions among them. This paper describes a project to develop a new language for accelerator modeling, together with a portable suite of programs to implement it. These programs will assist the user while editing, visualizing, developing, simulating, and sharing models of accelerator components and systems. This suite is based on a Graphical User Interface (GUI) that will permit users to assemble their system graphically and then display it and check its sanity visually, even while using modeling programs that have no graphical or visualization capabilities. Incorporating the concept of libraries as a primary component of the language will encourage collaboration among geographically diverse teams. The requirements for developing this language and its tools will be based on generality, flexibility, extensibility, portability, usability, and sharability.

• T.J. Roberts, K.B. Beard
  Muons, Inc, Batavia
• S. Ahmed, D. Huang, D.M. Kaplan, L.K. Spentzouris
  Illinois Institute of Technology, Chicago, Illinois

The G4beamline program* is a useful and steadily improving tool to quickly and easily model beam lines and experimental equipment without user programming. It has both graphical and command-line user interfaces. Unlike most accelerator physics codes, it easily handles a wide range of materials and fields, being particularly well suited for the study of muon and neutrino facilities. As it is based on the Geant4 toolkit**, G4beamline includes most of what is known about the interactions of particles with matter. We are continuing the development of G4beamline to facilitate its use by a larger set of beam line and accelerator developers. A major new feature is the calculation of space-charge effects. G4beamline is open source and freely available at: http://g4beamline.muonsinc.com

* http://g4beamline.muonsinc.com
** http://geant4.cern.ch

• J.-L. Vay, E. Cormier-Michel, W.M. Fawley, C.G.R. Geddes
  LBNL, Berkeley, California

Numerical simulation of some systems containing charged particles with highly relativistic directed motion can be speeded up dramatically by choice of the proper Lorentz-boosted frame*. Orders of magnitude speedup has been demonstrated for simulations from first principles of laser-plasma accelerator, free electron laser, and particle beams interacting with electron clouds. We summarize the technique and the most recent examples. We then address the application of the Lorentz-boosted frame approach to coherent synchrotron radiation (CSR), which can be strongly present in bunch compressor chicanes. CSR is particularly relevant to the next generation of x-ray light sources and difficult to simulate in the lab frame because of the large ratio of scale lengths. It can increase both the incoherent and coherent longitudinal energy spread, effects that often lead to an increase in transverse emittance. We use the WARP code** to simulate CSR emission around dipole simple bends. We present some scaling arguments for the possible computational speed up factor in the boosted frame and initial 3D simulation results for some standard CSR test cases.

* J.-L. Vay, Phys. Rev. Lett. 98 (2007) 130405
** D.P. Grote, A. Friedman, J.-L. Vay, and I. Haber, AIP Conf. Proc. 749 (2005), 55.

• D.T. Abell, I.V. Pogorelov, P. Stoltz
  Tech-X, Boulder, Colorado

Imagine a virtual cylinder passing through an rf cavity. Given field data on the surface of this cylinder, one can compute accurate high-order transfer maps for particles traversing the cavity*. This technique is robust against errors or noise present in the surface data; moreover, it is not limited to accelerating modes. We describe this technique and present recent work that uses VORPAL** field data as a starting point for modeling crab cavities. In addition, we present realistic models, including fringes, for several standing-wave modes. These models, which include a simple accelerating mode and a TM-110 (crab) mode, are useful for the accurate computation of transfer maps as well as for constructing model fields that can be used for testing and comparing a variety of rf cavity codes.

* D.T. Abell, Phys. Rev. ST Accel. Beams 9, 052001, (2006).
** C. Nieter and J. R. Cary, J. Comput. Phys. 196, 448 (2004).

• S.G. Shasharina, D. Alexander, J.R. Cary, M.A. Durant, S.E. Kruger, S.A. Veitzer
  Tech-X, Boulder, Colorado

Data organization of simulations outputs differs from application to application. This makes development of uniform visualization and analysis tools difficult and impedes comparison of simulation results. VizSchema is an effort to standardize metadata of HDF5 format so that the subsets of data needed to visualize physics can be identified and interpreted by visualization tools. Based on this standard, we developed a powerful VisIt-based visualization tool. It allows a uniform approach for 3D visualization of large data of various kinds (fields, particles, meshes) from the COMPASS suite for SRF cavities and laser-plasma acceleration. In addition, we developed a specialized graphical interface to streamline visualization of VORPAL outputs and submit remote VORPAL runs. In this paper we will describe our approach and show some visualizations results.

