Enhancements of high-resolution gamma-ray computed tomography

Recently, we developed a transportable high-resolution gamma-ray computed tomography (GCT) measurement system for the investigation of phase distributions in multi-phase flows in technical apparatus. The GCT measurement system contains a collimated isotopic source (137Cs), a radiation detector arc and an external signal processing as well as thermal stabilisation unit. For tomographic scans radiographic projections are obtained from different angular positions by rotating either the measuring ensemble or the object of interest. To improve the mechanical and thermal handling of the existing radiation measurement electronics, in a first step a new modular signal processing board was developed. It implements variable gain amplifier stages, gamma photon counters as well as data transfer and communication to a standard PC into the detector arc. Furthermore, the new developed electronics allows various arrangements of multiple detector modules. In a second step the thermal stabilisation system was integrated into the detector arc. Two 30 W (thermal power) Peltier elements directly placed onto the top side of the detector base plate undertake the task of thermal stabilisation. Into the back side of the base plate, a spatially optimised channel is milled in which a fluid, driven by an integrated centrifugal pump, realises a homogeneous temperature distribution. Thus, the heat losses of the active electronics that are connected to the base plate can be efficiently dissipated, which is the key for a good measuring repeat accuracy. The functionality of the thermal stabilisation design was proven by an IR camera.