A note on measurement accuracy and thermal stability of filter polychromators for Thomson scattering diagnostics

This note is devoted to a filter polychromator combining built-in optical, data acquisition and processing subsystems designed for electron temperature and density measurements in fusion plasma by Thomson scattering (TS). Special attention is paid to assessing the accuracy of TS signals measured in the polychromator spectral channels. The potential for estimating TS error caused by background emission is demonstrated using high-pass signal. The recent polychromator tests have shown APD gain stabilization better than ±0.5% over the ambient temperature range from 17.5 °C to 35 °C