The construction of the European X-ray Free-Electron Laser (XFEL) in Hamburg was finished in 2017. Since then the facility is successfully operated and delivers photon beam for many scientific experiments. The XFEL is driven by a 17.5 GeV superconducting linac, a machine which is the worldwide largest installation based on superconducting radio-frequency acceleration. Other large-scale...
Large accelerator projects have been booming in China over the last decade, represented mainly by synchrotron light sources, free-electron lasers, particle colliders, accelerator-driven subcritical systems (ADS), and spallation neutron sources. Several new projects are currently being planned, while others have already begun construction. Additionally, some existing projects have been...
High-order mode (HOM) damping is a critical aspect of ensuring beam stability and operational reliability in the future circular collider (FCC-ee). The FCC-ee RF system must accommodate a wide range of beam parameters, covering working points from the Z energy level, with Ampere-level beam currents, up to the $\mathrm{t\bar{t}}$ energy, with a total RF voltage of 11.3 GV. This presentation...
In recent years, a new generation of high-energy circular electron-positron colliders and diffraction-limited light sources have been proposed or are under construction. These advanced circular accelerators impose significantly more demanding requirements on beam performance. To meet the design objectives, the accelerator design has been pushed to a new parameter range. Among the various...
The baseline design for the proposed UK XFEL (United Kingdom X-ray Free Electron Laser) facility includes main linear accelerating linacs, which are comprised of 600 9-cell TESLA style superconducting RF cavities, which will accelerate a 1 MHz repetition-rate irregularly spaced composite electron beam comprised of varying bunch charges up to an energies of 8 GeV. Here the TESLA cavities are...
Concatenation methods are powerful tools to compute the electromagnetic properties of large accelerating structures, i.e., chains of cavities with HOM- and input couplers. The talk will review the methods CSC, SSC and CSC$^\mathrm{BEAM}$, which have been predominantly developed at the University of Rostock. Common features as well as the differences between the three methods will be discussed...
The Hard X-ray Free-Electron Laser Facility SHINE adopted 1.3GHz 9-cell superconducting (SC) cavities for electron acceleration, with a maximum bunch charge of 300 pC, a maximum repetition frequency of 1 MHz, and a minimum bunch length of 26 μm. Multiple higher-order modes (HOMs) are excited and coupled outside. HOMs above the cutoff frequency will propagate through the entire module cavity...
Bulk niobium (Nb) is the standard material for superconducting RF (SRF) cavities, due to its high critical temperature and magnetic field compared to other pure metals. However, Nb is costly, challenging to manufacture, and has relatively poor thermal conductivity. The superconductor-insulator-superconductor multilayer geometry offers an alternative, using a sputtered superconducting film to...
The development of compact, high-current superconducting electron linacs for industrial applications requires balancing system simplicity, thermal management, and beam stability. In this work, we investigate the higher order mode (HOM) characteristics and damping requirements for 915 MHz superconducting accelerating structures specifically designed for conduction-cooled operation. Two cavity...
The Electron-Ion Collider (EIC) Electron Storage Ring (ESR) will circulate high-intensity electron beams, making beam–cavity interactions and higher order mode (HOM) effects a central concern for stability. This work presents wakefield and impedance simulations of the ESR cryomodule containing two back-to-back 591 MHz single-cell RF cavities and associated beamline components. The contribution...
This talk presents numerical methods for analysing Higher-Order Mode (HOM) couplers in elliptical TESLA-type superconducting radio-frequency (SRF) cavities. Emphasis is placed on practical simulation approaches, including S-parameter calculations, basic optimisation, sensitivity analysis and uncertainty quantification, and multipacting studies. The discussion will show how these tools can be...
The ECHO code family provides advanced numerical tools for calculating wake fields and impedances in accelerator components. In recent years, the codes have been extended to cover a wide range of geometries: rotationally symmetric (ECHOz1, ECHOz2), rectangular and 2D structures (ECHO2D), fully 3D models (ECHO3D), and anisotropic waveguides (ECHO1D). Key implementations include low-dispersive...
The Beam Line Absorbers (BLA) are the crucial component of high-current particle accelerators. In particular, Energy Recovery Linac (ERL) has stringent requirements on Higher-Order-Modes (HOMs) damping. In IJCLab, we are starting to develop warm BLA for FCCee and cryogenic BLA for the PERLE project. Thanks to the international collaborators and the literature, we are identifying the list of...
