Author: Suminski, M.    [Sumiński, M.]
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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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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TUPOST025 Beam Commissioning of the New Digital Low-Level RF System for CERN’s AD 911
 
  • M.E. Angoletta, S.C.P. Albright, D. Barrientos, A. Findlay, M. Jaussi, A. Rey, M. Sumiński
    CERN, Meyrin, Switzerland
 
  CERN’s Antiproton Decelerator (AD) has been re-furbished to provide reliable operation for the Extra Low ENergy Antiproton ring (ELENA). In particular, AD was equipped with a new digital Low-Level RF (LLRF) system that was successfully commissioned during the summer 2021. The new AD LLRF system has routinely captured and decelerated more than 3·107 antiprotons from 3.5 GeV/c to 100 MeV/c in successive steps, referred to as RF segments, interleaved by cooling periods. The LLRF system implements the frequency program from Btrain data received over optical fiber. Beam phase/radial and cavity amplitude/phase feedback loops are operated during each RF segment. An extraction synchronization loop is triggered on the extraction RF segment to transfer a single bunch of antiprotons to ELENA. Extensive diagnostics features are available and operational modes such as bunched beam cooling and bunch rotation have been successfully deployed. The LLRF parameters can be different for each RF segment and are controlled by a dedicated application. This paper gives an overview of the AD LLRF beam commissioning results obtained and challenges overcome. Hints on future steps are also provided.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOST025  
About • Received ※ 25 May 2022 — Accepted ※ 15 June 2022 — Issue date ※ 17 June 2022  
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