Accelerator Technology

Paper Title Page
WOPA001 Wilson Prize Talk
  • K.R. Symon
    UW-Madison/PD, Madison, Wisconsin
  The formula for the center-of-mass energy as a function of the energy of the incident particle in a collision with a stationary target shows that the required beam energy is greatly reduced if we collide incident and target particles with equal and opposite momenta. Unfortunately the cross sections for collisions of interest are so small that until the middle 1900's it was not possible to achieve colliding beams of sufficient intensities to reach needed collision rates. In 1954 fixed field alternating gradient (FFAG) accelerators were invented. With a fixed magnetic guide field, it was possible to consider stacking successively injected beams to achieve very high intensity circulating beams. Calculations using Liouville's theorem showed that colliding beam experiments were now practical. Circulating electron beams over 10 amperes were achieved in a model accelerator built by the Midwestern Universities Research Association (MURA). With the invention of storage rings, a much cheaper accelerator configuration than FFAG, and utilizing beam stacking, colliding beams are now utilized to study high energy interactions.  
ROAD001 Recent Progress in Power Refrigeration Below 2 K for Superconducting Accelerators 9
  • S.D. Claudet
    CERN, Geneva
  As a result of technico-economical optimization and quest for increased performance, 2 K cryogenics is now present in large accelerator projects using superconducting magnets or acceleration cavities. Consequently, large cryogenic systems producing refrigeration capacity below 2 K in the kW range and with high efficiency over a large dynamic range are needed. After CEBAF and SNS, this is now the case for the Large Hadron Collider (LHC) project at CERN for which eight 2.4 kW @ 1.8 K refrigeration units are needed to cool each a 3.3 km long sector of high-field magnets. Combining cold hydrodynamic compressors in series with warm volumetric compressors, complete pre-series units as well as sets of series cold compressors have been intensively tested and validated from two different industrial suppliers. After recalling the possible 2 K refrigeration cycles and their comparative merits, this paper describes the specific features of the LHC system and presents the achieved performance with emphasis on the progress in terms of efficiency, operational compliance, reliability and maintenance. Perspectives of application to a future International Linear Collider based on cold RF technology are then briefly evoked.  
ROAD002 Remote Handling in High-Power Proton Facilities 174
  • G.R. Murdoch
    ORNL, Oak Ridge, Tennessee
  Design for remote handling of highly activated accelerator components is becoming more prevalent as proton facilities are designed and constructed to provide ever-increasing beam powers. During operation of these facilities it is expected that many components will become activated, consequently mechanical engineering design work must address this issue if components are to be maintained by traditional hands-on methods. These design issues are not new and operating proton facilities around the world have gone through the same process to varying degrees. In this paper we discuss the design and design philosophy of remote handling of active accelerator components, using as examples designs which have been proven at operating facilities, as well as new approaches which are being incorporated into accelerator facilities under construction, such as the Spallation Neutron Source and J-PARC.

SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge.

ROAD003 Post-Irradiation Properties of Candidate Materials for High-Power Targets 333
  • H.G. Kirk, H. Ludewig, L.F. Mausner, N. Simos, P. Thieberger
    BNL, Upton, Long Island, New York
  • Y. Hayato, K. Yoshimura
    KEK, Ibaraki
  • K.T. McDonald
    PU, Princeton, New Jersey
  • J. Sheppard
    SLAC, Menlo Park, California
  • L.P. Trung
    Stony Brook University, Stony Brook
  Funding: U.S. DOE.

The long term survivability of materials which can be used either for high-intensity targets or for the environment surrounding the target can be greatly influenced by how the physical properties of the material are altered by radiation damage. We have irradiated several candidate materials and report here on physical properties before and after irradiation.

ROAD005 Status of NEG Coating at ESRF 422
  • M. Hahn
    ESRF, Grenoble
  • R. Kersevan
    ORNL, Oak Ridge, Tennessee
  The ESRF non-evaporable getter (NEG) coating facility is in operation since two years now. A large part of the insertion device straight sections of the electron storage ring has been equipped with in-house coated 5m long aluminum vacuum chambers with an inner vertical aperture of 8 mm. Operational experience with different coating parameters leading to different film thicknesses will be given and compared to bremsstrahlung data. The paper deals also with improvements of the coating production and chamber preparation, and describes some aspects of NEG coating data acquisition, visualization, and remote control. The R&D program leading to a more powerful DC solenoidal coating tool to further improve the NEG coating production throughput and quality aspects is also discussed.  
RPPE040 Development of Copper Coated Chamber for Third Generation Light Sources 2633
  • H. Sakai, I. Ito, H. Kudo, N. Nakamura, S. Shibuya, K. Shinoe, H. Takaki
    ISSP/SRL, Chiba
  • K. Kobayashi
    KEK, Ibaraki
  For the 3rd generation light sources, it is essential to reduce the beam instability in order to produce the highly bright synchrotron light much stably. Especially, to avoid the coupled bunch instability, the resistive wall impedance must be reduced. The copper-coating inner surface of the chamber(especially in insertion device section)is much effective method for the reduction of the resistive wall impedance, whose method was already proposed by our group (N.Nakamura, EPAC 1998 p984). We have already produced the copper coated chamber. In this paper, we describe the measurement of the outgassing from the copper coated chamber to evaluate if this chamber is valid on the ultra-low high vacuum condition.  
FOAC002 Status of Neutrino Factory Design and R&D 209
  • D. Li
    LBNL, Berkeley, California
  Funding: Work supported by the US Department of Energy under contract No. DE-AC0376SF00098

