Fast neutron-based instruments for application to fusion and spallation sources

As the increasing interest in MeV range neutrons for applied physics studies, the development of dedicated fast neutron-based instruments, which have the capabilities to deal with complex background and to measure high counting rate (MHz), is demanded. This thesis presents the development both on a fast response scintillation detector that has been developed as a neutron emission monitor for deuterium beam diagnostics on large current negative beam test facility (like ELISE or SPIDER), and on the design and test of Telescope Proton Recoil (TPR) neutron spectrometers dedicated for neutron spectrum measurements on the fast neutron beam line ChipIr at ISIS. These instruments have been studied at accelerator-based platforms, tested at the ISIS spallation neutron source, as well as been applied in dedicated experiments on ELISE. Development of the two types of fast neutron-based instruments in applications to fusion and spallation neutron sources are presented in the following two parts: (1). Measurement of the deuterium beam-target neutron emission that occurs when the deuterium beam penetrates in the metallic dump of the NBI (neutral beam injector) prototype has been proposed as a means of diagnostics on beam homogeneity at SPIDER and MITICA. In order to present the deuterium beam profile by measuring the produced neutrons from the DD reactions between the deuterium beam and deuterons previously implanted in the beam dump, a relative model should be built to predict the neutron emission based on understanding the process of deuterium implantation in dump, and to aid the CNESM detection system which is based on the GEM technique for beam profile diagnostics in SPIDER. To this end, a calibrated EJ301 liquid scintillation detector has been developed and used on ELISE to measure the time trace of neutron emission and to benchmark calculations based on the Local Mixing Model (LMM), which has been applied to describe the deuterium implantation in the dump. The scintillation detector shows good capabilities on neutron/gamma-rays discrimination and radioactive resistance. In particular, a similar liquid scintillator will be installed at SPIDER as a neutron emission monitor. (2). On the atmospheric-like fast neutron beam-line ChipIr, which is designed for electronics radiation studies at ISIS, direct measurement of the neutron spectrum and flux distribution could be used for characterizing the neutrons profile and benchmarking the simulations. As the challenges of high intensity neutrons, wide energy range and complex background, TPR neutron spectrometers have been proposed as an effective way by applying the deltaE-E technique and coincidence analysis. In this thesis, two types of TPR spectrometers based on silicon detectors (silicon-based TPR) and a YAP scintillator together with silicon detectors (scintillator-based TPR), respectively, have been designed and tested. Two prototypes of scintillator-based TPR have been designed for long-term measurements as the good radioactive resistance of YAP scintillators. The response of the used YAP scintillator to protons has been studied up to 80 MeV. Two scintillator-based prototypes have been tested on ChipIr and ROTAX beam line, respectively. With the collimator installed on the ROTAX beam line for incident neutrons, the triple coincidence scintillator-based TPR shows a good capability on charged particles discrimination and background suppression. The prototype of silicon-based TPR, which consists of four silicon detectors, has been tested on the ROTAX beam line. The recoil proton spectrum obtained by the two types of TPR prototypes on the ROTAX beam-line have been compared. Results show the possible of high intense neutrons measurements by using the silicon-based TPR.