TJ-II:Reflectometry

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Profile Reflectometer

TJ-II has an AM reflectometer [1] for measuring electron density profiles with a temporal resolution of 2 ms (located between sectors A4 and A5).

Fluctuation Reflectometer

A fast frequency hopping reflectometer [2] working in the Q-band (33 - 50 GHz) was used from 2004 - 2008 in perpendicular incidence (conventional reflectometry) [3] .

Doppler Reflectometer

Schematic drawing of the Doppler Reflectometer System of TJ-II.

Since February 2009, the frequency hopping system is in operation in oblique incidence (Doppler reflectometry, sector C6) [4], measuring plasma density fluctuation velocities and their wave number spectra. The system is able to measure in a radial range of about ρ = 0.6 - 0.9 (ρ = r/a is the effective plasma radius) and the perpendicular wavenumber can be selected between 3 and 15 cm-1.

References