Start Diodes - What is best?

[Matt Wilkinson]

Hi all

What start diode setups are stations currently using in their lasers to detect laser fires and trigger a timer start? I'll go and find the details of the Herstmonceux diode and post it here, but i know we use a rather cheap diode in to a threshold discriminator.  Is there anything better out there anyone could recommend? Are people satisfied with their start diodes?

When we moved to kHz SLR and lower energy pulses (from 20mJ to 1mJ), the threshold for a start had to be dropped considerably.  And so alignment is critical.  If it is not optimised we can get large RMS values in our calibrations.

Matt

[Matt Wilkinson]

We use an AEPX silicon photodiode from Centronic http://www.centronic.co.uk/products/3/high-speed which has a ~0.6ns rise time.

We align the diode, control the intensity with ND, observe the output signal and set the discriminator threshold to give the lowest possible calibration RMS.

Is there something out there that's better?