Review of Possibilities for a Collective Thomson Scattering System on ITER
The radiation source wavelength useful for a Collective Thomson Scattering (CTS) on ITER is analyzed in this paper, and the related scattering geometry, signal to noise ratio and technology needed for the measurement of the alpha particles are specified. The ITER plasma parameters taken for reference1 in the calculations are: ne= 1.2 1020m-3, Te = 22keV , Ti = 20KeV, n∝/ne = 0.0017, BT=5.7T, R =8.1m,a=3.0m,k=1.55.The plasma, machine and alpha parameters are quite different from those included in the first proposal2 for a Collective Scattering System, where a FEL(Free Electron Laser) source at 1.5THz(λ=200µm) was proposed.In the present work three sources are considered with wavelength λ=l0.6µm(CO2 laser P(20)line), 200µm(FEL),4.61mm(65GHz gyrotron). For the evaluation of source figures the calculation of ECE background radiation level is needed, after some geometry constraints are discussed,and then the evaluation of scattered power and signal to noise ratio is performed, adding observations on the technology needed.
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