Charge exchange recombination spectroscopy on the T-10 tokamak

Abstract

The charge exchange recombination spectroscopy (CXRS) diagnostics on the T-10 tokamak is described. The system is based on a diagnostic neutral beam and includes three high etendue spectrometers designed for the ITER edge CXRS system. A combined two-channel spectrometer is developed for simultaneous measurements of two beam-induced spectral lines using the same lines of sight. A basic element of the combined spectrometer is a transmitting holographic grating designed for the narrow spectral region 5291 ± 100 Å. The whole CXRS system provides simultaneous measurements of two CXRS impurity spectra and Hα beam line. Ion temperature measurements are routinely provided using the C(6+) CXRS spectral line 5291 Å. Simultaneous measurements of carbon densities and one more impurity (oxygen, helium, lithium etc.) are carried out. Two light collecting systems with 9 lines of sight in each system are used in the diagnostics. Spatial resolution is up to 2.5 cm and temporal resolution of 1 ms is defined by the diagnostic neutral beam diameter and pulse duration, respectively. Experimental results are shown to demonstrate a wide range of the CXRS diagnostic capabilities on T-10 for investigation of impurity transport processes in tokamak plasma. Developed diagnostics provides necessary experimental data for studying of plasma electric fields, heat and particle transport processes, and for investigation of geodesic acoustic modes.

The development of charge exchange recombination spectroscopy diagnostics for the T-15MD tokamak

“…This value is 10 -15 times higher that the contrast of the active signal that was obtained during the operation of the CXRS-complex on T-10. And yet reliable measurements of the T i (r), n z (r) and main gas nuclei concentrations were provided [7]. This all together will allow for much more accurate CXRS-measurements at T-15MD.…”

Atomic collisional data for neutral beam modeling in fusion plasmas

“…Such data are available and analyzed for instance in the Atomic Database and Analysis Structures (ADAS) package [106]. Charge exchange recombination spectroscopy in tokamak plasmas is another example of application where neutral beam interaction data comes in play: While the temperature and flow velocity of the impurity particles can be inferred directly from spectral measurements without the knowledge of the cross section data [4,5,34,107] the measurements of the impurity ion density X Z+1 in ( 41) requires detailed calculations on beam penetration and interaction with bulk plasma species. The expression for the population of the excited level N Z i from [108] is:…”

“…The ACX component is in addition shifted from the weak PCX one through the Doppler effect. The example of the spectra from different impurities can be found in [4,5,34,107]. Figure 8 illustrates the carbon impurity charge exchange spectra measured from one of the central chords (R = 2.0 m) integrated over 5 msec by the KSTAR CXRS system.…”

“…Due to the fact that the bound electrons observe the Zeeman-Stark effect with crossed fields in the rest frame of the ion the bundle-n model could be valid in the magnetic devices with strong magnetic field even at low ion plasma density. Whereas the static Zeeman effect and polarization of spectral components can be easily incorporated into the line shape modeling of the CXRS spectra [107], the calculation or even the criterion at which the bundle-n picture can be valid is still an open question [111]. Thus, the bundle-n situation can exist at lower plasma density compared to the calculations based on the collisional quenching due to the proton and electron impacts [112].…”

Study of Plasma Impurities Composition in the Experiments With Carbon, Tungsten and Lithium Limiters on Т-10

“…Электронная температура T e (r) измеряется многоканальной ECE-диагностикой, а также одноканальной диагностикой спектров в SXR-области на базе ППД. Профили ионной темпера-туры T i (r) и концентрации ядер лёгких примесей измеряются CXRS-диагностикой одновременно в девя-ти точках по сечению шнура [6]. Для измерений профилей эффективного заряда плазмы Z эф (r) из интен-сивности тормозного излучения применяется комплекс спектроскопического оборудования, описанный в работе [7].…”