Hi,
In order to verify that the two magnets close to the target bend
low momentum particles into the chamber and create tracks
from downstream, we have asked CCR to turn off these two magnets.
After long tuning, they gave us the beam with 20 min. lifetime.
We set the wire target at 3.2 mm which reduced beam life time ~5 min.
and increased event rate ~10 Hz. We still see majority of tracks from
downstream
as shown in the attached picture. Looking at TDC distribution, we
have signal to background ratio better than 3:1 for all chambers. Putting
lead shield in the left sector really improved this ratio. One box
from each sector (L21 and R24) is still tripping. There are still a few of
wires quiet or counting too fast. We need to fix them!
In general, space-charge effect is not seen in either chamber, events
are very clean, and we can reconstruct many tracks. However, we still
see tracks coming from downstream.
-T
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