Problems of Radiation Energy Flux Measurement at Transport Infrastructure Facilities with Radiating Plasma

Abstract

Purpose: Transport infrastructure objects comprise numerous technical devices containing radiating plasma. They include visible and spectral radiation sources, switching devices at traction substations, high-temperature heat exchangers and combustion chambers. During experimental study of such devices, the measurements of power and spectral composition of radiation emitted by plasma are carried out. For this, as a rule, photodiodes of small sizes are used, installed at a certain distance from plasma formation. The purpose of the present work is to establish relationship between plasma emission power and radiation flux amount incident on photodiode working surface. Methods: To solve the set task, the method of direct integration of radiation transfer equation in homogeneous plasma structure assumption, but in the absence of local thermodynamic equilibrium presence assumption, is used. The cases of reflecting and absorbing surfaces, limiting a plasma, are considered. Results: Explicit expressions are found for radiation flux which exits plasma formation surface and for flux incident on photodiode surface. The dependence for the ratio of the values of these radiation fluxes to plasma geometric sizes and optical thickness is numerically studied. For the case of reflecting surfaces that bound plasma, simple asymptotic expression is found for ratio value for the fluxes and applicability field of the expression is determined. Practical significance: The ratios, which establish relationship between plasma radiation power and power value for radiation flux incident on photodiode working surface, make it possible to solve the main task of the experimental study of plasma formations — the restoration of plasma characteristics according to photocurrent measurement results. Obtained in the work results can be used at experimental study of technical devices containing emitting plasma.