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ZnS/LiF scintillation detector with readout via wavelength shifting fibers

Due to the worldwide shortage of 3He and the price development caused by this, alternative concepts of neutron detection are in demand. One possible alternative is a ZnS/LiF scintillation detector with readout via wavelength shifting fibers. The presented dissertation describes the development of a model of the physical frontend, which enables computer-aided simulations with different configurations and conditions.
The model regards the microscopic structure of the scintillator during the tracking of alpha and triton particles created by the conversion of a neutron at a 6Li as well as the propagation of photons through the scintillator plate. In the first case, the structure is simulated via randomly placed spherical grains, through which the charged secondary particles are tracked. In the second case, the photons are subject to a random walk with parameters dependend on the composition of the scintillator. The model is validated in several steps, during which single aspects of the model are verified. There is a good agreement between measurements and simulations of neutron absorption and pulse height spectra of different scintillator samples. A comparison with optical transmission measurements shows, that the simulated effective optical absorption coefficent is of the same order of magnitude as the measured value of samples of one manufacturer, but is smaller by a factor of 6 than the value of samples of another manufacturer.
For the validation of the entire model, measurements of a prototype are compared to simulations. In order to compare the data event-wise, a detection algorithm based on cluster finding is developed. Measurements and simulations are in good agreement, so the model can be regarded as validated.
To optimize multiple parameters at the same time, a generalization of the Golden Section Search can be used. This algorithm optimizes parameters with respect to an optimization function, e.g. detection efficiency, which is calculated dependend on simulation data. This way it is possible to optimize detector parameters for new developments.


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