The recently completed MST2 upgrade to the Thomson scattering (TS) system on TCV (Tokamak à Configuration Variable) at the Swiss Plasma Center aims to provide an enhanced spatial and spectral resolution while maintaining the high level of diagnostic flexibility for the study of TCV plasmas. The MST2 (Medium Sized Tokamak) is a work program within the Eurofusion ITER physics department, aimed at exploiting Europe's medium sized tokamak programs for a better understanding of ITER physics. This upgrade to the TCV Thomson scattering system involved the installation of 40 new compact 5-channel spectrometers and modifications to the diagnostics fiber optic design. The complete redesign of the fiber optic backplane incorporates fewer larger diameter fibers, allowing for a higher resolution in both the core and edge of TCV plasmas along the laser line, with a slight decrease in the signal to noise ratio of Thomson measurements.The 40 new spectrometers added to the system are designed to cover the full range of temperatures expected in TCV, able to measure electron temperatures (T e ) with high precision between (6 eV and 20 keV). The design of these compact spectrometers stems originally from the design utilized in the MAST (Mega Amp Spherical Tokamak) TS system located in Oxfordshire, United Kingdom. This design was implemented on TCV with an overall layout of optical fibers and spectrometers to achieve an overall increase in the spatial resolution, specifically a resolution of approximately 1% of the minor radius within the plasma pedestal region. These spectrometers also enhance the diagnostic spectral resolution, especially within the plasma edge, due to the low T e measurement capabilities. These additional spectrometers allow for a much greater diagnostic flexibility, allowing for quality full Thomson profiles in 75% of TCV plasma configurations. K: Nuclear instruments and methods for hot plasma diagnostics; Plasma diagnosticscharged-particle spectroscopy; Optics; Spectrometers 1Corresponding author.
The ITER Heating and Current Drive Upper Launcher (H&CD EC UL) uses a pneumomechanical steering-mirror assembly (SMA) to steer the RF beams for their deposition in the appropriate location in the plasma to control magnetohydrodynamic activity (neoclassical tearing modes (NTMs) and sawtooth oscillations). For NTM stabilization, the mirror rotation needs to be controlled to an accuracy that is better than 0.1 • . A 10 • · s −1 mirror steering speed is also required. To assess the performance of the two SMA prototypes that have been manufactured, a test stand that reproduces the expected pneumatic configuration of the UL has been built. So far, only the first SMA prototype has been tested, and tests on the second prototype are foreseen in the 2009-2010 period. The steering angle of the mirror will be deduced from the pressure applied to the mechanism since there is no in situ angle measurement at present. An "off-the-shelf" commercial servo valve with a proportional-integral-derivative controller has been used to control the pressure with good results for the switching cycle. These tests show that a more advanced controller will be required to attain the desired accuracy and speed for the modulation cycles.Index Terms-Millimeter-wave antennas, pressure control.
This paper reports the mechanical and electrical tests performed for the prototyping of the ITER high-frequency magnetic sensor and the analysis of the measurement performance of this diagnostic. The current design for the sensor is not suitable for manufacturing for ITER due to the high likelihood of breakages of the un-guided tungsten wire during the winding. A number of alternative designs and manufacturing processes have been investigated, with the Low Temperature Co-fired Ceramic technology giving the best results. The measurement performance of the baseline system design for the high-frequency magnetic diagnostic cannot meet the intended ITER requirements due to its intrinsic spatial periodicities.
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