SUPG —  Student Poster Session and Reception   (31-Aug-14   16:00—21:00)
Chair: S. Ramberger, CERN, Geneva, Switzerland
Paper Title Page
SUPG001
 Design and Beamloading-Simulations of a Pre-Bunching Cavity for the CLIC Drive Beam Injector  
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  • M. Dayyani Kelisani, S. Döbert, H. Shaker
    CERN, Geneva, Switzerland
  • H. Shaker
    IPM, Tehran, Iran
  
  The CLIC project is developing a multi-TeV center-of-mass electron-positron collider based on high-gradient, room-temperature accelerating structures and a novel two-beam RF power generation scheme. The RF power for the CLIC accelerating structures is provided by the so-called drive beam which is a low energy, high current electron beam. The drive beam will be generated from a high current (up to 5 A) pulsed (142μs) thermionic electron gun and then followed by a bunching system. The bunching system is composed of three sub-harmonic bunchers operating at a frequency of 499.75 MHz, a pre-buncher and a traveling wave buncher both operating at 999.5MHz. The pre-buncher cavity, which has a great importance on minimization the satellite population, should be designed with special consideration of the high beam loading effect due to the high current beam crossing the cavity. In this work we report on RF design, analytical beam loading calculations and simulations for the CLIC drive beam injector pre-buncher cavity.  
 
SUPG002
 Diagnostics and Analysis Techniques for High Power X-Band Accelerating Structures  
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  • A. Degiovanni, S. Döbert, W. Farabolini, I. Syratchev, W. Wuensch
    CERN, Geneva, Switzerland
  • J. Giner Navarro
    IFIC, Valencia, Spain
  • J. Tagg
    National Instruments Switzerland, Ennetbaden, Switzerland
  • B.J. Woolley
    Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
  
  The study of high gradient limitations due to RF breakdowns is extremely important for the CLIC project. A series of diagnostic tools and analysis techniques have been developed in order to monitor and characterize the behaviour of CLIC accelerating structures under high power operation in the first CERN X-band klystron-based test stand (Xbox1). The data collected during the last run on a TD26r05 structure are presented in this paper. From the analysis of the RF power and phases, the location of the breakdowns inside the structure could be determined. Other techniques based on the field emitted dark current signals collected by Faraday cups placed at the two extremities of the structure have also been investigated. The results of these analyses are reported and discussed.  
 
SUPG003
 Deceleration Measurements of an Electron Beam in the CLIC Test Facility 3  
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  • R.L. Lillestøl, S. Döbert
    CERN, Geneva, Switzerland
  • E. Adli
    University of Oslo, Oslo, Norway
  
  The Test Beam Line at the CLIC Test Facility 3 at CERN is a proof-of-principle of the future CLIC decelerators, which will extract a large amount of beam energy for acceleration of the main CLIC beams. The current beamline consists of a FODO lattice with 13 Power Extraction and Transfer Structures (PETS). We discuss beam deceleration measurements of up to 37 %, taking into account effects from the bunch length and the bunch phase. The 12 GHz phase is reproduced based on measurements in a PETS with an uncombined beam. The spectrometer measurements are also compared to predictions based on the beam current and on the produced rf power in the PETS, as well as particle tracking simulations with the Placet code.  
 
SUPG004
 Optimization of the RF Cavity of the Medical Purpose Electron Linac by Using Genetic Algorithm  
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  • S. Shin, J.-S. Chai
    SKKU, Suwon, Republic of Korea
  
  A compact electron linear accelerator for the medical application has been developing at Sungkyunkwan University. Due to this electron linac is attached on the robot arm or gantry, it should be compact enough to be held by the structure. An X-band technology has been used to meet the requirements for the compact linac. Because the particle accelerator is complex and sensitive machine to design it takes a lot of time to get a good performance accelerator. In this research, a special technique named single-objective genetic algorithm for the optimization process has been applied to achieve a better RF cavity design by changing various geometric parameters.  
 
SUPG005
 Sawtooth-wave prebuncher with two gaps in SSC-LIANC  
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  • X.H. Zhang
    IMP, Lanzhou, People's Republic of China
  
  A new heavy ion linac is under construction in HIRFL (Heavy Ion Research Facility in Lanzhou), which replaces the present SFC (Sector Focusing Cyclotron) cyclotron as the injector of SSC (Separated Sector Cyclotron).  
 
