Log entry time 10:41:49 on March 17, 2011

Entry number 352266

This entry is a followup to: 352225

Followups:

• 352273 03/17/11 10:58 saw Notes on the F1

Here's my best guesses after looking at it this morning.  I'm offsite
until after lunch, but will try to check in then so we can discuss
things further.

> I think that we have some hardware issues for BigBite. I think that the
> this hardware issue arrise from two points that I need to clarify.
> 1) retiming for BigBite
> 2) Data recording for the 1190 TDCs
> 3) the readout window for F1 TDCs
> 4) reference channels for BB TDCs
> 
> ================
> 1)I will start from the question concernig the point 4.
> The reference channel for the TDCs are comming after the retiming or
> befor? I mean that is the ref signal is copy of L1A or is it retimed L1A?

It should be the retimed L1A.  You want the timing for gates, etc on the
BigBite side to come from the particle in BigBite, not from the L1A which is
timed off the HRS.

> 2) I have problem with the reference signal for 1190. The BigBite
> libraries are built in such way that they deal with specific structure of
> the signal and the ref, However both raw TDC and ref signal spectra are
> different between 1190 and F1. (plot for ref channel attached. The TDCs
> spectra are posted in Halog:  352165   )

Note that for the 1190, any non-ref-time-subtracted plots will look strange.
If you plot the raw reference channel (unsubtracted) you should get a ~25ns
wide (I think) "spike" with a flat top.  If you look at the ref-time
subtracted ref-time, you should get (obviously) a single channel spike.

The F1s operate differently.  I think that they effectively subtract the
common gate/trigger internally, so the reference channel we plug in is
just a useful cross check and is not required.  So, a plot of a 'reference
pulse' plugged into an F1 should be a very narrow spike.

> 3) we have a cut off if we look on the TDC vs ADC spectra that I posted
> earlier (halog:  352159   )

This should be easy to chase down and understand.  The two most probable
explanations are listed at the top of 
  http://www.jlab.org/~adaq/halog/html/1103_archive/110316175228.html
I think the F1 window timing was adjusted yesterday, so you may have data on
the first option already.  If not, it wouldn't take too long to check with a
couple short runs.

> 1) This is more complicated...
> if I look on the DBB.t3[0] distribution (LHRS trigger copyt that comes to
> ROC 10, fastbus for wirechambers) I see to peaks. one peak is when we
> have retiming from L1A and the second is when we retime from L1A (L1A
> carry the time and NOT BB). All the events in middle are from "succeded"
> retiming. This distribution is with cut on trigger type 3 (LHRS). The
> common stop for this crate is Retimed L1A.
> 
> When I plot this distribution VS left TDC + right TDC for 1190 I get NOT
> CORRET PATTERN.
> I expect to get vertical line (without any slope). 
> For 1190 for some reason if I plot raw TDC left+ right I get vericla
> line, however, it doesnot make sense becose I didn't substruct ref
> channel, this shouldn't work (I think)!
> I post same plots for F1 TDCs to compare. However it's clearly seen that
> our readout window is to short.

In Figure 4:

As you point out, the horizontal lines around 160 and 640 are when the
hit (random) in BB misses the retiming window, so the stop for the TDC is
timed off the L1A (which is T3).  The stuff in between is where the common
stop timing comes from BB.  Most of that is still randoms though.

I don't know how the BB.tp.e.tof variable is constructed.  ToF is presumably
time of flight -- you can't get that from just from data taken from a single
arm (which is what you have in the BB TDC, timed off BB).  I'm not sure what
the sloped 'line' is coming from, but I suspect it's software driven.

> =================================
> Due to all of the reasons above I can't be sure that we can identify even
> the double coincidence peak for BB.
> =================================
> 
> 1) Why we are using retimed signal for E/ dE TDCs and ADCs? Shouldn't we
> use the retimed signal only for wirechambers?

It's a choice.  In both cases is boils down to where you want to spend
the time in software.  Since you have copies of the LHRS trigger in
TDCs timed off BigBite you can generate a TDC histogram with timing
relative to the LHRS simply by subracting that time off your other BB
signal.

> 2) Should we send one copy of the E TDCs to 1877 (In ROC 8. ROC that
> don't get retimed signal)

Probably not, since you can do it in software.

> 3) Why we are sending all our DBB databases to ROC 10 where we have
> retiming from BB, while most of the parameter have nothing to do with it?

Can't comment on this one -- I'm not sure what the DBB databases are...  I
suspect the answer is the same as (2) though.