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Thomson Scattering

Description: A method of measuring the temperature and density of a plasma via the interaction between electro-magnetic radiation and matter

Recommended Product: Quantel YG980

Thomson scattering is a laser measurement technique that relies on the interaction between electro-magnetic radiation and matter.

It is a useful remote measurement method for determining the temperature and density of, for example, a plasma where due to the high temperatures and other restrictions, direct measurement techniques cannot be used.

By using a laser to illuminate a plasma, the E-vector of the incident laser beam causes the electrons in the plasma to move and oscillate at the same frequency as the laser.

The oscilliating electron is then a dipole radiation source with its radiation being emitted in a donut shape.

By measuring the emitted radiation, one can plot a graph of intensity versus wavelength, where the full width half maximum is proportional to temperature and the area under the curve is proportional to the density.

We recently supplied a custom-built Nd:YAG laser to JET for their High Resolution Thomson Scattering project. The specification of this laser was as follows:

Wavelength

Energy

Pulse duration

Repetition rate

Polarisation ratio

1064nm

5J

~15ns

20Hz

>98%