SUPG006
 Magnetic Characterization of Fast-Pulsed Quadrupole Magnets for Linac4  
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  • S. Kasaei, M.C.L. Buzio, O. Crettiez, V. Della Selva, L. Fiscarelli, J. Garcia Perez, J.-B. Lallement
    CERN, Geneva, Switzerland
  
  Linac4, currently being built at CERN, includes 24 quadrupole magnets characterized by narrow apertures and fast excitation cycles which make accurate magnetic measurements challenging. This paper describes the method used for the measurement, which is a combination of techniques based on stretched wire, rotating and fixed search coils. We show how these different instruments can be used in a complementary way to derive information on different aspects of the magnetic behaviour, such as the impact of hysteresis and dynamic eddy current effects. We summarize the results of the series measurement campaign, which include field strength, harmonic components, and the offset and orientation of the magnetic axis. Finally, we discuss the relevance of these measurements as their impact to the operation of the linac.  
 
SUPG007
 Error Study on the Normal Conducting ESS Linac  
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  • R. De Prisco, M. Eshraqi, R. Miyamoto, E. Sargsyan
    ESS, Lund, Sweden
  • A.R. Karlsson
    Lund University, Lund, Sweden
  
  One of the preliminary, but important test to evaluate the robustness of the accelerator design is performing the statistical error study by introducing realistic tolerances on the machine components. In this paper the guidelines to define the tolerances and the correction system are summarized in order to validate the design. Firstly statistical studies have been performed in order to define the sensitivity to single errors and to fix the tolerances. Then all errors, within the previous defined tolerances, are applied with the correction system to evaluate the beam quality and to check if the system guarantees a radiologically safe operation.  
 
SUPG008
 SSR1 Tuner Mechanism: Passive and Active Device  
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  • D. Passarelli
    Fermilab, Batavia, Illinois, USA
  
  In this paper we present the methodology adopted in designing the mechanism responsible for controlling the resonant frequency of Single Spoke Resonators of first type (SSR1). Such device is capable of compensating the effects of external perturbations, such as pressure fluctuations and microphonics, on the frequency of SSR1. The compensation is achieved through active responses via an actuation system and passive responses which are inherent to the elastic behavior of the overall system. The first experiences in the design, assembly, QA and testing are reported.  
 
SUPG009
 Development of a 217 MHz Superconducting CH Structure  
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  • M. Basten, M. Amberg, M. Busch, F.D. Dziuba, D. Mäder, H. Podlech
    IAP, Frankfurt am Main, Germany
  • M. Amberg, K. Aulenbacher, W.A. Barth, S. Mickat
    HIM, Mainz, Germany
  • W.A. Barth, S. Mickat
    GSI, Darmstadt, Germany
  
  Funding: Helmholtz-Institut Mainz, Bundesministerium für Bildung und Forschung contract number 05P12RFRBL
To compete in the production of Super Heavy Elements (SHE) in the future a 7.3 AMeV superconducting (sc) continuous wave (cw) LINAC is planned at GSI. The baseline design consists of 9 sc Crossbar-H-mode (CH) cavities operated at 217 MHz. Currently an advanced cw demonstrator is under design at the Institute for Applied Physics (IAP) at Frankfurt University. The purpose of the advanced demonstrator is to investigate a new concept for the superconducting CH structures. It is based on shorter CH-cavities with 8 equidistant gaps without girders and with stiffening brackets at the front and end cap to reduce the pressure sensitivity. One major goal of the advanced demonstrator is to show that the new design leads to higher acceleration gradients and smaller Ep/Ea values. In this contribution first simulation results and technical layouts will be presented. 		 
 
SUPG010
 R&D of the 17 MeV MYRRHA Injector  
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  • D. Mäder, M. Basten, D. Koser, H.C. Lenz, N.F. Petry, H. Podlech, A. Schempp, M. Schwarz, M. Vossberg
    IAP, Frankfurt am Main, Germany
  • C. Zhang
    GSI, Darmstadt, Germany
  
  Funding: Project supported by the EU, FP7 MAX, Contract No. 269565
MYRRHA is designed as an accelerator driven system (ADS) for transmutation of long-lived radioactive waste. The challenge of the linac development is the very high reliability of the accelerator to limit the thermal stress inside the reactor. With the concept of parallel redundancy the injector will supply a cw proton beam with 4 mA and 17 MeV to the main linac. The new MYRRHA injector layout consists of a very robust beam dynamics design with low emittance growth rates. Sufficient drift space provides plenty room for diagnostic elements and increases the mountability. Behind a 4-Rod-RFQ and a pair of two-gap QWR rebunchers at 1.5 MeV the protons are matched into the CH cavity section. A focussing triplet between the rebunchers ensures an ideal transversal matching into the doublet lattice. Each of the 7 RT CH structures has a constant phase profile and does not exceed thermal losses of 29 kW/m. The transition to the 5 SC CH cavities with constant beta profile is at 5.9 MeV. For a safe operation of the niobium resonators the electric and magnetic peak fields are defined below 25 MV/m and 57 mT respectively. 		 
 
