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plasma

Paper Title Other Keywords Page
MOP058 A Test Bench for the Heidelberg Ion Beam Therapy Centre ion, ion-source, dipole, simulation 187
 
  • R. Cee, E. Feldmeier, M. Galonska, Th. Haberer, J.M. Mosthaf, A. Peters, S. Scheloske, T.W. Winkelmann
    HIT, Heidelberg
 
 

The Heidelberg Ion Beam Therapy Centre (HIT) is the only medical facility in Europe for cancer treatment with protons and carbon ions. To broaden the range of available ion species towards helium the low energy beam transport (LEBT) will be extended by a third ion source and the associated spectrometer section. Following a novel ion optical approach the LEBT-branch has been redesigned. A dedicated test bench will be used to commission and validate the new design prior to its integration into the medical accelerator. In its final stage the test bench will comprise an ECR-ion source, a LEBT and an RFQ with diagnostics line. It opens up the unique opportunity to perform comprehensive investigations not only of the ion source but also of other devices like the RFQ which have been optimised in the frame of the LINAC upgrade. Here, particular emphasis will be placed on the new design of the analyser dipole and the macro pulse chopper. Furthermore results of beam optical simulations and first measurement results will be presented.

 
MOP066 Numerical Modeling of Arcs in Accelerators vacuum, laser, acceleration, electron 205
 
  • J. Norem, Z. Insepov, Th. Proslier
    ANL, Argonne
  • S. Mahalingam, S.A. Veitzer
    Tech-X, Boulder, Colorado
 
 

We are developing a model of arcing to explain breakdown phenomena in high-gradient rf systems used for particle accelerators. This model assumes that arcs develop as a result of mechanical failure of the surface due to electric tensile stress, ionization of fragments by field emission, and the development of a small, dense plasma that interacts with the surface primarily through self sputtering and terminates as a unipolar arc capable of producing field emitters with high enhancement factors. We are modeling these mechanisms using Molecular Dynamics (mechanical failure, Coulomb explosions, self sputtering), Particle-In-Cell (PIC) codes (plasma evolution), mesoscale surface thermodynamics (surface evolution), and finite element electrostatic modeling (field enhancements). We believe this model may be more widely applicable and we are trying to constrain the physical mechanisms using data from tokamak edge plasmas.

 
MOP070 Breakdown Studies for the CLIC Accelerating Structures simulation, vacuum, collider, target 217
 
  • S. Calatroni, J.W. Kovermann, M. Taborelli, H. Timko, W. Wuensch
    CERN, Geneva
  • A. Descoeudres
    EPFL, Lausanne
  • F. Djurabekova, A. Kuronen, K. Nordlund, A.S. Pohjonen
    HIP, University of Helsinki
 
 

Optimizing the design and the manufacturing of the CLIC RF accelerating structures for achieving the target value of breakdown rate at the nominal accelerating gradient of 100 MV/m requires a detailed understanding of all the steps involved in the mechanism of breakdown. These include surface modification under RF fields, electron emission and neutral evaporation in the vacuum, arc ignition and consequent surface modification due to plasma bombardment. Together with RF tests, experiments are conducted in a simple DC test set-up instrumented with electrical diagnostics and optical spectroscopy. The results are also used for validating simulations which are performed using a wide range of numerical tools (MD coupled to electrostatic codes, PIC plasma simulations) able to include all the above phenomena. Some recent results are presented in this paper.

 
MOP102 Space Charge Lens for Focusing Heavy Ion Beams electron, space-charge, ion, emittance 298
 
  • K. Schulte, M. Droba, O. Meusel, U. Ratzinger
    IAP, Frankfurt am Main
 
 

Space charge lenses use a confined electron cloud for the focusing of ion beams. Due to the electric space charge field, focusing is independent of the particle mass. For this reason the application of the space charge lens especially in the field of heavy ion beams is advantageous. Moreover, the trapped non neutral plasma cloud compensates the space charge forces of the ion beam. The focusing strength is given by the confined electron density whereas the density distribution influences the mapping quality of the space charge lens. An important parameter for the focusing capability of the space charge lens is besides the homogeneous electron distribution a high electron density. In ongoing theoretical and experimental work methods have been developed to determine the most important parameters like electron temperature and electron density distribution for an optimized lens design. Based on the experimental results a new space charge lens has been designed to focus low energy heavy ion beams like 2,4 AkeV U4+ at the low energy transport section into the GSI High Current Injector. Experimental results will be presented and compared with numerical simulations.


