Active Collimator Interface Specification

--Hall D Collimator and Beam Feedback Electronics-- 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.

1. 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
2. Feedback control
   • bandwidth 1 kHz
   • latency less than 150 μs
3. 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?