BCM Calibration
On the injector side, there are the Faraday Cup (FC) and the OLO2 cavity. The Faraday Cup is a destructive measurement, so no beam may be sent to the hall during its measurements, but as the OLO2 location is upstream from the cup, measurements of the FC and the OLO2 can be done simultaneously to calibrate the two relative to each other.
In the Hall, there are the BCM cavities (upstream and downstream) and the Unser coil. Typically the BCM cavities, which measure voltage differences, are calibrated against the OLO2 cavity measurements, and the Unser is calibrated relative to the BCM cavities.
A BCM calibration was done on March 3rd, 2011, during the N-Delta experiment. It consisted of four MCC runs, 170 to 173, and three corresponding CODA runs, 2252 to 2254. The table below shows the relationships between the different set of runs.
| MCC | # Events | CODA | # Events | Notes |
| 170 | 642 | 2252 | 20420 | Calibration of Faraday Cup and OLO2 cavity; no beam to Hall |
| 171 | 1898 | ---- | ------ | No corresponding CODA run; no beam to Hall |
| 172 | 953 | 2253 | 16155 | Ended early due to beam trips; not used for this analysis |
| 173 | 2036 | 2254 | 35887 | Beam trip during 5 uA segment |
BCM LOG 170
For this calibration run, the faraday cup and the OLO2 cavity were both used, which meant there was no beam into the Hall, and the BCM cavities recorded no voltage.
As can be see, the faraday cup is in the whole time, with the OLO2 kicking in after about 70 counts. The current started at approximately 80 µA, then stepped down to 50, 20, 10, 5, 2, 1, 0.5, and 0.2 µA. From this graph, points were selected near the middle of each step and used to populate the graph below.
Specifically, the points used were count numbers 100, 160, 220, 280, 340, 400, 460, 520, and 580.
The linear fit produced the following equation:
I(FC) = [0.9988427 ± 0.01233123] * I(OLO2) + [-0.02105594 ± 0.4081156] µA
BCM LOG 171
Like 170, this calibration run used both the Faraday Cup and the OLO2 cavity. Additionally, the Faraday Cup was removed at times to allow recording of the BCM cavities.
Again the Faraday Cup was inserted and the OLO2 cavity's current read, though this time the Faraday Cup is removed (when the red drops to zero) so the BCM cavities in the Hall could be read as well. Also like the previous run, the current started at 80 µA and was dropped incrementally to 0.2 µA.
The points used for this plot were count numbers 150, 375, 500, 700, 875, 1050, 1250, 1400, 1600.
The linear fit produced the following equation:
I(FC) = [0.9781932 ± 0.01235834] * I(OLO2) + [0.02467829 ± 0.4079592] µA
Since the Faraday Cup was removed during parts of this run, data was taken from the BCM cavities in the Hall. As you can see, when the Faraday Cup is removed, the BCM voltages appear, with the upstream BCM cavity voltage in green and the downstream BCM cavity in yellow.
Much like in Figure 4, nine points from Figure 5 to populate this graph and the next: 250, 425, 600, 800, 975, 1150, 1325, 1500, and 1675.
These points give the following equation relating the voltage of the upstream BCM cavity and the OLO2 current:
I(OLO2) = [99.09772 ± 1.230532] * V(BCM1) + [-0.06890053 ± 0.4086554] µA
Using the same five points as in Figure 6a, for the downstream BCM cavity we get
I(OLO2) = [82.90815 ± 1.029475] * V(BCM2) + [-0.05804659 ± 0.4085742] µA
BCM LOG 173
Unlike the other runs, no data was taken for the Faraday Cup during run 173.
Even though there was no data for the Faraday Cup, it was almost certainly inserted as there are times when the BCM cavities are not collecting data.
As before, nine points were picked from Figure 8: 225, 400, 575, 750, 1175, 1350, 1525, 1700, and 1900.
These points give the following equation relating the voltage of the upstream BCM cavity and the OLO2 current:
I(OLO2) = [98.14531 ± 1.233147] * V(BCM1) + [0.01156503 ± 0.4089817] µA
Using the same five points as in Figure 8a, for the downstream BCM cavity we get
I(OLO2) = [82.03567 ± 1.030736] * V(BCM2) + [-0.004459749 ± 0.4090982] µA
CODA RUN 2254
Here we have a plot showing the the OLO2 current and the x1 BCM scaler rates. Because the EPICS data and the scalers are not synchronous, points had to be arbitrarily chosen to represent each of the different currents to create plots showing the relationships between the different BCM scaler rates and the OLO2 current.
The points for the OLO2 current are the same points as used in BcmLog_173 above. The points for all the scaler rates were indices 46, 91, 136, 180, 284, 329, 374, 419, and 463. The points for the OLO2 current and the points for the scaler rates were then compiled into graphs and their results are shown below.
