| Paper |
Title |
Page |
| MPPE011 |
Expected Emittance Growth and Beam Tail Repopulation from Errors at Injection into the LHC
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1266 |
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- B. Goddard, H. Burkhardt, V. Kain, T. Risselada
CERN, Geneva
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The preservation of the transverse emittance of the proton beam at injection into the LHC is crucial for luminosity performance. The population of the beam tails is also important for beam losses and collimation. The transfer and injection process is particularly critical in this respect, and several effects can contribute to the expected emittance increase and tail repopulation, like optical and geometrical mismatch, injection offsets and coupling, etc. The various effects are described, together with the tolerance limits on the parameters, and the expected contributions evaluated analytically where possible. The emittance growth and tail distributions are also simulated numerically using realistic errors. The implications for the tolerances on the matching of the transfer lines are discussed.
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| MPPE047 |
Optics Flexibility and Matching at LHC Injection
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2983 |
| |
- H. Burkhardt, O.S. Brüning, B. Goddard, V. Kain, V. Mertens, T. Risselada, A. Verdier
CERN, Geneva
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An excellent match between the SPS, the several kilometers long transfer lines and the LHC will be required to minimise emittance blow-up at injection. Several optics changes in the SPS and the LHC injection insertions had to be accommodated in the design phase. The new 3-phase collimation system in the transfer lines results in additional phase advance constraints. It will be important to maintain some tuning range for the LHC commissioning phase and to accommodate possible further optics changes. We analyse the requirements, the constraints, the current status and options to enhance the optics flexibility.
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| MPPE048 |
Beam Based Alignment of the LHC Transfer Line Collimators
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3034 |
| |
- V. Kain, H. Burkhardt, B. Goddard, S. Redaelli
CERN, Geneva
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At LHC injection energy the aperture available in the transfer lines and in the LHC is small and the intensities of the injected beams are an order of magnitude above the damage level. The setting of protection elements such as the transfer line collimators is therefore very critical; mechanical and optical tolerances must be taken into account to define the nominal setting. Being able to measure and control the collinearity of the collimator jaws with the beam relaxes the requirement on the settings considerably. A method to measure angular misalignment of the collimator jaws in the transfer line based on a transmission measurement is discussed. Simulations have been made and are compared with the results of an alignment test performed with beam during the 2004 commissioning of the transfer line TI 8.
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| TPAP009 |
Collimation in the Transfer Lines to the LHC
|
1135 |
| |
- H. Burkhardt, B. Goddard, Y. Kadi, V. Kain, T. Risselada, W.J.M. Weterings
CERN, Geneva
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Injection intensities for the LHC are over an order of magnitude above damage level. The TI 2 and TI 8 transfer lines between the SPS and LHC are each about 2.5 km long and comprise many active elements running in pulsed mode. The collimation system in the transfer lines is designed to dilute the beam energy sufficiently in case of accidental beam loss or mis-steered beam. A system using three collimator families spaced by 60 degrees in phase advance, both in the horizontal and the vertical plane has been chosen. We discuss the reasons for this choice, the layout and, the expected performance of the system in terms of maximum amplitudes and energy deposition.
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| TPAP015 |
Commissioning of the LHC Beam Transfer Line TI 8
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1461 |
| |
- J.A. Uythoven, G. Arduini, B. Goddard, D. Jacquet, V. Kain, M. Lamont, V. Mertens, A. Spinks, J. Wenninger
CERN, Geneva
- Y.-C. Chao
Jefferson Lab, Newport News, Virginia
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The first of the two LHC transfer lines was commissioned in autumn 2004. Beam reached an absorber block located some 2.5 km downstream of the SPS extraction point at the first shot, without the need of any threading. The hardware preparation and commissioning phase will be summarised, followed by a description of the beam tests and their results regarding optics and other line parameters, including the experience gained with beam instrumentation, the control system and the machine protection equipment.
