X-ray absorption tomography of a high-pressure metal-halide lamp with a bent arc due to Lorentz-forces

Abstract

Due to its practical importance x-ray absorption (XRA) tomography is becoming a widely applied technique for reconstruction of gas temperature distribution in high intensity discharge lamps. Most of the previous papers have dealt with the cylindrically symmetric plasmas that normally occur when lamps are burned vertically. In this work, a XRA tomographic diagnostic is applied for the first time to a high-pressure metal-halide lamp with a bent arc. X-ray lamp-off and lamp-on measurements have been made for two orthogonal directions. The maximum entropy-based algorithm was applied for the reconstruction of local absorption coefficients which are directly related to the local values of mercury density and plasma temperature. For correct reconstruction of the temperature profile at the edges a new numerical strategy based on the adaptive regularization parameter is developed. This strategy allows use of the measured value of the wall temperature as a reference point to obtain a quantitative temperature distribution.