Dissertation: Multi-sightline neutron emission spectroscopy of D and T fusion plasmas at JET

  • Date:
  • Location: Zoom: https://uu-se.zoom.us/j/67473929656?pwd=L3ZrcE1JVERqd05hclQyVTZLa2htQT09 Häggsalen (10132)
  • Doctoral student: Arne Sahlberg
  • Organiser: Department of Physics and Astronomy
  • Contact person: Åsa Andersson
  • Phone: 018-4717306
  • Disputation

Arne Sahlberg defends his thesis "Multi-sightline neutron emission spectroscopy of D and T fusion plasmas at JET"

Opponent: Dr. Manuel Garcia-Muñoz (University of Seville)

The dissertation is held in English.

Abstract

An analysis of the neutron emission from a fusion plasma can be used to determine plasma properties and diagnose fusion performance. In this thesis, several analysis methods for neutron spectroscopy are presented and applied to data from the experimental fusion device JET. JET has numerous instruments for neutron measurements installed, and data from several of them are used in this thesis.

The work presented here describes how various plasma parameters affect the neutron emission and how this information can be used to determine properties of the fusion plasma. Forward fitting of models parameterized in terms of the relevant plasma properties are a central part of most of the analysis methods and are used to determine key features of supra-thermal (“fast”) ion distributions for prediction of plasma performance in deuterium-tritium (d-t) experiments, and to determine the branching ratio for the formation of a short-lived 5He resonance in t+t reactions. The thesis also includes work concerning uncertainty quantification of the modeling of the neutron emission rate and the calculation of pile-up distortion of light-yield spectra from liquid scintillator detectors.

A major contribution of this thesis is the novel methods for measuring properties of a fast-ion distribution using neutron spectroscopy with multiple sightlines. The combination of data from instruments viewing different parts of the plasma and/or with different viewing angles permits us to study fast-ion behavior in a more consistent and detailed fashion than if we analyze each measurement separately. Another interesting result is the first-ever observation of the neutron spectrum from t+t reactions in a magnetically confined fusion plasma, from which we can learn important things about the t+t reaction in reactor relevant conditions.