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WPAE063 CERN-PS Main Power Converter Renovation: How To Provide and Control the Large Flow of Energy for a Rapid Cycling Machine? acceleration, synchrotron, superconductivity, superconducting-magnet 3612
  • F. Bordry, J.-P. Burnet, F. Voelker
    CERN, Geneva
  The PS (Proton-Synchrotron) at CERN, which is part of the LHC injector chain, is composed of 101 main magnets connected in series. During a cycle (about 1 second), the active power at the magnet terminals varies from plus to minus 40 MW. Forty years ago, the solution was to insert a motor-generator (M-G) set between the AC supply network and the load. The M-G set acts as a fly-wheel with a stored kinetic energy of 233 MJ. The power converter is composed of two 12-pulse rectifiers connected in series. A renovation or replacement of the installation is planned in the near future as part of the consolidation of the LHC injectors. This paper presents a first comparison of technical solutions: - a direct connection to the 400 kV mains; - a kinetic energy storage system either by the existing or by a new “state of the art” M-G set; - a new local inductive or capacitive energy storage system. All these solutions need new power electronics equipment, which should be based on proven industrial topologies, techniques and components. The related studies will address the challenge of controlling by a modern power converter with local energy storage the positive and negative flow of energy to a rapid cycling accelerator load.  
ROAB006 Pulsed Power Drivers and Diodes for X-Ray Radiography electron, impedance, vacuum, plasma 510
  • K.J. Thomas
    AWE, Reading
  Flash radiography has been used as a diagnostic for explosively driven hydrodynamics experiments for several decades following the pioneering work of J C Martin and his group at AWE. Relatively simple pulsed power drivers operating between 1 and 10 MV coupled to experimentally optimised electron beam diodes have achieved great success in a number of different classes of these experiments. The next generation of radiographic facilities will aim to improve even further the radiographic performance achievable by developing both the electron beam diodes used and the accelerators that drive them. The application of the rod-pinch diode to an Inductive Voltage Adder at 2 MV in the US has already advanced the quality of radiography available for relatively thin objects. For the thickest objects accelerators operating at up to 15 MV and diodes capable of focusing electron beams to intensities of ~ 1 MA/cm2 for tens of nanoseconds will be required in the future. Since the various candidate diode configurations operate in both high and low impedance regimes there is a further challenge to design and engineer an accelerator capable of driving whichever one, or more, are eventually used.  
ROAB007 Pulsed Power Applications in High Intensity Proton Rings kicker, extraction, impedance, proton 568
  • W. Zhang, J. Sandberg
    BNL, Upton, Long Island, New York
  • R.I. Cutler
    ORNL, Oak Ridge, Tennessee
  • L. Ducimetière, T. Fowler, V. Mertens
    CERN, Geneva
  • T. Kawakubo, Y. Shirakabe
    KEK, Ibaraki
  Funding: Work performed under the auspices of the U.S. Department of Energy.

The pulsed power technology has been applied in particle accelerators and storage rings for over four decades. It is most commonly used in injection, extraction, beam manipulation, source, and focusing systems. These systems belong to the class of repetitive pulsed power. In this presentation, we review and discuss the history, present status, and future challenge of pulsed power applications in high intensity proton accelerators and storage rings.

ROAB010 Development of a Compact Radiography Accelerator Using Dielectric Wall Accelerator Technology laser, cathode, vacuum, acceleration 716
  • S. Sampayan, G.J. Caporaso, Y.-J. Chen, S.A. Hawkins, L. Holmes, J.F. McCarrick, S.D. Nelson, C. Nunnally, B.R. Poole, A. Rhodes, M. Sanders, S. Sullivan, L. Wang, J.A. Watson
    LLNL, Livermore, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

We are developing of a compact accelerator system primarily intended for pulsed radiography. Design characteristics are an 8 MeV endpoint energy, 2 kA beam current and a cell gradient of approximately 3 MV/m. Overall length of the device is below 3 m. Such compact designs have been made possible with the development of high specific energy dielectrics (> 10 J/cc), specialized transmission line designs and multi-gap laser-triggered low jitter (<1 ns) gas switches. In this geometry, the pulse forming lines, switches and insulator/beam pipe are fully integrated within each cell to form a compact stand-alone stackable unit. We detail our research and modeling to date, recent high voltage test results, and the integration concept of the cells into a radiographic system.

RPPT066 Electromigration Issues in High Current Horn target, electron, secondary-beams, radiation 3700
  • W. Zhang, S. Bellavia, J. Sandberg, N. Simos, J.E. Tuozzolo, W.-T. Weng
    BNL, Upton, Long Island, New York
  • B. Hseuh
    JHU, Baltimore, Maryland
  Funding: Work performed under the auspices of the U.S. Department of Energy.

The secondary particle focusing horn for the AGS neutrino experiment proposal is a high current and high current density device. The peak current of horn is 300 kA. At the smallest area of horn, the current density is near 8 kA/mm2. At very high current density, a few kA/mm2, the electromigration phenomena will occur. Momentum transfer between electrons and metal atoms at high current density causes electromigration. The reliability and lifetime of focusing horn can be severely reduced by electromigration. In this paper, we discuss issues such as device reliability model, incubation time of electromigration, and lifetime of horn.

