Speaker
Description
In this contribution, we describe the absolute calibration procedure of the heterodyne radiometer at WEST for the measurement of the Electron Cyclotron Emission (ECE). The ECE radiometer [1] at WEST has 32 channels, with a purely horizontal line-of-sight, and can operate in both O-mode fundamental or X-mode 2nd harmonic, depending on the toroidal magnetic field intensity. The corresponding frequency ranges are 78.5–109.5 GHz and 94–126 GHz, respectively. The measured signals are split into a slow (1 kHz) and a fast (1 MHz) acquisition independent units. While the fast acquisition system [2] is not absolutely calibrated, the slow acquisition undergoes an absolute calibration procedure, which is the focus of this contribution.
The absolute calibration relies on a black-body source heated to 600 °C, whose emitted power is modulated by a two-blade rotating chopper operating at 11 Hz. The calibration is performed over 50k cycles to ensure enough statistical accuracy. Dedicated filters and amplifiers are implemented along the signal path to appropriately attenuate and amplify the black-body signal to the required levels. Further technical details will be reported in the presentation.
This absolute calibration procedure has been successfully employed for more than 25 years, including Tore Supra operations. However, recent investigations have revealed some issues, mainly associated with the ageing of specific components, in particular the black-body source. Possible upgrades to the absolute calibration scheme have therefore been explored and will be discussed during the presentation.
[1] J.-L.Segui et al., Rev. Sci. Instrum. 76, 123501 (2005)
[2] K.-W. Chen et al., to be submitted to Rev. Sci. Instrum. (2026)
