Ion optics
 Screen grid CAD model | |
| Grids | Screen grid, accelerator grid |
|---|---|
| Simulation software | FEMM 4.2 |
The ion optics of a gridded ion thruster are the perforated grids that extract ions from the discharge plasma and accelerate them into a beam. ION-I’s design goal is a grid set that produces thrust efficiently while resisting erosion from heat and ion impingement.1
Function
The ion optics draw ions out of the Discharge chamber and accelerate them. Two grids are used:
- The screen grid pulls ions from the plasma and pushes them toward the accelerator grid, shaping the beam.
- The accelerator grid sits just downstream. The potential difference between the grids creates the electric field that accelerates the ions, and the grid’s negative bias keeps outside electrons from entering the thruster.1
Components
| Component | Role |
|---|---|
| Screen grid | Extracts ions from the plasma and shapes the beam |
| Accelerator grid | Accelerates and focuses ions using the potential difference |
| Mounting structure | Holds the grids in place |
| Alignment and spacing hardware | Keeps the grids coaxial to tight tolerance, avoiding impingement and erosion |
| Thermal management | Conducts and radiates heat away from the grids |
| Electrical feedthroughs | Carry grid voltages into the vacuum chamber |
Simulation
Grid designs are modeled electrostatically in FEMM 4.2, so that each iteration can be checked before it is machined.1