Measurement of temporal evolution of plasma rotation in the TCABR tokamak

In toroidal plasma configurations there is a great interest in the damping of poloidal and toroidal plasma rotation. However the diagnostic techniques used to measure the temporal profiles (charge- exchange spectroscopy and multichannel diode array detector) do not have sufficient time resolution and in general are not available in small laboratories. Other methods, such as Mach probes are also frequently used, although the latter technique is related to edge plasma rotation measurements. A new method for measuring the temporal evolution of plasma rotation in tokamaks is used in this work. It is based on the ratio of spectral line intensities of an impurity detected with two different photomultipliers installed at the exit slits of a monochromator. The light from the plasma is collected and transmitted to the entrance slit of the monochromator through an optical fiber. Inside the monochromator, using a semi-transparent mirror, the light is divided into two parts and directed to the photomultipliers. Therefore the photomultiplier at the exit slit 1 detects the left part of spectral line profile while the slit 2 detects the right part. When the plasma begins to move, the centre of the spectral line will move changing the ratio, which is directly correlated to the plasma rotation velocity. Preliminary results of the temporal profile of the poloidal rotation velocity of CIII (464.74 nm) at r = 16 cm in TCABR tokamak obtained using this set up show good agreement, within experimental uncertainty, with previous results. (author)