In order to improve the coupling of the RF power injected to heat the plasma, a detailed knowledge of the plasma density profile in front of the launching antennas is essential. Reflectometry is one of the best candidates to achieve this since it is a non-invasive method, requiring only a limited access space to the plasma, while guaranteeing a very good spatial and temporal resolution. A new multichannel reflectometer is installed inside one of the new ICRF antenna at ASDEX Upgrade (AUG): it consists of three channels that can be switched between 10 antenna pairs with different lines-of-sight (accesses) to the plasma, working in the frequency range 40-68 GHz, using the upper (right-hand) X mode cut-off, with a frequency scan in 10 ms, every 15 ms. The transmission system is composed of standard WR19 waveguides in fundamental mode, and includes DC breaks and low pass filters to reject frequencies of the ECRH systems. WR19 rectangular horns and truncated WR42 waveguide have been used as antennas. All in-vessel components have been tested by pre-installation on a spare Vacuum Vessel Octant and are now fully assembled and tested in AUG. Reflection and transmission coefficient, as well as the coupling between the antennas, have been measured. The results of this measurements, their comparison with the simulations of a full wave code and an estimation of the power level expected at the receiver are reported in this paper. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
Design, laboratory characterization and installation of the multichannel reflectometer's transmission lines at ICRF antenna in Asdex Upgrade
Rocchi, G.;Ceccuzzi, S.;Tudisco, O.;D'Arcangelo, O.;Tuccillo, A.A.
2015-01-01
Abstract
In order to improve the coupling of the RF power injected to heat the plasma, a detailed knowledge of the plasma density profile in front of the launching antennas is essential. Reflectometry is one of the best candidates to achieve this since it is a non-invasive method, requiring only a limited access space to the plasma, while guaranteeing a very good spatial and temporal resolution. A new multichannel reflectometer is installed inside one of the new ICRF antenna at ASDEX Upgrade (AUG): it consists of three channels that can be switched between 10 antenna pairs with different lines-of-sight (accesses) to the plasma, working in the frequency range 40-68 GHz, using the upper (right-hand) X mode cut-off, with a frequency scan in 10 ms, every 15 ms. The transmission system is composed of standard WR19 waveguides in fundamental mode, and includes DC breaks and low pass filters to reject frequencies of the ECRH systems. WR19 rectangular horns and truncated WR42 waveguide have been used as antennas. All in-vessel components have been tested by pre-installation on a spare Vacuum Vessel Octant and are now fully assembled and tested in AUG. Reflection and transmission coefficient, as well as the coupling between the antennas, have been measured. The results of this measurements, their comparison with the simulations of a full wave code and an estimation of the power level expected at the receiver are reported in this paper. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
