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Beam Instrumentation for Orbit Stability

Beam Instrumentation for Orbit Stability. I. Pinayev. Complement of Storage Ring Diagnostics/Beam Instrumentation. Monitor Quantity Function 4-button pick-ups 226 Beam position, dispersion, response matrix, turn-by-turn dynamics

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Beam Instrumentation for Orbit Stability

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  1. Beam Instrumentation for Orbit Stability I. Pinayev

  2. Complement of Storage Ring Diagnostics/Beam Instrumentation Monitor Quantity Function 4-button pick-ups 226 Beam position, dispersion, response matrix, turn-by-turn dynamics Stripline pick-up 1 Longitudinal and transverse frequency components Tune monitor 1 Betatron tunes measurement, impedance Loss monitors 10 Beam losses monitoring Fluorescent flags 4 Position and profile of injected beam Transverse feedback 2 Suppress beam instabilities Streak-camera 1 Bunch length measurement DCCT 2 Beam current measurement FCT 2 Filling pattern monitoring Beam scrapers 4 Machine studies (beam size, energy aperture), halo FireWire camera 1 Transverse beam characteristics Emittance monitor 1 Transverse beam sizes Undulator radiation 1 Energy spread, beam divergence, momentum compaction factor Pinhole camera 1 Horizontal emittance (using undulator radiation) Counter 1 RF frequency monitor Photon BPMs 10 Photon beam angle and position

  3. RF BPMs • Design similar to one adopted at RHIC • 5-mm radius buttons • Stray capacitance 1-4 pF (2π×500MHz×50Ω×3pF≈0.5) • Signal level -1.1 dBm for 500 mA at 500 MHz • Dependence of vacuum chamber shape/size and button capacitance (and hence sensitivity) on fill pattern and circulating current can be significant • Switch to strip-line geometry? • Electronics front-end overload • Monitors of the vacuum chamber position can be affected by the EM noise • Other factors?

  4. Processing Units • Utilized at Elettra, NSSRC, Diamond, Soleil, PLS • Fast acquisition 10 kHz sampling rate, 2 kHz BW • Slow acquisition: 10 Hz sampling rate, ~4 Hz BW • 32 bit data • RMS uncertainty (for 10 mm scale in 1 kHz BW) -90.5dB →0.3µm @ Pin = -20 dBm • 8-hour stability (ΔT=±1°C) -80dB→1µm • Temperature drift (T=10–35°C) -94dB/°C → 0.2µm/°C • MTBF ≥ 100,000 hours • For 270 units failure rate will be one unit in 17 days • Can filtering improve RMS uncertainty to required level? • Spares? • In-situ calibrators? • Other receivers?

  5. Photon Beam Position Monitors • Will provide information on photon beam position and angle (to account for errors in the wiggler field) • Use of photon BPMs will allow sub-microradian pointing stability • Contamination with dipole radiation can be of less concern due to reduced magnetic field in the bending magnet • Can be used for orbit feedback and/or control of users optics • 2D translation stages will precisely locate the photon BPM • Should withstand high power density • Response time? • Noise susceptibility? • Other sensors: CVD diamond photoresistors, bolometers, etc?

  6. E=3 GeV ρ=25 m B= 0.4 T εc=2.4 keV λc=0.52 nm ψ=1/γ=0.17 mrad Ptot=143 kW (@ 0.5 A) U19: λU=19 mm K=1 LU=3 m (NU=158) λU=0.4 nm εU=3.1 keV σr′≈(λU/LU)½=11.5 μrad Ptot=2.7 kW (@ 0.5 A) Photon Beam Intensities for Dipole and Undulator Low dipole field – do we need Decker distortion?

  7. Back-Fluorescent Hard X-ray BPMs • Hard X-rays hit Cu target which re-radiates 8.05 keV photons • Insensitive to dipole radiation • High level signals • 12 keV photons are presently tested • A lot of R&D still required • Can we extend range down to softer X-rays? Presented by G. Decker at BIW’06

  8. Diagnostics with Synchrotron Radiation • FireWire Camera eliminates need for frame-grabber • Exposure from 20 μs • Trigger jitter ±10 ns • 120 fps (full resolution) • 463 fps (100×100 ROI) • Position sensitive diodes provide signal proportional to the displacement of center of gravity • 0.3 μs response time • 0.6 μ position sensitivity • Can be used to monitor beam motion in the dipole

  9. Auxiliary Equipment • Two DCCT for monitoring of circulating current • Two fast current transformer for monitoring filling pattern • What other beam parameters we need to monitor to insure high stability?

  10. Fast Orbit Stabilization System (FOSS) • BW ultimately limitedby corrector magnets (<500Hz) • Basic building blocks • Libera Electron • Fast private communication system • Computational engines • PS interfaces and corrector magnets • What is optimal configuration? • reliability • cost • flexibility

  11. Characteristics for FOSS Components • Available data: amplitudes, positions, status • FPGA communication module is user specific • Synchronization to external clock • Fast network • 270 Liberas * 72 bytes * 10 kHz = 194 MB/s • Latency • 1Gb/s: 40 μs on one cable • Processing latency 350 usec • Reliability of GB switch is a must • Different computational engines are available Following Tomaž Karčnik from I-Tech

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