Conveners
Poster Session: Poster Session
- Qing Qin (Institute of High Energy Physics, Chinese Academy of Sciences)
Description
Posters will be hanging in the main workshop hall from 4pm on Tuesday till 12pm on Friday. Posters can be discussed at any time. The time slot allocated to your abstract in the timetable should be ignored.
The LHC Injectors Upgrade (LIU) project plans doubling the bunch intensity in the LHC injector chain in order to meet the requirements of the High Luminosity LHC (HL-LHC) project. The longitudinal beam impedance of the Super Proton Synchrotron (SPS), part of the injector of the LHC, is currently one of the limitations in reaching higher beam intensities due to instability issues. In the...
For future synchrotron light sources different acceleration modes are of interest. Therefore various modes are currently being tested at the Karlsruhe Research Accelerator (KARA) including optics for a negative momentum compaction factor. These optics have been calculated and are under commissioning at KARA. Additionally, studies about expected collective effects in this regime are being...
The SIS100 synchrotron, presently under construction in Darmstadt, Germany, will provide high intensity ion beams to the different experiments of FAIR. Numerous types of RF and ramp cycles for the full range of ions are planned for the operation. Here we identify a few reference cycles for the heavy-ion and proton beams and consider the transverse stability along the time scenario of the...
Modern accelerators and light sources often require special treatment of the vacuum chamber surface in order to avoid undesirable effects and to maximize machine performance. Coatings with Amorphous Carbon (a-C) have been extensively tested and used with very effective results since it allows to reduce the secondary electron yield (SEY) of the pipe walls due to electron cloud and to avoid the...
When a high intensity charged beam passes through locations with narrow apertures, such as the rod of a collimator, undesirable wake fields can be generated and adversely affect the beam. The Compact ERL at KEK mainly uses five beam collimators (one at the injector line, one at the merger section, and three in the recirculation loop) to remove the beam halo and to localize the beam losses....
Electron clouds are produced by photo-emissions, residual gas ionizations and secondary emissions during positively charged beam circulations in particle accelerators. The interaction between the beam and electron clouds leads to critical instabilities which may cause beam losses, trajectory changes and wake fields. In this study, we investigate electron cloud build-up for CLIC-DR's with 0.5ns...
Beam intensities required by the High-Luminosity (HL-) LHC can presently not be delivered by the CERN SPS, mainly due to beam loading, but also due to a longitudinal multi-bunch instability. This instability is known to be triggered by the third harmonic passband of the 200 MHz multi-cell accelerating structures at an intensity threshold three times below the nominal LHC intensity in the 200...
At the end of 2017, the conceptual design for an upgrade of the Swiss Light Source was finished, promising a 50 fold increase of the brilliance from the current value. From the point of view of collective effects, the main changes in the new design are a reduced chamber size, fully coated with NEG, and operation at small and negative momentum compaction with low synchronous frequency. We give...
Two Vlasov solvers for the longitudinal and transverse planes are used to study the frequency shift of coherent oscillation modes and possible mode-coupling instability in case of a broad-band resonator impedance model. In parallel to this approach, a new method to study the coherent frequency shift from the results of simulation codes is presented. Comparisons between the two methods are...
At KARA, the Karlsruhe Research Accelerator of the Karlsruhe Institute of Technology synchrotron, the so-called short-bunch operation mode allows the reduction of the bunch length down to a few picoseconds. The microbunching instability resulting from the high degree of longitudinal compression leads to fluctuations in the emitted terahertz radiation. For highly compressed bunches at KARA, the...
The High Luminosity Large Hadron Collider (HL-LHC) Project at CERN calls for increasing beam brightness and intensity.
In this framework, it is crucial to reduce the electromagnetic coupling between the particle beams and the surrounding environment (by means of the concepts of wakefield and impedance) in order to minimize undesired effects as beam instabilities and RF-heating.
In the past...
In recent years, strong-strong simulations and following theoretical analysis has shown a novel strong coherent head-tail type instability induced by the beam-beam interaction in case of large Piwinski angle The width of stable working point limited by the instability is very narrow when we try to reach the beam-beam limit at CEPC. In this paper the chromaticity is considered, the luminosity...
The CERN FCC-ee top-up booster synchrotron will accelerate electrons and positrons from an injection energy of 20 GeV up to an extraction energy between 45.6 GeV and 182.5 GeV depending on the operation mode. These accelerated beams will be used for the initial filling of the high-luminosity FCC-ee collider and for keeping the beam current constant over time using continuous top-up injection....
Electron lenses are one of the ways to provide incoherent betatron tune spread for Landau damping of transverse coherent beam instabilities. We investigated the effect of transverse electron beam profile size and shape for Landau damping with electron lens. Another point of interests is Landau damping provided by a pulsed electron lens with homogeneous transverse beam profile. This type of...
Resistive-wall impedance constitutes a significant percentage of the total beam-coupling impedance budget of an accelerator. A number of different reduction techniques have been proposed during the years depending on the specific applications, ranging from higher order modes damping to solutions entailing high electrical-conductivity coatings of the pipe. This paper investigates the use of...
Based on the recent work of R. Lindberg on transverse collective instabilities (PRAB 19, 124402,(2016)) it was observed that if the ratio of quadrupolar to dipolar impedance is equal to -1, there is no TMC-instability. This relationship is actually fulfilled by horizontal resistive wall impedance. "Headtail" simulations were carried out to check if this formal observation could be confirmed....
