Simulations of long-range beam-beam interaction and wire compensation with BBTrack

We present weak-strong simulation results for the effect of long-range beam-beam (LR-BB) interaction in LHC as well as for proposed wire compensation schemes or wire experiments, respectively. In particular, we discuss details of the simulation model, instability indicators, the effectiveness of compensation, the difference between nominal and PACMAN bunches for the LHC, beam experiments, and wire tolerances. The simulations are performed with the new code BBTrack [1]

Wire compensation: Performance, SPS MDs, pulsed system

A wire compensation (BBLR) scheme has been proposed in order to improve the long range beam-beam performance of the nominal LHC and its phase 1 and phase 2 upgrades[1]. In this paper we present experimental experience of the CERN SPS wires (BBLR) and report on progress with the RF BBLR

Long-range beam-beam compensation with wires

The wire compensation is one of the possible LHC upgrade plans to overcome the beam-beam limit. We present weak-strong simulation results for the effect of long-range beam-beam interaction (LR-BBI) in LHC. In particular, we discuss the effectiveness of compensation, the difference between nominal and PACMAN bunches for the LHC, and wire tolerances

Beam-beam issues for LHC upgrade phases 1 and 2

While long-range beam-beam interaction will not be the limiting effect in the first years after LHC start-up, it will definitely become one in the upgrade scenarios. Upgrade phase 1 will include an exchange of the triplet magnets allowing for a = 25 cm optics. Phase 2 is an even more ambitious upgrade that will include a modification of the detectors. Currently two phase-2 upgrade scenarios are proposed: the “Dipole Zero” (D0) and the “Large Piwinski Angle” (LPA) option. After some general notes and a brief description of the applied simulation model, the upgrade phase 1 issues and optics will be discussed with regard to beam-beam performance. The following two sections will deal with upgrade phase 2

Simulations on a potential hybrid and compact attosecond X-ray source based on RF and THz technologies

We investigate through beam dynamics simulations the potential of a hybrid layout mixing RF and THz technologies to be a compact X-ray source based on Inverse Compton Scattering (ICS), delivering few femtoseconds to sub-femtosecond pulses. The layout consists of an S-band gun as electron source and a dielectric-loaded circular waveguide driven by a multicycle THz pulse to accelerate and longitudinally compress the bunch, which will then be used to produce X-ray pulses via ICS with an infrared laser pulse. The beam dynamics simulations we performed, from the photocathode up to the ICS point, allows to have an insight in several important physical effects for the proposed scheme and also in the influence on the achievable bunch properties of various parameters of the accelerating and transverse focusing devices. The study presented in this paper leads to a preliminary layout and set of parameters able to deliver at the ICS point, according to our simulations, ultrashort bunches (around 1 fs rms), at 15 MeV, with at least 1 pC charge and transversely focused down to around 10 um rms or below while keeping a compact beamline (less than 1.5 m), which has not yet been achieved using only conventional RF technologies. Future studies will be devoted to the investigation of several potential ways to improve the achieved bunch properties, to overcome the limitations identified in the current study and to the definition of the technical requirements. This will lead to an updated layout and set of parameters.Comment: To be published in Nucl. Inst. Meth. A as proceedings of the EAAC17 conference 9 pages, 11 figure

Small Angle Crab Crossing for the LHC4

A small angle crab compensation ( 0.5 mrad) is foreseen to improve the LHC luminosity independently of the IR upgrade paths to enhance the luminosity of the LHC by 15% for the nominal and factor of 2-3 for various upgrade scenarios. Crab cavities ensure head-on collisions and recover the geometric luminosity loss from the presence of a finite crossing angle at the interaction point (IP). An R&D program is underway to design and fabricate superconducting RF (SRF) prototype cavity at 800 MHz to test several SRF limits in the deflecting mode. If the prototype is installed in the LHC, it can be used for a first demonstration of crab crossing in hadron beams to understand potential emittance growth mechanisms due to crab cavities

Beam Dynamics and Tolerance Studies of the THz-driven Electron Linac for the AXSIS Experiment

A dielectric-loaded linac powered by THz-pulses is one of the key parts of the "Attosecond X-ray Science: Imaging and Spectroscopy" (AXSIS) project at DESY, Hamburg. As in conventional accelerators, the AXSIS linac is designed to have phase velocity equal to the speed of light which, in this case, is realized by tuning the thickness of the dielectric layer and the radius of the vacuum channel. Therefore, structure fabrication errors will lead to a change in the beam dynamics and beam quality. Additionally, errors in the bunch injection will also affect the acceleration process and can cause beam loss on the linac wall. This paper numerically investigates the process of electron beam acceleration in the AXSIS linac, taking into account the aforementioned errors. Particle tracking simulations were done using the code ECHO, which uses a low-dispersive algorithm for the field calculation and was specially adapted for the dielectric-loaded accelerating structures.Comment: EAAC'17 conference proceeding

Small Angle Crab Compensation for LHC IR Upgrade

A small angle crab scheme is being considered for the LHC luminosity upgrade. In this paper we present a 400MHz superconducting cavity design and discuss the pertinent RF challenges. We also present a study on the beam-beam performance and proton-beam emittance growth in the presence of crab compensation, with RF noise sources