Abstract
This dissertation summarizes the neutronic characterization work performed in the epithermal neutron beam at Tsing Hua Open-pool Reactor (THOR) in the past years, before entering the clinical trial of Boron Neutron Capture Therapy (BNCT). Part of this study was also performed at the High Flux Reactor (HFR) in Petten, The Netherlands. The completion of this dissertation owes to many conscientious people and their hard work.In order to provide a reliable estimation of boron dose in tumor and in normal tissue, a well-characterized epithermal neutron beam is demanded for BNCT. In this dissertation, we have established a new systematic methodology to characterize the neutron beam in time, energy, spatial, and angular domains. This is a breakthrough for BNCT dosimetry based on many other previous studies and efforts; this is the first time we are able to determine all these parameters of interest, especially the spatial and angular distributions.Chapter 1 introduces the basic concept of BNCT, the THOR and HFR facilities, and the aims of this dissertation. Chapter 2 presents the on-line neutron monitoring system installed at THOR, which is applied to monitor the beam variation in the time domain. In Chapter 3, it introduces the idea of the activation detector and the two-foil method, which are generally used for determining the absolute neutron fluence rates. Following Chapter 3, Chapter 4 is the implementation of the two-foil method in the THOR beam.The application of Indirect Neutron Radiography (INR) is one of the main features of this dissertation. The INR can map the neutron flux distribution in space. In Chapter 5, the key component of INR, the imaging plate (or imagine plate) is presented and its responses to activation detectors is discussed. The neutron flux mappings free-in-air and in-phantom are shown in Chapters 6 and 7.Chapter 8 presents the spectra adjustment of the epithermal neutron beam of the THOR and HFR. It utilizes a creative algorithm named “coarse-scaling adjustment” to provide smooth fine-group energy spectra (640 groups) based on multiple activation detectors and unfolding techniques. The common self-shielding problem is discussed in Chapter 9, in which the idea of Monte Carlo determined self-shielded cross-sections is brought in. The most interesting part, Chapter 10 shows you an integrated methodology to determine the spatial and angular distribution of the THOR epithermal neutron beam, which utilizes the INR from Chapter 7, the unfolding techniques from Chapter 8, and the Monte Carlo determined groupwise detector responses from Chapter 9.All the parameters of an epithermal neutron beam can now be determined.