I've just changed the trigger supervisor readout list
(~/pro2004/coda/crl/ts2_pro2004_pri_ps7.crl) and remade it (need to source
coda_user.setup in ~/pro2004/coda, then in /crl type ./makelist
ts2_pro2004_pri_ps7.crl 68k ts2_pro2004_pri). Now PHYS6 (trig==7) is
prescaled by a factor of 30 instead of 6. Tavi stopped the run, clicked
Abort, Configure (l2trig), Download to pick up the new factor. Starting
with run 5335, trig==7 is prescaled by 30.
Karen
At 01:42 PM 3/4/2004 -0500, Richard Milner wrote:
>Following Tancredi's mail, I think we should significantly prescale the
>inclusive and put more lead shielding in front of the forward LADS. Ernie
>is working up a modification of the collimator which has the potential to
>improve the deadtime situation for the inclusive trigger. Until we can
>implement that, we should optimize running conditions for (e,e'd), (e,e'p)
>and (e,e'n) both vector and tensor.
>Richard
>
>
>
>On Thu, 4 Mar 2004, Tancredi Botto wrote:
>
> >
> > A brief summary of the present understanding of deadtime sources from the
> > analysis of recent data:
> >
> > Deadtime is limiting us in the use of higher beam currents. There are many
> > components to this: the most significant is "trackless" triggers that pass
> > the 2nd level trigger thanks to random hits in the wch. The ratio of
> > these fake 2ndl level triggers (abot 2/3 of total data) is consistent with
> > the Wch S/N ratios. The ratio of trackless triggers is nearly independent
> > of trigger type.
> >
> > Trackless triggers have no known vertex or momentum distribution of course
> > but they contribute fully to DAQ deadtime. They are very sensitive to Wch
> > multiplicity and S/N. Possibly this is related also to the collimator
> design.
> > Trackless events really have too few wch hits (often < 3 hits in the tdc
> > range used in the reconstruction of the wch events). We can't use a
> > momentum cut to truly speak about deadtime..
> >
> > A second contribution is coming from low-momentum particles that originate
> > mostly upstream of the target. These events constitute the vast majority
> > of "tracked" triggers, but a smaller fraction of the overall yield. They
> > are well characterized in momentum (100-200 MeV/c), charge (positrons for
> > inbending field, electrons for outbedending - both fire the Cerenkovs) and
> > location in the detector (tof #'s 10-14).
> >
> > These events must originate from 300 MeV photons in a EM shower. The
> shower
> > having photons (which are not "bent") may contribute again to the Wch S/N.
> > Note that trackless triggers are instead *uniformly* distributed in the
> TOF's
> >
> > We have never experienced such a harsh environment before because we were
> > not running with an inclusive trigger (requires a cerenkov) prescaled by 6
> > and because we did not add the LADS to the e,e'n trigger. Having done so
> > it offers many more opportunities for trackless and low-energy-background
> > triggers. Indeed trig==2 and trig==7 are the dominant distribution of
> > trigger types.
> >
> > To make matters worse, any of these trigger rates will show a dependence
> > on beam current and as mentioned in the prev email it is important to
> > operate in a linear region. Regards,
> >
> >
> > -- tancredi
> >
> ________________________________________________________________________________
> > Tancredi Botto, phone: +1-617-253-9204 mobile:
> +1-978-490-4124
> > research scientist MIT/Bates, 21 Manning Av Middleton MA,
> 01949
> >
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> >
> >
>
>--
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