| Paper |
Title |
Page |
| TUPCH082 |
The EuroTeV Confocal Resonator Monitor Task
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1202 |
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- V.G. Ziemann, T. J. C. Ekelof, A. Ferrari, M. A. Johnson, E. A. Ojefors, A. B. Rydberg
UU/ISV, Uppsala
- F. Caspers
CERN, Geneva
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We describe the progress in the analysis of the confocal resonator monitor task which is part of the diagnostics workpackage of EuroTeV. The initial design was analyzed both numerically and experimentally and found limitations. We therefore digressed from strict confocality and report the numerical analysis and S-parameter measurements of a modified design. Furthermore, we discuss the mechanical design needed for planned tests with beam in CTF3 which requires integration of the monitor into the beam pipe, damping of trapped modes, and frequency tunability.
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| TUPLS011 |
The Beam Screen for the LHC Injection Kicker Magnets
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1508 |
| |
- M.J. Barnes, F. Caspers, L. Ducimetière, N. Garrel, T. Kroyer
CERN, Geneva
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The two LHC injection kicker magnet systems must each produce a kick of 1.2 T.m with a flattop duration variable up to 7.86 μs, and rise and fall times of less than 0.9 μs and 3 μs, respectively. Each system is composed of four 5 Ω transmission line kicker magnets with matched terminating resistors and pulse forming networks (PFN). The LHC beam has a high intensity, hence a beam screen is required in the aperture of the magnets This screen consists of a ceramic tube with conducting "stripes" on the inner wall. The stripes provide a path for the image current of the beam and screen the magnet ferrites against Wake fields. The stripes initially used gave adequately low beam impedance however stripe discharges occured during pulsing of the magnet: hence further development of the beam screen was undertaken. This paper presents options considered to meet the often conflicting needs for low beam impedance, shielding of the ferrite, fast field rise time and good electrical and vacuum behaviour.
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| WEPLS099 |
Fault Detection and Identification Methods Used for the LHC Cryomagnets and Related Cabling
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2607 |
| |
- D. Bozzini, F. Caspers, V. Chareyre, Y. Duse, T. Kroyer, R. Lopez, A. Poncet, S. Russenschuck
CERN, Geneva
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Several non-standard methods for electrical fault location have been successfully developed and tested. As part of the electrical quality assurance program, certain wires have to be subjected to a (high) DC voltage for the testing of the insulation. With the time difference of spark-induced electromagnetic signals measured with an oscilloscope, fault localization within a ± 10 cm range has been achieved. Another method used and adapted for the particular needs, was the synthetic pulse time-domain reflectometry (TDR) by means of a vector network analyzer. This instrument has also been applied as a low frequency sweep impedance analyzer in order to measure fractional capacities of cable assemblies where TDR was not applicable.
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| WEPLS141 |
Operational Experience with the LHC Waveguide Mode Reflectometer
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2709 |
| |
- T. Kroyer, P. Borowiec, F. Caspers, Z. Sulek, L.R. Williams
CERN, Geneva
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The LHC microwave mode reflectometer (assembly version) reached operational status by the end of 2005. It is now routinely used in the LHC tunnel to take data on the beam-screen of the individual LHC magnets and also groups of magnets with lengths up to 200 meter. The reflectometer operates in the frequency range from about 4GHz to 8 GHz and employs mode selective launchers. Data traces of typically 16000 data points are taken in the frequency domain with subsequent Fourier transformation into the time domain and numerical waveguide mode dispersion compensation. This paper discusses the operational aspects of the system as well as methods for clutter (fake reflection) elimination and procedures for cross-checks in case of a suspected obstacle or other fault.
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| THPCH059 |
Kicker Impedance Measurements for the Future Multi-turn Extraction of the CERN Proton Synchrotron
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2919 |
| |
- E. Métral, F. Caspers, M. Giovannozzi, A. Grudiev, T. Kroyer, L. Sermeus
CERN, Geneva
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In the context of the novel multi-turn extraction, where charged particles are trapped into stable islands in transverse phase space, the ejection of five beamlets will be performed by means of a set of three new kickers. Before installing them into the machine, a measurement campaign has been launched to evaluate the impedance of such devices. Two measurement techniques were used to try to disentangle the driving and detuning impedances. The first consists in measuring the longitudinal impedance for different transverse offsets using a single displaced wire. The sum of the transverse driving and detuning impedances is then deduced applying Panofsky-Wenzel theorem. The second uses two wires excited in opposite phase and yields the driving transverse impedance only. Finally, the consequences on the beam dynamics are also analyzed.
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| THPCH061 |
Tune Shift Induced by Nonlinear Resistive Wall Wake Field of Flat Collimator
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2925 |
| |
- F. Zimmermann, G. Arduini, R.W. Assmann, H. Burkhardt, F. Caspers, M. Gasior, O.R. Jones, T. Kroyer, E. Métral, S. Redaelli, G. Robert-Demolaize, F. Roncarolo, G. Rumolo, R.J. Steinhagen, J. Wenninger
CERN, Geneva
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We present formulae for the coherent and incoherent tune shifts due to the nonlinear resistive wall wake field for a single beam traveling between two parallel plates. In particular, we demonstrate that the nonlinear terms of the resistive wall wake field become important if the gap between the plates is comparable to the transverse rms beam size. We also compare the theoretically predicted tune shift as a function of gap size with measurements for an LHC prototype graphite collimator in the CERN SPS and with simulations.
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| THPCH143 |
The Fast Extraction Kicker System in SPS LSS6
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3125 |
| |
- E.H.R. Gaxiola, F. Caspers, L. Ducimetière, P. Faure, T. Kroyer, B. Versolatto, E. Vossenberg
CERN, Geneva
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A new fast extraction has been set up in SPS LSS6 to transfer 450 GeV/c protons as well as ions to Ring 1 of the LHC, via the transfer line TI 2. The system includes four travelling wave kicker magnets, recuperated from earlier installations and upgraded to fit the new application. All four magnets are powered in series, energised by a single PFN generator and terminated by a short circuit. The layout and the modifications to the magnets and the high voltage circuit are described along with the impact of design choices on the performance of the system. Results from laboratory tests and first machine experience are reported on approaches to overcome the effects of the beam induced kicker heating observed earlier, including a beam screen in form of metallic stripes printed directly onto the ferrites and the use of ferrite blocks with high Curie temperature. Prospects for further improvements are briefly discussed.
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