Developing a Target Imaging System for the European Spallation Source

Nicolo Borghi

Research output: Book/ReportPh.D. thesis

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This PhD project is the result of a joint research collaboration between the Technical University of Denmark (DTU) and the European Spallation Source (ESS). The objective was to conduct a feasibility study for the development of a diagnostic instrument intended to monitor the ESS spallation target material over the course of its lifetime.
The ESS will be the most powerful spallation neutron source in the world. Neutrons will be extracted from 7000 tungsten bricks arranged in a grid layout and encased in a steel rotating wheel.
The ESS target technology is largely untested, hence several diagnostic instruments will continuously assess its structural and operational condition to ensure consistent neutronic performance as well as prompt response in case of failures. The proposed Target Imaging System (TIS) is intended to perform online imaging of the inner structure of the target wheel to ensure that its geometry is preserved over the course of the expected 5 years of target lifetime.
The TIS consists of a 1D scintillator array detecting collimated decay radiation originating from the activated tungsten bricks. Modifications in the grid layout due to accumulation of debris or to cloven bricks will result in a localized increase of
-ray emission. The TIS will be capable of multi-scale imaging: coarse spatial resolutions will allow fast detection of such increases, whereas the full 1 mm resolution will provide the precise (r, θ) location of the detected anomaly. A prototype instrument has been designed, built and commissioned at DTU to investigate the basic functionalities of the proposed TIS. Reconstructed images obtained from a specialized rotating resolution target wheel demonstrate the feasibility of the TIS principle. 
The prototype development allowed to formulate design and manufacturing recommendations, to identify suitable materials for the structural and optical TIS components, to develop software for instrument control and to outline the principles for the TIS image reconstruction and anomaly detection.
This PhD project is providing a baseline for the TIS development and will provide guidelines to benchmark the forthcoming design choices.
Original languageEnglish
PublisherDTU Nutech
Number of pages138
Publication statusPublished - 2019


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