Electron Accelerators and Applications
Energy recovery linacs
Paper Title Page
THPOJO21 Higher Order Modes Investigation in the PERLE Superconducting RF Cavity 731
SUPCGE01   use link to see paper's listing under its alternate paper code  
  • C. Barbagallo, P. Duchesne, W. Kaabi, G. Olry, Z.F. Zomer
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • R.A. Rimmer, H. Wang
    JLab, Newport News, Virginia, USA
  The regenerative Beam Break Up (BBU) excited by the dipole Higher Order Modes (HOMs) in superconducting RF (SRF) cavities is a crucial issue for continuous-wave high-current energy recovery linacs. Beam-induced monopole HOMs can increase the cryogenic losses of the linac also. One of the ways to limit these effects is to use HOM couplers on the beam tubes of cavities to absorb and untrap cavity eigenmodes. These couplers feature antennas designed to damp dangerous HOMs and adequately reject the fundamental mode. This study illustrates an investigation of the HOMs of a 5-cell 801.58 MHz elliptical SRF cavity designed for PERLE (Powerful Energy Recovery Linac for Experiments), a multi-turn energy recovery linac (ERL) currently under study and later to be hosted at IJCLab in Orsay. Time-domain wakefield and frequency-domain eigenmode simulations have been used to calculate the cavity broadband HOM impedance spectra and identify the dangerous BBU HOMs. The transmission characteristics of several coaxial HOM couplers have been studied. The efficiencies of several HOM-damping schemes have been compared to propose a HOM endgroup to be fabricated and added to the existing bare SRF cavity.  
poster icon Poster THPOJO21 [2.090 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOJO21  
About • Received ※ 24 August 2022 — Revised ※ 27 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 23 September 2022
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THPOJO25 HOM Damping in Multi-Cell Superconducting Cavities for the Future Electron Source BriXSinO 739
SUPCGE08   use link to see paper's listing under its alternate paper code  
  • S. Samsam, A. Bacci, C. Curatolo, I. Drebot, D. Giove, V. Petrillo, M. Rossetti Conti, A.R. Rossi, L. Serafini
    INFN-Milano, Milano, Italy
  • A. Bosotti, D. Giove, L. Monaco, R. Paparella, D. Sertore
    INFN/LASA, Segrate (MI), Italy
  • M.R. Masullo, A. Passarelli
    INFN-Napoli, Napoli, Italy
  • V. Petrillo
    Universita’ degli Studi di Milano, Milano, Italy
  High order modes (HOMs) in multi-cell superconducting cavities are of particular concern in beam dynamics of linear accelerators, mainly those operating in CW mode with high current and high repetition rate. These undesired modes may invoke beam instabilities, beam breakup and increase the energy spread if not correctly pulled out and damped. The study reported in this paper is applied for damping the HOMs in the main Linac of BriXSinO, an ongoing project of an Energy Recovery Linac at LASA INFN laboratory. We developed a numerical model to study the interaction of monopole HOMs with the beam in long timescale. The presented model, named HOMEN (High Order Modes Evolution based on eNergy budget), allows the evaluation of the loss factor Kloss, crucial for evaluating the perturbing modes. At the same time, electromagnetic simulations of the standing wave multicell cavity, highlighted the dangerous modes and revealed a tolerable beam energy spread induced by HOMs. This method allows us to distinguish all dangerous modes of our interest for implementing the necessary damping mechanisms.  
poster icon Poster THPOJO25 [1.111 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOJO25  
About • Received ※ 22 August 2022 — Revised ※ 17 August 2022 — Accepted ※ 29 August 2022 — Issue date ※ 15 September 2022
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THPOJO26 Conceptual Design of the PERLE Injector 743
  • B. Hounsell, M. Klein, C.P. Welsch
    The University of Liverpool, Liverpool, United Kingdom
  • B. Hounsell, B.L. Militsyn, C.P. Welsch
    Cockcroft Institute, Warrington, Cheshire, United Kingdom
  • B. Hounsell, W. Kaabi
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • B.L. Militsyn
    STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
  Energy Recovery Linacs such as PERLE require high average current high brightness beams. This sets particular requirements on the kind of injectors that they can use as the injectors must be capable of producing bunches at MHz repetition rates, compressing the bunches to the specified value and transporting those bunches while they are still in the space charge dominated regime into the main ERL all while keeping the emittance low. In particular, PERLE will require a 20 mA beam consisting of 500 pC bunches with a repetition rate of 40 MHz. These bunches will be required to have rms lengths of 3mm, a total beam energy of 7 MeV, appropriate Twiss parameters to match them to the main loop and transverse emittances of < 6 mm mrad. In this paper, a DC gun based injector capable of meeting this specification will be presented with beam dynamics simulation showing the behaviour of the beam from the photocathode to the exit of the first main linac pass. The beam dynamics challenges will be discussed in terms of both the transverse emittance growth and the sources of non-linearity in the longitudinal phase space.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-LINAC2022-THPOJO26  
About • Received ※ 20 August 2022 — Revised ※ 24 August 2022 — Accepted ※ 01 September 2022 — Issue date ※ 15 September 2022
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