Microwave current drive in prototype spherical tokamak reactors

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EPSRC
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Sept. 30, 2021

Sept. 30, 2025

My background is an integrated masters in Natural Sciences specialising in Physics at the University of York, graduating in 2021. During my degree I was fortunate enough to complete a summer internship working on microwave current drive for STEP which triggered my interest in plasma physics and passion for bringing fusion energy to the National Grid. My masters project was also in plasma physics, looking at how we can model the effect of drifts in the divertor of high power tokamaks.

For my project on the Fusion CDT, I am back to working on microwave current drive, particularly the use of Electron Bernstein Waves during start-up for prototype spherical tokamaks.

In order to confine a plasma inside a tokamak, we need to generate a current through the plasma itself. So far, this has been done through induction using a solenoid down the centre of the device. However, there are disadvantages in this approach if we are designing a spherical tokamak power plant. This includes that there is not very much space in the centre column and that we want to be operating the powerplant for substantial amounts of time. Microwave current drive offers a solution to both of these problems as the gyrotrons can be located a long way away from the device and can be used for long periods of time. Therefore, it would be ideal if we could design a system to drive the plasma current throughout both phases of operation: start-up (when the plasma is being formed) and steady-state (the main phase of operation, when energy is generated). Microwave current drive in steady-state has been studied extensively but start-up is less well understood.

Therefore, my project will aim to find a microwave system for the start-up phase of the plasma. It is a collaboration between the University of York, CCFE and Tokamak Energy and I will be working under the supervision of Roddy Vann, Simon Freethy, Vladimir Shevchenko and Erasmus du Toit.

Potential Impact:
Identifying a sustainable energy supply is one of the biggest challenges facing humanity. Fusion energy has great potential to make a major contribution to the baseload supply - it produces no greenhouse gases, has abundant fuel and limited waste. Furthermore, the UK is amongst the world leaders in the endeavour to commercialise fusion, with a rapidly growing fusion technology and physics programme undertaken at UKAEA within the Culham Centre for Fusion Energy (CCFE). With the construction of ITER - the 15Bn Euro international fusion energy research facility - expected to be completed in the middle of the 2020's, we are taking a huge step towards fusion power. ITER is designed to address all the science and many of the technology issues required to inform the design of the first demonstration reactors, called DEMO. It is also providing a vehicle to upskill industry through the multi-million pound high-tech contracts it places, including in the UK.
ITER embodies the magnetic confinement approach to fusion (MCF). An alternative approach is inertial fusion energy (IFE), where small pellets of fuel are compressed and heated to fusion conditions by an intense driver, typically high-power lasers. While ignition was anticipated on the world's most advanced laser fusion facility, NIF (US), it did not happen; the research effort is now focused on understanding why not and the consequences for IFE, as well as alternative IFE schemes to that employed on NIF.

Our CDT is designed to ensure that the UK is well positioned to exploit ITER and next generation laser facilities to maximise their benefit to the UK and indeed international fusion effort. There are a number of beneficiaries to our training programme: (1) CCFE and the national fusion programme will benefit by employing our trained students who will be well- equipped to play leading roles in the international exploitation of ITER and DEMO design; (2) industry will be able to recruit our students, providing companies with fusion experience as part of the evolution necessary to prepare to build the first demonstration power plants; (3) Government will benefit from a cadre of fusion experts to advise on its role in the international fusion programme, as well as to deliver that programme; (4) the UK requires laser plasma physicists to understand why NIF has not achieved ignition and identify a pathway to inertial fusion energy.

As well as these core fusion impacts, there are impacts in related disciplines. (1) Some of our students will be trained in low temperature plasmas, which also have technological applications in a wide range of sectors including advanced manufacturing and spacecraft/satellite propulsion; (2) our training in materials science has close synergies with the advances in the fission programme and so has impacts there; (3) AWE require expertise in materials science and high energy density plasma physics as part of the national security and non-proliferation strategy; (4) the students we train in socio-economic aspects of fusion will be in a position to help guide policy across a range of areas that fusion science and technology touches; (5) those students involved in inertial fusion will be equipped to advance basic science understanding across a range of applications involving extreme states of matter, such as laboratory astrophysics and equations of state at extreme pressures, positioning the UK to win time on the emerging next generation of international laser facilities; (6) our training in advanced instrumentation and control impacts many sectors in industry as well as academia (eg astrophysics); (7) finally, high performance computing underpins much of our plasma and materials science, and our students' skills in advanced software are valued by many companies in sectors such as nuclear, fluid dynamics and finance.