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MPPT009 HTS Power Leads for the BTeV Interaction Region quadrupole, interaction-region, magnet-design, power-supply 1147
  • SF. Feher, R. H. Carcagno, D.F. Orris, Y.M.P. Pischalnikov, R. Rabehl, C. Sylvester, M. Tartaglia, J. Tompkins
    Fermilab, Batavia, Illinois
  Funding: DOE

A new Interaction Region for the BTEV experiment is planned to be built soon at Fermilab. This IR will require new superconducting quadrupole magnets and many additional power circuits for their operation. The new "low beta" quadupole magnet design is based upon the Fermilab LHC quadrupole design, and will operate at 9.56 kA in 4.5 K liquid helium. The use of conventional power leads for these circuits would require substantially more helium for cooling than is available from the cryogenic plant, which is already operating close to its limit. To decrease the heat load and helium cooling demands, the use of HTS power leads is necessary. Fermilab is in the process of procuring HTS leads for this new interaction region. Several 6 kA HTS leads produced by American Superconductor Corporation have been tested at over-current conditions. Based on the test results, design requirements are being developed for procuring the HTS current leads. This paper summarizes the test results and describes the design requirements for the 9.65 kA HTS power leads.

TOAA001 Limits of Nb3Sn Accelerator Magnets dipole, superconducting-magnet 107
  • S. Caspi, P. Ferracin
    LBNL, Berkeley, California
  Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098.

Pushing accelerator magnets beyond 10T holds a promise of future upgrades to machines like the Tevatron at FermiLab and the LHC at CERN. Exhausting the current density limits of NbTi, superconductor, Nb3Sn is at the present time the only practical superconductor capable of generating fields beyond 10T. Several Nb3Sn pilot magnets, with fields as high as 16T, have been built and tested, paving the way for future attempts at fields approaching 20T. The combination of high current density and the required high magnetic fields has resulted in reduced conductor volume and significantly increased the accumulated Lorentz forces. Future coil and structure designs will be required to deal with stresses of several 100’s of MPa and forces of 10’s of MN/m. The combined engineering requirements on size and cost of accelerator magnets will require a magnet technology that diverges from the one currently used with NbTi conductor. How far can the engineering of high field magnets be pushed, what are the issues and limitations, and what tools will we need before such magnets can be used in particle accelerators. In this paper we shall address such issues and attempt to provide possible answers.

TPAT023 Tests of a 3D Self Magnetic Field Solver in the Finite Element Gun Code MICHELLE gun, simulation, electron, beam-transport 1814
  • E.M. Nelson
    LANL, Los Alamos, New Mexico
  • J.J. Petillo
    SAIC, Burlington, Massachusetts
  Funding: Work supported by ONR.

We have recently implemented a prototype 3d self magnetic field solver in the finite-element gun code MICHELLE. The new solver computes the magnetic vector potential on unstructured grids. The solver employs edge basis functions in the curl-curl formulation of the finite-element method. A novel current accumulation algorithm takes advantage of the unstructured grid particle tracker to produce a compatible source vector, for which the singular matrix equation is easily solved by the conjugate gradient method. We will present some test cases demonstrating the capabilities of the prototype 3d self magnetic field solver. One test case is self magnetic field in a square drift tube. Another is a relativistic axisymmetric beam freely expanding in a round pipe.

RPPT048 HLS Turn-By-Turn System and Its Application injection, feedback, storage-ring, pick-up 3022
  • J.H. Wang, W. Li, J.H. Liu, L. Liu, B. Sun, Y.L. Yang, K. Zheng
    USTC/NSRL, Hefei, Anhui
  Design and experimental application of the turn-by-turn system of Hefei Light Source (HLS) are presented in this paper. The front-end signal measurement adopts a log-ratio electronics circuitry. The system is designed to be capable of up to 2 seconds data acquisition. Injection kickers are used to excite beam for monitoring ß oscillation and damping rate. Some of experimental applications are also illustrated, in commission of both the upgraded injection system of HLS and the lower frequency feedback system. The results shows that in order to improve the accumulation of the injected beam, it is very necessary to investigate integral magnet fields equilibrium of injected system and proper measures to control restrain remnants ß-oscillation caused by the injected system error.  
FPAE070 A Collimation Scheme for Ions Changing Charge State in the LEIR Ring ion, vacuum, electron, lattice 3816
  • J. Pasternak, C.B. Bal, C. Carli, M. Chanel, E. Mahner
    CERN, Geneva
  Avalanche-like pressure rise and an associated decrease of the beam lifetime, caused by (i) beam loss due to charge exchange interactions with rest gas molecules and (ii) ion impact induced outgassing, is a potential limitation for heavy ion accelerators operating at low energy. Capture of electrons from the electron cooler is another source of ion losses and thus, of pressure rise. The vacuum system of the LEIR ring has to be upgraded to reach the dynamical vacuum pressure in the low 10-12 Torr range necessary to reach design performance. A collimation system to intercept lost ions by absorber blocksmade of low beam induced outgassing material will be installed. This paper reviews the collimation scheme and simulations of beam loss patterns around the ring.  
FPAT066 The SNS Ring LLRF Control System SNS, feedback, extraction, proton 3697
  • S. Peng
    ORNL, Oak Ridge, Tennessee
  • L.T. Hoff, K. Smith
    BNL, Upton, Long Island, New York
  Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a collaboration of six U.S. National Laboratories: ANL, BNL, JLab, LANL, LBNL, and ORNL.

The low-level RF control system for the SNS Ring differs considerably from that for the Linac. To accommodate requirements for higher data throughput and improved performance the system is based on a PCI Digital Signal Processor (DSP). In accordance with SNS standards, a VME-based PowerPC© is used, but advantage is taken of the on-board PMC slot which houses a Bittware© Hammerhead© PMC card with four AD-21162 DSPs.The EPICS system handles system configuration and data traffic while the DSP performs the low-level RF controls. Protocol and software to support both the PowerPC and the DSP have been developed. This paper presents the system design and initial testing experience.

FOAA009 SRF Performance of CEBAF After Thermal Cycle to Ambient Temperature vacuum, linac, pulsed-power, site 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.