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LTCC magnetic sensors at EPFL and TCV: Lessons learnt for ITER

Severino Antonioni, Adrien Aymeric Thibault Corne, Steve Couturier, Frédéric Dolizy, Matthias Garcin, Aylwin Iantchenko, Caroline Jacq, Pierre Lavanchy, Jonathan Bryan Lister, Xavier Llobet, Thomas Maeder, Blaise Marlétaz, Philippe Marmillod, Christian Moura, Ugo Siravo, Lorenzo Stipani, Duccio Testa, Matthieu Toussaint

Innovative 3D high-frequency magnetic sensors have been designed and manufactured in-house for installation on the Tokamak a Configuration Variable (TCV), and are currently routinely operational. These sensors combine the Low Temperature Co-fired Ceramic (LTCC) and the thick-film technologies, and are in various aspects similar to the majority of the inductive magnetic sensors currently being procured for ITER (290 out of 505 are LTCC-1D). The TCV LTCC-3D magnetic sensors provide measurements in the frequency range up to 1MHz of the perturbations to the toroidal (quasi-parallel: delta B-TOR(similar to)delta B-PAR), vertical (quasi-poloidal: delta B-V(ER)similar to delta B-PO(L)), and radial (delta B-RAD) magnetic field components, the latter being generally different from the component normal to the Last Closed Flux-Surface (delta B-NOR). The LTCC-3D delta B-RAD measurements improve significantly on the corresponding data with the saddle loops, which are mounted onto the wall and have a bandwidth of (similar to)3 kHz (due to the wall penetration time). The LTCC-3D delta B-TOR measurements (not previously available in TCV) provide evidence that certain MHD modes have a finite delta B-P(AR) at the LCFS, as recently calculated for pressure-driven instabilities. The LTCC-3D delta B-PO(L) measurements allow to cross-check the data obtained with the Mirnov coils, and led to the identification of large EM noise pick-up for the Mirnov DAQ. The LTCC-3D data for delta B-POL agree with those obtained with the Mirnov sensors in the frequency range where the respective data acquisition overlap, routinely up to 125kHz, and up to 250kHz in some discharges, when the EM noise pick-up on the Mirnov DAQ is removed. Finally, we look at what lessons can be learnt from our work for the forthcoming procurement, installation and operation of the LTCC-1D sensors in ITER.

2019

New capabilities of the incoherent Thomson scattering diagnostics in the TCV tokamak: divertor and real-time measurements

Yanis Andrebe, Severino Antonioni, Patrick Blanchard, Steve Couturier, Joan Decker, Basil Duval, Federico Alberto Alfredo Felici, Cristian Galperti, Pierre-François Isoz, Pierre Lavanchy, Xavier Llobet, Blaise Marlétaz, Philippe Marmillod

This work reports developments of the incoherent TS diagnostic capabilities in the Tokamak a Configuration Variable (TCV). Their goals are to (i) diagnose the TCV divertor region, and (ii) provide Te and ne profiles of the plasma bulk in real-time. These two new TS diagnostic capabilities are implemented within the framework of a TCV upgrade that will insert baffles in the lower divertor region. 20 new TS spectrometers are being installed to access electron temperatures down to similar to 1 eV, for densities above similar to 1.5 x 10(19) m(-3) within the TCV divertor region. They will measure the Thomson light scattered along the vertical propagation path of the three legacy Nd:YAG lasers. The light at each of the 20 measurement plasma volumes is collected by three optical fibers with a laser-mapped spatial resolution of 5-6 mm each, providing a vertical spatial resolution of 15-18mm. Interference filters with central. Interference filters with central wavelengths from 1025 to 1061 nm and widths as low as similar to 2 nm are employed to obtain the spectroscopic resolution required at these low temperatures. The acquisition chain and analysis of the TS signal will be integrated into the TCV monitoring and control system to provide electron density and temperature profiles in real-time, at a sampling rate up to 60 Hz. The real time electron property profiles complement existing systems provided by the far-infrared interferometer and the soft X-ray diagnostics. The latter are restricted to provide integrated values of the electron density and temperature respectively, but at higher sampling rates (10 kHz and 20 kHz respectively). The whole diagnostic ensemble will be integrated into TCV's control system to improve the accuracy and robustness of real-time plasma profile and equilibrium estimation for control purposes.

IOP PUBLISHING LTD2019

Thomson scattering measurements in the divertor region of the TCV Tokamak plasmas

Riccardo Agnello, Yanis Andrebe, Severino Antonioni, Patrick Blanchard, Steve Couturier, Joan Decker, Basil Duval, Ivo Furno, Pierre-François Isoz, Pierre Lavanchy, Xavier Llobet, Blaise Marlétaz

In order to better study conventional and alternative divertor configurations, the TCV Tokamak was recently upgraded. In-vessel graphite baffles were installed in the TCV chamber to delimit a separate divertor chamber from the core that required enhanced diagnostic capabilities. To date, TCV’s Thomson scattering diagnostic provided electron temperature and density profiles of the hot core and the pedestal of the plasma with an array of 96 polychromators. To study the new divertor region, an upgrade added 20 new polychromators specifically to diagnose the plasma in the relatively cold divertor region. New 4-channel polychromators were designed to provide Te measurements down to ~1eV with ne~1.5x1019m-3. Interference filters of only 1.9nm FWHM were required to achieve this goal. Te and ne measurements from the TCV divertor region have been obtained for the first time. Specific diverted plasma discharges where the outer divertor leg is scanned in and out of the TS laser beam’s path are used to demonstrate the diagnostic’s new capabilities and potential with measurements of Te as low as 1.4eV obtained for electron densities of 2 x1018m-3. The system’s 16mm integration length along the laser line is providing, for the first time, Te and ne profiles with sufficient spatial resolution across the divertor legs to resolve the divertor plasma dynamics.

2019

New capabilities of the incoherent Thomson scattering diagnostics in the TCV tokamak: divertor and real-time measurements

IOP PUBLISHING LTD2019

LTCC magnetic sensors at EPFL and TCV: Lessons learnt for ITER

2019