Author: Egli, J.
Paper Title Page
TUPOST021 The CERN SPS Low Level RF: The Beam-Control 895
 
  • A. Spierer, P. Baudrenghien, J. Egli, G. Hagmann, P. Kuzmanović, I. Stachon, M. Sumiński, T. Włostowski
    CERN, Meyrin, Switzerland
 
  The Super Proton Synchrotron (SPS) Low Level RF (LLRF) has been completely upgraded during the CERN long shutdown (LS2, 2019-2020). The old NIM and VME based, mainly analog system has been replaced with modern digital electronics implemented on a MicroTCA platform. The architecture has also been reviewed, with synchronization between RF stations now resting on the White Rabbit (WR) deterministic link. This paper is the first of a series of three on the SPS LLRF upgrade. It covers the Beam-Control part, that is responsible for the generation of the RF reference frequency from a measurement of the magnetic field, and beam phase and radial position. It broadcasts this frequency word to the RF stations, via a White Rabbit network. The paper presents the architecture, gives details on the signal processing, firmware, hardware and software. Finally, results from the first year of beam commissioning are presented (2021).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST021  
About • Received ※ 07 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 05 July 2022  
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TUPOST022 The CERN SPS Low Level RF: Lead Ions Acceleration 899
 
  • P. Baudrenghien, J. Egli, G. Hagmann, A. Spierer, T. Włostowski
    CERN, Meyrin, Switzerland
 
  This paper is the third of a series of three on the Super Proton Synchrotron (SPS) Low Level RF (LLRF). Its focus is the upgrade concerned with the acceleration of Lead ions for injection into the LHC. Lead ions are far from relativistic at injection into the SPS. Therefore, the classic acceleration scheme at constant harmonic number (h=4620) does not work as the RF frequency swing does not fit within the cavity bandwidth. Fixed Frequency Acceleration (FFA) is therefore used. The upgraded LLRF uses a completely new implementation of the FFA, based on a Numerically Controlled Oscillator (NCO) implemented as an FPGA IP in the Controller of each cavity. In addition, the 2022 scheme for LHC ions filling calls for slip stacking of two families of bunches, 100 ns spacing, to generate a 50 ns spacing after interleaving. The paper presents the key components for FFA and ions slip stacking as implemented in the new system, together with successful first tests performed in Autumn 2021.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST022  
About • Received ※ 08 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 24 June 2022  
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TUPOST023 The CERN SPS Low level RF: The Cavity-Controller 903
 
  • G. Hagmann, P. Baudrenghien, J. Egli, A. Spierer, M. Sumiński, T. Włostowski
    CERN, Meyrin, Switzerland
 
  This paper is the second of a series of three on the Super Proton Synchrotron (SPS) Low Level RF (LLRF) upgrade. It covers the 200MHz Cavity-Controller part, that is responsible for the regulation of the accelerating field in a single SPS cavity. When the SPS is used as Large Hadron Collider (LHC) proton injector, the issue is the high beam loading that must be compensated to guarantee longitudinal stability and constant parameters over the bunch train. That calls for strong One-Turn Delay Feedback (OTFB) and Feed-Forward (FFWD). The SPS is also accelerating Lead ions (Pb). There the issue is Frequency-Modulation (FM) and Amplitude-Modulation (AM) over the turn (so called Fixed Frequency Acceleration - FFA) plus RF gymnastics for the new ions slip-stacking. The paper reviews the functional requirements, presents the block diagram, then gives details on the signal processing, firmware and hardware. Finally results from the first year of beam commissioning are presented (2021).  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST023  
About • Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 19 June 2022
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