Neutrino physics has become increasingly interesting to the high-energy physics community, as it may provide clues to new physics beyond the standard model. The physics potential of a Neutrino Factory–a facility to produce high-energy, high-intensity, high-brightness neutrino beams from decays of muons stored in a muon storage ring–is thus very high. There has been a global R&D effort aimed at a Neutrino Factory design that meets the physics requirements and addresses the key technologies, such as targetry, muon ionization cooling and acceleration. Tremendous progress has been made in the past few years in many aspects of accelerator technology. In this paper, we will review recent worldwide progress toward a cost-effective Neutrino Factory design, with emphasis on the associated R&D programs under the auspices of the U.S. Neutrino Factory and Muon Collider Collaboration.

FOAA001 New Technology in Hydrogen Absorbers for Muon Cooling Channels 84
  • M.A.C. Cummings
    Northern Illinois University, DeKalb, Illinois
  Funding: National Science Foundation.

Ionization cooling is the only technique fast enough to cool and focus muons for neutrino factories and muon colliders, and hydrogen is the optimal material for maximum cooling and minimal multiple scattering. Liquid hydrogen absorber R & D for the Muon Colloboration has proceeded on parallel and complementary fronts. The continuing LH2 absorber engineering and technical developments by the MuCool group conducted by ICAR* institutions (NIU, IIT and UIUC), the University of Mississippi and Oxford University, in cooperation with Fermilab, will be summarized, including results from the first hydrogen absorber tests at the newly constructed FNAL Mucool Test Area (MTA). The program includes designs for the high-powered test of an absorber prototype (external heat exchange) at the MTA which are nearing completion to be installed by summer 2005, an alternative absorber design (internal heat exchange) being finalized for the approved cooling experiment (MICE) at Rutherford-Appleton Laboratory, and a novel idea for gaseous hydrogen absorbers being developed at Fermilab for a high powered test at the MTA in 2006.

*Illinois Consortium for Accelerator Research.

FOAA002 Technological Improvements in the DARHT II Accelerator Cells 169
  • B.A. Prichard, R.J. Briggs
    SAIC, Los Alamos, New Mexico
  • J. Barraza, M. Kang, K. Nielsen
    LANL, Los Alamos, New Mexico
  • F.M. Bieniosek, K. Chow, W.M. Fawley, E. Henestroza, L. R. Reginato, W. Waldron
    LBNL, Berkeley, California
  • T.E. Genoni, T.P. Hughes
    ATK-MR, Albuquerque, New Mexico
  Funding: This work was supported by the U.S. National Nuclear Security Agency and the U.S. Department of Energy under contract W-7405-ENG-36.

DARHT employs two perpendicular electron Linear Induction Accelerators to produce intense, bremsstrahlung x-ray pulses for flash radiography. The second axis, DARHT II, features an 18 MeV, 2-kA, 2-microsecond accelerator. DARHT II accelerator cells have undergone a series of test and modeling efforts to fully understand their sub par performance. These R&D efforts have led to a better understanding of Linear Induction Accelerator physics for the unique DARHT II design. Specific improvements have been identified and tested. Improvements in the cell oil region, the cell vacuum region, and the PFNs have been implemented in the prototype units that have doubled the cell’s performance. A series of prototype acceptance test are underway on a number of prototype units to demonstrate that the required cell lifetime is met at the improved performance levels. Early acceptance tests indicate that the lifetime requirements are being exceeded. The shortcomings of the previous design are summarized. The improvements to the original design, their resultant improvement in performance, and various test results are included. The final acceptance test results will also be included.

FOAA003 HOM Effects in Vacuum System with Short Bunches 289
  • A. Novokhatski
    SLAC, Menlo Park, California
  Funding: Work supported by Department of Energy contract DE–AC02–76SF00515.

High luminosity in electron-positron factories requires high beam currents of very short bunches. SLAC PEP-II and KEKB B-factories are progressively increasing currents and gaining more and more luminosity. Because of this the interaction of high currents and vacuum chamber elements becomes more important for the operation of the rings. High Order Modes (HOM) excited by short intense bunches propagate along the vacuum chamber, penetrating and dissipating inside vital vacuum elements like shielded bellows, vacuum valves and vacuum pumps. As a result these elements can heat up or have temperature oscillations. Often HOM heating has a resonance character. HOM heating of vacuum pumps can lead to vacuum pressure increases. High frequency modes excited by short bunches “check” the quality of the vacuum chamber by detecting small gaps, weak RF screens or weak feed-through. At these high currents even smooth tapers and smooth collimators become a source of HOM production. We will discuss the physical nature of these very interesting HOM effects.

