Hi,
We couldn't send E-mail last night because we had no
ethernet connection to the outside world last night.
We got beam, 50 mA around 11:00 P.M. last night.
We took data with no gas in the targe and magnet on. None of
the drift chamber sense wire was drawing more than 0.5 microA,
which indicates very quiet and probably no space charge effect.
TDC distribution shows that good signal to back ground ratio
for left sector, but somewhat worse ratio for the right sector.
Actually, there are two boxes in the right sector counts
continously, suggesting something wrong with the boxes (probably
broken preamp cards). There are two boxes, one from each sector,
still (H.V.) trip. They must be repaired. Looking data on nsed, we see
a good number of curved tracks originating closer to the target.
Strangely, this run seems to have far less number of tracks originated
from downstream. It seems that the downstream tracks are caused by thick
gas target or wire target. I have asked the next shift takers to take
data with gas flow at 0.1, 0.2...0.5 sccm. Isn't 0.1 sccm still ~10 times more
flow than real target? We might decrease the gas flow even lower.
Anyways, with no gas in the target, drift chamber seems to work without the
front shield. Oh, we probably have to keep the magnet on.
Cheers,
Tong
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