Speaker
Description
The ITER High Frequency Radiometer (HFR) is designed to measure electron temperature and to detect neoclassical tearing modes in real time. In addition, it will provide numerous support measurements including detection of ELMS and MHD modes. A unique feature of the system is an in-situ calibration tool -- a hot source operating at 700 C -- which is needed to account for gradual degradation of the ECE collection optics which are directly exposed to the tokamak plasma and its environment.
The radiometer views the plasma through a quasi-optical front end which provides both radial and oblique views. Before reaching the radiometer the polarizations of the ECE are split into X-mode and O-mode. The 80 m transmission line to the radiometer consists of four over-moded waveguides (one waveguide for each polarization in each view) which are continuously purged with dry air. The emission is split among the EC detection instruments in a waveguide switch yard.
The HFR receives X-mode emission in the 220 to 340 GHz range, acquires data at a 1 MHz sampling rate, and covers the LFS of the plasma with approximately 100 channels with 1 GHz separation to meet the IO spatial and temporal requirements.
The spectrum reaching the HFR is simulated using realistic models of emission collection and transmission. The calibration of the instrument requires the use of coherent averaging techniques which will be discussed in detail together with the resulting measurement accuracy, and the clock-time required to reach a specified accuracy.
This work is supported by US DOE Contract No. DE-AC02-09CH11466. All US activities are managed by the US ITER Project Office, hosted by Oak Ridge National Laboratory with partner labs Princeton Plasma Physics Laboratory and Savannah River National Laboratory. The project is