• P. Chu, J. Wu
  SLAC, Menlo Park, California
• J. Qiang
  LBNL, Berkeley, California
• G.B. Shen
  BNL, Upton, Long Island, New York

There are many simulation codes for accelerator modeling. Each one has some strength but not all. Collaboration is formed for the effort of providing a platform to host multiple modeling tools. In order to achieve such a platform, a set of common physics data structure has to be set. Application Programming Interface (API) for physics applications should also be defined within a model data provider. A preliminary platform design and prototype will be presented.

• P. Chu, S. Chevtsov, J. Wu
  SLAC, Menlo Park, California
• G.B. Shen
  BNL, Upton, Long Island, New York

High level applications often suffer from poor performance and reliability due to lengthy initialization, heavy computation and rapid graphical update. Service oriented architecture (SOA) is trying to separate the initialization and computation from applications to distributed service providers. Heavy computation such as beam tracking will be done periodically on a dedicated server and data will be available to client applications at all time. Industrial standard service architecture can help to improve the reliability and maintainability of the service providers. Robustness will also be improved by reducing the complexity of individual client applications.

• G. Wang, M. Blaskiewicz, A.V. Fedotov, Y. Hao, J. Kewisch, V. Litvinenko, E. Pozdeyev, V. Ptitsyn
  BNL, Upton, Long Island, New York

We present our studies on various aspects of the beam dynamics in 'racetrack' design of the first stage electron-ion collider at RHIC (eRHIC), including transverse beam break up instabilities, electron beam emittance growth and energy loss due to synchrotron radiation, electron beam losses due to Touschek effects and residue gas scattering, beam-beam effects at the interaction region and emittance growth of ion beam due to electron bunch to bunch noises. For all effects considered above, no showstopper has been found.

• L. Wang, X. Huang, M.T.F. Pivi
  SLAC, Menlo Park, California

The Cornell Electron Storage Ring (CESR) has been reconfigured as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D. One of the primary goals of the CesrTA program are to investigate the interaction of the electron cloud with low emittance positron beam, to explore methods to suppress the electron cloud, and to develop suitable advanced instrumentation required for these experimental studies. This paper report the simulation of the electron-cloud formation in the wiggler and quadrupole magnets using 3D code CLOUDLAND. The transverse distribution of electron cloud in a wiggler magnet is similar to a dipole magnet except in the zero vertical field regions where the electrons have complicated trajectories and therefore a longer lifetime. Fortunately, these electrons are dominantly direct-photo-electrons and can be easily reduced by properly arranging photon absorbers. Simulations show that the electron cloud in a quadrupole magnet can be trapped for long time due to the mirror field effect.

• L. Wang, L. Lee, G.V. Stupakov
  SLAC, Menlo Park, California

A new method, using the parabolic equation (PE), for the calculation of both high-frequency and small-angle taper (or collimator) impedances is developed in [1]. One of the most important advantages of the PE approach is that it eliminates the spatial scale of the small wavelength from the problem. As a result, the numerical solution of the PE requires coarser spatial meshes. We developed a new code based on Finite Element Method (FEM) which can handle arbitrary profile of a transition. As a first step, we completed and benchmarked a two-dimensional code. One of the important advantages of the code is its fast execution time.

• L. Xiao, S.A. Lundgren, T.W. Markiewicz, C.-K. Ng, J.C. Smith
  SLAC, Menlo Park, California

SLAC is proposing a rotatable collimator design for the LHC phase II collimation upgrade. This design has 20 facet faces on each cylindrical jaw surface and the two jaws, which will move in and out during operation, are rotatable in order to introduce a clean surface in case of a beam hitting a jaw in operation. When the beam crosses the collimator, it will excite broadband and narrowband modes that can contribute to the beam energy loss and power dissipation on the vacuum chamber wall and jaw surface. In this paper, the parallel eigensolver code Omega3P is used to search for all the trapped modes in the SLAC collimator design. The power dissipation generated by the beam in different vacuum chamber designs with different jaw end geometries is simulated. It is found that the longitudinal trapped modes in the circular vacuum chamber design with larger separation of the two jaws may cause excessive heating. Adding ferrite tiles on the vacuum chamber wall can strongly damp these trapped modes. The short-range wakefields will also be calculated to determine the broadband beam heating and transverse kick on the beam. We will present and discuss the simulation results.

