|E08-010 ~ N-Delta
During HAPPEX, eight scintillators were installed downstream of the target in Hall A. The signals from the PMTs attached to these
scintillators were sent to V-to-F converters in the right HRS, which were then connected to scalers in that arm.|
While it would have been best to calibrate these scintillators by adjusting their HV settings, this was not done. Nonetheless, it may still be possible to obtain a relative calibration of the luminosity (per each scintillator) by examining their output at different current settings.
The initial results are based on the boiling tests taken on March 6th, in which the 4cm LH2 target was subjected to a series of runs at 10, 20, 30 40, 50, 60, 70, and 80 μA. The table below shows the results.
(Note: It was not possible to use the BCM calibration runs for this purpose, as the intense beam and lack of target saturated the detectors.)
Please note that run 2443, set for 50 μA, was not included in this analysis, as it was ended early due to a beam trip. Also, scintillator #4 was not used because, possibly due to a saturation issue, its rate held constant independent of current.
Figure 1 - ROOT macro for this image
Figure 2 - ROOT macro for this image
Figure 3 - ROOT macro for this image
Figure 4 - ROOT macro for this image
Figure 5 - ROOT macro for this image
Figure 6 - ROOT macro for this image
Figure 7 - ROOT macro for this image
As can be seen, each of the luminosity scintillators, except #4, gave wonderfully linear results, with the values shown below.
Also, these results clearly indicate that there was no boiling at high current in the 4 cm target.
With regard to the 15 cm target, no boiling was found in that target either up to 50 µA, though some saturation of the scintillator bars was found, so the linear nature could only be seen with bar 5.