*W. Barth, "THE INJECTOR SYSTEMS OF THE FAIR PROJECT", LINAC08, Victoria, BC, Canada

 
TUP106 Development of Stripper Options for FRIB ion, linac, vacuum, electron 662
 
  • F. Marti
    NSCL, East Lansing, Michigan
  • A. Hershcovitch, P. Thieberger
    BNL, Upton, Long Island, New York
  • Y. Momozaki, J.A. Nolen, C.B. Reed
    ANL, Argonne
 
 

The US Department of Energy Facility for Rare Isotope Beams (FRIB) at Michigan State University includes a heavy ion superconducting linac capable of accelerating all ions up to uranium with energies higher than 200 MeV/u and beam power up to 400 kW. To achieve these goals with present ion source performance it is necessary to accelerate simultaneously two charge states of uranium from the ion source in the first section of the linac. At an energy of approximately 17 MeV/u we plan to strip the uranium beam to reduce the voltage needed in the rest of the linac to achieve the final energy. Up to five different charge states are planned to be accelerated simultaneously after the stripper. The design of the stripper is a challenging problem due to the high power deposited (approximately one kW) in the stripper media by the beam in a small spot. To assure success of the project we have established a research and development program that includes several options: carbon or diamond foils, liquid lithium films, gas strippers and plasma strippers. We present in this paper a summary of the requirements and a general description of the status of the different options.

 
THP033 Superconducting Sputtered Nb/Cu QWR for the HIE-ISOLDE Project at CERN cavity, cathode, niobium, linac 827
 
  • S. Calatroni, P. Costa Pinto, A. D'Elia, L.M.A. Ferreira, G. Lanza, M. Pasini, M. Scheubel, M. Therasse
    CERN, Geneva
  • R.E. Laxdal, V. Zvyagintsev
    TRIUMF, Vancouver
 
 

For the foreseen intensity and energy upgrade of the ISOLDE complex at CERN (HIE-ISOLDE project) a new superconducting LINAC based on sputtered Nb/Cu Quarter Wave Resonators (QWRs) of two different beta families will be installed in the next three to five years. A prototype cavity of the higher beta family is currently being developed. In this paper we will discuss the latest developments on the sputtering technique for this kind of cavity geometry. First cold RF measurements will be reported.

 
THP112 CW Superconducting RF Photoinjector Development for Energy Recovery Linacs cavity, cathode, SRF, niobium 998
 
  • A. Neumann, W. Anders, M. Dirsat, A. Frahm, A. Jankowiak, T. Kamps, J. Knobloch, O. Kugeler, T. Quast, J. Rudolph, M. Schenk, M. Schuster
    HZB, Berlin
  • P. Kneisel
    JLAB, Newport News, Virginia
  • R. Nietubyc
    The Andrzej Soltan Institute for Nuclear Studies, Centre Swierk, Swierk/Otwock
  • T. Rao, J. Smedley
    BNL, Upton, Long Island, New York
  • J.K. Sekutowicz
    DESY, Hamburg
  • I. Will
    MBI, Berlin
 
 

ERLs have the powerful potential to provide very high current beams with exceptional and tailored parameters for many applications, from next-generation light sources to electron coolers. However, the demands placed on the electron source are severe. It must operate CW, generating a current of 100 mA or more with a normalized emittance of order 1 μm rad. Beyond these requirements, issues such as dark current and long-term reliability are critical to the success of ERL facilities. As part of the BERLinPro project, Helmholtz Zentrum Berlin (HZB) is developing a CW SRF photoinjector in three stages, the first of which is currently being installed at HZB's HoBiCaT facility. It consists of an SRF-cavity with a Pb cathode and a superconducting solenoid. Subsequent development stages include the integration of a high-quantum-efficiency cathode and RF components for high-current operation. This paper discusses the HZB roadmap towards an ERL-suitable SRF photoinjector, the present status of the facility and first cavity tests.

