SUPB —  Student Poster Session & Reception   (09-Sep-12   18:00—21:00)
Paper Title Page
SUPB001 Analyzing Surface Roughness Dependence of Linear RF Losses 1
  • C. Xu, M.J. Kelley
    The College of William and Mary, Williamsburg, USA
  • C.E. Reece
    JLAB, Newport News, Virginia, USA
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Topographic structure on Superconductivity Radio Frequency (SRF) surfaces can contribute additional cavity RF losses describable in terms of surface RF reflectivity and absorption indices of wave scattering theory. At isotropic homogeneous extent, Power Spectrum Density (PSD) of roughness is introduced and quantifies the random surface topographic structure. PSD obtained from different surface treatments of niobium, such as Buffered Chemical Polishing (BCP), Electropolishing (EP), Nano-Mechanical Polishing (NMP) and Barrel Centrifugal Polishing (CBP) are compared. A perturbation model is utilized to calculate the additional rough surface RF losses based on PSD statistical analysis. This model will not consider that superconductor becomes normal conducting at fields higher than transition field. One can calculate the RF power dissipation ratio between rough surface and ideal smooth surface within this field range from linear loss mechanisms.
SUPB003 Feasibility Study of Short Pulse Mode Operation for Multi-turn ERL Light Source 4
  • T. Atkinson, A.V. Bondarenko, A.N. Matveenko, Y. Petenev
    HZB, Berlin, Germany
  The optics and simulation group at HZB are designing Germany’s future light source. Based on the emerging Energy Recovery Linac super conducting technology, the Femto-Science-Factory (FSF) will provide its users with ultra-bright photons of Angstrom wavelength at 6 GeV. The FSF is intended to be a multi-user facility and offer a wide variety of operation modes. A low emittance ~0.1 μm rad mode will operate in conjunction with a short-pulse ~10 fs mode. This paper highlights the physical limitations when trying to offer interchangeable modes and preserve beam high quality.  
SUPB004 Linac Optics Design for Multi-turn ERL Light Source 7
  • Y. Petenev, T. Atkinson, A.V. Bondarenko, A.N. Matveenko
    HZB, Berlin, Germany
  The optics simulation group at HZB is designing a multi-turn energy recovery linac-based light source. Using the superconducting Linac technology, the Femto-Science-Factory (FSF) will provide its users with ultra-bright photon beams of angstrom wavelength at 6 GeV. The FSF is intended to be a multi-user facility and offer a variety of operation modes. In this paper a design of transverse optic of the beam motion in the Linacs is presented. An important point in the optics design was minimization of the beta-functions in the linac at all beam passes to suppress beam break-up (BBU) instability.  
SUPB006 Study of Beam-Based Alignment for Shanghai Soft X-Ray FEL Facility 10
  • D. Gu, Q. Gu, D. Huang, M. Zhang, M.H. Zhao
    SINAP, Shanghai, People's Republic of China
  In linear accelerators, dispersion caused by quadrupole misalignment and transverse wake-field effect caused by alignment errors of accelerate structures will lead to a significant emittance growth. There are more stringent restrictions on SXFEL, the traditional optical alignment can no longer meet its requirements, but the Beam-Based Alignment(BBA) method allows more precise alignment, further reduce the Linac errors to meet SXFEL requirements .In undulator sections, orbit changes are not only caused by misalignments of quadrupole magnet position ,but also the errors of undulator magnetic. In order to achieve alignment accuracy over longer distance, we measuring BPM data under different conditions and using SVD algorithm for calculation and analysis, we can get the quadrupole magnet errors and BPM offset. With the method above, software based on MATLAB has been designed and compared the results with other software.  
SUPB007 On-Line Dispersion Free Steering for the Main Linac of CLIC 13
  • J. Pfingstner, D. Schulte
    CERN, Geneva, Switzerland
  For future linear colliders as well as for light sources, ground motion effects are a severe problem for the accelerator performance. After a few minutes, orbit feedback systems are not sufficient to mitigate all ground motion effects and additional long term methods will have to be deployed. In this paper, the long term ground motion effects in the main linac of the Compact Linear Collider (CLIC) are analysed via simulation studies. The primary growth of the projected emittance is identified to originate from chromatic dilutions due to dispersive beam orbits. To counter this effect, an on-line identification algorithm is applied to measure the dispersion parasitically. This dispersion estimate is used to correct the beam orbit with an iterative dispersion free steering algorithm. The presented results are not only of interest for the CLIC project, but for all linacs in which the dispersive orbit has to be corrected over time.  