SUPG011
 A Rebunching CH Cavity for Intense Proton Beams  
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  • M. Schwarz, C. Claessens, M. Heilmann, O. Hinrichs, D. Koser, O. Meusel, D. Mäder, H. Podlech, U. Ratzinger, A. Seibel
    IAP, Frankfurt am Main, Germany
  
  Funding: Project supported by the EU, FP7 MAX, Contract No. 269565
The Frankfurt Neutron Source at the Stern-Gerlach-Zentrum (FRANZ) will provide ultra short neutron pulses at high intensities and repetition rates. The facility is currently under construction at the Goethe-University in Frankfurt am Main (Germany). A 5-Gap CH rebuncher is installed behind a coupled RFQ/IH-DTL combination at the end of the LINAC section between two magnetic quadrupole triplets. It will be used for varying the final proton energy as well as for focusing the bunch longitudinally to compensate huge space charge forces at currents up to 200 mA at the final stage of extension. High current beam dynamic simulations have been performed. They include benchmarking of different beam dynamic codes like LORASR and TraceWin, as well as validating the results by measurements. Detailed examination of multipole field impact, due to the cavity’s geometry, together with error tolerance studies and thermal simulations are also performed. Furthermore, this CH rebuncher serves as a prototype for rt CH cavities at MYRRHA (Belgium), an Accelerator Driven System for transmutation of high level nuclear waste. After copper plating the cavity, RF conditioning will start soon. 		 
 
SUPG012
 Cold Power Tests of the SC 325 MHz CH-Cavity  
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  • M. Busch, M. Amberg, F.D. Dziuba, H. Podlech, U. Ratzinger
    IAP, Frankfurt am Main, Germany
  • M. Amberg
    HIM, Mainz, Germany
  
  Funding: Work supported by GSI, BMBF Contr. No. 06FY7102
At the Institute for Applied Physics (IAP), Frankfurt University, a superconducting 325 MHz CH-Cavity has been designed, built and first tests have successfully been performed. The cavity is determined for a 11.4 AMeV, 10 mA ion beam at the GSI UNILAC. Consisting of 7 gaps this resonator is envisaged to deliver a gradient of 5 MV/m. Novel features of this structure are a compact design, low peak fields, improved surface processing and power coupling. Furthermore a tuner system based on bellow tuners driven by a stepping motor and a piezo actuator and attached inside the resonator will control the frequency. In this contribution measurements executed at 4 K and 2 K at the cryo lab in Frankfurt will be presented. 		 
 
SUPG013
 Spatially Periodic RF Quadrupole LINAC  
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  • A.S. Plastun, A. Kolomiets
    ITEP, Moscow, Russia
  
  Spatially-periodic RF quadrupole structure is proposed as second section of front end of ion linac. It consists of conventional drift tubes and RF quadrupoles. Quadrupoles are 4-vane segments with nonzero electric potential on the longitudinal axis. Thus the accelerating electric field is formed between drift tubes and RF quadrupoles. Moreover accelerating field can be provided even inside the RF quadrupoles. It allows building structures with different focusing lattices and provides high energy gain rate.  
 
SUPG014
 The Beam Envelope Control in SC Linac for the Proton Radiotherapy  
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  • A.V. Samoshin, I.A. Ashanin, S.M. Polozov
    MEPhI, Moscow, Russia
  
  Proton cancer therapy is conventionally based on normal conducting synchrotrons and cyclotrons. The high electrical power consumption and especial devices necessary to energy variation are main problems of such facilities. Superconducting linacs based on short identical independently phased cavities have a seriously progress and it's development allow to propose their using for medical application. High accelerating gradient and small capacity losses nearly 10-4 Vt/m are main advantages in advance of normal conducting facilities, the energy variation can be realized by means of RF field amplitude and phase variation in a number of cavities. Besides linac structures are lack of unwieldy magnetic system, simplicity of input and output of particles and high current densities. The parameters choose and the optimization for SC linac structure with energy up to 240 MeV and envelope control will discuss in this paper. The simulation was done using BEAMDULAC-SCL code*. The study of beam dynamics will direct to realize the energy variation in range 150-240 MeV with beam quality preservation.
* A.V. Samoshin. Proc. of LINAC2012, Tel-Aviv, Israel, TUPB069, p. 630 - 632 		 
 
SUPG015
 Beam Dynamics of Multi Charge State Ions in RFQ Linac  
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  • Y. Fuwa, S. Ikeda, M. Kumaki
    RIKEN, Saitama, Japan
  • Y. Fuwa, Y. Iwashita
    Kyoto ICR, Uji, Kyoto, Japan
  • T. Kanesue, M. Okamura
    BNL, Upton, Long Island, New York, USA
  
