Closed Orbit Feedback and Tune Measurement: Status of realization at SIS18 P. Forck, P. Kowina, M. Schwickert, R. Singh for the GSI Beam Diagnostics Group and DELTA (TU-Dortmund) 5th FAIR Machine Advisory Committee Meeting May 9th/10th 2011

Overview Outline Status of Closed Orbit Feedback for SIS18 performed in collaboration with DELTA (TU-Dortmund) & COSY (FZ-Jülich) Status of Tune Measurement System at SIS18 The BPM signals are digitized by the I-Tech LIBERA Digitalization Units SIS18 serves as a test installation for FAIR: Validation the general design consideration Preparation of final realization for FAIR Gain of operational experiences 09.05.2011

Digital BPM Readout: Digitalization and Evaluation System Description: Digitalization of BPM signals at LIBERA with 14 bit and 125 MS/s ADC Individual bunch position evaluation with FPGA (presently Virtex-II Pro) Monitoring: data transfer to PC for either further down conversion for CO or bunch by bunch evaluation e.g. tune Planned Closed Orbit Feedback (COFB): Digital Down Conversion on LIBERA, Real-time transfer to concentrator via Diamond Com. Controller (DCC) Advantage: Single bunch position for flexible further processing For FAIR: Comparable successor system Scalable software realized at SIS18 Integration & Δ/ delivers bunch position I-Tech LIBERA Hadron 09.05.2011

Closed Orbit Feedback at SIS18: Hardware for BPM Data System Description COFB: Position data reduction on LIBERA 10 kHz input to ‘BPM Extender’ Input of time-dependent (triplett  duplett) Orbit Response Matrix from Control System SVD Algorithm for correction calculation Digital output to corrector power converter with  1kHz (to be tested) Beam DCC over SFP Corrector Hardware: Design & test by TU-Dortmund 09.05.2011

designed by GSI EET Group Closed Orbit Feedback at SIS18: Hardware for Power Converter Multi Function Unit designed by GSI EET Group System Description PS control: Multi Function Unit (MFU) as standard for all PS at FAIR (10 kHz digital bandwidth, 32 bit DAC) Input from BPM-Extender via USB  Quasi real-time communication for corrector value, bandwidth > 1 kHz Installation of MFU-control for SIS18 correctors required (foreseen end 2011) First tests for communication performed SIS18: 12 BPMs and 12 hor. & vert. correctors SIS100: 84 BPMs and 84 hor. & vert. correctors 09.05.2011

Closed Orbit Feedback at SIS18: Status General: System design according to Synchrotron Light Source standards Implementation at DELTA (TU-Dortmund): summer 2011 Readout of 54 BPMs and control of 20 hor. & vert. correctors Reaction bandwidth: 0.3 to 1 kHz (projected) About 1 year delay due to severe illness of PhD student at TU-Dortmund ! Implementation at SIS18: Foreseen in 2012 12 BPMs and 12 hor.& vert. correctors, projected reaction bandwidth 1 kHz Ongoing: Input of time-dependent Orbit Response Matrix via Control System Ongoing: Digital interface to power converter controller MFU Design for SIS100: 84 BPMs will be installed and 84 correctors  data treatment can be scaled Constant lattice  time-independent Orbit Response Matrix Hierarchical scheme for CO stabilization: 1. Magnetic field control by reference dipole  correction of e.g. hysteresis 2. Feed-forward using position data for creation of new set-values  correction of reproducible errors 3. Real-time feedback  residual, non-reproducible errors on 10 ms time scale 09.05.2011

Tune Determination at SIS18: Hardware The beam is excited to betatron oscillation → the beam position is measured each revolution (’turn-by-turn’) → Fourier Transformation gives the non-integer tune q. Advantage of digital processing: Digital bunch identification for turn-by-turn evaluation Varying revolution frequency: Matched ‘filter’ due to individual bunch integration  Precise determination of bunch position required for low excitation 09.05.2011

Maximum Position Variation Tune Determination at SIS18: Online Display of Results Tune versus time horizontal vertical Working Diagram Tune at fixed time Maximum Position Variation Qy  0.02 Qx  0.015 2 mm 5 mm Online display for tune measurement: Time resolution for plot: 4096 turns  20 – 4.5 ms Features: Minor emittance growth but good signal-to-noise Online display Ready for users DAQ in FESA GUI according FAIR spec. Ongoing: Improvement of algorithm Tune variation due to triplett  duplett lattice Beam parameter: Ar18+ acc. 11  300 MeV/u within 0.7 s 09.05.2011

Tune Determination at SIS18: Exploration of Working Range Condition for ‘Working Range’: Sufficient signal strength & minor emittance growth Orbit and tune for 3.5 W exciter power (50mW/Hz) Turns x 1000 Vertical Beam parameter: 6·109 Ar18+, 11  300 MeV/u within 0.4 s, Measurement parameter: Vertical excitation only, 516 turn FFT 09.05.2011

Tune Determination at SIS18: Exploration of Working Range Condition for ‘Working Range’: Sufficient signal strength & minor emittance growth Result: Measurement without significant emitance growth Transverse profile by an Ionization Profile Monitor Beam parameter: 6·109 Ar18+, 11  300 MeV/u within 0.4 s, Measurement parameter: Vertical excitation only, 516 turn FFT 09.05.2011

Conclusion Tune measurement system for SIS18: ‘Oversampling’ of bunches with 125 MSa/s > 20 · frf One position value per bunch by integration  cuf-off low-frequency noise Calculation of FFT  flexible time resolution e.g. 512 turns  1 ms Resolution Δq << 0.01 i.e. better than specified (spectrum broadening by tune spread contribution, to be investigated) Working range determined, no significant transverse emittance growth or beam loss Tests of ‘BBQ’ analog system: at SIS18 low-frequency noise is an issue Tune measurement: Demonstrated for SIS18, system design suited for SIS100 Tune feedback: Detailed consideration not started (CO stabilization as precaution) Possible solutions: Hardware comparable to COFB or ‘PLL tune tracking’ Closed Orbit Feedback: Anticipated bandwidth: 1 kHz Electronics realization comparable to Synchrotron Light Sources Collaboration with TU-Dortmund  demonstration expected late 2011 FAIR: Comparable systems will be installed. 09.05.2011