A comprehensive study of measurement uncertainty in tomographic reconstruction of void-profiles in a mercury-nitrogen flow

 The liquid–metal magneto-hydrodynamic (LMMHD) facility at the Bhabha Atomic Research Centre (Mumbai) has a two-phase mercury–nitrogen flow system which is currently used for various studies related to void-fraction, flow, pressure, slip-ratio, of the flow system. Non-invasive measurements of steady-state void-fraction profiles has been carried out by a 60 mCi Cesium-137 gamma-ray source and a NaI(Tl) detector mounted on a trolley. The reconstructed cross-sectional void-fraction profiles were in the riser section of the LMMHD loop, and in this process radial tomographic methods were used, e.g. least-squares and chord-segment-inversion (CSI). The present work investigates the possible uncertainties in the profiles thus measured. A simple statistical model has been developed for the CSI algorithm due to the inherent “square nature” of the data matrix. The inherent Poisson error has been also investigated in this exercise. Received: 1 December 1997/Accepted: 30 May 1998