New fADC with cosmics
- 50/50 mixed Ar, CO2
- Recalibrated MFCs
- Outer plenum added to CDC prototype to prevent leaks
- New preamp
- New HVB
Below: Cosmics, 2050V, max amplitude histograms, new fADC with unmodified HVB (left), with modified HVB (attenuation x0.5 before the preamp input) (center) and Struck fADCs with modified HVB (right), same straw for each.
Each event contributes one entry to the histogram, if the ADC value goes above a threshold and if the ADC passes the track-finding test. The threshold is the pedestal mean (calculated for 100 events, the first 100 time samples in each event are included) + 5 x its standard deviation. The max amplitude is the first maximum in the ADC value after crossing the threshold, minus the pedestal mean. The pedestal is around 100 for the new fADC, could go down to 50.
If the ADC value passes the threshold, that is a hit channel. 5 or more hits are required for track-finding.
The track-finding test entails fitting the drift time histogram to find tzero (the earliest track arrival time), calculating the drift time, drift radius, finding the track which best fits any 2 hit straws and then the best track for all combinations of pairs, then fitting the drift radii for that one best track. This is described in [Yves's NIM paper] (start at page 9) The test value is true if the straw is included in the best track.
NB different x axis scales, full scale is 4096 for both ADCs.
Below: threshold reduced to mean + 3sigma (left) and mean + 4sigma (right) for new fADC, modified HVB. (We used mean + 10sigma for the first preamp) Black: all hits Blue: tracked hits only (Statistics box is for tracked hits)
Below: Cosmics, 2050V, drift time - untracked, new fADC (left) and Struck fADCs (right), same straw for both.
Below: Cosmics, 2050V, drift radius fit residuals (radius of fitted track - radius interpolated from Garfield drift time calcs)
New fADC with unmodified HVB (left), with modified HVB (center) and Struck fADCs with modified HVB (right), same straw for each.
Below: Cosmics, 2050V, drift radius fit residuals with chosen straw omitted from fit
New fADC with unmodified HVB (left), with modified HVB (center) and Struck fADCs with modified HVB (right), same straw for each.
Below: Fits to drift radius fit residuals