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Study of non-uniformity of magnetic field

Study of non-uniformity of magnetic field. Simulation Real data analysis (CR) Summary and outlook. Simulation of electron drift in E and non-uniformed B field. Drift velocity of electron in E, B field (Langevin equation) First order Runge-Kutta integration was applied.

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Study of non-uniformity of magnetic field

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  1. Study of non-uniformity ofmagnetic field Simulation Real data analysis (CR) Summary and outlook

  2. Simulation of electron drift in E andnon-uniformed B field • Drift velocity of electron in E, B field (Langevin equation) • First order Runge-Kutta integration was applied

  3. Strategy of simulation • Determine T0 in the case of B=0 (vd=5cm/usec). T0 = L0/ vd(B=0), where L0 is a drift length in z-direction between the pad plane and the source point. • Execute Runge-Kutta intergration in non-uniform B • Calculate the drift length Lsim (Lsim = zf-zi) • Calculate the residual in z-direction (ResZ) ResZ = Lsim-L0 <- corresponding to the resZ in the real data?

  4. Result of simulation • tracks of electrons • Source point: center of each pad, zi = 40cm • Pad plane: z = -35.6cm • Deviation is larger at outer pads. Z direction (cm) Radius (cm) Phi-direction (cm)

  5. Electron tracks (Zi =0 cm)

  6. ResZ vs. radius ResZ is decreasing as the radius is increased. In the worst case, the gap is 1.6mm (zi = 40 cm)

  7. Source files • saho:/home/uchida/sim/eDrift/ • Please check the bugs in the program!

  8. Real data (CR) analysis • Run #: 28895, before correction • Cut condition: chi2Pad > 0.02, chi2Z > 0.02, • -0.4 < lambda (dip angle) <0.4

  9. Correction • offset values are added in deriving the z-position. zcorr [ilay] = z0[ilay]+offset[ilay] = vd t + offset[ilay] • offset valued are determined to adjust the mean of the residual-Z into zero in each layer at -1400<z<-1300. • See the source code (saho:/home/uchida/ana/TPC/TPCana0.41/src/anaCluster.c Function: setHit() )

  10. Run # 28895 after correction Mean values are improved (not perfect), the RMS not!

  11. Summary and outlook • Simulation and CR data have the same tendency due to non-uniformity of the magnetic field. • Offset correction would be effective for improvement of the mean value of the resZ, but not for the RMS of the resZ. • We need the detailed investigation for the optimizations of the offset values. Sawada-kun is now under construction of the frame-work. • Z-dependence of resZ will be also studied in his frame-work.

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