RadPhi TechNote
radphi-2000-901
October 16, 2000
Analysing the analog signal (adc) from the BSD detector it is observed that the position of the maximum of the adc distributions varies with the counter number. This is corrected by finding the relative gain constants that make integrated adc spectra equal to one chosen reference counter. In addition, it is seen that average gain depends on pixel position. It decreases exponentially as pixel index increases, independent of the trigger type. Comparing standard and minimum-bias data it is concluded that the observed gain dependence comes from the attenuation of light along the BSD paddle. The gain dependence on pixel index is best described by a superposition of one falling exponential and one increasing linear function. Fit to the pixel gain distributions yields coefficients that can be used to correct for attenuation losses. These coefficients have similar values for different BSD counters.