Qweak scintillator prototype building and cosmic test results (1)

1. Build a prototype of the Qweak scintillator (205 x 23 x 1 cm, excluding the light guide), using triangular light guides (23 x 23 cm) and 3" PMTs. The SCIN prototype and the electronic are set up in room 126 of EEL building at JLab, using a data acquisition system (DAQ) similarly to the current Hall C DAQ. Draft of the prototype design (not a picture) is shown below.




2. Run several cosmic runs to check the SCIN prototype, as well as the time and position resolutions. Two 6"x6" trigger paddles (each attached with a 2' PMT) are used in the cosmic test, one on top of the SCIN, and the other below the SCIN. The cosmic data were taken at different z positions along the SCIN (z=15, 45, 75, 115, 150, 180 cm; y=11.5 cm, at the center.) by moving the trigger paddles along z direction of SCIN.

When analyzed the cosmic data, a "good event" is defined by requiring both the trigger paddles are fired (raw TDC value > 0), the SCIN TDC value > 0, and time_L + time_R (the sum of time for photon to travel to L and R SCIN PMT) is within some reasonable range.

1) ADC histograms of one cosmic run (z=115 cm)



2) TDC histograms of one cosmic run (z=115 cm)



3) ADC raw value of L and R SCIN PMT as a function of z positions .
According to the fitting of the data, we got

6.528*R_ADC + 12.04*L_ADC = 38974.6



4) TDC raw value of L and R SCIN PMT as a function of z positions .
According to the fitting of the data, we got

Distance to L_PMT = (L_TDC - R_TDC)/2.726 + 110.1 (cm)



5) Comparison of cosmic runs to guideit simulations



6) Comparison of cosmic data taken at Y=11.5 cm (center) and Y= 4 cm, at Z=13, 115, and 192 cm.

a. ADC histograms at Y = 4 cm.



. b. ADC histograms at Y = 11.5 cm (center).



. c. Comparison of cosmic runs to guideit sim at Y = 4 cm.



. d. Comparison of cosmic runs to guideit sim at Y = 11.5 cm (center).



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