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====IU Pulser calibration====

The Indiana University pulser system nominally pulses one ASIC channel at a time through the normal detector input.  In reality it tends to pulse one channel strongly and neighboring channels weakly.  It is also possible to leave the detector attached and thus account for its capacitance.  In the past, [[calibrations|calibrations]] using a [[Pulser Ramp|pulser ramp]] through the IU pulser have been used to determine readout order corrections, and to check that the internal motherboard pulser distribution is linear.

===Description===

The IU pulser itself is a small, nearly cubic metal box.  It takes a pulser signal as input on a BNC connection, and +5V power and a TTL logic pulse on a Molex connector.  The TTL input is used to tell the IU pulser to move on to the next channel.  As output, the box has a 34 pin male connector.  The box will step through the channels corresponding to detector strips/ASIC inputs, and output the same pulser signal as is input to it, but scaled to be a similar size as signals from the detector.
:!: We could use a picture here

In addition to the box, the system includes a +5V NIM double-wide power supply and external filter, cable to take the power and logic signal on two BNC connectors and combine them into the required Molex connector, and a set of cables for the output, which are different depending on whether you are pulsing E or dE detectors (see detector and ASIC channel mapping for explanation).  The output cables have three connections: one for the detector, one for the ASIC chipboard, and one for the pulser box. 
:!: more pictures would really help

===Setup===

This assumes that you already have a working setup of HiRA telescope(s) and ASIC electronics.

Detach the cable that connects the detector to the ASIC electronics on the ASIC end.  Connect the loose end of that cable to the male 34 pin connector that's in the middle of the IU pulser output cable, and then connect the end of the cable labeled "tower" to the ASIC electronics tower.  Be careful here, it's easy to offset this cable by a row of pins.  Now you should have restored the connection between the detector and the ASICs, but you have an additional open connector.  Attach this to the output of the pulser box.

Now you need to connect the inputs.  If you're working in a vacuum chamber that you want to close, you need three lemo or BNC feedthroughs for the three inputs - power, logic, pulser.  Use the provided cable inside the chamber to take the power and logic signals into the pulser box.  A normal lemo or BNC cable works for the pulser.  Outside the chamber, connect the pulser line to one of our nice BNC tail pulsers.  The power line is just connected to the +5V power supply.  

For the logic line, you need a way to provide a TTL pulse whenever you want.  I suggest the Lecroy 222 gate generator, which has a manual start button to press and a TTL output.  I set the pulse output anywhere from 100 ns to tens of us wide.  This tends to produce multiple pulses and thus skip past channels.  To get around this, you can use the second gate generator to veto the multiple pulses: take the NIMbar output from the top panel (which I'm assuming you're using for your TTL pulse) into the input of the second panel, and the NIM output of the second panel into the "blank" input on the top.  Set the range of the second input to around a second to be sure you get no repeated pulses.

===Running===

Run this just like a normal pulser ramp (more information there, eventually).  Get your HiRA electronics ready to take data (:!://need a page for this//), triggering either on the OR or the pulser trigger output.  Run a pulser ramp on one channel, and when you're done, push the start button on the Lecroy gate generator to go to the next channel.  For experiment 06035, we used the low gain jumper setting on the ASICs, and used ramp settings of 0 to 3V in 31 steps, 10s each.  Note that there is a fair amount of cross talk onto the neighboring channels on the Si, but that these channels are on the next chip.  So we can step through the 16 channels on one chip in one run, then start a new run for the other chip, and the cross talk won't be a difficulty.

===Analysis===

who knows.
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