Longitudinal beam dynamics for different initial distributions at cSTART

The compact STorage ring for Accelerator Research and Technology (cSTART) project aims to store electron bunches of LPA-like beams in a very large momentum acceptance storage ring. The project will be realized at the Karlsruhe Institute of Technology (KIT, Germany). Initially, the Ferninfrarot Linac- Und Test-Experiment (FLUTE), a source of ultra-short bunches, will serve as an injector for cSTART to benchmark and emulate laser-plasma accelerator-like beams. In a second stage a laser-plasma accelerator will be used as an injector, which is being developed as part of the ATHENA project in collaboration with DESY and Helmholtz Institute Jena (HIJ). With an energy of 50 MeV and damping times of several seconds, the electron beam does not reach equilibrium emittance within the storage time of about 100 milliseconds. Therefore, the initial phase space distribution influences the later dynamics and beam properties. We perform longitudinal particle tracking simulations to investigate the evolution of the bunch lengths and phase space densities for different initial beam distributions

Status of a monitor design for single-shot electro-optical bunch profile measurements at FCC-ee

At the KIT electron storage ring KARA (Karlsruhe Research Accellerator) an electro-optical (EO) near-field monitor is in operation performing single-shot, turn-by-turn measurements of the longitudinal bunch profile using electro-optical spectral decoding (EOSD). In context of the Future Circular Collider Innovation Study (FCCIS), a similar setup is investigated with the aim to monitor the longitudinal bunch profile of each bunch for dedicated top-up injection at the future electron-positron collider FCC-ee. This contribution presents the status of a monitor design adapted to cope with the high-current and high-energy lepton beams foreseen at FCC-ee

Status of Operation With Negative Momentum Compaction at KARA

For fu­ture syn­chro­tron light source de­vel­op­ment novel op­er­a­tion modes are under in­ves­ti­ga­tion. At the Karl­sruhe Re­search Ac­cel­er­a­tor (KARA) an op­tics with neg­a­tive mo­men­tum com­paction has been pro­posed, which is cur­rently under com­mis­sion­ing. In this con­text, the col­lec­tive ef­fects ex­pected in this regime are stud­ied with an ini­tial focus on the head-tail in­sta­bil­ity and the mi­cro-bunch­ing in­sta­bil­ity re­sult­ing from CSR self-in­ter­ac­tion. In this con­tri­bu­tion, we will pre­sent the pro­posed op­tics and the sta­tus of im­ple­men­ta­tion for op­er­a­tion in the neg­a­tive mo­men­tum com­paction regime as well as a pre­lim­i­nary dis­cus­sion of ex­pected col­lec­tive ef­fects

Effect of Negative Momentum Compaction Operation on the Current- Dependent Bunch Length

New operation modes are often considered during the development of new synchrotron light sources. An understanding of the effects involved is inevitable for a successful operation of these schemes. At the KIT storage ring KARA (Karlsruhe Research Accelerator), new modes can be implemented and tested at various energies, employing a variety of performant beam diagnostics devices. Negative momentum compaction optics at various energies have been established. Also, the influence of a negative momentum compaction factor on different effects has been investigated. This contribution comprises a short report on the status of the implementation of a negative momentum compaction optics at KARA. Additionally, first measurements of the changes to the current-dependent bunch length will be presented

Longitudinal Beam Dynamics and Coherent Synchrotron Radiation at cSTART

The compact STorage ring for Accelerator Research and Technology (cSTART) project aims to store electron bunches of LWFA-like beams in a very large momentum acceptance storage ring. The project will be realized at the Karlsruhe Institute of Technology (KIT, Germany). Initially, the Ferninfrarot Linac- Und Test-Experiment (FLUTE), a source of ultra-short bunches, will serve as an injector for cSTART to benchmark and emulate laser-wakefield accelerator-like beams. In a second stage a laser-plasma accelerator will be used as an injector, which is being developed as part of the ATHENA project in collaboration with DESY and Helmholtz Institute Jena (HIJ). With an energy of 50 MeV and damping times of several seconds, the electron beam does not reach equilibrium emittance. Furthermore, the critical frequency of synchrotron radiation is 50 THz and in the same order as the bunch spectrum, which implies that the entire bunch radiates coherently. We perform longitudinal particle tracking simulations to investigate the evolution of the bunch length and spectrum as well as the emitted coherent synchrotron radiation. Finally, different options for the RF system are discussed

Chromaticity Compensation Schemes for the Arc Lattice of the FCC-ee Collider

FCC-ee is an 100 km e⁺/e⁻ collider that is being designed within the Future Circular Collider Study organised by CERN. It's layout is optimised for precision studies and rare decay observations in the range of 90 to 350 GeV center of mass energy with luminosities in the order of 10³⁵ cm⁻²s⁻¹. Extremely small vertical beta functions of 1 - 2 mm are required at the two interaction points to reach this goal. The strong focusing required in the final doublet quadrupoles drives the chromaticity to more than -2000 units, far beyond the values that had been achieved in previous storage rings. As a consequence a pure linear chromaticity compensation scheme will not be sufficient to obtain the required ± 2 % energy acceptance. A state of the art multi-family sextupole scheme will have to be combined with a local chromaticity correction. This paper presents the design of the arc lattice, optimised for highest momentum acceptance and the results of systematic studies of the sextupole scheme in the arcs in order to gain highest chromaticity performance

Tapering Options and Emittance Fine Tuning for the FCC-ee Collider

The lepton collider version of the FCC study describes a future electron-positron collider with a circumference in the order of 100 km, optimised for operation with collision energies in the range of 90 GeV to 350 GeV (FCC- ee). This paper presents the layout of the machine and the constraints on the design of the arc lattice in the context of the four different beam energies that are foreseen for beam operation. Special emphasis is put on the compensation of the effect of the strong synchrotron radiation losses. The beam orbit as well as the optics have to be re-optimised for a given operation energy in order to achieve the foreseen emittance of ε = 1 nm in the horizontal and 1 pm in the vertical plane. Counter measures of the so-called saw-tooth effect of the design orbit are needed as well as a compensation of the energy loss on the beam optics. The paper summarizes different scenarios of how to achieve this goal as well as the need for additional emittance fine tuning using wiggler magnets