ITSIM Simulations

1. Equation for Inner and Outer electrodes

Makarov, Anal. Chem., 2000, 72, 1156

   subscripts 1 and 2 mean inner and outer electrodes, respectively   
   R1 = 4 mm = max. radius for inner electrode
   R2 = 10 mm = max. radius for outer electrode
   Rm = characteristic radius; radial trapping for r < Rm


2. Generate 2D solution using AutoCAD (Autodesk)

  • rotational symmetry: 2D solution in r-z plane (r > 0)
  • electrodes truncated at z = ±11 mm (exact position proprietary, unknown to us)
  • outer electrode split at equator (z = 0 plane)
  • ion injection slot not modeled in this study 

G. Wu, R. J. Noll, W. R. Plass, Q. Hu, R. H. Perry, R. G. Cooks, Int. J. Mass Spectrom., 254, 1-2, 2006, 53-62.


3. Solve for Electric Field in COMSOL


4. Validate against analytical solution

The Electric field was solved a second time for an electrode geometry without truncations or a gap in the outer electrode, for the purpose of validating against the analytical solution (above).

For this numerical field, field values along the section Er(z = 0) deviated from the analytical solution by no more than 0.5%. Along the section Ez(r= 7 mm), field values deviated by no more than 0.2%.


5. Import into ITSIM

  • Convert to field array file
  • Sample along rectangular r,z grid
  • 106 points
  • Import into ITSIM 6.0, using 
  • home-written program CreatPot