Beam Instrumentation for Orbit Stability I. Pinayev

Complement of Storage Ring Diagnostics/Beam Instrumentation MonitorQuantityFunction 4-button pick-ups226Beam position, dispersion, response matrix, turn-by-turn dynamics Stripline pick-up 1 Longitudinal and transverse frequency components Tune monitor1 Betatron tunes measurement, impedance Loss monitors 10 Beam losses monitoring Fluorescent flags4Position and profile of injected beam Transverse feedback2Suppress beam instabilities Streak-camera1Bunch length measurement DCCT2Beam current measurement FCT2Filling pattern monitoring Beam scrapers4Machine studies (beam size, energy aperture), halo FireWire camera1Transverse beam characteristics Emittance monitor1Transverse beam sizes Undulator radiation1Energy spread, beam divergence, momentum compaction factor Pinhole camera1Horizontal emittance (using undulator radiation) Counter1RF frequency monitor Photon BPMs10Photon beam angle and position

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?

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 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?

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?

Photon Beam Intensities for Dipole and Undulator E=3 GeV ρ=25 m B= 0.4 T ε c =2.4 keV λc=0.52 nm ψ=1/γ=0.17 mrad P tot =143 kW 0.5 A) U19: λ U =19 mm K=1 L U =3 m (N U =158) λ U =0.4 nm ε U =3.1 keV σ r ′≈(λ U /L U ) ½ =11.5 μrad P tot =2.7 kW 0.5 A) Low dipole field – do we need Decker distortion?

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

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

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?

Fast Orbit Stabilization System (FOSS) BW ultimately limited by 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

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