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Published bySharyl Horn Modified over 8 years ago
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Gain Curves Continued Peter Litchfield Phone Meeting 29 th September 2005 Previously: Some LEDs gave ~linear PMT v PIN ADC curves Some didn’t Same PMT is linear with low gain PIN and non-linear with high gain and vice versa. PIN problem How prevalent is it? High gain PIN PMT ADC Residual PIN ADC
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Procedure Fit Gain curve with a straight line passing through (0,0) between 0 and 8000 PMT ADCs Corrected for zeros Avoids most of the saturation non-linearities Require at least 5 points in this range (significant number of near strip ends fail) Calculate the 2 divided by number of data points for the straight line fit. Plot for all the strip ends (~600) fed by each led Calculate mean 2 /NDP for each LED
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PB2 LED 20 2 /#data points of linear fit High PIN Near PMT Mean=4.2 High PIN Far PMT Mean=2.4 Low PIN Near PMT Mean=2.3 Low PIN Far PMT Mean=2.0 NOTE DIFFERENT HORIZONTAL SCALES Linear fit OK Near PMT a little worse than far, saturation effects?
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PB2 LED 9 High PIN Near PMT Mean=2.2 High PIN Far PMT Mean=1.5 Low PIN Near PMT Mean=57.3 Low PIN Far PMT Mean=70.1 NOTE DIFFERENT HORIZONTAL SCALES High gain PIN OK Low gain PIN otherwise
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PB2 LED 8 High PIN Near PMT Mean=110.9 High PIN Far PMT Mean=147.4 Low PIN Near PMT Mean=3.5 Low PIN Far PMT Mean=2.6 NOTE DIFFERENT HORIZONTAL SCALES Low gain PIN OK High gain PIN otherwise
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Mean 2 per LED PB1 High near High far Low near Low far NOTE DIFFERENT VERTICAL SCALES
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Mean 2 per LED PB2 <50% of LEDs OK The ones that aren’t seem pretty random I can supply the other PBs Maybe somebody who knows the hardware can see a pattern? LED 2 is missing High near High far Low near Low far
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Mean 2 per LED (low values) PB1PB2 High gain Low gain near far near far
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Conclusions and To Do ? I will do far v near pmt. Far PMT 2 always better than near PMT. Could be OK for linearising the near PMT if we assume the far PMT is linear. At least to the level required. Not how it was designed to work.
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