< Back to previous page

Project

High intensity surface ion source towards long-term irradiations for ISOL@MYRRHA

This thesis presents the development and experimental testing of a novel surface ion source for the ISOL@MYRRHA project at the Belgian Nuclear Research Centre SCK CEN. The MYRRHA project is the first prototype of a subcritical lead-bismuth cooled reactor driven by a linear particle accelerator. Part of the beam  coming from the accelerator will be extracted towards an ISOL facility, ISOL@MYRRHA, for radioactive ion beam production. The research focuses on enhancing the efficiency and reliability of ion sources under the unique conditions of this facility, which include a primary beam of 100 MeV protons with up to 0.5 mA beam intensity.

A comprehensive overview of existing ISOL ion sources is provided, categorised by their ionisation mechanisms: ion impact, electron impact, surface, and laser ionisation. Due to its simplicity and robustness, a surface ion source was selected for ISOL@MYRRHA as a first source, with potential for conversion into a laser ion source. The thesis explores the surface ionisation principle, examining the interactions at the heated material surface, the formation of plasma sheath potential, and the impact of these phenomena on ionisation efficiency.

The importance and impact of the surface ion source's heating system were studied: electron-bombardment and Ohmic heating. The former was used during the development of surface ionisation theory and the latter is the typical form used nowadays in ISOL facilities. The implications of Ohmic heating on temperature and potential distribution within the ion source are discussed. An active thermal screen concept to mitigate cold spots, identified in Ohmic heating systems, has been developed. This concept, along with its variations for different manufacturing methods – Welded, 3D-printed, and Assembled designs – were explored, resulting in a prototype of the Assembled design constructed at SCK CEN, then successfully tested at CERN.

Experimental results from initial tests are detailed, including the prototype's thermal-electric behaviour and its performance under various operational conditions.

The thesis concludes with insights into the ionisation efficiency of different elements, the impact of ion load and temperature on ion origin, and the prototype's durability over extended operation and under stress conditions. The findings and their consequences for the understanding of the surface ion source are then summarised. Finally, practical solutions and advancements for the future ISOL@MYRRHA facility and the development of a next surface ion source are discussed.

Date:1 Dec 2019 →  13 Dec 2023
Keywords:Ion sources, Surface ionization, Radioactive ion beams, Isotope Seperator On-Line
Disciplines:Atomic physics, Applied aspects of nuclear physics, Experimental aspects of nuclear physics
Project type:PhD project