Hello, All:
Tonight I did a series of runs with the basic purpose of just collecting
data and getting a baseline for the chamber gas setup (He:Isobutane
70:30).
I did three runs (without the power supply) with the chambers at 3900V and
with the elastic_tof_wire.settings trigger (any of the front 8 with any of
the back 8). Those runs were:
run number of BUILT events
1963 55000
1964 63000
1965 100000
After analyzing these events, the following was evident:
1. All chambers now have a signal to noise ratio of at least 1.5. The
right sector chambers have higher ratios than the left ones, presumably
due to the thin lead sheet placed between the target and the right sector
chambers.
2. 3900V is nicely efficient for all the chambers. The TDC's look really
nice.
3. A handful of boxes and wires need to be looked at, either because they
are "hot", not efficient, or else don't continuously "fit" the cell hit
distribution pattern formed by the other cells in a layer. I have listed
these wires in the log book as well as printed out a cell distribution
plot labeling them and all the boxes they belong to.
4. Most events that reconstruct to a track reconstruct downstream from
the target by about a meter. The cause of this is presumably the
scattering of low-theta quasielastically scattered electrons off of some
of the beam flanges.
In an effort to try to eliminate (or at least reduce) this downstream
originating, I ran a run (Run 1966) with a modified trigger:
(any of the front 4) and (any of the back 4)
During the run, the (initial) noise trigger rate (i.e. the rate before the
wire target is put in) was around 5Hz (compare this to noise trigger rates
of around 25Hz with the full (any of front 8)and(any of the back 8)
trigger). Additionally, the physics trigger rate was down to. When I
analyzed this run (27000 built events), the following was seen:
1. All six chamber signal to noise ratios dropped slightly but
nonnegligibly.
2. Nearly all events (when viewed on nsed) had lots of noise.
Additionally, there weren't enough tracks for me to say whether or not
more tracks were now orignating from the target (as opposed to
downstream).
Aaron
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