# Presentation: 414584

## 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
- 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

## 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 →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?

## 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
- 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)1⁄2=11.5 μrad
- Ptot=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**