SUPB008 Specifications of the Distributed Timing System for the CLIC Main Linac 16
  • A. Gerbershagen, A. Andersson, D. Schulte
    CERN, Geneva, Switzerland
  • P. Burrows
    JAI, Oxford, United Kingdom
  • F.Ö. Ilday
    Bilkent University, Bilkent, Ankara, Turkey
  The longitudinal phase stability of CLIC main and drive beams is a crucial element of CLIC design. In order to measure and to control the phase, a distributed phase monitoring system has been proposed. The system measures the beam phase every 900 m. The relative phase between the measurement points is synchronized with an external reference system via a chain of reference lines. This paper presents the simulations of error propagation in the proposed distributed monitoring system and the impact on the drive and main beam phase errors and the luminosity. Based on the results the error tolerances for the proposed system are detailed.  
SUPB009 Linear Accelerator based on Parallel Coupled Accelerating Structure 19
  • A.E. Levichev, A.M. Barnyakov, V.M. Pavlov
    BINP SB RAS, Novosibirsk, Russia
  • Y.D. Chernousov
    ICKC, Novosibirsk, Russia
  • V. Ivannikov, I.V. Shebolaev
    ICKC SB RAS, Novosibirsk, Russia
  Accelerating stand based on parallel coupled accelerating structure and electron gun is developed and produced. The structure consists of five accelerating cavities. The RF power feeding of accelerating cavities is provided by common exciting cavity which is performed from rectangular waveguide loaded by reactive pins. Operating frequency is 2450 MHz. Electron gun is made on the basis of RF triode. Linear accelerator was tested with different working regimes. The obtained results are following: energy is up to 4 MeV, accelerating current is up to 300 mA with pulse duration of 2.5 ns on the half of the width; energy is up to 2.5 MeV, accelerating current is up to 100 mA with pulse duration of 5 μs; energy is up to 2.5 MeV, accelerating current is up to 120 mA with pulse duration of 5 μs and beam capture of 100%. The descriptions of the accelerator elements are given in the report. The features of the parallel coupled accelerating structure are discussed. The results of the measuring accelerator’s parameters are presented.  
SUPB010 Measurements of a Reduced Energy Spread of a Recirculating Linac by Non-Isochronous Beam Dynamics 22
  • F. Hug, C. Burandt, M. Konrad, N. Pietralla
    TU Darmstadt, Darmstadt, Germany
  • R. Eichhorn
    Cornell University, Ithaca, New York, USA
  Funding: supported by DFG through SFB 634
The Superconducting Linear Accelerator S-DALINAC at the University of Darmstadt (Germany) is a recirculating linac with two recirculations providing beams for measurements in nuclear physics at small momentum transfers. For these experiments an energy spread of better than 10-4 (rms) is needed. Currently acceleration in the linac section is done on crest of the accelerating field. The recirculation path is operated achromatic and isochronous. In this recirculation scheme the energy spread of the resulting beam in the ideal case is determined by the electron bunch length. Taking into account the stability of the RF system the energy spread increases drastically to more than 10-3 (rms). We will present a new non-isochronous recirculation scheme which helps cancelling out these errors from the rf-control. This scheme uses longitudinal dispersion in the recirculation paths and an acceleration off-crest with a certain phase with respect to the maximum. We will present results of the commissioning of the new system including measurements of the longitudinal dispersion in the recirculation arcs as well as measurements of the resulting energy spread using an electron spectrometer.
SUPB011 Computational Model Analysis for Experimental Observation of Optical Current Noise Suppression Below the Shot-noise Limit 25
  • A. Nause, A. Gover
    University of Tel-Aviv, Faculty of Engineering, Tel-Aviv, Israel
  Funding: We acknowledge support of the Israel Science Foundation grant
We report first demonstration of optical frequency current shot-noise suppression in a relativistic e-beam. This process is made possible by collective Coulomb interaction between the electrons of a cold intense beam during beam drift, and is essentially a process of longitudinal beam-plasma oscillation [1]. Suppression of beam current noise below the classical “shot-noise” level has been known in the microwave tubes art [2]. This is the first time that it is demonstrated in the optical regime. We predict that the scheme can be extended to the XUV and possibly to shorter wavelengths with further development of technology. The fundamental current shot-noise determines the level of incoherent spontaneous radiation emission from electron-beam optical radiation sources and SASE-FELs [3]. Suppressing shot-noise would make it possible to attain spontaneous emission sub-radiance [4] and surpass the classical coherence limits of seed-injected FELs. The effect was demonstrated by measuring sub-linear growth as a function of current of the OTR Radiation. This finding indicates that the beam charge homogenizes due to the collective interaction, and its distribution becomes sub-Poissonian.
