TJ-II:Reflectometry

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 sector B8 in perpendicular incidence (conventional reflectometry). The system allowed studies of the velocity shear layer in TJ-II ^[3] and of the radial position of its origin. ^[4]

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) ^[5], 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

[1] T. Estrada et al., Plasma Phys. Control. Fusion 43 (2001) 1535–1545

[2] L. Cupido, J. Sánchez and T. Estrada, Rev. Sci. Intrum. 75 (2004) 3865

[3] T. Estrada, E. Blanco, L. Cupido, M.E. Manso, and J. Sánchez, Nucl. Fusion 46 (2006) S792–S798

[4] T. Happel, T. Estrada, and C. Hidalgo, Europhys. Lett. 84 (2008) 65001

[5] T. Happel, T. Estrada, E. Blanco, V. Tribaldos, A. Cappa, and A. Bustos, Rev. Sci. Instrum. 80 (2009) 073502

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