Re: FEU84-3

[Matthew Shepherd <mashephe@indiana.edu>]

Hi all,

I think the reason for the slow rise time is that Mihajlo was running  
the PMT at a pretty low voltage (much lower than the nominal operating  
point) because the light source was pretty bright.  We are reworking  
the setup to have a dimmer source and we will crank up the voltage on  
the tube.  This should tighten the timing of the leading edge.

This is not the only "bug" we're trying to work out.  We also  
anticipate a problem due to the fact that we have single channel fADCs  
which have their own clocks.  Because the clock freq. is not exact  
there may be some phase drift between the two that introduces a +-4 ns  
jitter in the triggers sent to each card.  We will let you know how  
things progress -- we have ideas also for how to work around this.

-Matt


On Apr 8, 2008, at 10:58 AM, Fernando J. Barbosa wrote:
> Hi Eugene,
>
> The numbers you quote are about what I expected. Perhaps Mihajlo  
> (sorry I don't have his email) could find out what is causing such a  
> slow pulse from the laser as that really impacts the ultimate timing  
> resolution that can be achieved with the flash, after pulse fitting.
>
> Thanks and regards,
> Fernando