WGB  —  Beam Dynamics in High-Intensity Linacs   (25-Aug-08   08:30—18:30)

Paper Title Page
WGB01 Phase Damping in the SNS Linac 184
 
  • Y. Zhang, S. Henderson
    ORNL, Oak Ridge, Tennessee
 
 

Beam phase synchronous oscillations and the damping curves of the SNS linac are investigated with linac models and measured with all the linac beam phase monitors. It provides a useful beam diagnostic solution to detect RF cavity phase and/or field amplitude errors in the linac with many independently phased cavities. And the phase damping curves predicted in the longitudinal model could also be utilized to analyze the longitudinal lattice of the superconducting linac, in which each cavity gradient varies widely from the nominal design and smooth the beam longitudinal focusing is very important to preserve beam emittance.

 

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WGB02 Impact Simulation and the SNS Linac Beam 190
 
  • Y. Zhang
    ORNL, Oak Ridge, Tennessee
  • J. Qiang
    LBNL, Berkeley, California
 
 

Multi-particle tracking simulations for the SNS linac beam dynamics studies are performed with the IMPACT code. Beam measurement results are compared with the simulations, including beam halos and beam loss in the superconducting linac, measurement of beam transverse twiss parameters and beam longitudinal emittance in the SNS linac. And in most cases, the simulations show good agreement with the measured results.

 
WGB03 Linac Beam Dynamics Codes: State of the Art and Perspectives 194
 
  • R.D. Ryne
    LBNL, Berkeley, California
 
 

In this talk I first discuss the historical development of beam dynamics codes. I then describe the current state of the art in linac codes and present several examples. I conclude by presenting my view of future accelerator code R&D efforts.

 

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WGB04 Simulation of Experiments on Transverse RMS-Emittance Growth Along an Alvarez DTL 195
 
  • L. Groening, W. Barth, W.B. Bayer, G. Clemente, L.A. Dahl, P. Forck, P. Gerhard, I. Hofmann, G. Riehl, S. Yaramyshev
    GSI, Darmstadt
  • D.-O. Jeon
    ORNL, Oak Ridge, Tennessee
  • D. Uriot
    CEA, Gif-sur-Yvette
 
 

Systematic measurements on transverse rms-emittance growth along the Alvarez DTL of the GSI UNILAC were performed. A high intensity argon beam was used to measure rms-growth for different transverse phase advances along the DTL. The transverse tune depression varied from 21% to 43%. For benchmarking of the experimental results four different beam dynamics codes were used: DYNAMION, PARMILA, PARTRAN, and LORASR. This paper is on the results of the experiments, the reconstruction of the initial conditions for the simulations, and on the agreement between simulations and experiments. Additionally, successful suppression of rms-growth by systematic matching is reported.

 
WGB05 Simulations of High-Intensity Beams Using BG/P Supercomputer at ANL 200
 
  • J. Xu, B. Mustapha, P.N. Ostroumov
    ANL, Argonne, Illinois
  • V.N. Aseev
    Fermilab, Batavia, Illinois
 
 

Large-scale beam dynamics simulations are important in accelerator design and optimization. With the new BG/P supercomputer installed at ANL, tera-scale computing can be easily accessed. In order to make use of this emerging technology to increase the speed and efficiency of accelerator simulations, we have systematized and upgraded our software. In this paper, we will first introduce the new version of the parallel beam dynamic code PTRACK [1] updated to run on BG/P with more than 104 processors. The new PTRACK includes possibility to track ~100,000,000 particles through multiple accelerator seeds in the presence of machine errors. An example of SNS linac simulations will be presented.


[1]. J. Xu, B. Mustapha, V.N. Aseev and P.N. Ostroumov, “Parallelization of a beam dynamics code and ***”, Physics Review Special Topic-Accelerator and Beams 10, 014201, 2007.

 

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WGB06 Using the Online Single Particle Model for SNS Accelerator Tuning 203
 
  • A.P. Shishlo, A.V. Aleksandrov
    ORNL, Oak Ridge, Tennessee
 
 

The paper describes a usage of the XAL online model for transverse and longitudinal tuning of the SNS linac. Most of the SNS control room physics applications based on the XAL online model which allows synchronizing the model with an accelerator live state and using this model for tuning the machine. Peculiarities of applying of the simplest single particle mode of the model for orbit correction and longitudinal dynamics control of the SNS linac are discussed. The procedure of parameters finding, algorithms, and results are presented.