• J.A. Holmes
  ORNL, Oak Ridge, Tennessee

At an age of twelve years, the collective beam dynamics particle tracking code, ORBIT, is considered mature. Even so, we continue to enhance ORBIT's capabilities. Two such enhancements are reported here. The first enhancement allows for the use of time dependent waveforms for the strengths of all magnetic elements, a capability that previously was limited to kickers and to RF cavities. This capability should prove very useful for applications to synchrotrons, in which tunes are often manipulated during acceleration. The second enhancement provides an internal calculation of the lattice functions. Previously, these had to be read from an external file, but given the capability of dynamically programming the lattice magnet strengths, it is extremely useful to be able to calculate the lattice functions on demand. Examples illustrating these new ORBIT capabilities will be presented.

• A. Kanareykin, C.-J. Jing, A.L. Kustov, P. Schoessow
  Euclid TechLabs, LLC, Solon, Ohio
• A. Altmark
  LETI, Saint-Petersburg
• W. Gai, J.G. Power
  ANL, Argonne

Beam breakup (BBU) effects resulting from parasitic wakefields are a serious limitation to the performance of dielectric structure based accelerators. We report here on numerical studies and experimental investigations of BBU and its mitigation. An experimental program is underway at the Argonne Wakefield Accelerator facility that will focus on BBU measurements in dielectric wakefield devices. We examine the use of external FODO channels for control of the beam in the presence of strong transverse wakefields. We present calculations based on a particle-Green's function beam dynamics code (BBU-3000) that we are developing. We will report on new features of the code including the ability to treat space charge. The BBU code is being incorporated into a software  framework that will significantly increase its utility (Beam Dynamics Simulation Platform). The platform is based on the very flexible Boinc software environment developed originally at Berkeley for the SETI@home project. The package can handle both task farming on a heterogeneous cluster of networked computers and computing on a local grid. User access to the platform is through a web browser.

• Y. Luo
  BNL, Upton, Long Island, New York

SimTrack is a simple C++ library designed for numeric particle tracking in high energy accelerators. It adopts a 4th order symplectic integrator for optical transportat in the magnetic elements. 4-D and 6-D weak-strong beam-beam treatments are included for beam-beam studies. It provides versatile functions to manage elements and lines. New type of elements can be easily created in the library. It calculates Twiss and coupling, fits tunes and chromaticities, and corrects closed orbits. During tracking, the parameters of elements can be changed or modulated on the fly.

• B. Terzić
  CASA, newport news
• Y. Zhang
  JLAB, Newport News, Virginia

One key limiting factor to a collider luminosity is bean-beam interactions which usually can cause serious emittance growth of colliding beams and fast reduction of luminosity. Such nonlinear collective beam effect can be a very serious design challenge when the machine parameters are pushed into a new regime. In this paper, we present simulation studies of the beam-beam effect for a medium energy ring-ring electron-ion collider based on CEBAF.

• B. Terzić
  CASA, newport news
• R. Li
  JLAB, Newport News, Virginia

We present early stage of a new code for self-consistent, 2D simulations of beam dynamics affected by CSR. The code is of the particle-in-cell variety: the beam bunch is sampled by macroparticles, which are deposited on the grid; the corresponding forces on the grid are then computed using retarded potentials according to causality, and interpolated so as to advance the particles in time. The retarded potentials are evaluated by integrating over the 2D path history of the bunch, with the charge and current density at the retarded time obtained from interpolation of the particle distributions recorded at discrete timesteps. The code is benchmarked against analytical results obtained for a rigid-line bunch. We also outline the features and applications which are currently being developed.