Keyword: survey
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MOPRB078 Beam Based Measurements of the CBeta Main Linac Cavity Alignment cavity, linac, cryomodule, acceleration 755
  • C.M. Gulliford, A.C. Bartnik, J.A. Crittenden, P. Quigley
    Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
  • J.S. Berg
    BNL, Upton, Long Island, New York, USA
  Funding: This work was funded by NYSERDA, the New York State Energy Research and Development Agency.
Initial attempts at steering the beam through the CBETA main linac indicated the cavities were vertically offset with respect to the BPMs on either side of the linac.  In particular, manual alignment of the beam in the first and last cavities suggested a vertical offset of roughly 5 mm.  This work presents the results of beam based measurements of the individual cavity offsets taken during the CBETA Fractional Arc Test.  With only a single cavity powered at a time, beam was injected at several different vertical offsets, the RF phase was scanned over 360 degrees, and the beam position was measured at the end of the cryomodule. We analyzed the data in two ways. We first compute the RMS spread in the measurements at a given position, and considered the offset with the minimum RMS spread to be the cavity offset. We also fit the measurements at a given phase to a line as a function of initial displacement, and use a model for the transfer matrix of the cavity and downstream drift to compute the offset. The two methods agree well, resulting in an average vertical offset of the main linac cavities of 4.0 plus/minus 1 mm.
DOI • reference for this paper ※  
About • paper received ※ 15 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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TUPMP039 Data-driven Controller Design Using the CERN Power Converter Control Libraries (CCLIBS) controls, experiment, interface, factory 1335
  • A. Nicoletti, M. Martino
    CERN, Geneva, Switzerland
  The data-driven control approach is a control methodology in which a controller is designed without the need of a model. Parametric uncertainties and the associated unmodeled dynamics are therefore irrelevant; the only source of uncertainty comes from the measurement process. The CERN Power Converter Control Libraries (CCLIBS) have been updated to include data-driven H-infinity control methods recently proposed in literature. In particular, a two-step convex optimization algorithm is performed for obtaining the 2-degree-of-freedom controller parameters. The newly implemented tools in CCLIBS can be used both for frequency response measurement of the load and for controller synthesis. A case study is presented where these tools are used for an application in the CERN East Area Renovation Project for which a high-precision 900 A trapezoidal current pulse is required with 450 ms flat-top and 350 ms ramp-up and ramp-down times. The tracking error must remain within ± 100 parts-per-million (ppm) during the flat-top (before the ramp-down phase starts). The magnet considered in the case study is of non-laminated iron type, hence the necessity of data-driven techniques since the dynamics of such a magnet is difficult to be modeled accurately (due to eddy currents losses). The Power Converter used is a SIRIUS 2P (with a current and voltage rating of 400 Arms and 450 V, respectively) whose digital control loop is regulated at a sampling rate of 5 kS/s.  
DOI • reference for this paper ※  
About • paper received ※ 08 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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