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TJ-II:Reflectometry: Difference between revisions
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Updated and corrected references
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== Profile Reflectometer == | == Profile Reflectometer == | ||
[[File:Reflectometry density profile.png|300px|thumb|right|Time evolution of density profiles measured by the AM reflectometer during the transition to an enhanced confinement mode (from: Estrada et al., Plasma Phys. Control. Fusion '''43''' (2001) | [[File:Reflectometry density profile.png|300px|thumb|right|Time evolution of density profiles measured by the AM reflectometer during the transition to an enhanced confinement mode (from: <ref name="Estrada">T. Estrada et al., [[doi:10.1088/0741-3335/43/11/308|Plasma Phys. Control. Fusion '''43''' (2001) 1535–1545]]</ref>)]] | ||
[[TJ-II]] has an AM reflectometer | [[TJ-II]] has an AM reflectometer<ref name="Estrada"></ref> | ||
<ref> | |||
for measuring electron density profiles with a temporal resolution of 2 ms. | for measuring electron density profiles with a temporal resolution of 2 ms. | ||
Separate antennas are used for launching and receiving the signal. The antennas are located in the equatorial plane of the toroidal cross-section at φ = 135° (between [[TJ-II:Sectors|sectors]] A4 and A5), and view the plasma from the low-field side. | Separate antennas are used for launching and receiving the signal. The antennas are located in the equatorial plane of the toroidal cross-section at φ = 135° (between [[TJ-II:Sectors|sectors]] A4 and A5), and view the plasma from the low-field side. | ||
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A fast frequency hopping reflectometer | A fast frequency hopping reflectometer | ||
<ref> | <ref>L. Cupido, J. Sánchez and T. Estrada, [[doi:10.1063/1.1788834|Rev. Sci. Intrum. '''75''' (2004) 3865]]</ref> | ||
working in the Q-band (33 - 50 GHz) was used from 2004 - 2008 in [[TJ-II:Sectors|sector]] B8 in perpendicular incidence (''conventional'' reflectometry). The system allowed studies of the velocity shear layer in [[TJ-II]] | working in the Q-band (33 - 50 GHz) was used from 2004 - 2008 in [[TJ-II:Sectors|sector]] B8 in perpendicular incidence (''conventional'' reflectometry). The system allowed studies of the velocity shear layer in [[TJ-II]] | ||
<ref> | <ref>T. Estrada, E. Blanco, L. Cupido, M.E. Manso, and J. Sánchez, [[doi:10.1088/0029-5515/46/9/S14|Nucl. Fusion '''46''' (2006) S792–S798]]</ref> | ||
and of the radial position of its origin. | and of the radial position of its origin. | ||
<ref> | <ref>T. Happel, T. Estrada and C. Hidalgo, ''First experimental observation of a two-step process in the development of the edge velocity shear layer in a fusion plasma'', [[doi:10.1209/0295-5075/84/65001|EPL 84 (2008) 65001]]</ref> | ||
== Doppler Reflectometer == | == Doppler Reflectometer == | ||
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[[File:DRscheme.jpg|200px|thumb|right|Schematic drawing of the Doppler Reflectometer System of [[TJ-II]]. The rays are calculated using the 3D ray/beam-tracing code [[TRUBA]].]] | [[File:DRscheme.jpg|200px|thumb|right|Schematic drawing of the Doppler Reflectometer System of [[TJ-II]]. The rays are calculated using the 3D ray/beam-tracing code [[TRUBA]].]] | ||
Since February 2009, the frequency hopping system is in operation in oblique incidence (''Doppler'' reflectometry, [[TJ-II:Sectors|sector]] C6, φ = 337°) | Since February 2009, the frequency hopping system is in operation in oblique incidence (''Doppler'' reflectometry, [[TJ-II:Sectors|sector]] C6, φ = 337°) | ||
<ref> | <ref>T. Happel, T. Estrada, E. Blanco, V. Tribaldos, A. Cappa, and A. Bustos, [[doi:10.1063/1.3160106|Rev. Sci. Instrum. '''80''' (2009) 073502]]</ref> | ||
, 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 ''k''<sub>⊥</sub> = 3 and 15 cm<sup>-1</sup>. | , 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 ''k''<sub>⊥</sub> = 3 and 15 cm<sup>-1</sup>. | ||
The system consists of a circular choked-corrugated antenna | The system consists of a circular choked-corrugated antenna | ||
<ref> | <ref>J. Teniente, R. Gonzalo, and C. del-Rio, [[doi:10.1109/LAWP.2006.881919 |IEEE Antennas Wireless Propag. Lett. '''5''' (2006) 380]]</ref> | ||
(fabricated by the [http://antenas.unavarra.es/ ''Antenna Group of the Public University of Navarra, Spain'']) which emits a microwave beam with a gaussian electric field distribution. The beam is reflected by a steerable ellipsoidal mirror to the plasma. The mirror serves for two purposes: 1) focus the microwave beam (obtaining plane wavefronts) to the region where backscattering takes place and 2) change the angle of incidence between beam and plasma, giving the possibility to select the turbulence scale to be measured. | (fabricated by the [http://antenas.unavarra.es/ ''Antenna Group of the Public University of Navarra, Spain'']) which emits a microwave beam with a gaussian electric field distribution. The beam is reflected by a steerable ellipsoidal mirror to the plasma. The mirror serves for two purposes: 1) focus the microwave beam (obtaining plane wavefronts) to the region where backscattering takes place and 2) change the angle of incidence between beam and plasma, giving the possibility to select the turbulence scale to be measured. | ||