No abstract

The use of an active measurement system to localize contamination in concrete structures of nuclear facilities offers advantages like an easy on-site analysis within short measurement time. A measuring system based on a scintillation crystal connected to a long optical fiber with a large diameter could satisfy the demands of a measuring system for gamma-ray spectroscopy in boreholes. This work describes the developement of a gammaray spectroscopy system using a fiber optic radiation sensor. A prototype was built with a GAGG scintillation crystal, that could reach an energy resolution of 33 % at the 662 keV gamma-ray emission energy of 137 Cs. A minimal time for the detection of a contamination of a 137 Cs source with an activity of 21 kBq and a layer of 6 cm concrete between sensor and radiation source was determined to under one minute with three different evaluation methods. They were based on the decision threshold and the Kolmogorov-Smirnov test corresponding to the energy distribution and the distribution of time differences between detector events. Additionally, it was possible to estimate the distance of a point like source from the sensor by establishing a further analysis parameter comparing different energy regions of a spectrum.

Using the radioluminescence light of solid state probes coupled to long and flexible fibers for dosimetry in radiotherapy offers many advantages in terms of probe size, robustness and cost efficiency. However, especially in hadron fields, radioluminophores exhibit quenching effects dependent on the linear energy transfer. This work describes the discovery of a spectral shift in the radioluminescence light of beryllium oxide in dependence on the residual range at therapeutic proton energies. A spectrally resolving measurement setup has been developed and tested in scanned proton fields. It is shown that such a system can not only quantitatively reconstruct the dose, but might also give information on the residual proton range at the point of measurement.