As a promising method for the fast ion diagnostic, the collective Thomson scattering can measure the one-dimensional velocity distribution of fast ions with high spatial and temporal resolution. The feasibility of diagnosing fast ions in the compact high-field tokamak by CTS was studied in this work, and the result showed that a wide range of probing frequencies could be applied. A high-frequency case and a low-frequency case were mainly considered for the fast ion diagnostic in the compact high-field tokamak. The use of high probing frequency could effectively avoid the refraction effect of the beams, while the application of low probing frequency allows a greater flexibility in the selection of scattering angle which may help to improve the spatial resolution. Based on a typical plasma condition (B0 = 12.2 T, ne0 = 4.3×1020 m−3, Te0 = 22.2 keV, Ti0 = 19.8 keV) for the compact high-field tokamak, a 220 GHz CTS diagnostic that utilizes a small scattering angle of θ = 30° and a 160 GHz CTS diagnostic that utilizes an orthogonal geometry were proposed. Further study showed that the high-frequency case could operate in a wider range of plasma conditions and provide more information on fast ions while the low-frequency could achieve higher spatial resolution of the poloidal direction.

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