  Laser ion source with DPIS (Direct Plasma Injection Scheme) is a promising candidate for a pre-injector of the high-intensity accelerator. Eliminating LEBT (Low Energy Beam Transport) where the space charge effect is severe, DPIS provides high current ion beam from laser plasma at the entrance of a RFQ linac and ion beams are injected directly into the RFQ linac. However, the injected beam consists of multi charge state ions and their behavior in RFQ linac has not been well understood. In this research, we study the beam dynamics of multi charge state ions in a RFQ. Using the result of computer simulation, a set of 100MHz 4-rod RFQ vanes, which accelerates Al 12+ ion among various charge states of aluminum ions from 8.9 keV/u to 200 keV/u, is newly designed and fabricated to be tested with beams. The result of beam acceleration test using the vane will be reported.  
 
SUPG016
 Nb3Sn Materials Studies  
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  • S. Posen, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • Th. Proslier
    ANL, Argonne, Illinois, USA
  
  Nb3Sn is a very promising material for use in SRF cavity applications, potentially offering significant improvements in quality factor and energy gradient compared to niobium. In order to better understand how to optimize this material for SRF applications, Nb3Sn samples were prepared at Cornell via vapor deposition, using varying parameters in the coating process. Microscopic studies were performed with SEM/EDX, and studies were performed on bulk samples to measure secondary electron yield, energy gap, and upper critical magnetic field. The results are presented here, with discussion for how they might point the way towards reaching even higher fields in Nb3Sn cavities.  
 
SUPG017
 Nb3Sn - Present Status and Potential as an Alternative SRF Material  
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  • S. Posen, M. Liepe
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  
  Nb3Sn is a material that has the potential to have a transformative impact on SRF linacs. Due to its large critical temperature of approximately 18 K, Nb3Sn cavities can have far smaller surface resistances at a given temperature than standard Nb cavities. This could significantly reduce the costs for infrastructure and power in cryoplants for large CW linacs. In addition, the predicted superheating field of Nb3Sn is approximately double that of Nb, potentially doubling the maximum energy gradient. This would significantly decrease the size and cost of high energy linacs. In this work, we present recent progress in research and development for this promising material.  
slides icon Slides SUPG017 [3.357 MB]  
 
SUPG018
 Tuning and Field Stabilization of the CERN Linac4 Drift Tube Linac  
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  • M.R. Khalvati
    IPM, Tehran, Iran
  • S. Ramberger
    CERN, Geneva, Switzerland
  
  The Drift Tube Linac (DTL) for the new linear accelerator Linac4 at CERN will accelerate H–beams of up to 40 mA average pulse current from 3 to 50 MeV. The structure consists of three cavities. The first cavity (Tank1) is a 3.9 m long tank containing 38 drift tubes, 10 fixed tuners, 2 movable tuners and 12 post-couplers, operating at a frequency of 352.2 MHz and an average accelerating field of 3.1 MV/m. This paper reports on the results and procedures used for the low–power tuning, stabilization and power coupler tuning carried out on the first Linac4 DTL tank. The upgrade of the bead pull measurement system and twists to the well-known tilt sensitivity technique are discussed.  
 
SUPG019
 Development of Slow Neutron Accelerator for Rebunching Pulsed Neutrons  
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  • S. Imajo
    Kyoto University, Kyoto, Japan
  • Y. Fuwa, Y. Iwashita, R. Kitahara
    Kyoto ICR, Uji, Kyoto, Japan
  • T. Ino
    KEK, Ibaraki, Japan
  • M. Kitaguchi, H.M. Shimizu
    Nagoya University, Nagoya, Japan
  • K. Mishima
    ICEPP, Tokyo, Japan
  
  Low energy neutrons can be accelerated or decelerated by the technique of AFP-NMR with RF and gradient magnetic fields. The neutrons have magnetic moments, hence their potential energy are not cancelled before and after passage of magnetic fields and their kinetic energy change finally when their spins are flipped in the fields. Nowadays most measurements of the neutron electric dipole moment (nEDM) are carried out with ultra cold neutrons (UCN), whose kinetic energies are lower than about 300 neV, and with a small storage bottle to reduce the systematic errors. In such experiments highly dense UCNs are desired. The spallation neutron sources generate high-density neutrons, however, the pulsed neutrons with several velocities are diffused in guide tubes under long beam intervals. It is necessary to focus and rebunch UCN temporally upon the bottle by controlling their velocities in nEDM experiments at those facilities. We demonstrated such rebuncher and have been developed the advanced apparatus which makes it possible to handle broader energy range UCN. The design, measured characteristics, the experimental setup and the obtained results at J-PARC will be described.  
 
