# ReadMe_FieldMap.txt 

The field map given by the text file b0_01jul21_field.txt was created 
via the Opera3D post processor using the following ".cond" files:
b0pf_q01jul21e1.cyw.m34off.cond -  first main 2-layer coil set, quad, b0pf
b0pf_q01jul21e1.cyw.m34off.cond - second main 2-layer coil set, quad, b0pf
b0pf_q01jul21e1.cyw.m34off.cond -  third main 2-layer coil set, quad, b0pf
b0pf_q01jul21e1.cyw.m34off.cond -  main dipole single-layer coil set, b0pf

The main coils are run in series with 1560.7581 A excitation current
and have a common -34. mm horizontal offset.

In order to complete the dipole compensation at the e-beam axis there
is a small diameter corrector dipole coil set:
b0pf_de01jul21d1.cyw.cond      - small diameter e-dipole corrector

The corrector dipole excitation current is -55.49 A and has no x-offset.

Note: The coordinate system is aligned with the e-beam direction with
      x=0, y=0, z=0 the center (horizontal, vertical  and longitudinal)
      of the electron gradient tuning coil, q0ef. See pdf file:
      "722021 - Set Up for Field Map Calculation.pdf" for more information.

The field map ranges from: x= -400 mm to   50 mm in 10 mm steps
                           y= -350 mm to  350 mm in 10 mm steps
                           z=-2000 mm to 2000 mm in 10 mm steps
with the Bx, By and Bz field strengths given in Tesla.

For the present field map, the impact of the electron gradient tuning
quadrupole (coil not present) is not included.

for the 3D coil the view “from the IP” so that +X is on the left and +Y is up with the hadron beam going away from the viewer, 
this follows the right handed coordinate system circulated earlier. 
 
In this corrected coordinate system the field map 3D lattice will run from X=-400 mm to +50 mm in 10 mm steps again 
with the convention that X=0 corresponds to the electron beam center