[1] A. Gover, E. Dyunin, PRL, 102, 154801, 2009
[2] H. Haus, N. Robinson, Proc. IRE, 43, 981 (1955)
[3] P. Emma, et al , Nature Photonics 4, 641 (2010)
[4] A. Dicke, Phys. Rev. 93, 99 (1954)
SUPB012 Status of CH Cavity and Solenoid Design of the 17 MeV Injector for MYRRHA 29
  • D. Mäder, H. Klein, H. Podlech, U. Ratzinger, C. Zhang
    IAP, Frankfurt am Main, Germany
  Funding: This work has been supported by the EU (FP7 MAX contract number 269565)
The multifunctional subcritical reactor MYRRHA (Multi-purpose hybrid research reactor for high-tech applications) will be an accelerator driven system (ADS) located in Mol (Belgium). The first accelerating section up to 17 MeV is operated at 176 MHz and consists of a 4-rod-RFQ followed by two room temperature CH cavities with integrated triplet lenses and four superconducting CH structures with intertank solenoids. Each room temperature CH cavity provides about 1 MV effective voltage gain using less than 30 kW of RF power. The superconducting resonators have been optimized for electric peak fields below 30 MV/m and magnetic peak fields below 30 mT. For save operation of the superconducting resonators the magnetic field of the intertank solenoids has to be well shielded towards the CH cavity walls. Different coil geometries have been compared to find the ideal solenoid layout.
SUPB013 The Beam Commissioning Plan of Injector II in C-ADS 32
  • Z.J. Wang, Y. He, H. Jia, C. Li, S.H. Liu, W. Wu, X.B. Xu, B. Zhang, H.W. Zhao
    IMP, Lanzhou, People's Republic of China
  The design work of the Injector II, which is 10 MeV proton linac, in C-ADS project is being finished and some key elements are being fabricated. Now it is necessary to definite the operation mode of beam commissioning, including the selection of the beam current, pulse length and repetition frequency. Also the beam commissions plan should be specified. The beam commissions procedures is simulated with t-mode code GPT. In this paper, the general beam commissioning plan of Injector II in CIADS and simulation results of commissions procedures are presented.  
SUPB014 RF Setup of the MedAustron RFQ 35
  • B. Koubek, A. Schempp, J.S. Schmidt
    IAP, Frankfurt am Main, Germany
  • J. Haeuser
    Kress GmbH, Biebergemuend, Germany
  A Radio Frequency Quadrupole (RFQ) was built for the injector of the cancer treatment facility MedAuston in Austria. For the RF design simulations were performed using CST Microwave Studio and the structure was manufactured by Firma Kress in Biebergemuend, Germany. The simulations and the RF setup of the delivered RFQ are presented in this paper.  
SUPB015 Production and Quality Control of the First Modules of the IFMIF-EVEDA RFQ 38
  • F. Scantamburlo, R. Dima, A. Pepato
    INFN- Sez. di Padova, Padova, Italy
  • C. Roncolato
    INFN/LNL, Legnaro (PD), Italy
  The IFMIF-EVEDA RFQ, designed to accelerate a 125 mA D+ beam from the initial energy of 0.1 MeV to the final energy of 5 MeV at the frequency of 175 MHz, consists of 18 mechanical modules whose length is approximately 54 cm each. The production of the modules has started and, in particular, the modules 16, 17, 15 and 11, plus the prototype modules 1 and 2 have undergone all the production steps, including precision milling and brazing. In this article, the progress of the production, and the quality control during the phases of the production of the modules will be described.  
