Fig. 3(Color online) These (a)–(d) waveforms were generated using a KFADC 500 MHz USB module with a 2-inch PMT H7194 and standard 370 kBq
137Cs and
252Cf radioisotope (RI) sources. These (e)–(f) waveforms represent the first derivatives (or convolutions with a Sobel kernel) of the waveforms illustrated in figure (a)–(d). The mounting of the radioisotope was constructed in such a way that it was attached to the top of a 100 ml container containing Sample A (Ref. LAB) and Sample B (EJ309), as illustrated in
. The supply voltage of the PMT was set at 1750 V, and the data acquisition (DAQ) settings were configured to align with the recommended settings for liquid scintillators. Given that the voltage gain ratio of DAQ system is 10, the leading edge discrimination trigger threshold (thr) of the DAQ is, in fact, 20 mV.