I(OLO2) = [4.814090e-04 ± 6.048646e-06] * (L_BCM_U1) + [-2.111357e-01 ± 4.106089e-01] µA
I(OLO2) = [1.552099e-04 ± 1.950167e-06] * (L_BCM_U3) + [5.004270e-02 ± 4.087040e-01]
I(OLO2) = [5.340630e-05 ± 7.013163e-07] * (L_BCM_U10) + [2.135478e+00 ± 3.992659e-01] µA
In this graph, we see a problem with the largest two current values. As the x10 BCM chamber shouldn't be used above 30 µA, we should be okay if we simply remove these two points, producing the nicer graph below.
I(OLO2) = [5.163151e-05 ± 2.841630e-06] * (L_BCM_U10) + [2.061602e-03 ± 4.890946e-01] µA
I(OLO2) = [8.032944e-04 ± 1.009296e-05] * (L_BCM_D1) + [-3.482333e-02 ± 4.093192e-01] µA
I(OLO2) = [1.298518e-04 ± 1.631518e-06] * (L_BCM_D3) + [6.387552e-03 ± 4.090189e-01] µA
I(OLO2) = [8.276541e-05 ± 1.077140e-06] * (L_BCM_D10) + [-3.993832e+00 ± 4.468406e-01] µA
The same thing as happened with L_BCM_U10 happens here, and the same solution applies, as seen below.
I(OLO2) = [4.127585e-05 ± 2.271687e-06] * (L_BCM_D10) + [6.114162e-03 ± 4.889530e-01] µA
I(OLO2) = [9.657131e-04 ± 1.213367e-05] * (R_BCM_U1) + [-2.307084e-01 ± 4.107525e-01] µA
I(OLO2) = [3.139227e-04 ± 3.944269e-06] * (R_BCM_U3) + [-2.867822e-02 ± 4.092744e-01] µA
I(OLO2) = [1.031439e-04 ± 1.295949e-06] * (R_BCM_U10) + [2.566138e-03 ± 4.090469e-01] µA
I(OLO2) = [8.053690e-04 ± 1.011903e-05] * (R_BCM_D1) + [-5.153536e-02 ± 4.094412e-01] µA
I(OLO2) = [2.603440e-04 ± 3.271083e-06] * (R_BCM_D3) + [-9.679963e-03 ± 4.091360e-01] µA
I(OLO2) = [8.624819e-05 ± 1.084261e-06] * (R_BCM_D10) + [-3.233104e-01 ± 4.115117e-01] µA
Summary
| Faraday Cup Current vs OLO2 Current | |||||
| Run | Coefficient | Constant (µA) | |||
| 170 | 0.9988427 ± 0.01233123 | -0.02105594 ± 0.4081156 | |||
| 171 | 0.9781932 ± 0.01235834 | 0.02467829 ± 0.4079592 | |||
| OLO2 Current vs BCM1 Voltage | |||||
| Run | Coefficient (µA/V) | Constant (µA) | |||
| 171 | 99.09772 ± 1.230532 | -0.06890053 ± 0.4086554 | |||
| 173 | 98.14531 ± 1.233147 | 0.01156503 ± 0.4089817 | |||
| OLO2 Current vs BCM2 Voltage | |||||
| Run | Coefficient (µA/V) | Constant (µA) | |||
| 171 | 82.90815 ± 1.029475 | -0.05804659 ± 0.4085742 | |||
| 173 | 82.03567 ± 1.030736 | -0.004459749 ± 0.4090982 | |||
| OLO2 Current vs BCM Rate (2254) | |||||
| Scaler | Coefficient (µA/Hz) | Constant (µA) | |||
| Left U1 | 4.814090e-04 ± 6.048646e-06 | -2.111357e-01 ± 4.106089e-01 | |||
| Left U3 | 1.552099e-04 ± 1.950167e-06 | 5.004270e-02 ± 4.087040e-01 | |||
| Left U10 | 5.163151e-05 ± 2.841630e-06 | 2.061602e-03 ± 4.890946e-01 | |||
| Left D1 | 8.032944e-04 ± 1.009296e-05 | -3.482333e-02 ± 4.093192e-01 | |||
| Left D3 | 1.298518e-04 ± 1.631518e-06 | 6.387552e-03 ± 4.090189e-01 | |||
| Left D10 | 4.127585e-05 ± 2.271687e-06 | 6.114162e-03 ± 4.889530e-01 | |||
| Right U1 | 9.657131e-04 ± 1.213367e-05 | -2.307084e-01 ± 4.107525e-01 | |||
| Right U3 | 3.139227e-04 ± 3.944269e-06 | -2.867822e-02 ± 4.092744e-01 | |||
| Right U10 | 1.031439e-04 ± 1.295949e-06 | 2.566138e-03 ± 4.090469e-01 | |||
| Right D1 | 8.053690e-04 ± 1.011903e-05 | -5.153536e-02 ± 4.094412e-01 | |||
| Right D3 | 2.603440e-04 ± 3.271083e-06 | -9.679963e-03 ± 4.091360e-01 | |||
| Right D10 | 8.624819e-05 ± 1.084261e-06 | -3.233104e-01 ± 4.115117e-01 | |||