View source for Active Collimator Interface Specification

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 RMS resolution on photon beam centroid at collimator entrance
#* bandwidth is 1 kHz above 50 nA, and I(electron beam)/50nA 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:	10<sup>12</sup>, 10<sup>11</sup>, 10<sup>10</sup>, 10<sup>9</sup>, 10<sup>8</sup>, 10<sup>7</sup>, 10<sup>6</sup> 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: 10<sup>13</sup> 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?