Hi, Matt.

See here:

https://confluence.slac.stanford.edu/display/ilc/How+do+I+change+the+delta+of+intersection+with+the+chord+for+the+field+stepper

https://confluence.slac.stanford.edu/display/ilc/How+do+I+change+the+delta+of+one+step+for+the+field+stepper

This sets geometric tolerance:

/field/setDeltaIntersection 1 mm

This sets the maximum distance between the segments and the chord:

/field/setDeltaOneStep 1 mm

The idea is that you should set these to well below the cell size of the mag field grid, or you can look at it as setting these to values that are lower than the acceptable errors for the experiment.  The settings given are just examples.  Likely you will want to set these to around 10 micron.

You may also want to read the following for background:

http://geant4.web.cern.ch/geant4/UserDocumentation/UsersGuides/ForApplicationDeveloper/html/ch04s03.html

It gives all the details on what these settings actually mean.  Our “deltaOneStep” corresponds to the miss distance.  And the the “deltaIntersection” is the geometric tolerance.

--Jeremy