CDC transfer func attempt
Circuit
 Charge injection circuit from Fernando's GlueX-doc-1364 |
Actual component values used were... 51.1 Ohms, 908 Ohms and 2pF.
The aim is to inject a charge impulse into the electronics chain and measure its response.
Early results
Final results
Borrowed Phillips 5771 (no attenuators needed)
Fitted function
Beware typos in filenames, this was run #31941!
Input charge: 2 pF x 103 mV = 206 fC
Input current: divide by 12ns peaking time of preamp: 206 fC / 12 ns = 17.2 uA
Peak value of output data is 635 adc_units ~ 635 * 495 mV / 4096 = 76.7 mV
Electronics gain is 76.7 mV / 206 fC = 0.37 mV/fC
(Gain of preamp alone measured earlier (before modifications) by FJB as 0.57 mV/fC)
Convert to current using 50 Ohm resistance: 76.7 mV / 50 Ohm = 1.53 mA
Current gain is 1.53 mA / 17.2 uA = 89.0
Integrated value of output data is 19.03 adc_units.us ~ 19.03 * 495 mV / 4096 = 2.30 mV.us
Convert to charge using 50 Ohm resistance: 2.3 mV.us / 50 Ohm = 0.046 mA.us = 0.046 nC = 46 pC
Charge gain is 46 pC / 206 fC = 223
To convert histograms of summed ADC data (with 8ns sample time) to charge, multiply by 8 ns * 46 pC / 19.03 us = 19.3 fC
Garfield uses uA for signals, but I want to see the resulting histograms in adc units, for direct comparison with cosmics data. So... I need to convert my impulse response to input of 1 uA, ie use (1 / 17.2) * fitted function above as the transfer function.?? (Fitted function already includes current gain x 89).
The remaining gain factor needed to match garfield adc data to real life data is the gas gain.
