High temperature superconductors (HTS) in the form of coated conductors are an enabling technology for the next generation of compact nuclear fusion reactors that require higher magnetic fields than Nb₃Sn can provide. However, in operation, the superconducting magnet windings will be exposed to a flux of fast neutrons which will introduce structural damage at cryogenic temperatures. Many previous studies using both fission spectrum neutrons and ions at room temperature (or slightly elevated temperatures) have shown that an initial increase in the superconducting current carrying performance upon irradiation is followed at higher fluences by a severe degradation of the properties and eventually complete loss of superconductivity. The superconducting transition temperature is found to decrease monotonically with fluence, strongly suggesting that radiation-induced defects occur throughout the entire crystal lattice, even at relatively low fluence. This talk will outline the research being carried out to improve understanding of radiation damage in HTS materials. This includes innovative in situ ion irradiation experiments to assess radiation damage of HTS at cryogenic temperatures, superconducting property measurements at ultra-high magnetic fields, and studies aimed at elucidating the nature of irradiation induced lattice defects using state-of-the-art microscopy and spectroscopy techniques.