Abstract
The Electron Cyclotron Emission (ECE) and correlation ECE diagnostics in TCV have been upgraded during its 2014 shutdown; this paper will provide a brief overview on their updated architecture and capabilities. The ECE system is equipped with two radiometers, each with 24 channels (750 MHz bandwidth) looking at the plasma both from the low and high field side covering the whole vessel. Of particular interest is the possibility of acquiring signals through a vertical line of sight and a dual-axis steerable antenna to study the electron distribution function (EDF) in plasmas with Electron Cyclotron Current Drive (ECCD) or EC Resonant Heating (ECRH). The correlation ECE system has been equipped with a new independent front end connected to the steerable antenna. The main characteristics of the radiometer are the six YIG independently tunable (between 6–18 GHz) 170 MHz bandwidth channels that can be moved on the whole LFS of the vessel. Using correlation analysis techniques it is possible to study very small temperature fluctuations. A brief presentation of some applications where these capabilities have been exploited in past TCV experiments for the study of micro instabilities characteristics is also included.
Highlights
Tokamak à Configuration Variable (TCV) is a medium sized machine for the study of the physics of magnetically confined plasmas for nuclear fusion applications
For example the LFS system makes it possible to study the bulk plasma temperature even in conditions where EC Resonant Heating (ECRH) or Electron Cyclotron Current Drive (ECCD) generate a consistent fraction of suprathermal electrons: Electron Cyclotron Emission (ECE) radiation coming from this population, having a lower frequency than that of the correspondent emission layer due to relativistic effects, would be reabsorbed before reaching the LFS receivers
The RF stage of the CECE radiometer is similar to those, already discussed, of the standard ECE: two notch filters stop the ECRH power from reaching the mixing stage, a directional splitter divides the power between two mixers connected with local oscillator (LO) at 81.9 and 61.1 GHz, the lower side band is rejected and the down converted signals are amplified in low noise amplifiers (LNA) with 30 dB gain over the 2-20 GHz interval and P1dB=10 dBm
Summary
Tokamak à Configuration Variable (TCV) is a medium sized machine for the study of the physics of magnetically confined plasmas for nuclear fusion applications. Its most relevant characteristics are the ability to work with a large range of different plasma shapes, its versatile heating system and the large variety of diagnostic systems available for the study of the plasma. In the past year the Electron Cyclotron Emission (ECE) diagnostic systems have been significantly upgraded. This kind of diagnostic allows the measurement of local electron temperature with high spatial and temporal resolution. TCV has been equipped for the first time with ECE diagnostics in 2002 (HFS) and 2003 (LFS). We will describe the current status of the ECE systems on TCV
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