Paper |
Title |
Page |
TUPZ013 |
Calculation Method for Safe Beta* in the LHC |
1828 |
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- R. Bruce, R.W. Assmann, W. Herr, D. Wollmann
CERN, Geneva, Switzerland
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One way of increasing the peak luminosity in the LHC is to decrease the beam size at the interaction points by squeezing to smaller values of beta*. The LHC is now in a regime where safety and stability determines the limit in beta*, as opposed to traditional optics limits. In this paper, we derive a calculation model to determine the safe beta*-values based on collimator settings and operational stability of the LHC. This model was used to calculate the settings for the LHC run in 2011. It was found that beta* could be decreased from 3.5 m to 1.5 m, which has now successfully been put into operation.
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TUPZ023 |
Observation of Bunch to Bunch Differences due to Beam-beam Effects |
1855 |
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- G. Papotti, R. Alemany-Fernandez, R. Giachino, W. Herr, T. Pieloni, M. Schaumann, G. Trad
CERN, Geneva, Switzerland
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Due to the bunch filling schemes in the LHC the bunches experience a very different collision schedule and therefore different beam-beam effects. These differences and the effect on the performance have been observed and compared with the expectations. Possible limitations due to these effects are discussed.
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TUPZ025 |
Experience with Offset Collisions in the LHC |
1858 |
|
- G. Papotti, R. Alemany-Fernandez, F. Follin, R. Giachino, W. Herr, T. Pieloni, M. Schaumann
CERN, Geneva, Switzerland
- R. Calaga, R. Miyamoto
BNL, Upton, Long Island, New York, USA
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To keep the luminosity under control, some experiments require the adjustment of the luminosity during a fill, so-called luminosity leveling. One option is the separate the beams transversely and adjust the separation to the desired collision rate. The results from controlled experiments are reported and interpreted. The feasibility of this method for ultimate luminosities is discussed.
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TUPZ029 |
Observation of Coherent Beam-beam Effects in the LHC |
1870 |
|
- X. Buffat
EPFL, Lausanne, Switzerland
- R. Calaga, S.M. White
BNL, Upton, Long Island, New York, USA
- R. Giachino, W. Herr, G. Papotti, T. Pieloni
CERN, Geneva, Switzerland
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Early collisions in the LHC with a very limited number of bunches with high intensities indicated the presence of coherent beam-beam driven oscillations. Here we discuss the experimental results and compare with the expectations.
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WEODA01 |
Observations of Beam-beam Effects at High Intensities in the LHC |
1936 |
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- W. Herr, R. Alemany-Fernandez, R. Giachino, G. Papotti, T. Pieloni
CERN, Geneva, Switzerland
- R. Calaga
BNL, Upton, Long Island, New York, USA
- E. Laface
ESS, Lund, Sweden
- M. Schaumann
RWTH, Aachen, Germany
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First observations with colliding beams in the LHC with bunch intensities close to nominal and above are reported. In 2010 the LHC initially operated with few bunches spaced around the circumference. Beam-beam tune shifts exceeding significantly the design value have been observed. In a later stage crossing angles were introduced around the experiments to allow the collisions of bunch trains. We report the first experience with head-on as well as long range interactions of high intensity bunches and discuss the possible performance reach.
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Slides WEODA01 [0.409 MB]
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