FOAA005 Mechanical Vibration Measurements on TTF Cryomodules 434
  • A. Bosotti, C. Pagani, R. Paparella, P. Pierini, D. Sertore
    INFN/LASA, Segrate (MI)
  • R. De Monte, M. Ferianis
    ELETTRA, Basovizza, Trieste
  • R. Lange
    DESY, Hamburg
  Few of the TTF cryomodules have been equipped with Wire Position Monitors (WPM) for the on line monitoring of cold mass movements during cool-down, warm-up and operation. Each sensor can be used as a detector for mechanical vibrations of the cryostat. A Digital Receiver board is used to sample and analyze with high frequency resolution, the WPM picked up signals, looking to its amplitude modulation in the microphonic frequency range. Here we review and analyze the data and the vibration spectra taken during operation of the TTF cryomodules # 4 and #5.  
FOAA006 Digital Low-Level RF Controls for Future Superconducting Linear Colliders 515
  • S. Simrock
    DESY, Hamburg
  The requirements for RF Control Systems of Superconducting Linear Colliders are not only defined in terms of the quality of field control but also with respect to operability, availability, and maintainability of the RF System, and the interfaces to other subsystems. The field control of the vector-sum of many cavities driven by one klystron in pulsed mode at high gradients is a challenging task since severe Lorentz force detuning, microphonics and beam induced field errors must be suppressed by several orders of magnitude. This is accomplished by a combination of local and global feedback and feedforward control. Sensors monitor individual cavity probe signals, and forward and reflected wave as well as the beam properties including beam energy and phase while actuators control the incident wave of the klystron and individual cavity resonance frequencies. The operability of a large llrf system requires a high degree of automation while the high availability requires robust algorithms, redundancy, and extremely reliable hardware. The maintenance of the llrf demands sophisticated on-line diagnostics for the llrf subsystems to minimize downtime.  
FOAA007 Cryomodule Design Concepts and Operating Experience
  • C.H. Rode, J.P. Preble
    Jefferson Lab, Newport News, Virginia
  Funding: This work was supported by the U.S. Department of Energy under contract #DE-ACO-584ER40150.

Design concepts and operating experience of SRF cryostats will be discussed.

FOAA008 Superconducting RF Development at Nuclear Science Centre 625
  • A. Roy
    NSC, New Delhi
  Funding: Nuclear Science Centre, New Delhi, India.

A Superconducting Linac is being installed as a booster for the 15 UD Pelletron accelerator at Nuclear Science Centre (NSC). The accelerating structure for this linac is a Nb QWR cavity, designed and fabricated as a joint collaboration between NSC and ANL, USA. Initial cavities required for the first linac module were fabricated at ANL. For fabrication of cavities required for future modules a Superconducting Resonator Fabrication Facility has been set up at NSC. Three quarter wave resonator (QWR) cavities have been fabricated using the in-house facility. This facility has been used for repairs on the resonators which sprung leaks. Fabrication of fifteen resonators for the second and third linac modules is under progress. Eight resonators along with a superconducting solenoid has been installed in the first linac cryostat and tested for energy gain with a pulsed beam of 90 MeV Si from the Pelletron. Acceleration of the ions to 96 MeV was measured downstream and beam transmission through the linac was measured to be ~ 100%.

FOAA009 SRF Performance of CEBAF After Thermal Cycle to Ambient Temperature 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.

FOAA010 Full Characterization at Low Temperature of Piezoelectric Actuators Used for SRF Cavities Active Tuning 728
  • M. Fouaidy, S. Blivet, F. Chatelet, N. Hammoudi, G.M. Martinet, A. Olivier, H. Saugnac
    IPN, Orsay
  Funding: EU, CNRS-IN2P3.

In the frame of the CARE project activities, supported by EU, IPN Orsay participate to the development of a fast cold tuning system for SRF cavities operating at a temperature T=2 K. The study is aimed at full characterization of piezoelectric actuators at low temperature. A new experimental facility was developed for testing various prototypes piezoelectric actuators and successfully operated for T in the range 1.8 K-300 K. Different parameters were investigated as function of T: piezoelectric actuator displacement vs. applied voltage V, capacitance vs. T, dielectric and thermal properties vs. T and finally heating DT due to dielectric losses vs. modulating voltage Vmod and frequency. We observed a decrease of the Full Range Displacement (FRD or DX) of the actuator from ~40μm @ 300K down to 1.8μm-3μm @ 1.8K, depending on both material and fabrication process of the piezostacks. Besides, both material and fabrication process have a strong influence on the shape of the characteristics DX vs. T dependence. Moreover, the variations of losses tangent with T show a maximum at T in the range 30 K-120 K. Finally a dedicated facility located at CERI (Orléans, France) for radiation hardness tests of actuators with fast neutrons at T=4.2 K was developed and the first beam tests results are summarized.