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| FROAC01 |
The Spallation Neutron Source Accumulator Ring RF System
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3795 |
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- T. W. Hardek
- M. S. Champion, M. T. Crofford, H. Ma, M. F. Piller
ORNL, Oak Ridge, Tennessee
- K. Smith, A. Zaltsman
BNL, Upton, Long Island, New York
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Funding: SNS is managed by UT-Batelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy.
The Spallation Neutron Source (SNS) accumulator ring is a fixed-frequency proton storage ring located at the output of the SNS Linear Accelerator (Linac). Its purpose is to convert 1 millisecond H- beam pulses from the SNS Linac into high-intensity 695 nanosecond pulses of protons for delivery to the neutron target. The RF bunching system controls longitudinal beam distribution during the accumulation process and maintains a 250+ nanosecond gap required for beam extraction. The RF system consists of three stations which operate at a beam revolution frequency of 1.05 MHz while a fourth station provides a second harmonic component at 2.1 MHz. The beam pulse at extraction consists of 1.6·1014 protons representing a peak beam current of 52 amperes. The system utilizes four 600kW tetrodes to provide the RF current necessary to produce the 40kV peak-bunching voltage and to control phase and amplitude at this high beam current. In this paper we review the design concepts incorporated into this heavily beam-loaded RF system and discuss its commissioning status.
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Slides
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| FROAC02 |
RF Amplifier Choice for the ISAC Superconducting Linac
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3798 |
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- I. V. Bylinskii
- K. Fong, J. Lu, A. K. Mitra, C. Owen
TRIUMF, Vancouver
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A superconducting linac is being commissioned at TRIUMF as an extension to the existing room temperature accelerator of exotic ions at ISAC. It will increase the isotope final energy from 1.5 to 6.5 MeV/u. Acceleration is accomplished in 40 bulk niobium quarter wave superconducting cavities operating at 106 and 141 MHz. Each cavity is energized from an independent RF amplifier with power rating up to 1 kW cw. Both vacuum tube and solid state amplifiers were considered as a viable option for the drivers. The paper compares many important parameters of these 2 amplifiers such as reliability, serviceability, capital and maintenance costs, as well as operating characteristics: gain linearity, phase noise, phase drift and others. Test results of prototypes of both types of amplifiers and 1 year operational experience of 20 tube amplifiers are discussed. Based on that the amplifier design requirements are formulated.
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| FROAC03 |
The Commissioning of the LHC Technical Systems
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3801 |
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- R. I. Saban
- R. Alemany-Fernandez, V. Baggiolini, A. Ballarino, E. Barbero-Soto, B. Bellesia, F. Bordry, D. Bozzini, M. P. Casas Lino, V. Chareyre, S. D. Claudet, G.-J. Coelingh, K. Dahlerup-Petersen, R. Denz, M. Gruwe, V. Kain, G. Kirby, M. Koratzinos, R. J. Lauckner, S. L.N. Le Naour, K. H. Mess, F. Millet, V. Montabonnet, D. Nisbet, B. Perea-Solano, M. Pojer, R. Principe, S. Redaelli, A. Rijllart, F. Rodriguez-Mateos, R. Schmidt, L. Serio, A. P. Siemko, M. Solfaroli Camillocci, H. Thiesen, W. Venturini Delsolaro, A. Vergara-Fernandez, A. P. Verweij, M. Zerlauth
CERN, Geneva
- SF. Feher, R. H. Flora, R. Rabehl
Fermilab, Batavia, Illinois
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The LHC is an accelerator with unprecedented complexity; in addition, the energy stored in magnets and the beams exceeds other accelerators by one to two orders of magnitude. To avoid a plague of technical problems and ensure a safe machine start-up, the hardware commissioning phase was emphasized: the thorough commissioning of technical systems (vacuum, cryogenics, quench protection, power converters, electrical circuits, AC distribution, ventilation, demineralised water, injection system, beam dumping system, beam instrumentation, etc) is carried-out without beam. Activity started in June 2005 with the commissioning of individual systems, followed by operating a full sector of the machine as a whole. LHC architecture allows the commissioning of each of the eight sectors independently from the others, before the installation of other sectors is complete. Important effort went into the definition of the programme and the organization of the coordination in the field, as well as in the tools to record and analyze test results. This paper presents the experience with this approach, results from the commissioning of the first LHC sectors and gives an outlook for future activities.
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| FROAC04 |
Sub-10 Femtosecond Stabilization of a Fiber Link Using a Balanced Optical Cross Correlator
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3804 |
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- F. Loehl
- J. Chen, F. X. Kaertner, J. Kim, F. Wong
MIT, Cambridge, Massachusetts
- J. M. Mueller
TUHH, Hamburg
- H. Schlarb
DESY, Hamburg
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Synchronization of various components with fs stability is needed for the operation of free-electron-lasers such as FLASH or the European XFEL. One possibility to realize a high precision synchronization is to use a mode-locked Er-doped fiber laser as a master clock and to distribute ultra short laser pulses inside the machine using actively stabilized fiber links. In this paper we demonstrate the stabilization of a 300 m long fiber link with a self-aligned balanced cross-correlator using a single type II phase-matched PPKTP crystal. This approach allowed us to reduce the timing jitter added by the link to below 10 fs.
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| FROAC05 |
Systems Design Concepts for Optical Synchronization in Accelerators
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3807 |
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- R. B. Wilcox
- J. W. Staples
LBNL, Berkeley, California
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Funding: This work is supported by the Director, Office of Science, High Energy Physics, U. S. Dept. of Energy under Contract no. DE-AC02-05CH1121
Development of accelerator-based light sources is expanding the size of femtosecond laser systems from tabletop devices up to kilometer-scale facilities. New optical techniques are needed to maintain temporal stability in these large systems. We present methods for distributing timing information over optical fiber using continuous optical waves, and how these can be employed in advanced accelerators requiring less than 100fs timing stability. Different techniques combine to form a tool set that can provide for synchronization down to a few femtoseconds. Practical examples are given for timing systems applicable to FELs now under construction, with experimental results to show these systems can be built with required performance. For example, have demonstrated 2km fiber links with 5fs timing stability over 24 hours, and synchronized femtosecond lasers separated by a fiber link with 20fs RMS relative jitter.
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| FROAC06 |
Survey of LLRF Development for the ILC
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3810 |
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- J. Branlard
- B. Chase
Fermilab, Batavia, Illinois
- S. Michizono
KEK, Ibaraki
- S. Simrock
DESY, Hamburg
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Funding: FRA
The key to a successful LLRF design for the International Linear Collider (ILC) relies on a combined effort from the different laboratories involved in this global project. This paper covers the ILC LLRF design progress both long term and for current test facilities around the world. Much of the focus is towards the ILC Test Area and on inter-laboratories collaborations. The SIMCON controller board, originally developed at DESY has been successfully used at FNAL to control the superconducting capture cavity I and II. A joined effort is also underway to modify its hardware to improve its noise performance and upgrading the firmware to achieve a higher intermediate frequency operation. In parallel, several simulation models (U-Penn, FNAL) have been developed in addition to the Simulink based model from DESY. The motivation is to investigate such issues as variable gradients, low beam conditions and bunch compression. Finally, an active exchange of knowledge and expertise continues to occur during collaboration meetings and through mutual participation in accelerator tests and commissioning (Dec06/Jan07 at DESY).
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