Diagnostics of the Effective Ion Charge Using Measurements of the Bremsstrahlung in the T-15MD Plasma by Toroidal Equatorial Observation Chords

Diagnostics for measuring the value and spatial distribution of the effective ion charge Zeff(r): a key parameter characterizing the level of plasma contamination with impurities, have been developed and put into operation at the T-15MD tokamak. The proposed method is based on absolute measurements of the intensity of plasma bremsstrahlung in the visible spectrum. The diagnostic system is located in the equatorial plane of the installation and allows for recording the continuum along 12 toroidal observation chords. Absolute calibration of the system was performed in situ using a Labsphere USS-600C reference source. The paper analyzes the main sources of errors and evaluates the error in determining the Zeff value. The first experimental data on the average value of the plasma column cross-section ⟨Zeff⟩ obtained using this system during experiments on the T-15MD is presented.