| Paper |
Title |
Page |
| MOPC059 |
BBU Limitations for ERLs
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199 |
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- E. Wooldridge, C. D. Beard, P. A. McIntosh, B. D. Muratori, S. L. Smith
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
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The BBU threshold in ERLs is a limitation on the maximum beam current due to the interaction of the electron bunches and the Higher Order Modes (HOMs) contained within the RF cavities. Several factors are involved in determining the threshold current; from the cavity the Q, R/Q and degeneracy of the modes all play an important part. From the beam transport the values of the lattice functions α, β and μ have an effect. We will discuss the limits on these variables to provide a BBU current threshold greater than 100 mA for a multiple cavity machine and what will be required to provide higher currents. Also three different cavity profiles were investigated with the aim of reducing the BBU threshold. The TESLA 9-cell cavity was used as a baseline for comparison against possible 7-cell cavity designs, using the TESLA cell shape for their inner cells. The ends of the 7-cell cavities join to different sized beampipes, with radii of 39 mm and 54 mm, to allow the most of the HOMs to propagate to a broadband HOM absorber. Two different beampipe to cavity to transitions were investigated. The optimised 7-cell cavity will be shown to provide an increase in the BBU threshold.
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| MOPP009 |
Copper Prototype Measurements of the HOM, LOM and SOM Couplers for the ILC Crab Cavity
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568 |
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- G. Burt, P. K. Ambattu, A. C. Dexter
Cockcroft Institute, Lancaster University, Lancaster
- L. Bellantoni
Fermilab, Batavia, Illinois
- P. Goudket, P. A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- Z. Li, L. Xiao
SLAC, Menlo Park, California
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The ILC Crab Cavity is positioned close to the IP and hence is very sensitive to the wakefields induced by the beam. A set of couplers were designed to couple to and hence damp the spurious modes of the crab cavity. As the crab cavity is a deflecting mode cavity, it operates using a dipole mode and has different damping requirements than an accelerating mode cavity. A separate coupler is required for the monopole modes below the operating frequency of 3.9 GHz, known as the LOMs, the opposite polarization of the operating mode, the SOM, and the modes above the operating frequency, the HOMs. Each of these couplers have been manufactured out of copper and measured attached to an aluminium nine cell prototype of the cavity and their external Q factors were measured. The results were found to agree well with numerical simulations.
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| MOPP128 |
Comparison of Stretched-wire, Bead-pull and Numerical Impedance Calculations on 3.9 GHz Dipole Cavities
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859 |
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- P. Goudket, C. D. Beard, P. A. McIntosh
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- G. Burt, A. C. Dexter
Cockcroft Institute, Lancaster University, Lancaster
- R. M. Jones
Cockcroft Institute, Warrington, Cheshire
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In order to verify detailed impedance and wakefield simulations, the resonant modes in an aluminium model of the 9-cell ILC crab cavity were investigated using a stretched-wire frequency domain measurement, as well as frequency-domain bead-pull measurements. These measurements were compared to numerical simulations in order to verify that the complete cavity mode spectrum could be experimentally characterised for this high frequency structure. The analysis of the results and the accuracy and/or limitations of each method is presented.
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| MOPP141 |
Commissioning of the ERLP SRF Systems at Daresbury Laboratory
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889 |
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- P. A. McIntosh, R. Bate, R. K. Buckley, S. R. Buckley, P. A. Corlett, A. J. Moss, J. F. Orrett, S. M. Pattalwar, A. E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- F. G. Gabriel
FZD, Dresden
- A. R. Goulden
STFC/DL/SRD, Daresbury, Warrington, Cheshire
- P. vom Stein
ACCEL, Bergisch Gladbach
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The Energy Recovery Linac Prototype (ERLP) has been installed at Daresbury Laboratory and its baseline commissioning completed. The SRF systems for ERLP comprise two 9-cell, 1.3 GHz accelerating cavities in the injector (or Booster) cryomodule, which provide a nominal energy gain of 8 MeV for the injected 350 keV beam from the photo-injector. The beam is then accelerated in an identical two cavity cryomodule in the energy recovery main Linac, giving a final ERLP energy of 35 MeV. Each SRF accelerating cavity is powered by commercially available Inductive Output Tubes (IOTs) and the analog LLRF control system is identical to that employed on the ELBE facility at FZD Rossendorf. This paper details the commissioning experience gained for these systems and highlights the ultimate performance achieved.