SUPB016 RFQ With Improved Energy Gain 41
  • A. Kolomiets
    ITEP, Moscow, Russia
  • A.S. Plastun
    MEPhI, Moscow, Russia
  RFQ structure is practically only one choice for using in front ends of ion linacs for acceleration up to energy about 3 MeV. This limit is due to its relatively low acceleration efficiency. However it isn’t intrinsic feature of RFQ principle. It is defined only by vane geometry of conventional RFQ structure with sinusoidal modulation of vanes. The paper presents results of analysis RFQ with modified vane geometries that allow to improve acceleration efficiency. RFQ with modified vanes was used for design second section of heavy ion injector of TWAC for acceleration of ions with Z/A = 0.33 up to 7 MeV/u.  
SUPB017 Tuning Studies on 4-rod-RFQs 44
  • J.S. Schmidt, B. Klump, B. Koubek, A. Schempp
    IAP, Frankfurt am Main, Germany
  A NI LabVIEW based Tuning Software has been devel- oped to structure the tuning process of 4-rod Radio Fre- quency Quadrupole s (RFQs). Its results are compared to measurement data of 4-rod RFQs in different frequency ranges. For the optimization of RFQ design parameters, a certain voltage distribution along the electrodes of an RFQ is assumed. Therefore an accurate tuning of the voltage distribution is very important for the beam dynamic prop- erties of an RFQ. A variation can lead to particle losses and reduced beam quality especially at higher frequencies. Our electrode design usually implies a constant longitudi- nal voltage distribution. For its adjustment tuning plates are used between the stems of the 4-rod-RFQ. These pre- dictions are based, in contrast to other simulations, on mea- surements to define the characteristics of the RFQ as it was build - not depending on assumptions of the design. This will lead to a totally new structured process of tuning 4- rod-RFQs in a broad range of frequencies by using the pre- dictions of a software. The results of these studies are pre- sented in this paper.  
SUPB018 Studies of Parasitic Cavity Modes for Proposed ESS Linac Lattices 47
  • R. Ainsworth
    Royal Holloway, University of London, Surrey, United Kingdom
  • S. Molloy
    ESS, Lund, Sweden
  The European Spallation Source (ESS) planned for construction in Lund, Sweden, will be the worlds most intense source of pulsed neutrons. The neutrons will be generated by the collision of a 2.5 GeV proton beam with a heavy-metal target. The superconducting section of the proton linac is split into three different types of cavities, and a question for the lattice designers is at which points in the beamline these splits should occur. This note studies various proposed designs for the ESS lattice from the point of view of the effect on the beam dynamics of the parasitic cavity modes lying close in frequency to the fundamental accelerating mode. Each linac design is characterised by the initial kinetic energy of the beam, as well as by the velocity of the beam at each of the points at which the cavity style changes. The scale of the phase-space disruption of the proton pulse is discussed, and some general conclusions for lattice designers are stated.  
SUPB019 The Multipacting Simulation for the New-Shaped QWR using TRACK3P 50
  • C. Zhang, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, M.X. Xu, Y.Z. Yang, W.M. Yue, S.H. Zhang, S.X. Zhang, H.W. Zhao
    IMP, Lanzhou, People's Republic of China
  In order to improve the electro-magnetic performance of the quarter wave resonator, a new-shaped cavity with an elliptical cylinder outer conductor has been proposed. This novel cavity design can provide much lower peak surface magnetic field and much higher Ra/Q0 and G. The Multipacting simulation has been done for this new QWR cavity using ACE3P/TRACK3P code, in this paper the simulation results will be presented and analyzed.  
SUPB020 Structural Analysis of the New-Shaped QWR for HIAF in IMP 53
  • C. Zhang, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, Y.Z. Yang, W.M. Yue, S.H. Zhang, S.X. Zhang, H.W. Zhao
    IMP, Lanzhou, People's Republic of China
  • M.H. Xu
    IHEP, Beijing, People's Republic of China
  Since the QWR cavity is very successful for the operation with frequency of 48 to 160 MHz and beta value of 0.001 to 0.2, a new-shaped QWR is being designed for the low energy superconducting section of HIAF in the Institute of Modern Physics. The cavity will work at 81.25 MHz and \beta of 0.085,with a elliptical cylinder outer conductor to better its electro-magnetic performance and keep limited accelerating space. Structural design is an important aspect of the overall cavity implementation, and in order to minimize the frequency shift of the cavity due to the helium bath pressure fluctuations, the Lorentz force and microphonic excitation, stiffening elements have to be applied. In this paper, structural analyses of the new-shaped QWR are presented and stiffening methods are explored.  
