TJ-II:Helium Beam: Difference between revisions

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-TJ-II possesses a supersonic Helium beam diagnostic based on the line ratio method.
+[[TJ-II]] possesses a supersonic Helium beam diagnostic.
-<ref>[http://link.aip.org/link/?RSINAK/72/602/1 B. Brañas at al., Rev. Sci. Instrum. '''72''', 602 (2001)]</ref>
+The beam source consists of a fast-pulsed piezoelectric valve with a nozzle of
-<ref>[http://link.aip.org/link/?RSINAK/75/3478/1 A. Hidalgo et al., Rev. Sci Instrum. '''75''', 3478 (2004)]</ref>
+.3 mm diameter and a parabolic profile skimmer with a diameter
+of 0.5 mm.
+The mean beam velocity is 1500 m/s.
+The density of He atoms at the measurement region is estimated to be of
+the order of &lt; 10<sup>11</sup> cm<sup>-3</sup>.
+Three He emission lines (667.2, 706.5 and
+.1 nm) are simultaneously detected by means of a beam-splitter system and a set of three 16-channel photomultiplier arrays
+(Hamamatsu, model R5900U-20-L16) with interference filters
+(FWHM = 1 nm).
+<ref>B. Brañas et al., ''Atomic beam diagnostics for characterization of edge plasma in TJ-II stellarator'', [[doi:10.1063/1.1319868|Rev. Sci. Instrum. '''72''', 602 (2001)]]</ref>
+A Collisional Radiative (CR) model for the line emission intensity ratios is used
+to deduce electron densities and temperatures.
+<ref name="Hidalgo">A. Hidalgo et al., ''Multipulse supersonic helium beam diagnostic in the TJ-II stellarator'', [[doi:10.1063/1.1779617|Rev. Sci Instrum. '''75''', 3478 (2004)]]</ref>
+<ref name="Guzman">F. Guzmán et al, ''On the determination of edge Ti profiles by a supersonic He beam in TJ-II'', [[doi:10.1016/j.jnucmat.2009.01.290|Journal of Nuclear Materials '''390-391''' (2009) 1127-1130]]</ref>
 It provides profiles of the electron temperature and density in the plasma edge at a repetition rate of up to 200 Hz.
+It is located at &phi; = 355.3&deg; ([[TJ-II:Sectors|sector]] C8).
+[[File:TJ-II_Helium_beam.png|300px|thumb|right|The TJ-II Helium beam diagnostic. The laser can be crossed with the Helium beam for LiF measurements of the excited He population <ref name="Hidalgo" /> and validation of the CR model.]]
+== Data description ==
+The Helium beam pulse shape is stored in the [[TJ-II:Shot database|TJ-II database]] with the name 'HELIO_HAZ'.
+The detected line emission signals are stored with the names 'He_xxx_yy', where 'xxx' is the wavelength in nm (667, 706, or 728), while 'yy' is the position (from 01 through 16).
+[[File:TJ-II He beam.jpg|400px|thumb|left|Photo of Helium and [[TJ-II:Lithium Beam|Lithium]] beam diagnostics (top ports)]]
 == References ==
 <references />