| Paper |
Title |
Page |
| MOPAN069 |
Ultrasound Diagnostics of the Superconducting Cable Connections Between the Main Ring Magnets of LHC
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311 |
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- F. Caspers, T. Kroyer, J.-P. G. Tock, L. R. Williams
CERN, Geneva
- J. Kulka
AGH, Cracow
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As part of the LHC assembly program, the super-conducting magnets are interconnected after installation. Electrical continuity between the magnets is ensured via a specifically designed cable splice box which allows the cables to be electrically joined by an automated low temperature brazing technique. The electrical resistance and mechanical strength of the cable junctions depend on the quality of the brazed joint. An ultrasound diagnostic of the brazed joint has been developed to accompany the visual inspection and reinforce the quality control process. Non-standard ultrasound diagnostic techniques, without using matching liquids or gel in the harsh and congested working environment, applied to the sandwich structure of the cable splice box, which presents high ultra-sonic losses due to multiple scattering, have been developed. The equipment and methods implemented are described in detail, together with results of quality control tests made in the production environment.
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| TUPAN086 |
An Improved Beam Screen for the LHC Injection Kickers
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1574 |
| |
- M. J. Barnes, F. Caspers, L. Ducimetiere, N. Garrel, T. Kroyer
CERN, Geneva
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The two LHC injection kicker magnet systems must produce a kick of 1.3 T.m with a flattop duration variable up to 7860 ns, and rise and fall times of less than 900 ns and 3000 ns, respectively. Each system is composed of two resonant charging power supplies and four 5 Ω transmission line kicker magnets with matched terminating resistors and pulse forming networks. A beam screen is placed in the aperture of the magnets: the screen consists of a ceramic tube with conductors on the inner wall. The conductors provide a path for the image current of the, high intensity, LHC beam and screen the ferrite against Wake fields. The conductors initially used gave adequately low beam impedance however inter-conductor discharges occurred during pulsing of the magnet: an alternative design was discharge free at the nominal operating voltage but the beam impedance was too high for the ultimate LHC beam. This paper presents the results of a new development undertaken to meet the often conflicting requirements for low beam impedance, shielding of the ferrite, fast field rise time and good electrical behaviour. High voltage test results and thermal measurements are also presented.
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| TUPAN089 |
The LHC Beampipe Waveguide Mode Reflectometer
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1583 |
| |
- F. Caspers, P. Borowiec, T. Kroyer, Z. Sulek, L. R. Williams
CERN, Geneva
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Several specially developed waveguide-mode reflectometers for obstacle detection in the LHC magnet beampipes have been intensively used for more than 18 months. This "Assembly" version is based on the synthetic pulse method using a modern vector network analyzer. It has mode selective excitation couplers and uses a specially developed waveguide mode dispersion compensation algorithm with external software. In addition there is a similar "in situ" version of the reflectometer which uses permanently installed microwave couplers at the end of each of the nearly 3 km long LHC arcs. A considerable number of unexpected objects have been found in the beampipes and subsequently removed. Operational statistics and lessons learned are presented and the overall performance is discussed.
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| TUPAS033 |
Field Fluctuation and Beam Screen Vibration Measurements in the LHC Magnets
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1724 |
| |
- V. D. Shiltsev
Fermilab, Batavia, Illinois
- T. Kroyer, R. de Maria
CERN, Geneva
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We present experimental methods and results of magnetic field fluctuation and beam screen vibration measurements in the LHC magnets. These noises can lead to an emittance grwoth in proton beams if they have spectral components at the betatron lines. A preliminary estimates of the effects are given.
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| WEOAC02 |
A New Type of Distributed Enamel Based Clearing Electrode
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2000 |
| |
- F. Caspers, T. Kroyer, E. Metral, F. Zimmermann
CERN, Geneva
- F.-J. Behler
Eisenwerke Fried. Wilh. Dueker GmbH & Co. KGaA, Laufach
- C. Dr. Wendel
Wendel GmbH, Dillenburg
- P. P. Hellmold
Clausthal, Inst für Nichtmetall. Werkstoffe, Clausthal-Zellerfeld
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A practical technology for implanting thin strip-like enamel structures in metallic beam-pipes, to be used for e-cloud clearing, has been developed. We discuss the technical and technological issues of this method. Parameters of particular interest are the beam coupling impedance as a function of the conductive coating resistivity and also the secondary electron yield. A test-stand for multipactoring measurements on a first prototype using the coaxial resonator method is described.
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Slides
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| WEOAC03 |
Transverse Impedance of LHC Collimators
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2003 |
| |
- E. Metral, G. Arduini, R. W. Assmann, A. Boccardi, T. Bohl, C. Bracco, F. Caspers, M. Gasior, O. R. Jones, K. K. Kasinski, T. Kroyer, S. Redaelli, G. Robert-Demolaize, G. Rumolo, R. J. Steinhagen, Th. Weiler, F. Zimmermann
CERN, Geneva
- F. Roncarolo
UMAN, Manchester
- B. Salvant
EPFL, Lausanne
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The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
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Slides
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| FRPMN068 |
The 4.8 GHz LHC Schottky Pick-up System
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4174 |
| |
- F. Caspers, J. M. Jimenez, O. R. Jones, T. Kroyer, VC. Vuitton
CERN, Geneva
- T. W. Hamerla, A. Jansson, J. R. Misek, R. J. Pasquinelli, P. C. Seifrid, D. Sun, D. G. Tinsley
Fermilab, Batavia, Illinois
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Funding: LARP
The LHC Schottky observation system is based on traveling wave type high sensitivity pickup structures operating at 4.8 GHz. The choice of the structure and operating frequency is driven by the demanding LHC impedance requirements, where very low impedance is required below 2 GHz, and good sensitivity at the selected band at 4.8 GHz. A sophisticated filtering and triple down-mixing signal processing chain has been designed and implemented in order to achieve the specified 100 dB instantaneous dynamic range without range switching. Detailed design aspects for the complete systems and test results without beam are presented and discussed.
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