SUPB022 First Measurements on the 325 MHz Superconducting CH Cavity 56
  • M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger
    IAP, Frankfurt am Main, Germany
  • M. Amberg
    HIM, Mainz, Germany
  • W.A. Barth, S. Mickat
    GSI, Darmstadt, Germany
  • M. Pekeler
    RI Research Instruments GmbH, Bergisch Gladbach, Germany
  Funding: Work supported by HIM, GSI, BMBF Contr. No. 06FY161I
At the Institute for Applied Physics (IAP), Frankfurt University, a superconducting 325 MHz CH-Cavity has been designed and built. This 7-cell cavity has a geometrical \beta of 0.16 corresponding to a beam energy of 11.4 AMeV. The design gradient is 5 MV/m. Novel features of this resonator are a compact design, low peak fields, easy surface processing and power coupling. Furthermore a new tuning system based on bellow tuners inside the resonator will control the frequency during operation. After successful rf tests in Frankfurt the cavity will be tested with a 10 mA, 11.4 AMeV beam delivered by the GSI UNILAC. In this paper first measurements and corresponding simulations will be presented.
SUPB023 Status of the Superconducting CW Demonstrator for GSI 59
  • F.D. Dziuba, M. Amberg, M. Busch, H. Podlech, U. Ratzinger
    IAP, Frankfurt am Main, Germany
  • K. Aulenbacher
    IKP, Mainz, Germany
  • W.A. Barth, S. Mickat
    GSI, Darmstadt, Germany
  Funding: Helmholtz Institut Mainz (HIM), GSI, BMBF Contr. No. 06FY7102
Since the existing UNILAC at GSI will be used as an injector for the FAIR facility a new superconducting (sc) continous wave (cw) LINAC is highly requested by a broad community of future users to fulfil the requirements of nuclear chemistry, especially in the research field of Super Heavy Elements (SHE). This LINAC is under design in collaboration with the Institute for Applied Physics (IAP) of Frankfurt University, GSI and the Helmholtz Institut Mainz (HIM). It will consist of 9 sc Crossbar-H-mode (CH) cavities operated at 217 MHz which provide an energy up to 7.3 AMeV. Currently, a prototype of the cw LINAC is under development. This demonstrator comprises the first sc CH cavity of the LINAC embedded between two sc solenoids mounted in a horizontal cryomodule. One important milestone of the project will be a full performance test of the demonstrator by injecting and accelerating a beam from the GSI High Charge State Injector (HLI) in 2014. The status of the demonstrator is presented.
SUPB024 Development of Permanent Magnet Focusing System for Klystrons 62
  • Y. Fuwa, Y. Iwashita, H. Tongu
    Kyoto ICR, Uji, Kyoto, Japan
  • S. Fukuda, S. Michizono
    KEK, Ibaraki, Japan
  The Distributed RF System (DRFS) for the International Linear Collider (ILC) requires thousands of klystrons. The failure rate of the power supply for solenoid focusing coil of each klystron may be a critical issue for a regular operation of the ILC. A permanent magnet beam focusing system can increase reliability and eliminate their power consumption. Since the required magnetic field is not high in this system, inexpensive anisotropic ferrite magnets can be used instead of magnets containing rare earth materials. In order to prove its feasibility, a test model of a permanent magnet focusing beam system is constructed and a power test of the klystron for DRFS with this model is under preparation. The results of magnetic field distribution measurement and the power test will be presented.  
SUPB025 Development of Superconducting Radio-Frequency (SRF) Deflecting Mode Cavities and Associated Waveguide Dampers for the APS Upgrade Short Pulse X-Ray Project 65
  • J.P. Holzbauer, A. Nassiri, G.J. Waldschmidt, G. Wu
    ANL, Argonne, USA
  Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CHI1357.
The Advanced Photon Source Upgrade (APS-U) is a Department of Energy (DoE) funded project to increase the available x-ray beam brightness and add capability to enhance time-resolved experiments on few-ps-scale at APS. A centerpiece of the upgrade is the generation of short pulse x-rays (SPXs) for pump-probe time-resolved capability using SRF deflecting cavities[1]. The SPX project is designed to produce 1-2 ps x-ray pulses for some users compared to the standard 100 ps pulses currently produced. SPX calls for using superconducting rf (SRF) deflecting cavities to give the electrons a correlation between longitudinal position in the bunch and vertical momentum [2]. The light produced by this bunch can be passed through a slit to produce a pulse of light much shorter than the bunch length at reduced flux. The ongoing work of designing these cavities and associated technologies will be presented. This includes the design and prototyping of higher-order (HOM) and lower-order mode (LOM) couplers and dampers as well as the fundamental power coupler (FPC). This work will be given in the context of SPX0, a demonstration cryomodule with two deflecting cavities to be installed in APS in early 2014.
