From: Geary Eppley (eppley_at_physics.rice.edu)
Date: Tue Feb 11 2003 - 12:32:46 EST
Hi,
We can discuss this at the 2 pm EST phone conference 631 344 2261 if
you wish. The agenda is not crowded.
Geary
On Tue, 11 Feb 2003, Frank Geurts wrote:
> John,
> are you available somewhere tomorrow so Zhangbu and I can call. The
> issue still revolves around getting the pvpd east and west coincidences
> available at the STAR trigger. You know who things are currently set up
> (fanning out the EAST and WEST signals, and sending them on a 40ns cable
> to Zhangbu's stuff). As it turns out the signals arive too late ...
> zhangbu sees them in the zdc post one clock tick. Meaning that we are
> too late by at least some 40ns (Zhangbu??). I couldn't see any timing
> measurements on your trigger logic diagram for the path from the output
> of the ps706s until the outputs of the EAST or WEST coincidence units.
>
> * What would you guess this timing would be?
>
> * From the diagram I read that we had enough outputs for both
> coincidences so we could provide Zhangbu with regular negative logic,
> right? Or did we give him positive logic (w/ a pulsewidth of 20ns)?
>
> In order to push the timing back, we could reconsider removing the fan
> unit which we placed to protect ourselved from reflections. I suppose
> removing the cable to that unit + the unit itself could safe us 8ns
> (cable length?) + 6-7ns (transient time, according to specs for the
> LC428) about 15ns. Not much, but maybe Zhangbu can get his 40ns cable
> somewhat shorter too ...
>
> In any case, the reflections for which the fan-out unit should protect
> us could also be minimized by a attenuator in Zhangbu's signal path.
> Currently, he already has an 14dB attenuator in it.
>
> With the scheduled access, we just want to ran with you through some
> options before we touch anything. Maybe we could use the TOF phone
> bridge so Bill and Geary can join if they want to (if these guys can
> keep their meeting short :) ... )
>
> -frank
>
>
>
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