FPAT031 High Energy Pulsed Power System for AGS Super Neutrino Focusing Horn target, power-supply, proton, simulation 2191
  • W. Zhang, J. Sandberg, W.-T. Weng
    BNL, Upton, Long Island, New York
  Funding: Work performed under the auspices of the U.S. Department of Energy.

This paper present a preliminary design of a 300 kA, 2.5 Hz pulsed power system. This system will drive the focusing horn of proposed Brookhaven AGS Neutrino Super Beam Facility for Very Long Baseline Neutrino Oscillation Experiment. The peak output power of the horn pulsed power system will reach giga-watts, and the upgraded AGS will be capable of delivering 1 MW in beam power.

FPAT033 Numerical Model of the DARHT Accelerating Cell simulation, electron 2269
  • T.P. Hughes, T.C. Genoni
    ATK-MR, Albuquerque, New Mexico
  • H. Davis, M. Kang, B.A. Prichard
    LANL, Los Alamos, New Mexico
  Funding: NNSA/DOE

The DARHT-2 facility at Los Alamos National Laboratory accelerates a 2 microsecond electron beam using a series of inductive accelerating cells. The cell inductance is provided by large Metglas cores, which are driven by a pulse-forming network. The original cell design was susceptible to electrical breakdown near the outer radius of the cores. We developed a numerical model for the magnetic properties of Metglas over the range of dB/dt (magnetization rate) relevant to DARHT. The model was implemented in a radially-resolved circuit code, and in the LSP* electromagnetic code. LSP simulations showed that the field stress distribution across the outer radius of the cores was highly nonuniform. This was subsequently confirmed in experiments at LBNL. The calculated temporal evolution of the electric field stress inside the cores approximately matches experimental measurements. The cells have been redesigned to greatly reduce the field stresses along the outer radius.

*LSP is a software product of ATK Mission Research (www.lspsuite.net).

FPAT036 An Induction Linac Test Stand induction, linac, diagnostics, electron 2455
  • W. J. DeHope, D.A. Goerz, R. Kihara, M.M. Ong, G.E. Vogtlin, J.M. Zentler
    LLNL, Livermore, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. 7405-Eng-48.

A single-cell test stand has been constructed to facilitate study and guide improvements of the induction electron linac at the FXR radiographic facility at LLNL.* This paper will discuss how modifications in pulse compression and shaping, pulse power transmission, initial ferrite state, and accelerator cell loading have been performed on the test stand and can be applied to the entire accelerator. Some of the specialized diagnostics being used will be described. Finally, the paper will discuss how computer modeling and judicious timing control can be used to optimize accelerator performance by making only selective changes that can be accomplished at minimal cost.

*"Test Stand for Linear Induction Accelerator Optimization," Ong et al., Pulsed Power Conference, June 16, 2003, Dallas TX.

FPAT037 Electromagnetic Simulations of Helical-Based Ion Acceleration Structures ion, simulation, coupling, injection 2485
  • S.D. Nelson, G.J. Caporaso, A. Friedman, B.R. Poole
    LLNL, Livermore, California
  • R.J. Briggs
    SAIC, Alamo, California
  • W. Waldron
    LBNL, Berkeley, California
  Funding: This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

Helix structures have been proposed* for accelerating low energy ion beams using MV/m fields in order to increase the coupling effeciency of the pulsed power system and to tailor the electromagnetic wave propagation speed with the particle beam speed as the beam gains energy. Calculations presented here show the electromagnetic field as it propagates along the helix structure, field stresses around the helix structure (for voltage breakdown determination), optimizations to the helix and driving pulsed power waveform, and simulations showing test particles interacting with the simulated time varying fields.

*"Helical Pulseline Structures for Ion Acceleration," Briggs, Reginato, Waldron, this conference.

FOAA009 SRF Performance of CEBAF After Thermal Cycle to Ambient Temperature vacuum, linac, site, accumulation 665
  • R.A. Rimmer, J. F. Benesch, J.P. Preble, C.E. Reece
    Jefferson Lab, Newport News, Virginia
  Funding: This manuscript has been authored by SURA, Inc. under Contract No. DE-AC05-84ER-40150 with the U.S. Department of Energy.

In September 2003, in the wake of Hurricane Isabel, JLab was without power for four days after a tree fell on the main power lines feeding the site. This was long enough to lose insulating vacuum in the cryomodules and cryogenic systems resulting in the whole accelerator warming up and the total loss of the liquid helium inventory. This thermal cycle stressed many of the cryomodule components causing several cavities to become inoperable due to helium to vacuum leaks. At the same time the thermal cycle released years of adsorbed gas from the cold surfaces. Over the next days and weeks this gas was pumped away, the insulating vacuum was restored and the machine was cooled back down and re-commissioned. In a testament to the robustness of SRF technology, only a small loss in energy capability was apparent, although individual cavities had quite different field-emission characteristics compared to before the event. In Summer 2004 a section of the machine was again cycled to room temperature during the long maintenance shutdown. We report on the overall SRF performance of the machine after these major disturbances and on efforts to characterize and optimize the new behavior for high-energy running.