[1] A. Zholents, et al., NIM A 425, 385 (1999)
[2] A. Nassiri, et al., “ Status of the Short-Pulse X-Ray Project at the Advanced Photon Source,” IPAC 2012, New Orleans, LA, May 2012.
SUPB026 Multipacting Analysis of High-velocity Superconducting Spoke Resonators 68
  • C.S. Hopper, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  Some of the advantages of superconducting spoke cavities are currently being investigated for the high-velocity regime. When determining a final, optimized geometry, one must consider the possible limiting effects multipacting could have on the cavity. We report on the results of analytical calculations and numerical simulations of multipacting electrons in superconducting spoke cavities and methods for reducing their impact.  
SUPB027 Mechanical Study of the First Superconducting Half-wave Resonator for Injector II of CADS Project 71
  • S. He, Y. He, S.C. Huang, F.F. Wang, R.X. Wang, M.X. Xu, Y.Z. Yang, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao
    IMP, Lanzhou, People's Republic of China
  Funding: This work is Supported by the National Natural Science Foundation of China (Grant Agreement 91026001)
Within the framework of the China Accelerator-Driven Sub-critical Systems (CADS) project, Institute of Modern Physics (IMP) Chinese Academic of Sciences has proposed a 162.5 MHz Half-Wave Resonator (HWR) Superconducting cavity for low energy section (β=0.09) of high power proton linear accelerators as a new injector II for CIADS. For the geometrical design of superconducting cavities structure mechanical simulations are essential to predict mechanical eigenmodes and the deformation of the cavity walls due to bath pressure effects and the cavity cool-down. Additionally, the tuning analysis has been investigated to control the frequency against microphonics and Lorentz force detuning. Therefore, several RF, static structure, thermal and modal analysis with a three-dimensional Finite-Element Method (FEM) code Traditional ANSYS have been performed.
SUPB028 The Superconducting CH Cavity Development in IMP* 74
  • M.X. Xu, S. He, Y. He, S.C. Huang, Y.L. Huang, T.C. Jiang, R.X. Wang, Z.J. Wang, J.W. Xia, Y.Z. Yang, W.M. Yue, C. Zhang, S.H. Zhang, S.X. Zhang, H.W. Zhao
    IMP, Lanzhou, People's Republic of China
  Funding: Work supported by 91026001 Nature Science Foundation of China
The Cross-Bar H-type (CH) cavity is a multi-gap drift tube structure operated in the H21 mode [1]. The Institute of Modern Physics (IMP) has been doing research and development on this type of superconducting CH cavity which can work at the C-ADS (accelerator driver sub-critical system of China). A new geometry CH cavity has been proposed which have smaller radius. It’s suitable in fabrication, and it’s can reduce cost too .Detailed numerical simulations with CST MicroWave Studio have been performed. An overall surface reduction of 30% against the old structure seems feasible. A copper model CH cavity is being fabrication for validating the simulations and the procedure of fabricating niobium cavity.
SUPB029 Impact of Trapped Flux and Systematic Flux Expulsion in Superconducting Niobium 77
  • J.M. Vogt, J. Knobloch, O. Kugeler
    HZB, Berlin, Germany
  The intrinsic quality factor Q0 of superconducting cavities is known to depend on various factors like niobium material properties, treatment history and magnetic shielding. We already reported an additional impact of temperature gradients during the cool-down on the obtained Q0. We believe cooling conditions can influence the level of flux trapping and hence the residual resistance. For further studies we have constructed a test stand using niobium rods to study flux trapping. Here we can precisely control the temperature and approach Tc in the superconducting state. Although the sample remains in the superconducting state a change in the amount of trapped flux is visible. The procedure can be applied repeatedly resulting in a significantly lowered level of trapped flux in the sample. Applying a similar procedure to a superconducting cavity could allow for reduction of the magnetic contribution to the surface resistance and result in a significant improvement of Q0.  
