Voltages (2650v) for the small band 9423 is ok. Signals are nicely separated from background, thresholds can be easily set.
For the broadband 9422 the voltage is by far too low. Signals and BG are barely separated.
Increased voltage from 1500V to 1750V (according to datasheet Vmax = 2500V, 1500 V is the min voltage for gain 1e6...).
Now signals are better separated - threshold with mesycontrol can be set in such a way that the dark count rate is 300 - 400 Hz (was > 1kHz).
For detector south, the threshold in DAQ1 has to be readjusted.
Below are the settings for Mesytec CFD. Internally the 2nC chips (x 20 ??? ) are used for both groups. Please note that thre are also 20nC chips in "parking position" (lower amplfication).
The Mesytec PMT CFD Version uses "nC" chips while the other Mesytec Shapers "gain / amplification", i.e. chips labeled with 20 are x20 and have a large amplification while the "nC" chips give the full scale range , aka the 20nC is tghe small amplification.
Note as well: Externally, the channel numbering starts with "1" while the Mesycontrol starts with "0".
The sum of all Mesytec signals defines the gate for the ADC.
Group 4-7 are the x100 signals (similar to Vuprom TDC). These signals go to the 25ps TDC and are used for timing, and to the ADC.
Group 0-3 is x10; thresholds are artificially set slightly too high, signals are used in the ADC only. Since these are the same signals as in the x100 group, their (correct) gate signals can be used in the ADC. The x10 capture also the very high signals.
ch 0(1): PMT South x10 (A).
ch 1(2): PMT Mid x10 (B).
ch 2(3): PMT North x10 (C).
ch 4(5): PMT South x100 (B).
ch 5(6): PMT Mid x100 (D).
ch 6(7): PMT North x100 (F). |