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The so-called "goose trigger" is a system where the laser is fed by two triggers that add up to a nominal trigger value (i.e. 9 Hz + 1 Hz = 10 Hz) but the laser to e-beam locking system is only fed by one of those triggers. This allows a user to have some laser pulses synchronized to the e-beam and some not synchronized, or even delayed, with respect to the e-beam. The idea is that you can remove backgrounds if you have laser on and off shots, where the off shots are delayed by ~1 ~14 ns so that the amplifiers stay warm.
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Normally the laser timing system compares the signal from the regen diode, converted to a time by the "Laser Interface Module", to a reference trigger from the EVG that provides laser timing. The difference between "Regen Time Out" to the "Reference Trigger" (Start and Stop in the Keysight box) tells the laser timing software where the laser is in time compared to a fixed point in the timing system.
Laser Interface Module
The laser interface module turns the signal from the "Regen Diode" into a square wave that can be used by the Keysight 53230A. The Laser Interface Module turns the square wave on at (or near) the peak of the Regen Diode Signal. It turns the square wave off when it receives a reset signal. This is simply a reset so the Laser Interface Module is ready to turn the square wave on when the next Regen Diode Signal Arrives. The length of the Regen Timing Out signal does not matter.
Keysight 53230A
The Keysight 53230A measures the time delay between the rising edge of the signals sent into the two input channels. The Keysight is capable of measuring time differences out to several minutes. Those signals are the Regen Timing Out from the Laser Interface Module and the Reference Trigger from the EVR. A gate does not need to be supplied, but if it is the two rising edges must be within the window of the gate.
The "Raw Meas." value is stored in the SR620 "Raw Meas." box in the Vitara GUI.
"Counter Time" = "Inv & Offset" = Offset - Raw Meas. Offset seems to be totally arbitrary.
How does the goose trigger work?
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