BCM Calibration
1. Paul Stoler did the BCM calibration for the special BCM runs.
Results are here.
2. For runs 46070-46100 BCM1 was at gain 10x and BCM2 was at gain
3x. For runs above run 46100 the gain for BCM1 was changed to 1x.
3. So two sets of calibration are needed for the BARYON
experiment and have been used for the replay. We use the calibration of
run 46203 and 46667.
4. Plot of ratio of charge from BCM2/BCM1.
For the majority of the runs the ratio is within 0.5% of 1. But during
the period between runs 46070-46100 when the BCM1 was gain 10x, the
ratio deviates significantly from 1. There are also runs when the BCM1
gain was 1x that the ratio is around 0.97 .
5. To determine which BCM is wrong when the ratio is far away from 1 ,
compare the BCMs to the Unser during a run. Writeout scalers for the
BCM1,BCM2 and unser for the runs in question. The zero for the Unser is
unstable and can change, but the beam trips can be used to determine
the zero for the Unser. A kumac reads
in the scaler output and first
plots the Unser scaler rate. Then one can select the region when the
beam is off with the cursor. Then kumac takes the average for that
region and that is taken to be the zero for the Unser. Then the kumac
uses that zero and the known calibration constant of 0.00025 to convert
the Unser scaler rate into a current. The BCM scaler rates are
converted into current using the offset and calibration constant
determined by Paul. In the following table shows examples for certain
runs. The plots show the current as a function of time during the run.
The black curve is the Unser. The red curve is the BCM1 current and the
green curve is the BCM2 current. It is clear that BCM1 is the problem
BCM since BCM2 agrees well with the Unser.
| Run |
BCM2/BCM1 |
Plots |
| 46076 |
1.04 |
Current versus time |
| 46117 | 0.98 |
Current versus time |
| 46137 | 0.97 | Current versus time |