Qweak scintillator prototype cosmic test (8)

A. Checked the TDC and ADC response along the short axis (y=4, 11.5, 19 cm) at Z=10, 195 cm respectively for the prototype with triangular lightguide. Found NO obvious blind spots along the short axis of the SCIN bar.

1. Photoelectron number at Y=4, 11.5, 19 cm for Z=10 cm (close to L PMT).





2. Photoelectron number at Y=4, 11.5, 19 cm for Z=195 cm (close to R PMT).





3. TDC response at Y=4, 11.5, 19 cm for Z=10 cm (close to L PMT).





4. TDC response at Y=4, 11.5, 19 cm for Z=195 cm (close to R PMT).





B. Changed the scintillator prototype set-up, replacing the triangular lightguides with finger lightguides. Checked and found no obvious light leak for the new set-up. Based on the preliminary analysis (checking the L/R PMT signal with scope, and the analysis of a few cosmic runs), the finger lightguide has less light attenuation than the triangular lightguide. We can get the ADC signal of same amplitude with lower L/R PMT HV (reduced from 2250V for the triangular lightguide to 2040V for the finger lightguide). Right now, cosmic data is taken to estimate the number of photoelectron at the L and R PMTs, and check the TDC and ADC response along the long (z) axis and the short (y) axis. We plan to finish this cosmic test in two weeks.