Active Collimator Interface Specification
From GlueXWiki
The collimator provides 8 outputs that are dependent on current and position. The outputs have the following characteristics, listed below. Lead shielded local amplification is necessary within 1 m of the device in order to limit bandwidth truncation due to the extra input capacitance of the coaxial cable. Digital electronics are to be located elsewhere, in a VME crate mounted in an electronics rack in Hall D proper. The x,y position coordinates are computed from the 8 measured currents through an algorithm to be provided by the UConn group.
System Requirements
- Position measurements
- 500 pA to 5 μA electron beam
- 200 μm resolution
- bandwidth is 1 kHz above 50 nA, and 50nA/I(electron beam) in kHz below 50 nA
- Feedback control
- bandwidth 1 kHz
- latency less than 150 μs
- 8 preamplifiers
- dc gain dynamically selectable in 6 discrete ranges: 1012, 1011, 1010, 109, 108, 107, 106 V/A
- exact dc gain depends on termination load used on output
- nominal values above are stated by manufacturer for 100 Ohm load
- plans are to use 75 Ohm output cable (RG-59/U or equivalent)
- coordinates computed from diff/sum ratios, independent of gain scale
- bipolar output signals with range [-10, 10] V
- preamp bandwidth: varies with gain range, compute using gain-bandwidth product
- all 6 ranges have the same gain-bandwidth product: 1013 Hz * V/A
- bandwidth in any gain setting obtained as (gain-bandwidth product) / (dc gain)
- 8 analog outputs from the active collimator readout board
- x+ coarse, x- coarse, x+ fine, x- fine, y+ coarse, y- coarse, y+ fine, y- fine
- differential outputs (four signals, each in +/- pairs)
- each output is unipolar from 0 to 2 V
- output circuits have >1 kHz bandwidth
- coarse outputs gain: 100 mV difference / cm
- fine outputs gain: 10 V difference / cm
- 2 analog magnet control outputs
- single ended (?)
- unipolar from 0 to ? V (?)
- ? kHz bandwidth
- ? resolution
- Digital I/O
- Beam Sync input for pulsed mode
- 30 Hz input for line sync of waveforms
- 4(?) BPM inputs (just to be safe?)
- 0.5 nA to 5 μA electron beam
- ? kHz bandwidth
- Other and/or spare I/O ?
- EPICS control
- remote gain control for preamps, independent 3-bit values for 8 channels
- coarse and fine position read backs at 1 Hz for Ops
- waveform buffers
- adjustable up to 4k points at 4ksps, triggered by 30Hz or Beam Sync for Ops
- circular buffers for FSD captures for Ops
- Physics analog outputs for Hall D data acquisition system
- 8 buffered analog outputs providing raw collimator sector currents
- 8 analog outputs for processed signals (x+/x- coarse and fine, y+/y- coarse and fine)
- signals will be digitized and recorded using standard GlueX data acquisition
- Physics digital data outputs
- none
- 4 diagnostic analog outputs (?)
- single ended (?)
- bipolar +/- V (?)
- ? kHz bandwidth
- ? resolution
- 2 diagnostic analog inputs (?)
- single ended (?)
- bipolar +/- V (?)
- ? kHz bandwidth
- ? resolution
- Account code?