 

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WGB07 Beam Studies at the SNS Linac 207
 
  • Y. Zhang
    ORNL, Oak Ridge, Tennessee
 
 

Most recent beam dynamic studies of the Spallation Neutron Source linac, including the major beam loss reduction efforts in the normal conducting (nc) linac and in the superconducting linac (SCL), simulations and measurements of the longitudinal beam halos and the longitudinal acceptance at the entrance of the SCL are discussed. Oscillation of beam centroid around the linac synchronous phase and the beam phase adiabatic damping curves in the SNS linac are investigated with the linac longitudinal models and measured with all the linac beam phase monitors.

 

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WGB08 Measurement and Simulation in J-PARC Linac 213
 
  • M. Ikegami
    KEK, Ibaraki
  • Y. Kondo, T. Morishita, H. Sako
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
 
 

The beam commissioning of J-PARC linac has been started since November 2006. Numerical studies have been conducted since then to analyze the experimental results obtained in the beam commissioning and deepen our understanding on the underlying physics. Particular efforts are exerted on the analyses of the transverse emittance measurement at MEBT, the phase scan measurement for DTL, and the rms width response to a quadrupole magnet variation. All the measurements are essential to realize a fine tuning of the linac, and it is of practical importance to have a physical insight into the obtained results. In these studies, various simulation tools are employed in accordance with the required capacity. In this paper, the on-going numerical studies for J-PARC linac are reviewed, and we discuss on the directions in which we should pay further efforts.

 
WGB10 Physics Design of Front Ends for Superconducting Ion Linacs 218
 
  • P.N. Ostroumov
    ANL, Argonne, Illinois
  • J.-P. Carneiro
    Fermilab, Batavia, Illinois
 
 

Superconducting (SC) technology is the only option for CW linacs and is also an attractive option for pulsed linacs. SC cavities are routinely used for proton & H-minus beam acceleration above 185 MeV. Successful development of SC cavities covering the lower velocity range (down to 0.03c) is a very strong basis for the application of SC structures in the front ends of high energy linacs. Lattice design and related high-intensity beam physics issues in a ~400 MeV linac that uses SC cavities will be presented in this talk. In particular, axially-symmetric focusing by SC solenoids provides strong control of beam space charge and a compact focusing lattice. As an example, we discuss the SC front end of the H-minus linac for the High Intesity Neutrino Source (HINS) and Project X.

 

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WGB11 KONUS Beam Dynamics Designs Using H-Mode Cavities 223
 
  • R. Tiede, H. Podlech, U. Ratzinger, C. Zhang
    IAP, Frankfurt am Main
  • G. Clemente
    GSI, Darmstadt
 
 

The 'Combined Zero-Degree Structure' ('Kombinierte Null Grad Struktur - KONUS') beam dynamics concept is described in detail. A KONUS period consists of a quadrupole triplet or a solenoid lens, a rebuncher section at negative synchronous phase and a multi cell zero degree synchronous particle main acceleration section. This concept is especially effective when applied for accelerator designs using H-mode resonators with ‘slim’ drift tubes which carry no focusing elements. The definition and typical ranges of KONUS lattice parameters are discussed on a general level, as well as on the basis of examples for realized or planned high current accelerators, like the GSI High Current Injector (HSI), the 70 mA, 3-70 MeV Proton Injector for the FAIR Facility and our proposal of a 125 mA D+, 5-40 MeV superconducting CH-DTL section for the International Fusion Materials Irradiation Facility (IFMIF).

 

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WGB12 Prediction of the 4ν=1 Resonance of a High Intensity Linac 231
 
  • D.-O. Jeon
    ORNL, Oak Ridge, Tennessee
  • G. Franchetti, L. Groening, I. Hofmann
    GSI, Darmstadt
 
 

The 4ν=1 resonance of a linac is found when the depressed tune is around 90 deg. It is observed that this fourth order resonance is dominating over the better known envelope instability and practically replacing it. Simulation study shows a clear emittance growth by this resonance and its stopband. Experimental measurement of the stopband of this resonance is proposed and conducted in 2008 using the UNILAC at GSI. This study will serve as an excellent benchmarking.


SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.

 

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WGB13 Investigation of the Beam Dynamics Layout of the FAIR Proton Injector 235
 
  • G. Clemente, L. Groening
    GSI, Darmstadt
  • U. Ratzinger, R. Tiede
    IAP, Frankfurt am Main
 
 

The FAIR facility at GSI requires a dedicated proton injector for the production of secondary high intensity antiproton beams. This 325 MHz, 70 MeV machine will be the fist linac based on CH cavities operated with Konus beam dynamics. Two different options for the beam dynamics layout are under investigation including loss and error studies. Finally different RFQ output distribution are used to evaluate the injection current into the main linac.

 

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WGB14 Beam Dynamics in Linac4 at CERN 238
 
  • A.M. Lombardi, G. Bellodi, M. Eshraqi, F. Gerigk, J.-B. Lallement, S. Lanzone, E.Zh. Sargsyan
    CERN, Geneva
  • R.D. Duperrier, D. Uriot
    CEA, Gif-sur-Yvette
 
 

Linac4 is a normal conducting H- linac to be built at CERN as a new injector to the PS Booster and later on as a front end of a possible MultiMegaWatt Linac Facility. The layout consists of a H- RF source, a magnetic LEBT, a RFQ (accelerating the beam from 45 keV to 3 MeV), a chopper line, a conventional Drift Tube Linac (from 3 MeV to 50 MeV), a Coupled Cavity Drift Tube Linac (from 50 MeV to 100 MeV) and a pi-mode structure (PIMS, from 100 to 160 MeV), all operating at a frequency of 352 MHz. End-to-end beam dynamics simulations have been carried out to optimise the design and performance of the accelerator. An extensive statistical campaign of transverse error studies was then launched for accessing the required alignment tolerances and steering correction system.

 

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WGB15 Lattice Beam Dynamics Study at Low β for SARAF/EURISOL Driver 40/60 MeV 4 mA d&p Superconducting Linac 246
 
  • J. Rodnizki, B. Bazak, D. Berkovits, G. Feinberg, A. Shor, Y. Yanay
    Soreq NRC, Yavne
 
 

In this study we examine a lattice for the SARAF superconducting (SC) linac at the low velocity β range. The SC Half Wave Resonator cavities in the first cryostat have been optimized for a geometric β=0.09 and hence the β=0.0567 ions coming from the RFQ are mismatched. We developed a semi adiabatic tuning method for the low β side of the SC linac. The guidelines were derived from a study of two linac lattices that were considered for the SARAF 40 MeV proton and deuteron linac, extended up to 60 MeV for the low energy part of the EURISOL driver. Simulations were made using the TRACK and GPT codes. The lattices were tested for energy gain along the linac, emittance growth and acceptance. Further, error runs in GPT using a tail emphasis technique to enhance statistics by focusing on the bunch tail allowed us to examine compatibility of the lattices with hands-on maintenance requirements. We find our study relevant for other linacs that start with SC cavities right after the RFQ, such as SPIRAL2, and maybe IFMIF too, which are designed to start with similar β mismatch at the low β range.

 

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WGB17 Development of Large Scale Optimization Tools for Beam Tracking Codes 254
 
  • B. Mustapha, P.N. Ostroumov
    ANL, Argonne, Illinois
 
 

Matrix-based beam optics codes such as TRACE-3D are often used for small scale optimizations such as beam matching which involves a limited number of parameters. The limitation of such codes is further amplified for high-intensity and multiple charge state beams as their predictions start to deviate from the more realistic 3D particle tracking codes. For these reasons we have started developing large scale optimization tools for beam tracking codes. The large scale nature comes first from the possibility of optimizing a large number of parameters and second from the minimum number of particles to track especially for space charge dominated beams. The ultimate goal of these developments is not only to optimize the design of an accelerator but also to be able to use a beam dynamics code to operate it once built. A selected set of optimization options will be presented and discussed along with specific applications. We'll also emphasize the need for parallel computing to speed-up the optimization process.

 

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