SUPG020
 Multipole and Field Uniformity Tailoring of a 750 MHz RF Dipole  
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  • A. Castilla, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • A. Castilla
    DCI-UG, León, Mexico
  • A. Castilla, J.R. Delayen
    JLab, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
In recent years great interest has been shown in developing rf structures for beam separation, correction of geometrical degradation on luminosity, and diagnostic applications in both lepton and hadron machines. The rf dipole being a very promising one among all of them. The rf dipole has been tested and proven to have attractive properties that include high shunt impedance, low and balance surface fields, absence of lower order modes and far-spaced higher order modes that simplify their damping scheme. As well as to be a compact and versatile design in a considerable range of frequencies, its fairly simple geometry dependency is suitable both for fabrication and surface treatment. The rf dipole geometry can also be optimized for lowering multipacting risk and multipole tailoring to meet machine specific field uniformity tolerances. In the present work a survey of field uniformities, and multipole contents for a set of 750 MHz rf dipole designs is presented as both a qualitative and quantitative analysis of the inherent flexibility of the structure and its limitations. 		 
 
SUPG021
 Multipacting Optimization of a 750 MHz RF Dipole  
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  • A. Castilla, J.R. Delayen
    ODU, Norfolk, Virginia, USA
  • A. Castilla
    DCI-UG, León, Mexico
  • A. Castilla, J.R. Delayen
    JLab, Newport News, Virginia, USA
  
  Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Crab crossing schemes have been proposed to re-instate luminosity degradation due to crossing angles at the interaction points in next generation colliders to avoid the use of sharp bending magnets and their resulting large synchrotron radiation generation, highly undessirable in the detector region. The rf dipole has been considered for a different set of applications in several machines, both rings and linear colliders. We present in this paper a study of the effects on the multipacting levels and location depending on geometrical variations on the design for a crabbing/deflecting application in a high current (3/0.5 A), high repetition (750 MHz) electron/proton collider, as a matter to provide a comparison point for similar applications of rf dipoles. 		 
 
SUPG022
 HOM and Impedance Study of RF Separators for LCLS II  
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  • S.U. De Silva, J.R. Delayen, B.R.P. Gamage, G.A. Krafft, T. Satogata
    ODU, Norfolk, Virginia, USA
  • R.G. Olave
    Old Dominion University, Norfolk, Virginia, USA
  
  The LCLS-II upgrade requires an rf spreader system to guide bunches into a switchyard delivering beam to two undulators and the primary beam dump. The beam pattern therefore needs a 3-way beam spreader. An rf deflecting cavity concept was proposed that includes both superconducting and normal conducting options. We characterize the higher order modes (HOM) of these rf separator cavities and evaluate beam dynamics effects due to potential HOM excitation. This study includes both short term wake and multi-bunch effects.  
 
SUPG023
 Cryogenic Testing of High-Velocity Spoke Cavities  
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  • C.S. Hopper, J.R. Delayen, H. Park
    ODU, Norfolk, Virginia, USA
  • J.R. Delayen, H. Park
    JLab, Newport News, Virginia, USA
  
  Spoke-loaded cavities are being investigated for the high-velocity regime. The relative compactness at low-frequency makes them attractive for applications requiring, or benefiting from, 4 K operation. Additionally, the large velocity acceptance makes them good candidates for the acceleration of high-velocity protons and ions. Here we present the results of cryogenic testing of a 325 MHz, β0 = 0.82 single-spoke cavity and a 500 MHz, β0 = 1 double-spoke cavity.  
 
SUPG024
 Warming Rate Reduction of the SARAF RF Couplers by Application of a High Voltage Dc Bias  
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  • B. Kaizer, Y. Ben Aliz, I. Fishman, J. Rodnizki, L. Weissman
    Soreq NRC, Yavne, Israel
  
  Warming up of the coupler region of the SARAF Half Wave Resonator (HWR) cavities was one of the main limiting factors for long operation at high RF field values. The warming effect is, most likely, associated with multipacting in the coupler region. We have tried to suppress the multipacting discharge in the couplers by application a DC bias to their inner conductors. A bias-T, element that conducts up to 4 kW of 176 MHz RF power and provides DC insulation of the coupler inner conductor, was designed and built for this purpose. First on-line operation showed that the DC bias indeed reduces dramatically the warming rates of most of the cavities by an order of magnitude. Today, coupler warming is no longer the main factor hindering accelerator operation.  
 
