Toroidal Flow Velocity Measurement in the STOR-M Tokamak by Ion Doppler Spectroscopy
An Ion Doppler Spectrometer (IDS) was built for the purpose of toroidal ion flow velocity measurement in the STOR-M tokamak. Emission lines from carbon and oxygen ions C_III, O_V and C_VI were used for spectral profiles measurement. Based on the Doppler effect, the ion flow velocities were calculated from the spectral line shift. The IDS system was built based on a Czery-Turner spectrometer. A cylindrical rod lens was used to magnify the grating dispersion. The spectrum was recorded by a photomultiplier tube (PMT) detector, whose output current was converted to voltage through a current preamplifier. The IDS achieved a time resolution of 0.1 ms defined by the RC time, and the ion flow velocity resolution is 1 ~ 2 km/s. Profile measurement shows the impurity emission lines at different ionization stage populated at different radial positions in the chamber. The flow velocities were measured with various operation modes. A flow velocity shear was discovered for different ion species. The ions in the edge region are flowing in the same direction as plasma current, while the ions in the plasma center are flowing in the anti-current direction. The impurity flow directions are inversed with inversed plasma current configuration. It was found that the impurity flow velocities can be changed by compact torus (CT) injection, resonant magnetic perturbation (RMP) field, as well as rapid hydrogen puffing.
DegreeMaster of Science (M.Sc.)
DepartmentPhysics and Engineering Physics
CommitteeGhezelbash, Masoud; Xiao, Chijin; Koustov, Sasha; Szpunar, Jerzy
Copyright DateAugust 2012
Ion Doppler Spectroscopy
Flow Velocity Measurement