Diagnostics & Measurement
Interferometry
Measuring plasma density from how much it delays a probing beam.
A plasma slows electromagnetic waves in proportion to its density. By interfering a beam that has passed through the plasma with a reference beam, interferometry measures the line-integrated density continuously — a workhorse density diagnostic.
Common questions
What does interferometry measure?
The phase shift of a beam crossing the plasma gives the line-integrated electron density — a fast, robust density measurement used for control and fuelling.
How does it relate to density limits?
It monitors how close the breeder runs to the Greenwald density limit, informing fuelling and disruption avoidance.