The shift of the common start (or stop in case of the wire chamber) may
also be critical for the neutron counters. At present, the flasher peaks
at about channel 3000. The "photon peak" comes even somewhat later
(because a photon takes longer to reach the neutron counter compared to
the triggering electron), leaving only <50ns of additional time of flight
for the neutrons within the TDC range. The slowest neutrons may therefore
fall out of the TDC range.
Discussing this with Karen, the following might be favorable.
The common strobe signal which comes after the trigger supervisor (having
all the benefits of a smaller coinc window), and which is used to start
the scintillator/stop the Wch TDCs, could be additionally delayed
by 50 ns, in order to compensate for the shift introduced recently.
If the compensation can be made exact, it would even be possible to run on
with the old calibration files.
MK
On Tue, 24 Feb 2004, Douglas Hasell wrote:
> I think periodic checks with the buffer system are a good idea.
>
> But the resolution is due to the change in the timing I think. The new
> t0's are 50 ns less than before and these changes have not been
> incorporated into the crunch yet. The problem with introducing them is
> two fold: 1, are we finished changing the time of the common stop?, 2.
> with the current trigger there are not enough data in the right sector
> to determine t0 for all cells.
>
> If we are satisfied with the new coincidence window and the time of the
> common stop then we should do a shifts or two with a different trigger
> to get data in all cells from which the t0's can be determined.
>
>
> 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
> On Feb 24, 2004, at 7:18 AM, Bill Franklin wrote:
>
> > Chi,
> >
> > It's interesting that you can observe degradation in the resolution
> > from
> > 1-2 hours of hydrogen data with modest flow rate. Perhaps we should be
> > including an occasional unpolarized hydrogen run as a periodic
> > systematic
> > check. With the buffer system in reliable operation, it doesn't take
> > too
> > long to make the change.
> >
> > Bill
> >
> > On Mon, 23 Feb 2004, Electronic Log Book wrote:
> >
> >> Operators: adrian zhangchi shino
> >>
> >>
> >> at 5pm, all 4 HV crates had to be power recyled.
> >>
> >> L21 guard wire tripped and kept tripping, Doug gave instructions to
> >> recover that.
> >>
> >> D2 data takiing, smooth. had to deal with some trippings like usual.
> >>
> >> the two H2 runs after changing the timing coin window, show worse
> >> angular and vertex resolution, 1.5deg now. Doug had an email pointing
> >> out WC t0 shift.
> >>
> >>
> >
> > --
> > **********************************************************************
> > Wilbur A. Franklin * Phone: 617-253-9518
> > Bates Linear Accelerator Center * FAX: 617-253-9599
> > P.O. Box 846 * Email: wafrankl@mit.edu
> > Middleton, MA 01949 *
> > **********************************************************************
> >
>
>
--+-------------------------------------+--------------------------+ | Office: | Home: | |-------------------------------------|--------------------------| | Dr. Michael Kohl | Michael Kohl | | Laboratory for Nuclear Science | 5 Ibbetson Street | | MIT-Bates Linear Accelerator Center | Somerville, MA 02143 | | Middleton, MA 01949 | U.S.A. | | U.S.A. | | | - - - - - - - - - - - - | - - - - - - - - -| | Email: kohlm@mit.edu | K.Michael.Kohl@gmx.de | | Work: +1-617-253-9207 | Home: +1-617-629-3147 | | Fax: +1-617-253-9599 | Mobile: +1-978-580-4190 | | http://blast.lns.mit.edu | | +-------------------------------------+--------------------------+
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