SUPB031 The Nonresonant Perturbation Theory Based Field Measurement and Tuning of a Linac Accelerating Structure 80
  • W. Fang, Q. Gu, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  • D.C. Tong
    TUB, Beijing, People's Republic of China
  Assisted by the bead pull technique, the nonresonant perturbation theory is applied for measuring and tuning the field of the linac accelerating structure. The method is capable of making non-touch measurement, amplitude and phase diagnostics, real time mismatch feedback and field tuning. Main considerations on measurement system and of C-band traveling-wave structure are described, the bead pull measurement and the tuning of the C-band traveling-wave linac accelerating structure are presented.  
SUPB032 The C-band RF Pulse Compression for Soft XFEL at SINAP 83
  • C.P. Wang, Q. Gu, Z.T. Zhao
    SINAP, Shanghai, People's Republic of China
  A compact soft X-ray free electron laser facility is presently being constructed at shanghai institute of applied physics (SINAP), Chinese academy of science in 2012 and will be accomplished in 2014. This facility requires a compact linac with a high-gradient accelerating structure for a limited overall length less than 230 m. The c-band technology which is already used in KEK/Spring-8 linear accelerator is a good compromise for this compact facility and a c-and traveling-wave accelerating structure was already fabricated and tested at SINAP, so a c-band pulse compression will be required. AND a SLED type RF compression scheme is proposed for the C-band RF system of the soft XFEL and this scheme uses TE0.1.15 mode energy storage cavity for high Q-energy storage. The C-band pulse compression under development at SINAP has a high power gain about 3.1 and it is designed to compress the pulse width from 2.5 μs to 0.5 μs and multiply the input RF power of 50 MW to generate 160 MW peak RF power, and the coupling coefficient will be 8.5. It has three components: 3 dB coupler, mode convertors and the resonant cavities.  
SUPB035 RF Photoinjector and Radiating Structure for High-power THz Radiation Source 86
  • S.M. Polozov, T.V. Bondarenko
    MEPhI, Moscow, Russia
  • Y.A. Bashmakov
    LPI, Moscow, Russia
  Sources of high-power electromagnetic radiation in THz band are becoming promising as a new method of a low activation introscopy. Research and development of accelerating RF photoinjector and radiating system for THz radiation source are reported. The photoinjector is based on disk loaded waveguide (DLW). Two different designs of accelerating structures were modeled: widespread 1.6 cell of DLW structure and travelling wave resonator structure. The resonant models of these structures and the structures with power ports were designed. Electrodynamics characteristics and electric field distribution for all models were acquired. Results of picoseconds photoelectron beam dynamics in modeled structures are reported. Design of decelerating structures exciting Cherenkov radiation are based on corrugated metal channel and metal channel coated with dielectric. Analysis of radiation intensity and frequency band are presented.  
SUPB037 The Development of Timing Control System for RFQ 89
  • J.N. Bai, S. Xiao, T.G. Xu, L. Zeng
    IHEP, Beijing, People's Republic of China
  A Timing control system based on VME configuration is developed to meet the need of 3.5 MeV RFQ. An EPICS driver is provided to control its work. The timing control system satisfies request after examination. In the future, it will be used in the machine running. This paper introduces the Timing control hardware, VME interface, EPICS driver for Timing control system and MEDM operator interface.  
SUPB038 Multipole Field Effects for the Superconducting Parallel-Bar Deflecting/Crabbing Cavities 92
  • S.U. De Silva, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
  The superconducting parallel-bar deflecting/crabbing cavity is currently being considered as one of the design options in rf separation for the Jefferson Lab 12 GeV upgrade and for the crabbing cavity for the proposed LHC luminosity upgrade. Knowledge of multipole field effects is important for accurate beam dynamics study of rf structures. The multipole components can be accurately determined numerically using the electromagnetic surface field data in the rf structure. This paper discusses the detailed analysis of those components for the fundamental deflecting/crabbing mode and higher order modes in the parallel-bar deflecting/crabbing cavity.  
SUPB039 Compact Superconducting Crabbing and Deflecting Cavities 95
  • S.U. De Silva
    ODU, Norfolk, Virginia, USA
  • S.U. De Silva
    JLAB, Newport News, Virginia, USA
  Recently, new geometries for superconducting crabbing and deflecting cavities have been developed that have significantly improved properties over those the standard TM110 cavities. They are smaller, have low surface fields, high shunt impedance and, more importantly for some of them, no lower-order-mode with a well-separated fundamental mode. This talk will present the status of the development of these cavities.