Hi,
it seems that yesterday's problem of missing TOF TDCs was solved.
On the other hand, since then the data taking rate is significantly
lower, by about a factor 2. We are presently checking if this is a real
improvement or if we are still missing events.
Genya mentions that based on runs after yesterday 7/1/4 7pm the target
density may have increased compared to running with the 40cm cell between
50-100% (expected were 70-80%), based on (e,e'p) and (e,e'd) analysis.
Eugene generated plots of the trigger type distribution normalized to
charge for runs before shutdown, after shutdown before yesterday,
yesterday night and from this morning. The rates for trigger types 2
(e,e'n) and 7 (singles) are now considerably lower than both before the
shutdown and after it but before yesterday (i.e. before the missing TDCs
were recovered).
The reconstructed tracks per Coulomb with negative charge are about
constant since before the shutdown in the right sector and reduced by 40%
in the left sector. Neutral tracks are reduced by a factor 2 in both
sectors, left sector positive-charge tracks are reduced by a factor 2,
however right-sector positive-charge tracks are increased by 50%.
It looks like the former positron showering in the left sector is greatly
reduced, but is more pronounced now in the right sector.
The deadtime at the top of the fill (130mA) is now down to 15% (~30%
before yesterday).
The observation of missing ADC hits with cut on TDC hits for L15 has been
localized and temporarily fixed. During the shutdown, Karen switched
had all TDC modules from single-readout mode to buffer-readout mode. This
does not cause a problem for any other detectors but for LADS L15. Here,
it was found an event number misalignment (or desynchronization). The
buffered readout would read only the earliest hit if there is more than one.
Seemingly, if any noise fires the TDC then the real event hit would not be
synchronous with the readout of the ADC anymore as was noticed from raw
data dump. TDC of L15 is now set back to single-hit mode. The problem
needs to be addressed during downtime if buffered readout is desired for
future running.
Run plan:
We keep on running polarized Deuterium over the weekend. In case that the
nozzle freezes, we'll switch to unpol. The buffer system is prepared with
Hydrogen. Note that attention should be drawn to V14 which should be
*OPEN*. On Tuesday morning hall will be opened and snakes will be filled.
Have a nice 'independent' weekend,
Michael
--+-------------------------------------+--------------------------+ | 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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