SUPG025
 Fabrication and Measurements of 500 MHz Double Spoke Cavity  
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  • H. Park, J.R. Delayen
    JLab, Newport News, Virginia, USA
  • J.R. Delayen, C.S. Hopper, H. Park
    ODU, Norfolk, Virginia, USA
  
  The 500 MHz double spoke cavity has been designed for a high velocity application such as a compact electron accelerator at Center for Accelerator Science at Old Dominion University and is being built at Jefferson Lab. The geometry specific to the double spoke cavity requires a variety of tooling and fixtures. Also a number of joints are expected to make it difficult to maintain the geometric deviation from the design minimal. This paper will report the fabrication technique, resulting tolerance from the design, and comparison between the measurements and simulations.  
 
SUPG026
 Observation of >GV/m Decelerating Fields in Dielectric Lined Waveguides  
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  • B.D. O'Shea, G. Andonian, K.L. Fitzmorris, S. Hakimi, J. Harrison, J.B. Rosenzweig, O. Williams
    UCLA, Los Angeles, California, USA
  • M.J. Hogan, V. Yakimenko
    SLAC, Menlo Park, California, USA
  
  Recent experimental measurements of the energy lost to wakefields in a dielectric lined waveguide are presented. These measurements demonstrate average decelerating gradients on the order of >1 GV/m, for two different structures. The measurements were made at the Facility for Advanced aCcelerator Experimental Tests (FACET) at SLAC National Laboratory using sub-millimeter diameter fifteen-centimeter long quartz fibers of annular cross section. The unique extremely short, high charge, ultra relativistic beam at FACET (200 fs, 3 nC, 20 GeV) allows the use of dielectric wakefield structures of unprecedented size and length. In addition to experimental results, we support conclusions with simulation and theoretical work. This measurement builds on a large body of work previously performed using dielectric wakefield structures in an effort to provide high gradient accelerating structures for tomorrows linear colliders.  
 
SUPG027
 Beam Dynamics Studies of the CLIC Drive Beam Injector  
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  • S. Sanaye Hajari, S. Döbert, H. Shaker
    CERN, Geneva, Switzerland
  • S. Sanaye Hajari, H. Shaker
    IPM, Tehran, Iran
  
  In the Compact Linear Collider (CLIC) the RF power for the acceleration of the Main Beam is extracted from a high-current Drive Beam that runs parallel with the main linac. The beam in the Drive Beam Accelerator is phase coded. This means only every second accelerator bucket is occupied. However, a few percent of particles are captured in wrong buckets, called satellite bunches. The phase coding is done via a sub-harmonic bunching system operating at a half the acceleration frequency. The beam dynamics of the Drive Beam injector complex has been studied in detail and optimised. The model consists of a thermionic gun, the bunching system followed by some accelerating structures and a magnetic chicane. The bunching system contains three sub-harmonic bunchers, a prebuncher and a tapered travelling wave buncher all embedded in a solenoidal magnetic field. The simulation of the beam dynamics has been carried out with PARMELA with the goal of optimising the overall bunching process and in particular decreasing the satellite population and the beam loss in magnetic chicane and in transverse plane limiting the beam emittance growth.  
 
SUPG028
 Space Charge Compensation in the Linac4 LEBT for Three Injected Gas Types  
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  • C.A. Valerio, R. Scrivens
    CERN, Geneva, Switzerland
  • N. Chauvin
    CEA/IRFU, Gif-sur-Yvette, France
  
  The space charge of unbunched, high intensity beams can be compensated by the trapping of charged particles in the potential well of the beam. The source of these secondary charge particles can be the residual gas in the beam line. The effect is important in the Low energy beam transport (LEBT) regions. At CERN’s Linac4, the LEBT transports a pulsed 45keV H− beam, which is compensated by the positive ions, created by collision of the beam with the neutral gas in the beam pipe. The rise time and amount of compensation may be varied by the density of neutral gas and the type of gas used (through the cross-section for ion production and the mass of the resulting ion). In this paper we present measurement results for the transport of the beam at the Linac4 LEBT with the addition of hydrogen, nitrogen and krypton gases into the line, and compare them with simulations of the beam dynamics including the effect of compensating positive ions . The H− beam is provided by a cesiated 2MHz RF ion source with an external solenoidal antenna, operating with 600us pulses at 0.8Hz repetition rate.  
slides icon Slides SUPG028 [4.084 MB]  
 
SUPG029
 Transverse Beam Profile Measurements in the Linac4 Medium Energy Beam Transport  
TUPP038   use link to access more material from this paper's primary paper code  
 
  • M. Yarmohammadi Satri, G. Bellodi, V.A. Dimov, J.-B. Lallement, A.M. Lombardi, U. Raich, F. Roncarolo, F. Zocca
    CERN, Geneva, Switzerland
  
