# ITSIM Simulations

### 1. Equation for Inner and Outer electrodes

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

where

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