Enhancing Superconducting Properties of SRF Thin Films by Laser Processing

Superconducting niobium cavities are the most crucial components in particle accelerators to provide the acceleration to the desired particles via RF energy with low losses. Bulk niobium (Nb) has been the material of choice for superconducting RF (SRF) cavities since it has the highest critical temperature (Tc = 9.25 K) and the lower magnetic field of all the pure metals and it can be formed easily in cavity shape. The RF performance of bulk Nb cavities has continuously been improved over the years and is approaching the optimal performance. Although further improvement has been achieved with surface doping, long term solutions for SRF surface efficiency enhancement need to be pursued. One promising alternative to bulk Nb is to deposit a Nb thin films on a Cu cavity, as the RF only affects a few microns on the surface, typically less than 1 μm. Deposition of Nb has great benefits compared to bulk Nb cavities.

Laser polishing is a technology of smoothening the surface of various materials with highly intense laser beams. When these beams impact on the material surface to be polished, the surface starts to be melted due to the high temperature. The melted material is then relocated from the ‘peaks to valleys’ under the multidirectional action of surface tension. By varying the process parameters such as beam intensity, energy density, spot diameter, and feed rate, different rates of surface roughness can be achieved. High precision polishing of surfaces can be done using laser process. Conventional polishing techniques have many drawbacks such as less capability of polishing freeform surfaces, environmental pollution, long processing time, and health hazards for the operators. Laser polishing, on the other hand, eliminates all the mentioned drawbacks and comes as a promising technology that can be relied for smoothening of initial topography of the surfaces irrespective of the complexity of the surface.

The aim of this PhD project is to optimize the superconducting properties of thin film superconductor such as high first magnetic field entry, ultra-low surface resistance, high critical temperature, ultra-low surface roughness and low secondary electron emission. The student will be playing an important role in generation and characterization of these SRF thin films in the UK’s world-leading lab.

Qualifications applicants should have/expect to receive: The successful candidate will spend most of his/her time at the Cockcroft Institute near Warrington, working with STFC Daresbury Laboratory researchers and supervisory team members. The successful candidate will have or expect to obtain a first or upper second-class degree or equivalent (e.g. MPhys, MSci) in physics or material science.

Funding and eligibility: The project is fully funded by the Cockcroft Institute for 3.5 years. A full package of training and support will be provided by the Cockcroft Institute. Self-funded overseas students may apply. An IELTS score of at least 6.5 is required.

Contact for further information: guoxing.xia@manchester.ac.uk or visit Room 7.11, Schuster Building on the University of Manchester main campus.

How to apply: http://www.manchester.ac.uk/postgraduate/howtoapply/

This position will remain open until filled.