Speaker
Mr
Ivan Sorokin
(National Research Nuclear University "MEPhI")
Description
Stationary plasma diagnostics of local parameters and ion mass-spectrum are necessary to control discharge regimes and plasma composition during the experiments. Corpuscular diagnostics of plasma ion flux can provide information about plasma-chemical kinetic of the discharge. Usually optical spectroscopy is used for determination of the plasma composition [1, 2], but often it cannot deliver the reliable information. The residual gas analysis, for example by quadrupole mass-spectrometer, can provide information of the neutral species in vacuum chamber, but not of the ion composition of plasma.
In-situ mass-spectrometry systems based on the mass separation and detection of plasma ions are usually complicate, for example the omegatron mass-spectrometer [3] requires an additional RF source of the electrical field and ultra-high-vacuum differential pumping, the plasma ions mass-spectrometer (PIMS) [4] is based on the cycloidal focusing in the perpendicular electrical and strong magnetic field, which is not always used on linear plasma devices. A simpler ion separation method of magnetized plasmas is using own-magnetic field of the plasma device as a separating factor. The idea of stationary mass-spectrometer using own-magnetic field is widely used [5, 6], but usually it is not possible to measure both positive and negative ions in one experiment. Combined diagnostics module (CDM) for in-situ analysis of both the local parameters and ion mass spectrum of magnetized plasmas developed for the linear plasma device PR-2 is presented.
![Scheme of CDM on PR-2.][1]
Scheme of CDM is shown on Fig. 1. It consists of the static mass-spectrometer (MS) and the probe system containing twelve single Langmuir probes. MS is based on classical scheme of static magnetic ion separator with 180° magnetic deflection of the accelerated ions. Symmetrical MS allows to measure relative fluxes of both positive and negative ions from plasma column. Ions reaching the entrance slit are accelerated by the electrical field applied in the accelerating gap. Then they are deflected by the magnetic field of plasma device and as a result separated by M/Z ratio. Mass-spectrum of plasma ions is obtained by changing the accelerating voltage, and registered by four ion collectors placed at different radii of ion trajectories. The collector at the lower radius is used for a rough mass-analysis of typical light working gases. The second collector has a better mass resolution and is used for more accurate measurements in a heavier mass range.
1. D. Nishijima et al., Phys. Plasmas, 14, 103509 (2007)
2. A. Kreter et al., J. Nucl. Mater., 417, 651 (2011)
3. E.M. Hollman et al., Rev. of Sci. Instr., 72/1, 623 – 626 (2001)
4. G.F. Matthews, Plasma Phys. Control. Fusion, 31, 841 – 863 (1989)
5. H. Kojima et al., JNM, 128&129, 965-968 (1984)
6. O. Waldmann et al., 34th EPS Conf. On Plasma Phys. Warsaw, 31F, 5.108 (2007)
[1]: http://cs626623.vk.me/v626623294/d7d/u-qtafylKc0.jpg
Primary authors
Mr
Dobrynya Kolodko
(National Research Nuclear University "MEPhI")
Dr
Igor Vizgalov
(National Research Nuclear University "MEPhI")
Mr
Ivan Sorokin
(National Research Nuclear University "MEPhI")
