- Work in progress - intended more as a logbook than presentation of results*
CDC prototype cosmics data
- 50/50 mixed Ar, CO2
- Recalibrated MFCs
- Outer plenum added to CDC prototype to prevent leaks
- New pre-production HVB
- 2050V
- Modified preamp4 (terminating resistors removed)
- Prototype tilted at 30o to enclosing scintillators (scints trigger the daq)
Fed scintillator signals post-discriminator and coincidence signal through then level converter to ECL, then attenuator, into fADC. Took threshold as half peak value (also tried 1/4 and 3/4 peak but these broadened the timing spectra). Used interpolation algo. (The DAQ is triggered by the coinc signal.) The time offset in the first set is equal to the (uninterpolated threshold crossing bin - 10) x 8 ns.
 Interpolated signals for many events, ADC value vs time, time in ns after an offset |
 Histogram of threshold crossing time |
 Scintillator threshold crossing time |
 Histogram of threshold crossing time - coincidence time for scintillators and 2D plot |
Drift time histogram (for all straws) and expanded about t0
T0 was taken as the x-intercept of a straight line fitted to the leading edge over 10% to 90% of the maximum value. Here this value is 91.3ns.
Drift time vs fitted drift distance using Garfield calculations for 50/50 Ar/CO2 (left) and 49/51 (right).
Resolution (difference between fitted track radius including and excluding that hit from the fit) for ch 20 (straw close to center of prototype)
Resolution for various time increment (offset) dt added to fitted t0, ie t0 = 91.3 + dt, ignoring events before t0
Optimum is offset dt=11ns for 49/51 (14ns for 50/50 has slightly worse resolution)
Check how the mean varies with drift dist around optimum dt
 50/50 Ar/CO2 gas mix z-min=159 |
 49/51 Ar/CO2 gas mix z-min=151 |
 48/52 Ar/CO2 gas mix z-min=158 |
 50/50 Ar/CO2 gas mix Resolution for fitted track radius > 1mm z-min=149 |
 49/51 Ar/CO2 gas mix Resolution for fitted track radius > 1mm z-min=140 |
 48/52 Ar/CO2 gas mix Resolution for fitted track radius > 1mm z-min=147 |
 50/50 Ar/CO2 gas mix Resolution for fitted track radius > 2mm z-min=134 |
 49/51 Ar/CO2 gas mix Resolution for fitted track radius > 2mm z-min=126 |
 48/52 Ar/CO2 gas mix Resolution for fitted track radius > 2mm z-min=133 |
Use dt=14ns for 50/50 mix, 11ns for 49/51 mix
 50/50 Ar/CO2 gas mix Resolution dt=14ns |
 49/51 Ar/CO2 gas mix Resolution dt=11ns |
 50/50 Ar/CO2 gas mix Resolution vs drift time dt=14ns |
 49/51 Ar/CO2 gas mix Resolution vs drift time dt=11ns |
 50/50 Ar/CO2 gas mix Resolution vs fitted drift distance dt=14ns |
 49/51 Ar/CO2 gas mix Resolution vs fitted drift distance dt=11ns |
Re-assign events with time < t0 to a range of early times >= t0
 50/50 Ar/CO2 gas mix Resolution, early events reassigned to fixed drift time (y-axis) |
 49/51 Ar/CO2 gas mix Resolution, early events reassigned to fixed drift time (y-axis) |
 50/50 Ar/CO2 gas mix Resolution for fitted track radius > 1mm, early events reassigned to fixed drift time (y-axis) |
 49/51 Ar/CO2 gas mix Resolution for fitted track radius > 1mm, early events reassigned to fixed drift time (y-axis) |
 50/50 Ar/CO2 gas mix Resolution for fitted track radius > 2mm, early events reassigned to fixed drift time (y-axis) |
 49/51 Ar/CO2 gas mix Resolution for fitted track radius > 2mm, early events reassigned to fixed drift time (y-axis) |
Assign early events to t0+1ns
 50/50 Ar/CO2 gas mix Resolution dt=14ns |
 49/51 Ar/CO2 gas mix Resolution dt=11ns |
 50/50 Ar/CO2 gas mix Resolution vs drift time dt=14ns |
 49/51 Ar/CO2 gas mix Resolution vs drift time dt=11ns |
 50/50 Ar/CO2 gas mix Resolution vs fitted drift distance dt=14ns |
 49/51 Ar/CO2 gas mix Resolution vs fitted drift distance dt=11ns |
Resolution with drift distance for 49/51 mix, dt=11ns, early events assigned to t0 + 1ns
 50/50 Ar/CO2 gas mix Resolution vs fitted drift distance dt=11ns |
 50/50 Ar/CO2 gas mix Resolution vs fitted drift distance dt=11ns |
 50/50 Ar/CO2 gas mix Resolution vs fitted drift distance dt=11ns |
