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High resolution Cavity BPMs from RHUL

High resolution Cavity BPMs from RHUL. N Joshi* , S Boogert, F Cullinan, A Lyapin, et al. *Nirav.Joshi.2009@live.rhul.ac.uk JAI at Royal Holloway University of London, A Morgan, G Rehm et. al. DIAMOND L ight S ource. DITANET topical workshop on BPM , CERN, January 16, 2012.

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High resolution Cavity BPMs from RHUL

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  1. High resolution Cavity BPMs from RHUL N Joshi*, S Boogert, F Cullinan, A Lyapin, et al. *Nirav.Joshi.2009@live.rhul.ac.uk JAI at Royal Holloway University of London, A Morgan, G Rehm et. al. DIAMONDLight Source DITANET topical workshop on BPM , CERN, January 16, 2012

  2. JAI - John Adams Institute (NOT Japanese Accelerator Institute!) RHUL – Royal Holloway, University of London

  3. BPM work at JAI/RHUL • ATF • Running the BPM system • Provided electronics for the S-band system • Initiated both the S- and C-band designs • Main running system with ~40 BPMs • Resolution and stability studies • Will be covered in our talk tomorrow • CLIC • Have just established the collaboration with CERN and Fermilab • The first prototype built at CERN, measurements at RHUL • Details in Andrei Lunin’s talk • Diamond Light Source • Trying to come up with an improved solution for CBPMs • More in the following slides

  4. Working principle: Cylidrical cavity BPM

  5. Basic equations Voltage induced by position offset: Transverse Resonance mode frequency: Quality factor: Loaded quality factor: Typical power spectrum of modes excited inside the resonance cavity. Decay time constant: Normalized shunt impedance

  6. Computation and EM simulation codes • Electromagnetic (EM) simulation codes. • Advanced Computational Electromagnetic-3P (ACE3P) suit, SLAC, USA. • Parallel, higher order, finite element based. • Runs on NERSC super computers. • Omega3P : Eigenmodesolver to find normal modes of the cavity. • T3P : Time domain solver to calculate transient response. • S3P : S-parameter solver for transmission properties. • GdfidL : • 3D EM simulation code written in Fortran. • Finite difference time domain (FDTD) solver at core. • Runs on a cluster of 61 nodes at RHUL. • Solvers: • Eigen-mode solver • Time domain solver

  7. Cavity BPM project for NLS-DIAMOND • Science disciplines utilizing DIAMOND light source. • Chemistry • Cultural heritage • Earth science • Engineering • Environmental science • Life science • Physics and material science • Major parameters: • Accelerated particle : e- • Particle energy : 3GeV • Circumference : 561.6 m • Beam current : 300 mA • Bunch repetition rate: 500kHz

  8. DIAMOND BPM: RF design and simulation • BPM development project at DIAMOND1: BPM cavity with beam pipe and coupler with feed-through Waveguide coupler with feed-through • Basic design considerations : • Dipole frequency in C-Band range. • Relatively high Q • Frequency separation in XY to improve isolation via different slot size in X and Y • No tuning.

  9. DIAMOND Cavity BPM: simulation • Waveguide coupler

  10. DIAMOND Cavity BPM: simulation • Eigen mode solution : Monopole • Monopole frequency : 4.5 GHz • Monopole reduction by waveguide • fcut-off (Waveguide ) > fmonopole (Cavity) • Eigen mode solution : Dipole • Dipole frequency : 6.47 GHz • Dipole coupling into the waveguide • fcut-off (Waveguide ) < fdipole (Cavity)

  11. DIAMOND Cavity BPM: simulation • S-parameter simulation • CST A. Morgan, DLS

  12. DIAMOND Cavity BPM: Time domain simulation • Simulated using T3P. • Beam offset by 1mm in X and Y both. Field Propagation Output signal.

  13. DIAMOND Cavity BPM: simulation • Cavities were fabricatedbyFMB Berlin.

  14. RF Measurements • Peak Frequency S11: 6.376GHz • Peak Frequency S22: 6.371GHz • Coupling loss: ~ -10 dB • XY isolation : ~ -15 dB • Monopole suppression: > - 55 dB • Qload : 2892

  15. RF Measurements

  16. DIAMOND Cavity BPM: simulation • S-parameter simulation • ACE3P

  17. DIAMOND Cavity BPM: RF Measurements (Mode orientation) • -4…4 mm scan in 0.2 mm steps. • Movers and VNA were remote controled and synchonised using USB and VISA over LAN. • All S-parameters are recorded during single frequency sweep • 6400 S-para files were processed in parallel mode on cluster. • Rotation agrees with isolation. • Perhaps, can use external tuners to tune the X-coupling? • May also be an interesting study case for advanced analysis Dipole : Rotation angle= ~13

  18. DIAMOND Cavity BPM: Beam testing in ATF2 • Cavity Installation: • The cavity has been installed on a mover system. • Can be moved irrespective of other system in transversally in X and Yby +/- 1.5 mm • The main installation (3 BPMs) is at Diamond, but there dedicated time is needed for tests due to long bunches. 1 BPM was installed at ATF2 where it can be compared to the rest of the BPMs in the beamline and worked on parasitically. • Signal detection with diode: • Cavity outputs from one port for X and Y each is connected to a Shottky diode. • Dioe out digitized using network scope located outside the tunnel.

  19. DIAMOND Cavity BPM: Beam testing on ATF2 • Cavity moved in50 µm steps. • Sx = 0.4735 µV/µm • Sy= 0.427 µV/µm • Seems too low • Checking…

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