TJ-II:Helium Beam
TJ-II possesses a supersonic Helium beam diagnostic. The beam source consists of a fast-pulsed piezoelectric valve with a nozzle of 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 < 1011 cm-3. 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). [1] A Collisional Radiative (CR) model for the line emission intensity ratios is used to deduce electron densities and temperatures. [2] [3] 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 φ = 355.3° (sector C8).
Data description
The Helium beam pulse shape is stored in the 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).
References
- ↑ B. Brañas et al., Atomic beam diagnostics for characterization of edge plasma in TJ-II stellarator, Rev. Sci. Instrum. 72, 602 (2001)
- ↑ 2.0 2.1 A. Hidalgo et al., Multipulse supersonic helium beam diagnostic in the TJ-II stellarator, Rev. Sci Instrum. 75, 3478 (2004)
- ↑ 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