CDC peak lengths

To find the peak (signal) length I have to decide where the peak ends and noise takes over.

Histogram of difference between adc sample value and previous sample value for first 190 samples in many events (trigger is approx sample 200 so samples 0-190 should be almost all noise).

Change in adc value since previous sample, pre-trigger samples

Ch 20 (straw 17)

Ch 26 (straw 23)

Pedestal s.d is 11 (adc value) for these straws in this run. For other straws s.d. ranges from 9 to 13.

Change in adc value since previous sample, last 100 samples

Ch 20 (straw 17)

Ch 26 (straw 23)

Change in adc value since previous sample, last 50 samples

Ch 20 (straw 17)

Ch 26 (straw 23)

Peak length in ch20, counting from lower threshold crossing to end of peak

peak ends at last sample which decreases by 10 or more

peak ends at last sample which decreases by 12 or more

peak ends at last sample which decreases by 15 or more

peak ends at last sample which decreases by 20 or more

Peak length would be too long if the required decrease is too small and is caused by noise near the end of the signal window. Peak length=0 if it cannot be found (each decrease in adc value is smaller). These correspond to small signals (<200 adc value when requiring a decrease >15.) Required decrease>15 gives a good balance.

Max drift time (according to Garfield) is 660ns, 83 sample periods. Min peak length seems to be 5 samples so a max signal length of 88 samples is reasonable.

Peak length (ending at last sample decreasing >15)

Peak length vs max amplitude Ch 20 (straw 17)

Peak length vs drift time Ch 20 (straw 17)