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| TUOAM02 |
The Status of the Daresbury Energy Recovery Linac Prototype
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1001 |
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- D. J. Holder, P. A. McIntosh, S. L. Smith
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- N. Bliss
STFC/DL, Daresbury, Warrington, Cheshire
- A. R. Goulden
STFC/DL/SRD, Daresbury, Warrington, Cheshire
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This paper provides an update on the progress with the building and commissioning of the Energy Recovery Linac Prototype (ERLP). The past year has seen a number of notable achievements as well as a number of obstacles to overcome. The detailed results from the gun commissioning work are described elsewhere at this conference. ERLP is a 35 MeV technology demonstrator being built as part of the UK's R&D programme to develop its next-generation light source (NLS). It is based on a combination of a DC photocathode electron gun, a superconducting injector linac and a main linac operating in energy recovery mode. These drive an IR-FEL, an inverse Compton Back-Scattering (CBS) x-ray source and a terahertz beamline. The priorities for ERLP are to gain experience of operating a photoinjector gun and superconducting linacs; to produce and maintain high-brightness electron beams; to achieve energy recovery from an FEL-disrupted beam; the development of an electro-optic longitudinal profile monitor and to study challenging synchronisation issues. ERLP will also act as an injector for what will be the world's first non-scaling, Fixed-Field Alternating Gradient (FFAG) accelerator called EMMA.
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Slides
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| THPP002 |
EMMA RF Cavity Design and Prototype Testing at Daresbury
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3374 |
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- C. D. Beard, P. A. Corlett, D. M. Dykes, P. Goudket, C. Hill, P. A. McIntosh, A. J. Moss, J. F. Orrett, J. H.P. Rogers, A. E. Wheelhouse, E. Wooldridge
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- N. Bliss
STFC/DL, Daresbury, Warrington, Cheshire
- A. E. Bogle, T. L. Grimm, A. A. Kolka
Niowave, Inc., Lansing, Michigan
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At PAC’07 we discussed the design of a prototype cavity to be used on EMMA*. EMMA is a prototype non-scalling FFAG. It will contain 19 RF cavities operating at 1.3 GHz with a baseline accelerating voltage of 120 kV. A prototype cavity has been manufactured by Niowave, Inc. and we will present a discussion of its RF and mechanical design. This cavity was put through low power tests, to determine frequency, tuning range, shunt impedance and Q of the cavity; and high power tests, to confirm power handling ability, when it arrived at Daresbury Laboratory this spring. The results of these tests were compared to the simulations and a bead pull was carried out to obtain the field profile. The cavities for EMMA are likely to be powered by IOTs, these will be used for the high power tests, which will demonstrate cavity operation to the required maximum of 180 kV.
*E. Wooldridge et al. "RF Cavity Development for FFAG Application on ERLP at Daresbury," Proceedings of PAC’07, Albuquerque, NM (2007).
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| THPP003 |
RF System Design for the EMMA FFAG
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3377 |
| |
- C. D. Beard, S. A. Griffiths, C. Hill, P. A. McIntosh, A. E. Wheelhouse
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- N. Bliss, A. J. Moss, C. J. White
STFC/DL, Daresbury, Warrington, Cheshire
- D. Teytelman
Dimtel, San Jose
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In this report the RF system design for EMMA is described. The power source options, power supplies, waveguide distribution scheme and control system is discussed. The architecture necessary to meet the operation specifications requires a large degree of adjustment. To simplify commissioning and enhance the versatility of the machine a complex RF system is desired. This report details the RF "knobs" included to meet this.
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| THPP004 |
EMMA - the World's First Non-scaling FFAG
|
3380 |
| |
- T. R. Edgecock
STFC/RAL, Chilton, Didcot, Oxon
- C. D. Beard, J. A. Clarke, C. Hill, S. P. Jamison, A. Kalinin, K. B. Marinov, N. Marks, P. A. McIntosh, B. D. Muratori, H. L. Owen, Y. M. Saveliev, B. J.A. Shepherd, R. J. Smith, S. L. Smith, S. I. Tzenov, E. Wooldridge
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
- J. S. Berg, D. Trbojevic
BNL, Upton, Long Island, New York
- N. Bliss, C. J. White
STFC/DL, Daresbury, Warrington, Cheshire
- M. K. Craddock
UBC & TRIUMF, Vancouver, British Columbia
- J. L. Crisp, C. Johnstone
Fermilab, Batavia, Illinois
- Y. Giboudot
Brunel University, Middlesex
- E. Keil
CERN, Geneva
- D. J. Kelliher, S. Machida
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
- S. R. Koscielniak
TRIUMF, Vancouver
- F. Meot
CEA, Gif-sur-Yvette
- T. Yokoi
OXFORDphysics, Oxford, Oxon
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EMMA - the Electron Model of Many Applications - is to be built at the STFC Daresbury Laboratory in the UK and will be the first non-scaling FFAG ever constructed. EMMA will be used to demonstrate the principle of this type of accelerator and study their features in detail. The design of the machine and its hardware components are now far advanced and construction is due for completion in summer 2009.
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