25 research outputs found
Effect of pulsed hollow electron-lens operation on the proton beam core in LHC
Collimation with hollow electron beams is currently one of the most promising
concepts for active halo control in the HL-LHC. In order to further increase
the diffusion rates for a fast halo removal as e.g. desired before the squeeze,
the electron lens (e-lens) can be operated in pulsed mode. In case of profile
imperfections in the electron beam the pulsing of the e-lens induces noise on
the proton beam which can, depending on the frequency content and strength,
lead to emittance growth. In order to study the sensitivity to the pulsing
pattern and the amplitude, a beam study (machine development MD) at the LHC has
been proposed for August 2016 and we present in this note the preparatory
simulations and estimates
Resonant and random excitations on the proton beam in the Large Hadron Collider for active halo control with pulsed hollow electron lenses
We present the results of numerical simulations and experimental studies
about the effects of resonant and random excitations on proton losses,
emittances, and beam distributions in the Large Hadron Collider (LHC). In
addition to shedding light on complex nonlinear effects, these studies are
applied to the design of hollow electron lenses (HEL) for active beam halo
control. In the High-Luminosity Large Hadron Collider (HL-LHC), a considerable
amount of energy will be stored in the beam tails. To control and clean the
beam halo, the installation of two hollow electron lenses, one per beam, is
being considered. In standard electron-lens operation, a proton bunch sees the
same electron current at every revolution. Pulsed electron beam operation
(i.e., different currents for different turns) is also considered, because it
can widen the range of achievable halo removal rates. For an axially symmetric
electron beam, only protons in the halo are excited. If a residual field is
present at the location of the beam core, these particles are exposed to
time-dependent transverse kicks and to noise. We discuss the numerical
simulations and the experiments conducted in 2016 and 2017 at injection energy
in the LHC. The excitation patterns were generated by the transverse feedback
and damping system, which acted as a flexible source of dipole kicks. Proton
beam losses, emittances, and transverse distributions were recorded as a
function of excitation patterns and strengths. The resonant excitations induced
rich dynamical effects and nontrivial changes of the beam distributions, which,
to our knowledge, have not previously been observed and studied in this detail.
We conclude with a discussion of the tolerable and achievable residual fields
and proposals for further studies.Comment: 33 pages, 32 figures, 46 references. Revised manuscript submitted to
Phys. Rev. Accel. Beam
Design Study of the Large Hadron Electron Collider and a Rapid Cycling Synchrotron as Alternative to the PS Booster Upgrade at CERN
To further extend the discovery potential of the Large Hadron Collider (LHC), a major upgrade is foreseen around 2020 of the LHC itself and the LHC injectors. Furthermore it has been suggested to built a new electron accelerator in order to allow for deep inelastic lepton-nucleon scattering at the LHC, referred to as Large Hadron Electron Collider (LHeC). In this thesis design options for a new LHC injector - a Rapid Cycling Synchrotron - and an electron accelerator for the LHeC are presented
BPM Tolerances for HL-LHC Orbit Correction in the Inner Triplet Area
For the HL-LHC beam spot sizes as small as 7 mum are considered for the high luminosity insertions IR1 and IR5. In addition, the luminosity has to be levelled over several hours by changing beta* resulting in constant changes of the optics and thus orbit changes. The small beam size and the continuous optics changes in general make the alignment of the beams at the IP challenging. In order to avoid continuous luminosity scans for the alignment of the beams at the IP, the orbit correction has to rely on the readings of the BPMs in the IT region. In this paper we review the requirements on resolution and accuracy of the BPMs and compare different options for the placement of the BPMs in the IT regio
HLLHCV1.1 Optics Version for the HL-LHC Upgrade
The optics and layout of the HL-LHC are evolving as the new hardware is being studied and integrated, any additional requirements from the experiments detailed, and other constraints of different nature clarified. Here we present the changes of version 1.1 of the optics and layout with respect to the previous version 1.0, which include the current hardware choices and an outlook on the main resulting optics limitations and the possible future evolutions of the layout
Crossing Scheme and Orbit Correction in IR1/5 for HL-LHC
In this paper we review the orbit correction strategy and crossing scheme adjustment for the HL-LHC orbit correctors in IR1/5 in view of the new optics and layout version HLLHCV1.1. The main objectives are to optimize the crossing scheme, in particular to reduce the strength of the orbit correctors at D2, and to validate the strength specifications of the several orbit corrector magnets involved, including a budget reserved for the correction of the orbit distortions from various sources
Beam Dynamics Requirements for the Powering Scheme of the HL-LHC Triplet
For the HL-LHC, ÎČ â values as small as 15 cm are envisaged as baseline scenario for the high luminosity insertions IR1 and IR5, thus leading to an increase of the maximum ÎČ- functions in the inner triplet (IT). The larger beta-functions in the IT result in a higher sensitivity of the beam to any linear or non-linear, static or dynamic, field imperfections in the IT region. In this paper, we summarize accordingly the tolerances of the triplet power supplies in terms of current ripple, stability and reproducibility. Both the baseline IT powering scheme and other alternative schemes will be presented, the later reducing the tune shift caused by a current modulation and thus weakening its possible impact on the long term stability