The purpose of the test was to check the performance of the new ADDON module on the real cosmics signals from the TOF photomultipliers.
The ADDON is a 128channel leading edge discriminator LED providing the time signal and the "time above threshold" signal TOT (giving info on the pulse height).
The output of the module is then sent to the TRB board (128 ch. TDC), and the connected to HADES daq system.
The main idea of the test was to split the timing signal from the PMT and sent it both to a standard TOF chain (CAEN CFD+TDC)
and to the ADDON. Then the measured times and "pulse heights" are compared. The main result is the electronics resolution CFD+TDC vs ADDON LED+TRB.
The performance of the ADDON leading edge discriminator is good. At the threshold level of 30mV there is no crosstalk. The dependence of time on the pulse
height (time walk) is smooth, so this can be corrected.
With cosmics we get the same time resolution CFD+TDC vs ADDON LED+TRB as with the pulse generator about 140 ps.
Note that the same signal put into 2 LED channels gives a narrow peak (within 1 TRB channel == 100 ps), the same is valid for 2 CFD channels.
- 26 Nov 2008