CDC B field
From GlueXWiki
CDC volume occupies z=17 to 167 and r=10 to 60
At large drift radius, change in B field of 0.1T causes change in drift time of ~ 5ns. This would cause approx 30um error in drift radius. Resolution in 0T is 80um-100um at large drift radius.
Plan:
- measure drift time, r, z
- find B field at r, z
- use time-diff function(B) to calculate what drift time would be in 1.3T
- use garfield tables for 1.3T to find drift distance
Mostly backward angle z (16 to 86cm) pol3 fit parameters radius (cm) [0] [1] z [2] z^2 [3] z^3 10 1.049e+00 1.597e-02 -1.419e-04 5.523e-07 20 1.062e+00 1.660e-02 -1.616e-04 6.818e-07 30 1.084e+00 1.771e-02 -1.979e-04 9.257e-07 35 1.100e+00 1.851e-02 -2.252e-04 1.112e-06 40 1.119e+00 1.951e-02 -2.596e-04 1.352e-06 45 1.142e+00 2.077e-02 -3.040e-04 1.664e-06 50 1.169e+00 2.238e-02 -3.613e-04 2.072e-06 53 1.200e+00 2.448e-02 -4.361e-04 2.607e-06 57 1.217e+00 2.572e-02 -4.800e-04 2.922e-06 Mostly forward angle z (84 to 168cm) pol3 fit parameters radius (cm) [0] [1] z [2] z^2 [3] z^3 10 1.200e+00 8.748e-03 -3.533e-05 5.208e-08 20 1.184e+00 9.145e-03 -3.786e-05 5.646e-08 30 1.126e+00 1.056e-02 -4.785e-05 7.824e-08 35 1.059e+00 1.216e-02 -5.957e-05 1.055e-07 40 9.507e-01 1.477e-02 -7.907e-05 1.524e-07 45 7.758e-01 1.898e-02 -1.111e-04 2.311e-07 50 4.998e-01 2.567e-02 -1.627e-04 3.600e-07 53 7.226e-02 3.611e-02 -2.441e-04 5.662e-07 57 -2.104e-01 4.304e-02 -2.987e-04 7.055e-07
Fits to fit parameters above as function of r
Max error between fitted function and time difference is 5.5ns at radius 7.6mm in 1.5T dataset
Repeated the above with more datasets
Max error using one fit f(B,driftradius) for all curves is 2.4ns at 7.6mm for 1.7T
Param 0 fit status 0 function 10.72 + -19.17x + 10.68x^2 + -1.74x^3 Param 1 fit status 0 function 9.88 + -8.22x + 2.06x^2 1.35T Global fit av abs err 0.4ns max abs err -1.2ns at radius 5.8mm 1.40T Global fit av abs err 0.2ns max abs err -0.5ns at radius 4.5mm 1.45T Global fit av abs err 0.3ns max abs err 2.0ns at radius 7.6mm 1.50T Global fit av abs err 0.3ns max abs err 0.6ns at radius 2.4mm 1.55T Global fit av abs err 0.4ns max abs err -1.1ns at radius 6.4mm 1.60T Global fit av abs err 0.3ns max abs err 1.1ns at radius 7.6mm 1.65T Global fit av abs err 0.4ns max abs err 1.2ns at radius 7.0mm 1.70T Global fit av abs err 0.4ns max abs err 2.4ns at radius 7.6mm 1.75T Global fit av abs err 0.5ns max abs err -1.1ns at radius 6.1mm 1.80T Global fit av abs err 0.3ns max abs err 1.4ns at radius 7.6mm 1.85T Global fit av abs err 0.6ns max abs err -1.4ns at radius 6.2mm 1.90T Global fit av abs err 0.3ns max abs err 1.2ns at radius 7.6mm