The problem of jitter and its correction for diagnostics at ASDEX Upgrade

Different optical diagnostics are operated at fusion devices like ASDEX Upgrade. One of them is thermography for contactless temperature measurements of surfaces in the vessel using infrared cameras. These temperatures can be used for the calculation of the heat flux on the monitored surfaces. But for the correct analysis of the recorded data stable measurement conditions regarding mechanical aspects like vibrations are needed. Since these conditions are often not fulfilled the measurements are affected by jitter. This paper describes a method used at ASDEX Upgrade for the correction of 1D and 2D thermographic data to compensate the jitter. It is based on a correlation analysis and also deals with jitter in the subpixel range. Examples are shown for the correction of temperature data and also for the influence on heat flux calculations with corrected and uncorrected temperatures. The limits of the proposed algorithm are also mentioned.