TJ-II:Helium Beam: Difference between revisions

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[[File:TJ-II_Helium_beam.png|300px|thumb|right|The TJ-II Helium beam diagnostic]]
[[TJ-II]] possesses a supersonic Helium beam diagnostic.
 
The beam source consists of a fast-pulsed piezoelectric valve with a nozzle of
[[TJ-II]] possesses a supersonic Helium beam diagnostic based on the line ratio method.
0.3 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
728.1 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>[http://link.aip.org/link/?RSINAK/72/602/1 B. Brañas et al., ''Atomic beam diagnostics for characterization of edge plasma in TJ-II stellarator'', Rev. Sci. Instrum. '''72''', 602 (2001)]</ref>
<ref>[http://link.aip.org/link/?RSINAK/72/602/1 B. Brañas et al., ''Atomic beam diagnostics for characterization of edge plasma in TJ-II stellarator'', 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>[http://link.aip.org/link/?RSINAK/75/3478/1 A. Hidalgo et al., ''Multipulse supersonic helium beam diagnostic in the TJ-II stellarator'', Rev. Sci Instrum. '''75''', 3478 (2004)]</ref>
<ref>[http://link.aip.org/link/?RSINAK/75/3478/1 A. Hidalgo et al., ''Multipulse supersonic helium beam diagnostic in the TJ-II stellarator'', Rev. Sci Instrum. '''75''', 3478 (2004)]</ref>
<ref>[http://dx.doi.org/10.1016/j.jnucmat.2009.01.290 F. Guzmán et al, ''On the determination of edge Ti profiles by a supersonic He beam in TJ-II'', Journal of Nuclear Materials '''390-391''' (2009) 1127-1130]</ref>
<ref name="Guzman">[http://dx.doi.org/10.1016/j.jnucmat.2009.01.290 F. Guzmán et al, ''On the determination of edge Ti profiles by a supersonic He beam in TJ-II'', 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 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).
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="Guzman" /> and validation of the CR model.]]


== Data description ==
== Data description ==