Currently, superconducting RF (SRF) systems for high-current storage rings are generally limited to low-frequency, moderate voltage, and single-cell cavities. For a new class of cavities to be used in longitudinal beam phase-space manipulation, high-voltage third harmonic multi-cell cavities are required, resulting in very challenging impedance considerations and higher-order mode (HOM) powers...
The Electron Ion Collider (EIC) to be constructed at Brookhaven National Lab (BNL) is a high luminosity collider as the next major nuclear physics research facility. One major new sub-accelerator of EIC is the Electron Storage Ring (ESR) to be built in BNL’s RHIC (Relativistic Heavy Ion Collider) tunnel. The ESR is required to operate at 5-18 GeV with up to 2.5 A of beam current stored. A new...
SRF technology enable particle accelerators operate with greater average beam currents and higher duty cycles. In these regimes parasitic excitation of the cavity HOM spectrum become the limiting factor due to extra RF losses and instabilities appearing in the beam. We discuss the limitations of HOMs for large accelerator projects as the Fermilab MI upgrade and the proposed future circular and...
The study presented here focuses on the progress of the HOM (High Order Mode) coupler for 5-cell 801.6 MHz elliptical Superconducting RadioFrequency (SRF) cavity designed for PERLE (Powerful Energy Recovery Linac for Experiments), a multi-turn ERL planned to be hosted at IJCLab in Orsay (France). Due to the high operating current and multiple passes of this machine, HOM damping in the SRF...
The High Energy Photon Source is a 6 GeV diffraction-limited synchrotron light source with ultra-low beam emittance. A 166.6 MHz quarter-wave superconducting cavity with a beta=1 structure has been proposed as the main accelerating cavity for the storage ring. The high beam current of 200 mA requires heavy damping of higher order modes (HOM) in the 166.6 MHz cavities to avoid coupled...
A new class of HOM couplers is introduced based on the coupling of evanescent modes in coaxial waveguide structures, a mechanism that provides great flexibility for the implementation of notch and high-pass filter. Conventional HOM couplers and design approaches are reviewed prior to the new class of filters. Several evanescent field coupling mechanisms are analyzed. Their particular...
The interaction region (IR) crab cavity system is a special RF system to compensate the loss of luminosity due to a 25 mrad crossing angle at the interaction point (IP) for electron ion collider (EIC). There will be six crab cavities, with four 197 MHz crab cavities and two 394 MHz crab cavities, installed on each side of the IP in the proton/ion ring, and one 394 MHz crab cavity on each side...
Picosecond-long X-ray pulses of moderate intensity and high repetition rate are highly sought after by the light source community, especially for time-resolved fine spectroscope analysis of matter in the linear response regime. As part of the upgrade of the Elettra 2.0, two radio frequency deflecting cavities with slightly different frequencies will be installed to produce time-dependent orbit...
As part of the High Luminosity project of the Large Hadron Collider (LHC) at CERN, transverse deflecting cavities (crab cavities) have been developed to compensate for the luminosity reduction caused by the collision crossing angle. Initial estimations of the cavity HOM power in 2018 were not in agreement with measurements of the prototype cavities when tested with beam. Advancements in...
As part of the High Luminosity LHC (HL-LHC) upgrade, crab cavities will be installed near the ATLAS and CMS experiments to mitigate luminosity loss from large crossing angles. To accommodate the differing crossing planes, two compact cavity designs have been developed: the Double Quarter Wave (DQW) resonator and the RF Dipole (RFD) cavity. Both cavity types have been prototyped, built, and...
SuperKEKB is a luminosity frontier collider for electron and positron beams. One of the highly challenging targets is the RF system handling extremely large beam loading. The design beam current of the 4 GeV positron beam is 3.6 A and that of the 7 GeV electron beam is 2.6 A. The positron beam is accelerated by twenty-two normal-conducting ARES cavities, which are three-coupled cavity systems....
The conceptual design of the UK XFEL facility responds directly to user community requirements for a next-generation X-ray facility. Surveys and consultations highlighted the need for higher repetition rates, near-transform-limited pulses, broader photon energy coverage, and the capacity to serve many experiments simultaneously. Current facilities typically offer only 1–3 source points,...
The study investigated the continuous-wave (CW) performance of the spare 3.9 GHz third harmonic cryomodule for the European XFEL. While pulse mode operation exceeded specifications with high accelerating gradients, CW tests revealed strong limitations. The main issue was overheating of the first HOM coupler. Additional challenges included tuner backlash and mechanical resonances at 18.6 Hz...