  Linac4 is a 160 MeV H− linear accelerator presently under construction at CERN. It will replace the present 50 MeV proton Linac2 as injector of the proton accelerator complex as part of a project to increase the LHC luminosity. The Linac4 front-end, composed of a 45 keV ion source, a Low Energy Beam Transport (LEBT), a 352.2 MHz Radio Frequency Quadrupole (RFQ) which accelerates the beam to 3 MeV and a Medium Energy Beam Transport (MEBT) housing a beam chopper, has been commissioned in the Linac4 tunnel. The MEBT is composed of three buncher cavities and 11 quadrupole magnets to match the beam from the RFQ to the next accelerating structure (DTL) and it includes two wire scanners for beam profile measurement. In this paper we present the results of the profile measurements and we compare them with emittance measurements taken with a temporary slit-and-grid emittance measurement device located after the MEBT line.  
 
SUPG030
 Simulation of the Electron Beam Dynamics in the Biperiodical Structure  
THPP104   use link to access more material from this paper's primary paper code  
 
  • Yu.D. Kliuchevskaia, T.V. Bondarenko, S.M. Polozov
    MEPhI, Moscow, Russia
  
  А biperiodical accelerating structure (BAS) with operating frequency 27 GHz for the 6 MeV compact radiotherapy electron accelerator is considered. The operating frequency 27 GHz allows to significantly reduce the facility sizes, unlike the S-, X- and C-band operating linacs. The optimal geometrical parameters of BAS necessary for π/2 mode were defined by means of accelerating and coupling cell tuning. The BAS coupler was also simulated. Results of the electron beam dynamics analysis in designed structure are also discussed.  
 
SUPG031
 Quasi Nonlinear Plasma Wakefield Acceleration Experiments  
TUPP110   use link to access more material from this paper's primary paper code  
 
  • S.K. Barber, G. Andonian, B.D. O'Shea, J.B. Rosenzweig, Y. Sakai, O. Williams
    UCLA, Los Angeles, USA
  • M. Ferrario
    INFN/LNF, Frascati (Roma), Italy
  • P. Muggli
    MPI, Muenchen, Germany
  
  It is generally agreed that the best way forward for beam driven plasma wakefield acceleration (PWFA) is in the nonlinear or blowout regime. In this regime the expulsion of the plasma electrons from the beam occupied region produces a linear transverse focusing effect and position independent longitudinal accelerating fields, which can, in principle, produce high quality beams accelerated over many meters. However, certain aspects of a linear plasma response can be advantageous, such as the possibility for resonant excitation of wakefields through the use of pulse trains. Exploiting advantages of both linear and nonlinear PWFA may be achievable through the use of low emittance and tightly focused beams with relatively small charge. In this case the beam density can be greater than that of the ambient plasma while simultaneously having a smaller total charge than the plasma electrons contained in a cubic plasma skin depth allowing for blowout in the region of the beam while simultaneously maintaining a quasi linear response in the bulk plasma. Recent experiments at BNL have been aimed at probing various salient aspects of this regime and are presented here.  
 
SUPG032
 Study of a C-Band TW Electron Gun for SwissFEL  
TUPP112   use link to access more material from this paper's primary paper code  
 
  • M. Schaer, A. Citterio, P. Craievich, L. Stingelin, R. Zennaro
    PSI, Villigen PSI, Switzerland
  
  For a future upgrade of the SwissFEL facility, the replacement of the S-band standing wave electron gun by a C-band standing wave, or traveling wave gun is investigated. The full model of the C-band TW gun is calculated with HFSS and is characterized by an almost vanishing group velocity in the first cell to increase the field at the cathode. ASTRA simulations predict that in the case of the C-band SW gun, a two times higher peak current of ~ 40 A can be generated while still preserving the low slice emittance of ~ 0.2 um at 200 pC, due to the higher electric field on cathode and improved magnetic focusing. This would help to halve the overall beam compression factor, relax the phase stability requirement of S- and X-band systems operated off-crest for compression and decrease the gain curve in theμbunch instability. Compared to the SW gun, a TW gun provides a more homogeneous acceleration and does not require any circulator. In this study, the preliminary RF design and beam performance of a C-band TW gun is presented and compared to a pure C-band SW gun presently under design at Paul Scherrer Institut and to the operating S-band SW gun.  
 