 
THP113 Design of the 2.45 GHz ECR Proton Source and LEBT in CPHS (Compact Pulsed Hadron Source) proton, rfq, neutron, ion 1001
 
  • Z. Feng, X. Guan, J. Wei, H.Y. Zhang
    TUB, Beijing
  • Z.W. Liu, H.W. Zhao
    IMP, Lanzhou
 
 

Responding to the demand of accelerator front inject system of the Compact Pulsed Hadron Source (CPHS) in Tsinghua university in 2009, an electron cyclotron resonance (ECR) proton source (2.45 GHz, 1.5 KW) and a low-energy-beam-transport (LEBT) system are designed and manufacted. In this source, the H2 plasma is restricted by an axial magnetic field shaped by the source body produced by an all-permanent-magnet design (NdFeB rings). The 50-keV pulsed proton beam (50 Hz/0.5 ms) extracted by a four-electrode extraction system from the proton source passes through the LEBT system (1283 mm long), which is consist of two solenoid lens, two steering magnets and a cone configuration optically matches to the RFQ where the Twiss parameters α=1.354, β=7.731. The beam with 97% space charge neutralization rate has been simulated at 100 mA, 150 mm.mrad RFQ output current by Trace-3D and PBGUN. In this study, we describe the design of the proton source and LEBT technical systems along with intended operation.

 
THP114 H- Ion Source Development for High Performance ion, ion-source, emittance, controls 1004
 
  • K.F. Johnson, E. Chacon-Golcher, E.G. Geros, R. Keller, G. Rouleau, L. Rybarcyk, J. Stelzer
    LANL, Los Alamos, New Mexico
  • O.A. Tarvainen
    JYFL, Jyvaskyla
 
 

The Los Alamos Neutron Sciene Center (LANSCE) accelerator facility has the capability of accelerating both H+ and H- ion beams. LANSCE H- User Programs rely on the ion source's ability to deliver an appropriate beam current within a given emittance limit. An active H- ion source development program is ongoing with the goal of improving source performance (e.g. reliability, availability, increased out current, etc.) The formation of H- ions in the LANSCE negative ion source occurs on the surface of a negatively biased electrode (converter), exposed to a flux of positive ions incident from a cusp-confined, filament-driven discharge. The source typically delivers a 16 mA pulsed (60 Hz) H- beam with a source lifetime of 35 days. A program to reach 28-35 mA with the LANSCE source is outlined. It includes efforts to improve filament performance, elevating source body temperatures, optimizing converter geometry and location, optimizing converter cooling, and increasing the number of filaments from two to three.

 
THP116 Tests of the Versatile Ion Source (VIS) for High Power Proton Beam Production emittance, proton, extraction, permanent-magnet 1010
 
  • S. Gammino, G. Castro, L. Celona, G. Ciavola, D. Mascali, R. Miracoli
    INFN/LNS, Catania
  • G. Adroit, O. Delferrière, R. Gobin, F. Senée
    CEA, Gif-sur-Yvette
  • F. Maimone
    GSI, Darmstadt
 
 

The sources adapted to beam production for high power proton accelerators must obey to the request of high brightness, stability and reliability. The Versatile Ion Source (VIS) is based on permanent magnets (maximum value around 0.1 T on the chamber axis) producing an off-resonance microwave discharge. It operates up to 80 kV without a bulky high voltage platform, producing several tens of mA of proton beams and monocharged ions. The microwave injection system and the extraction electrodes geometry have been designed in order to optimize the beam brightness. Moreover, the VIS source ensures long time operations without maintenance and high reliability in order to fulfil the requirements of the future accelerators. A description of the main components and of the source performances will be given. A brief summary of the possible options for next developments of the project will be also presented, particularly for pulsed mode operations, that are relevant for future projects.

