Development of an SRF Reduced-beta Cavity for the Injector of the S-DALINAC

A recent major upgrade of the superconducting - Darmstadt linear accelerator (S-DALINAC) allowed to conduct the first operational tests in an energy recovery linac (ERL) mode. The ERL operating regime imposes strict requirements for many accelerator components as well as for the accelerated beam quality and the beam energy spread in particular. At present, a significant beam energy spread is being observed in the capture section of the S-DALINAC. In that regard, the capture section part of the S-DALINAC injector needs to be upgraded in order to reduce the beam energy spread growth. In this work, the 6-cell reduced-beta cavity development process is discussed and a final cavity design is proposed. The SRF cavity design is not limited by electromagnetic field simulations, but also includes the longitudinal beam dynamics computations and the cavity mechanical model investigation. The main challenge was to find an optimal upgrade solution that would satisfy contradictory requirements with minimised investments costs. The results of multi-physics simulations and qualitative analysis that allowed to make decisions related to the SRF cavity design considerations are discussed. The suggested 6-cell SRF cavity is expected to be manufactured by the end of 2019. The cavity commissioning tests are planned in 2020

Measurement of electrodynamics characteristics of higher order modes for harmonic cavity at 2400 MHz

In the frameworks of the High Luminosity Large Hadron Collider (HL-LHC) upgrade program an application of additional superconducting harmonic cavities operating at 800 MHz is currently under discussion. As a possible candidate, an assembly of two cavities with grooved beam pipes connected by a drift tube and housed in a common cryomodule, was proposed. In this article we discuss measurements of loaded Q-factors of higher order modes (HOM) performed on a scaled aluminium single cell cavity prototype with the fundamental frequency of 2400 MHz and on an array of two such cavities connected by a narrow beam pipe. The measurements were performed for the system with and without the matching load in the drift tube.

Characterization of the SPS 800MHz travelling wave cavities.

It is well known that HOMs in RF cavities are a potentially dangerous source of beam impedance. Therefore, HOMs (both longitudinal and transverse) can drive the beam unstable . The 800MHz cavities of the SPS were studied in the past. However, very little documentation was left behind. Currently, the performance of the SPS is limited by a longitudinal beam instability. In order to study this instability, an accurate impedance model of the whole SPS is needed

Development of an SRF Reduced-beta Cavity for the Injector of the S-DALINAC

A recent major upgrade of the superconducting - Darmstadt linear accelerator (S-DALINAC) allowed to conduct the first operational tests in an energy recovery linac (ERL) mode. The ERL operating regime imposes strict requirements for many accelerator components as well as for the accelerated beam quality and the beam energy spread in particular. At present, a significant beam energy spread is being observed in the capture section of the S-DALINAC. In that regard, the capture section part of the S-DALINAC injector needs to be upgraded in order to reduce the beam energy spread growth. In this work, the 6-cell reduced-beta cavity development process is discussed and a final cavity design is proposed. The SRF cavity design is not limited by electromagnetic field simulations, but also includes the longitudinal beam dynamics computations and the cavity mechanical model investigation. The main challenge was to find an optimal upgrade solution that would satisfy contradictory requirements with minimised investments costs. The results of multi-physics simulations and qualitative analysis that allowed to make decisions related to the SRF cavity design considerations are discussed. The suggested 6-cell SRF cavity is expected to be manufactured by the end of 2019. The cavity commissioning tests are planned in 2020

CW Operation of the European XFEL: SC-Gun Injector Optimization, S2E Calculations and SASE Performance

This note presents optimization results for an injector with a super-conducting gun for the cw operation of the European XFEL, the corresponding start-to-end simulation calculations for the beam transport to the undulators and SASE calculations of the X-ray intensities for the achievable photon energies.The optimizations for an injector with a super-conducting gun are done mainly for an already experimentally shown accelerating gradient of 40 MV/m. Different working points with respect to transverse emittance and bunch length are chosen to see whether the lower transverse emittance of the longer bunches survives the necessary stronger bunch compression to achieve comparable peak currents in the undulators. Also, results for possible further improvement of the gun gradient to 50 MV/m and a modified transverse laser profile (truncated Gaussian) are shown.The S2E calculations are taking into account all relevant collective effects, including a thorough treatment of the impact of the so called Micro-Bunching Instability. For that purpose, tracking with the real number of particles is done, with a resolution in space and time fine enough to calculate instability growth model-free

CW Operation of the European XFEL: SC-Gun Injector Optimization, S2E Calculations and SASE Performance

This note presents optimization results for an injector with a super-conducting gun for the cw operation of the European XFEL, the corresponding start-to-end simulation calculations for the beam transport to the undulators and SASE calculations of the X-ray intensities for the achievable photon energies.The optimizations for an injector with a super-conducting gun are done mainly for an already experimentally shown accelerating gradient of 40 MV/m. Different working points with respect to transverse emittance and bunch length are chosen to see whether the lower transverse emittance of the longer bunches survives the necessary stronger bunch compression to achieve comparable peak currents in the undulators. Also, results for possible further improvement of the gun gradient to 50 MV/m and a modified transverse laser profile (truncated Gaussian) are shown.The S2E calculations are taking into account all relevant collective effects, including a thorough treatment of the impact of the so called Micro-Bunching Instability. For that purpose, tracking with the real number of particles is done, with a resolution in space and time fine enough to calculate instability growth model-free