SUPG033
 Beam Dynamic Design of a 100 mA, 162.5 Mhz High-Current Linac  
MOPP120   use link to access more material from this paper's primary paper code  
 
  • F.J. Jia, J.E. Chen, Y.R. Lu, Z. Wang, W.L. Xia, X.Q. Yan, K. Zhu
    PKU, Beijing, People's Republic of China
  • W.P. Dou, Y. He
    IMP, Lanzhou, People's Republic of China
  
  Funding: This work is supported by the 973 program (No. 2014CB845503) and the NSFC (Grants No. 11079001).
The beam dynamic design of a 100 mA, 162.5 MHz Radio Frequency Quadrupole (RFQ) is presented in this paper. The RFQ will accelerate protons from 85 keV to 3 MeV under the operation mode of continuous-wave (CW). The code PARMTEQM is used to carry out the beam dynamics design and the transmission efficiency has been optimized and improved to more than 99%. In the design of this high-current linac, the space charge effect is analyzed as it can cause emittance growth, nonuniform particle density distribution and resonance effect. The electrode structure parameters generated by PARMTEQM also be adopted by the code of Toutatis to verify the result’s veracity. 		 
 
SUPG034
 High RF Power Test of Coupled RFQ-SFRFQ Cavity  
TUPP113   use link to access more material from this paper's primary paper code  
 
  • W.L. Xia, J.E. Chen, S.L. Gao, F.J. Jia, Y.R. Lu, Z. Wang, J. Zhao, K. Zhu
    PKU, Beijing, People's Republic of China
  
  Funding: This work was supported in part by the National Natural Science Foundation of China under Grant No. 11075008, 11079001 and 11175009.
A new combined accelerator that couples radio frequency quadrupole (RFQ) and separated function radio frequency quadrupole (SFRFQ) in a single cavity has been designed and manufactured. Recently, the performance of the cavity under high RF power was tested with an upgraded RF power source. The inter-vane voltages of both RFQ section and SFRFQ section were measured by using high purity germanium detector and the corresponding measurement system. The measured shunt impedance is about 546.9 kΩ•m, which means the cavity needs 19.5 kW for the designed inter-vane voltage of 65 kV. The results are well consistent with the cavity design. 		 
 
SUPG035
 Optimization of Beam Parameters in APF Channel  
TUPP130   use link to access more material from this paper's primary paper code  
 
  • V.V. Altsybeyev, D.A. Ovsyannikov
    St. Petersburg State University, St. Petersburg, Russia
  
  A new approach based on mathematical optimization methods to obtain a synchronous phase sequence in APF linacs is suggested. The optimization problem of intensity deuteron beam parameters is discussed. As an example, the results of beam dynamics simulations are presented.  
 
SUPG036
 Simulations for the High Gradient, Low Emittance Supergun RF Photoinjector  
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  • A.D. Cahill, A. Fukasawa, J.B. Rosenzweig
    UCLA, Los Angeles, California, USA
  • L. Faillace
    RadiaBeam, Marina del Rey, California, USA
  • B. Spataro
    INFN/LNF, Frascati (Roma), Italy
  • A. Valloni
    CERN, Geneva, Switzerland
  
  A new S-Band photoinjector is being developed at UCLA that will feature a large accelerating gradient at 160 MeV/m creating a beam with approximately 6.5 MeV at the exit. Because of the large accelerating gradient and other considerations, such as cooling and manufacturing, the new Supergun will be coupled into using a coaxial method, rather than side coupling. With the large accelerating gradient we hope to create very low emittance beams on the order of 0.025 mm mrad. These beams can then be used for a number of purposes, mainly for high quality beams used in FELs. Electric simulations have been done using HFSS and Superfish. Heating and mechanical simulations were done using Ansys. Finally, beam simulations were completed with GPT.  
 
SUPG037
 Design, Hardware Tests and First Results From the CLIC Drive Beam Phase Feed-Forward Prototype at CTF3  
MOPP033   use link to access more material from this paper's primary paper code  
 
  • J. Roberts, A. Andersson, P.K. Skowronski
    CERN, Geneva, Switzerland
  • P. Burrows, G.B. Christian, C. Perry
    JAI, Oxford, United Kingdom
  • A. Ghigo, F. Marcellini
    INFN/LNF, Frascati (Roma), Italy
  
  In the CLIC two beam acceleration concept the phase synchronisation between the main beam and the RF power extracted from the drive beam must be maintained to within 0.2 degrees of 12 GHz. A drive beam phase feed-forward system with bandwidth above 17.5 MHz is required to reduce the drive beam phase jitter to this level. The system will correct the drive beam phase by varying the path length through a chicane via the use of fast strip line kickers. A prototype of the system is in the final stages of installation at the CLIC test facility CTF3 at CERN. This paper presents results from preparations for the phase feedforward system relating to optics improvements, the development of a slow phase feedback that will be run in parallel with the feedforward system and first tests of the kicker amplifier and kickers.