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| TPAP017 |
Beam Stability of the LHC Beam Transfer Line TI8
|
1523 |
| |
- J. Wenninger, B. Goddard, V. Kain, J.A. Uythoven
CERN, Geneva
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Injection of beam into the LHC at 450 GeV/c proceeds over two 2.7 km long transfer lines from the SPS. The small aperture of the LHC at injection imposes tight constraints on the stability of the beam transfer. The first transfer line TI8 was commissioned in the fall of 2004 with low intensity beam. Since the beam position monitor signal fluctuations were dominated by noise with low intensity beam, the beam stability could not be obtained from a simple comparison of consecutive trajectories. Instead model independent analysis (MIA) techniques as well as scraping on collimators were used to estimate the intrinsic stability of the transfer line. This paper presents the analysis methods and the resulting stability estimates.
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| TPAP018 |
Optics Studies of the LHC Beam Transfer Line TI8
|
1578 |
| |
- J. Wenninger, G. Arduini, B. Goddard, D. Jacquet, V. Kain, M. Lamont, V. Mertens, J.A. Uythoven
CERN, Geneva
- Y.-C. Chao
Jefferson Lab, Newport News, Virginia
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The optics of the newly commissioned LHC beam transfer line TI 8 was studied with beam trajectories, dispersion and profile measurements. Steering magnet response measurements were used to analyze the quality of the steering magnets and of the beam position monitors. A simultaneous fit of the quadrupole strengths was used to search for setting or calibration errors. Residual coupling between the planes was evaluated using high statistics samples of trajectories. Initial conditions for the optics at the entrance of the transfer line were reconstructed from beam profile measurements with Optical Transition Radiation monitors. The paper presents the various analysis methods and their errors. The expected emittance growth arising from optical mismatch into the LHC is evaluated.
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| TPAP019 |
Aperture Studies of the SPS to LHC Transfer Lines
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1664 |
| |
- B. Goddard, V. Kain, J. Wenninger
CERN, Geneva
- R. Schmid
Bowdoin College, Brunswick, Maine
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The SPS to LHC transfer lines TI 2 and TI 8 are each several km in length and use magnets with small apertures. An aperture model for the lines has been developed in MAD-X format, with a full description of all installed vacuum elements and the possibility to interpolate at any length interval. This model has been used with tolerances and errors to simulate the expected line aperture available for the beam. The model features and simulation results are presented, with derived aperture limits. The results from aperture measurements made during the TI 8 line beam commissioning in 2004 are presented and compared to the expectations.
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| RPPE016 |
Protection Level During Extraction, Transfer and Injection into the LHC
|
1505 |
| |
- V. Kain, B. Goddard, R. Schmidt, J. Wenninger
CERN, Geneva
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Failures during the LHC transfer and injection process cannot be excluded and beam loss with the foreseen intensities and energies, which are an order of magnitude above the damage limit, could cause serious equipment damage. Consequences of equipment failures such as kicker erratics, power converter faults, etc. are investigated by means of a Monte Carlo based on MAD-X tracking with a full aperture model of the transfer line and the injection region. Geometrical and optical mismatch, orbit tolerances, mechanical tolerances for settings of protection elements, power converter ripples, misalignment of elements, etc. are all taken into account. The required performance of the protection system is discussed. The overall protection level for the LHC and the transfer lines during injection is presented.
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| RPPE018 |
Material Damage Test with 450 GeV LHC-Type Beam
|
1607 |
| |
- V. Kain, J. Ramillon, R. Schmidt, K.V. Vorderwinkler, J. Wenninger
CERN, Geneva
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The design of LHC protection elements is based on assumptions on damage levels, which are derived from simulations. A dedicated experiment was prepared and carried out to cross-check the validity of this approach by trying to damage material in a controlled way with beam. The impact of a 450 GeV beam extracted from the SPS on a specially designed high-Z target with a simple geometry, comprising several typical materials used for LHC equipment, was simulated. The beam intensities for the test were chosen to exceed the damage limits of parts of the target. Results of the simulations are presented and compared with test results.
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