The wire chamber TDC does not have a user-settable gain; it is fixed at
0.5ns per bin. So cutting on bins or time is equivalent for the raw
WCh. If the offset correction is done in units of time, rather than TDC
bins, then maybe you want to cut on corrected time.
We CAN however change the maximum TDC bin (the full-scale time
measurement); currently set to 4usec, or 8000 bins. Probably the only
reason to change the max bin would be if the common stop (the event
trigger) got drastically later.
Karen
Tancredi Botto wrote:
>
> I think/suggest that also for the Wch the cut is done on channels, not
> on converted time. In particular because we may change the range of the TDC
> one day (we also may not) so that say 8191 channels would be 8 us, and
> then it'd be hard to think again of this discussion.
>
> It's easy to do this right once and for all. The thing started since
> we realize that a few CC-tdc comes relatively late in recent runs and
> we may not recon a few events beyond channel 4090.
>
> -- t
> ________________________________________________________________________________
> Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124
> research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> On Thu, 5 Jun 2003, Douglas Hasell wrote:
>
> > Hi,
> >
> > I expect I am showing my ignorance here but the wire chamber TDC
> > values range from 0 to 8191 which corresponds to 0 to 4095.5 ns. I assume
> > your number corresponds to 4090 ns which is certainly a safe upper limit.
> >
> > However, the range of realistic drift times is between something
> > like 2000 and 6500 tdc counts or 1000 and 3250 ns before subtracting from
> > the T0 value which is around 6500 tdc counts or 3250 ns. One way to
> > eliminate some of the noise would be to only consider TDC values in the
> > range 2000 to 6500 which would remove about 45% of noise. This is
> > relatively safe so long as the trigger timing and cabling doesn't change.
> >
> > --On Wednesday, June 4, 2003 11:39 PM -0400 zhangchi
> > <zhangchi@general.lns.mit.edu> wrote:
> >
> > >
> > > Hi, maximal tdc value cuts in outer detector reconstruction is raised
> > > from 4000 channels to 4090 channels.
> > >
> > > The related line is in TBLDetHit.h: const int tdc_over = 4090;
> > >
> > > Chi
> > >
> >
> >
> >
> > Cheers,
> > Douglas
> >
> > 26-415 M.I.T. Tel: +1 617 258 7199
> > 77 Massachusetts Avenue Fax: +1 617 258 5440
> > Cambridge, MA 02139, USA E-mail: hasell@mit.edu
> >
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