Page 2 - End loss analyzer system for measurements of plasma flux at the C-2U divertor electrode

11D432-2 Sheftman et al.
Rev. Sci. Instrum. 87, 11D432 (2016)
FIG. 1. Experimental scheme of the MW interferometer.
collect impurity light, were coupled to the spectrometer slit via an imaging lens. The resulting spectra was imaged and magni- fied 30 times onto three 32-channel Hamamatsu H-7260-04 photo-multiplying tube (PMT) arrays, providing a wavelength range of 1.44 nm and channel resolution of 0.045 nm, well matching the minimal spectrometer resolution of 0.05 nm. The output of each PMT array was coupled to an array of 106 V/A trans-impedance amplifiers for final raw signal acquisition and processing. The ion velocity was calculated by the Doppler e↵ect as
FIG. 3. Integrated electron density, rescaled and normalized for compari- son, obtained by four FIR interferometer chords (solid lines), and one MW interferometer chord (dashed line), for one microburst event. The axial and radial coordinates of each chord are presented, respectively, on the right (a). Propagation velocity calculated by time of flight (b).
The ion temperature was calculated through the broaden-
v= c fit 0 / 0, (2)
where M = 16 is the atomic mass of Oxygen, is the measured line broadening, and inst is the instrumental broad- ening determined by the spectrometer resolution and optics of the system. Ion temperature and velocity for di↵erent chords are presented in Fig. 5. It is important to note that the relative velocity is presented, since the uncertainty of the spectrometer central wavelength results in an absolute velocity measurement error of ±10 km/s. However, the relative velocity error of each view obtained from fitting is ⇠±2 km/s. The error of velocity di↵erence between two di↵erent chord views is typically ±2-5 km/s. The ion temperature error is typically ±25 eV.
FIG. 4. Spectrometer chords and MW interferometer locations (not to scale). C.M. denotes the fiber collimator mount. The plasma jet flows out of the confinement section, through the FRC formation section, onwards through the mirror plug. Note that the confinement section is at the center of a symmetric apparatus, of which only the left half is shown.
where fit is the central wavelength of the measured impurity line and 0 = 278.1 nm is the O4+ impurity line center wave- length at v = 0.
FIG. 2. MW interferometer phase measurement, sin' and cos' which is (a) and (b), respectively, and calculated integrated electron density (d). Also shown is the sum of the respective squares of sin' and cos', an indication of the signal strength, where maximum amplitude equals to 1 (c). Deviation of amplitude from maximum level is an indication of MW beam refraction by plasma.
ing of the O4+ line (278.1 nm),
T [keV]=4.7⇥105M 2 2 / 2, (3)
i inst 0