Glossary
Abbreviations and technical terms used in this wiki.
Electric propulsion and plasma
| Term | Meaning |
|---|
| Accel grid | The downstream grid of the Ion optics; accelerates ions and blocks back-streaming electrons |
| Ar* | Metastable argon; see stepwise ionization |
| Discharge chamber | Where propellant is ionized; see Discharge chamber |
| EEDF | Electron energy distribution function: how electron energies are spread in a plasma |
| EP | Electric propulsion |
| Faraday cup | A metal cup that collects charged particles so their current can be measured |
| Field emission | Electron emission caused by a strong electric field at a metal surface, through quantum tunneling |
| Fowler–Nordheim, Murphy–Good | Equations that predict field-emission current from the field strength and the metal’s work function |
| Hollow cathode | An electron source for EP thrusters; ION-I’s is IonSpark |
| Langmuir probe | An electrode inserted into a plasma to measure its density and temperature |
| Metastable | An excited atomic state that cannot easily decay by emitting light, so it lasts a long time |
| Neutralizer | A cathode that emits electrons into the ion beam so the spacecraft does not charge up |
| Screen grid | The upstream grid of the ion optics; extracts ions and shapes the beam |
| Work function | The minimum energy needed to remove an electron from a metal surface |
Simulation and software
| Term | Meaning |
|---|
| 0D model | A model that tracks quantities over time but not in space, using rate equations |
| CAD | Computer-aided design |
| FEA | Finite element analysis: solving physics problems over a geometry broken into a mesh |
| FEMM | Finite Element Method Magnetics, free software for 2D electrostatic and magnetic problems |
| Mesh | The small elements a geometry is divided into for simulation |
| PIC | Particle-in-cell: simulating a plasma as many particles moving through fields solved on a grid |
| PIC-MCC | Particle-in-cell with Monte Carlo collisions |
Units
| Unit | Meaning |
|---|
| eV | Electronvolt, the energy an electron gains through a 1 V potential difference (about 1.6 × 10−19 J) |
| sccm | Standard cubic centimeters per minute, a gas flow rate |
| Torr | Unit of pressure; atmospheric pressure is 760 Torr |