Hey all!
As some of you may know from the previous threads I've been pestering you with, I'm messing around with a few gamma spectroscopy, cosmic ray detection etc. projects.
One universal tool I'm lacking is a detector simulator (as calibration with a real detector requires a fairly strong monoenergetic gamma ray source, which is not really an option).
Basically, what I need is a pulse generator to simulate particle detection events; sharp rise, slow decay, entire pulse duration somewhere between .5 and 10 ns.
Pulse looking something like this:

I'd like the pulse event to be triggerable by TTL pulse, so that the frequency can be set fairly easily with a standard function gen (or simple square wave osc).
How would one go about designing something like this? I know the old-school way is to discharge a capacitor through a resistor, switched with a mercury wetted relay.
If I can find one of those that might still be a possibility.
Another option is to just couple a narrow square wave pulse into a charge sensitive amplifier via a small value cap, but I'm unsure if this will ever get very good performance.
Thirdly, I've read about people using a photodiode coupled to a charge amp, with a VERY dim LED flashing it briefly.
What do you think? Thanks in advance!