Upgrade of the relative calibration methods and Bayesian inference processing for electron cyclotron emission radiometry

Abstract

An upgraded local oscillator (LO) hopping calibration method based on a blackbody hot source and a perturbation analysis of the magnetic field difference method are introduced in this work. The blackbody hot source is used to evaluate the difference in the relative coefficients between the two LO hopping frequencies in the same channels. Then the coefficients are obtained by multiplying the LO hopping frequencies coefficients by LO hopping calibration coefficients. In this way, it is more flexible and stable than the in-situ calibration. The magnetic field difference method provides another calibration method to obtain the relative calibration coefficients of the electron cyclotron emission radiometers (ECE). In general, the magnetic field difference method needs two similar shots but with a difference of 2.1% (for HL-2M) in the magnetic field. Meanwhile, there are some errors because of the deviation of detection positions in the same channels between the two shots. For evaluating the calibration errors, the impact of the displacement, Te perturbation of the core region, and magnetic field difference has been discussed. The result shows that a larger magnetic field difference can improve the accuracy of the calibration. In the end, Bayesian inference has been utilized to evaluate the calibration coefficients and get the most probable calibration coefficients along with its the confidence interval.