| Paper | Title | Other Keywords | Page |
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| MOPWO026 | Investigation of Numerical Precision Issues of Long Term Single Particle Tracking | simulation, dynamic-aperture, resonance, HOM | 942 |
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Funding: The HiLumi LHC Design Study is included in the HL-LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404. Long term single particle simplectic tracking is one of the most reliable tool to study the dynamic aperture of the circular accelerators. The present computational performance allows to explore the long term behaviour for an extended number of turns. It is well known that for instance single precision floating point arithmetic introduces too much numerical noise even after a moderate number of turns. In this paper we explore the artefacts of the double precision arithmetic that may be visible when the number of turns is in the order of 106, 107. |
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| TUPFI032 | Observation of Instabilities in the LHC due to Missing Head-on Beam-beam Interactions | damping, octupole, luminosity, betatron | 1412 |
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| We report the observation of coherent instabilities on individual bunches out of the LHC bunch train. These instabilities occured spontaneously after several hours of stable beam while in other cases they were related to the application of a small transverse beam separation during a luminosity optimization. Only few bunches were affected, depending on there collision scheme and following various tests we interprete these instabilities as a sudden loss of Landau damping when the tune spread from the beam-beam interaction became insufficient. | |||
| TUPME011 | Simulated Beam-beam Limit for Circular Higgs Factories | luminosity, synchrotron, simulation, radiation | 1586 |
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| We report simulation studies of the beam-beam limit for two proposed circular e+e− Higgs factories with circumference of 27 and 80 km, respectively, called LEP3 and TLEP. In particular we investigate the dependence of the steady-state luminosity and transverse beam sizes on the synchrotron tune (or momentum compaction factor) and on the betatron tunes, as well as the consequences of the strong radiation damping and the implications of the large hourglass effect. | |||
| TUPME028 | RF Orbit Separation for CPT-Test Experiment at VEPP-4M | electron, positron, betatron, closed-orbit | 1634 |
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Funding: This work was supported by the Ministry of Education and Science of the Russian federation and the Russian Foundation for Basis Research (grant 11-02-01422-a) In a special program of experiments which is under development in a background regime at the VEPP-4M storage ring we set an aim to realize a potential possibility to make the CPT invariance test with the accuracy better than 10-8. The test will be based on a precise comparison of the spin precession frequencies of simultaneously stored electrons and positrons. To exclude the presence of static electric fields increasing a systematic error we have developed and tested a special RF system driven at the half revolution frequency to subsitute for the electrostatic orbit separation system. The latter is needed for the electron and positron orbit separation at the parasitic interaction point where the beam-beam effects drastically cut the beam currents. |
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| WEPEA071 | Performance Limitations in the Lhc Due to Parasitic Beam-Beam Encounters - Parameter Dependence, Scaling, and Pacman Effects | dynamic-aperture, emittance, luminosity, target | 2672 |
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| We studied possible limitations due to the long-range beam-beam effects in the LHC. With a large number of bunches and collisions in all interaction points, we have reduced the crossing angles (separation) to enhance long-range beam-beam effects to evaluate their influence on dynamic aperture and losses. Different β*, number of bunches and intensities have been used in several dedicated experiments and allow the test of the expected scaling laws. | |||