IMPLEMENTATION OF LUMINOSITY LEVELING BY BETATRON FUNCTION ADJUSTMENT AT THE LHC INTERACTION POINTS

Abstract Growing expectations for integrated luminosity during upcoming LHC runs introduce new challenges for LHC beam operation in the scope of online luminosity control. Because some LHC experiments are limited in the maximum event rates, their luminosity is leveled to a constant value. Various techniques may be used for luminosity leveling, changing the betatron function at the interaction point is one of them. This paper explains the main operational requirements of a betatron function leveling scheme for the upcoming LHC run. Issues concerning the beam optics, orbits and collimator settings are discussed. The proposed architecture for control system integration will be discussed. A few operational scenarios with different beam configurations foreseen for the next LHC run will be presented. LUMINOSITY An important parameter that affects the quality of the recorded luminosity at the LHC is the event pile-up, the number of simultaneous particle interactions during one bunch crossing. A high event pile-up complicates the physics analysis and degrades the data quality for certain types of physics channels. The event pile-up µ is directly proportional to the luminosity per bunch crossing L bb , µ = L bb × σ P , where σ P is the total cross section for pp interactions at the LHC, σ P = 70 − 85 mbarn. The total luminosity L p is given by L p = k L bb where k is the number of bunch crossings per turn. The bunch pair luminosity for round beams at an interaction point can be written as where N stands for number of particles in the bunch, ε N for the normalized emittance and β * for the betatron function at the interaction point. f is the revolution frequency and γ the relativistic factor. F is a correction factor for the crossing angle. For round beams ε N and β * are identical for both transverse planes. d is the transverse offset (separation) between the colliding beams. The transverse separation d and the betatron function β* can be seen as a way for control luminosity. LHC RUN 2 BEAM PROJECTIONS After the long shutdown the LHC will restart beam operation in 2015 at an energy of 6.5 TeV. The LHC has two high luminosity experiments ATLAS and CMS that are installed at interaction points 1 and 5 (IR1 and IR5). Those experiments can cope with a maximum average pile-up of 50 and a time-averaged pile-up of 30 to 40. The LHCb experiment in IR8 on the other hand will operate at a maximum pile-up of µ = 1.6. Luminosity leveling is required for the LHCb experiment for all scenarios, while for the high luminosity experiments only the 50 ns scenario definitely requires leveling. With 25 ns some leveling is required in IR1 and IR5 only for the brightest beams. For the LHC luminosity upgrade HL-LHC (from 2023) [1] luminosity leveling by β* is part of the operational baseline

Second Opium Conference : convention protocol.

Conference proceedings of the League of Nations\u27 Second Opium Conferencehttps://digitalrepository.trincoll.edu/eastbooks/1033/thumbnail.jp

MODULES DEVELOPMENT FOR THE TTC SYSTEM

Abstract Some of the hardware components designed for the CERN -RD12 optical Timing, Trigger and Control system project [1] are presented, as well as some future developments

Luminosity Limitations at the Multi TeV Linear Collider Energy Frontier

Abstract To achieve the desired high luminosity in e + e − linear colliders with centre-of-mass energies above the TeV scale, careful optimisation of the beam parameters is necessary. Constraints arising from the RF structure design, the beambeam interaction, the damping ring and the beam delivery system have to be taken into account and compromises between different requirements have to be found. The nature of these different constraints is discussed and the resulting limits for the luminosity are detailed