 
THP117 Study of the Frequency Tuning Effect for the Improvement of Beam Brightness in ECR Ion Sources electron, ion, ECR, resonance 1013
 
  • S. Gammino, L. Celona, G. Ciavola, D. Mascali, R. Miracoli
    INFN/LNS, Catania
  • F. Maimone
    GSI, Darmstadt
 
 

According to the model that has driven the development of ECRIS in the last years, a large variation of the pumping microwave frequency (order of GHz) boosts the extracted current for each charge state because of a larger plasma density. Recent experiments have demonstrated that even slight frequency's changes (of the order of MHz) considerably influence the output current, and also the beam properties after the extraction (beam shape, brightness and emittance). In order to investigate how this fine tuning affects the plasma heating, a set-up for the injection of different microwave frequencies into the ECRIS cavity has been prepared. The microwave power is fed by means of a Travelling Wave Tube amplifier with a broad operating frequency range. The frequency can be systematically changed and the beam output is recorded either in terms of charge state distributions and beam emittance. The detected brehmsstralung X-rays are additionally analysed: they give insights about the electron energy distribution function (EEDF). The results are compared with simulations and data coming from previous preliminary experiments.

 
THP118 Status of the J-PARC Negative Hydrogen Ion Source ion, ion-source, vacuum, rfq 1016
 
  • H. Oguri, Y. Namekawa, K. Ohkoshi, A. Ueno
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
  • K. Ikegami
    J-PARC, KEK & JAEA, Ibaraki-ken
 
 

A cesium-free negative hydrogen ion source driven with a LaB6 filament is being operated for J-PARC. The beam commissioning of J-PARC accelerators started in November 2006. As of April 2010, there have been 32 beam commissioning or supply runs. In these runs, the ion source has been successfully operated in two different modes such as low current mode of 5 mA and high current mode of 30 mA. According to the task of the run, one of the two modes was selected. However, the beam current has been restricted to less than 15 mA for the stable operation of the RFQ linac which has serious discharge problem from September 2008. The beam run is performed during 4-5 weeks cycles, which consisted of a 3-4 weeks beam run and 4 days down-period interval. At the recent beam run, approximately 700 hours continuous operation was achieved, which is satisfied with the requirement of the ion source lifetime for the J-PARC first stage. At every runs, the beam interruption time due to the ion source failure is several hours, which correspond to the ion source availability of 99 %.

 
THP119 Developments for Performance Improvement of SNS H- Ion Source RF Systems ion-source, ion, impedance, vacuum 1019
 
  • Y.W. Kang, R.E. Fuja, T.W. Hardek, S.W. Lee, M.P. McCarthy, M.F. Piller, K.R. Shin, M.P. Stockli, A.V. Vassioutchenko, R.F. Welton
    ORNL, Oak Ridge, Tennessee
 
 

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is in the process of ramping up the H- ion beam power to 1.4 MW, its full design power for the neutron production. For robust operation of the neutron facility, work is underway for various improvements on the RF power systems of the ion source. For short and long-term higher beam power operations, an RF-driven H- ion source employing external antenna with a water-cooled, ceramic aluminum nitride (AlN) plasma chamber has been developed*. The new ion source has been tested to deliver up to 42 mA in the SNS Front End (FE) and unanalyzed beam currents up to ~100mA (60Hz, 1ms) in the ion source test stand. In addition to the external antenna design for improved antenna lifetime, other RF developments for improvement of reliability are running 2 MHz power amplifier system is with isolation transformer, employing full solid-state 2 MHz power amplifier, more precise 2 MHz capacitive impedance matching, and upgrading 13 MHz RF plasma gun system. This paper discusses the engineering solutions with analysis and development of the above RF systems for the new ion source system.


R.F. Welton, N.J. Desai, J. Carmichael, B. Han, Y.W. Kang, S.N. Murray, T. Pennisi, M. Santana, and M.P. Stockli, "The Continued Development of the SNS External Antenna H- Ion Source," ICIS2009