Evolution and dynamics of pellets and dust in dynamic gas-plasma systems
Lead Research Organisation:
University of Glasgow
Department Name: School of Physics and Astronomy
Abstract
Nuclear fusion offers the prospect of almost limitless power production with minimal environmental impact. Magnetic fusion in tokamaks (which are magnetic chambers that can hold plasma at a temperature in excess of that in the solar core) has demonstrated a practical route to power generation via JET, and the construction of the next generation of fusion power station, ITER, is well under way. Key elements in the realisation of practical fusion power are (i) maintaining plasma stability, and (ii) refuelling the reactor. The injection of cryogenically solid fuel pellets offers a way to address both aspects: these icy pellets of Deuterium-Tritium mixture are fired at speeds of up to 300m/s into the burning fusion plasma in order to replenish spent fuel, and also to drive the density profile across the plasma, so aiding the stability of the burning process. The evolution of the pellet as it encounters the energetic plasma presents technical challenges, demanding stringent modelling in order to optimise the process. The pellet evaporates under the intense bombardment of the energetic fusion plasma, shedding fuel gas in clouds along its trajectory. These clouds become ionized and polarized (charge-separated) as part of the process of equilibrating with the pre-existing reactor plasma, and at the same time the pellet also becomes charged; complex electromagnetic and fluid forces then determine the density deposition profile as the pellet trajectory evolves from being purely ballistic (ie with trajectory governed by initial conditions at launch) to a more sophisticated dynamics. Moreover, the response of the existing plasma to the new material affects the reactor conditions, and accounting for the transient feedback (over a few milliseconds) in both directions is a challenging problem. This research proposal aims to create new modelling of the evaporation, ionization and fluid/electromagnetic feedback on both the plasma conditions and the pellet evolution by exploiting new techniques in handling gas-magnetized plasma momentum and energy exchanges, and ionization mechanisms. By so doing, it is hoped that this proposed research can address gaps in the current approaches, and assist in the creation of a new, optimised design of pellet refuelling and stability for tokamaks. The impact of this science is broader than the immediate technological goal of carbon-free energy production: similar plasma-solid interface physics occurs in many situations, from cometary impact on stellar atmospheres to plasma catalysis and gas remediation. Indeed, there are many circumstances in which plasma impacting directly or indirectly onto a surface can promote beneficial changes to that surface, such as making it waterproof (hydrophobic) or biocidal (inhibiting bacterial attachment) or laying down new surface coatings (plasma vapour deposition). Though the analysis and modelling of frozen pellets for fusion may not seem initially to be relevant to these areas, there is major scope to explore whether or not small droplets or pellets in suspension may provide advantages over classical plasma processing techniques in applications such as coatings or catalysis; the insight offered by the research proposed here will be key to evaluating these new potential uses.
Planned Impact
The potential economic and societal impacts are as follows.
Fusion as a clean energy source will reduce our dependence on fossil fuels, and consequently our national carbon footprint - clearly a highly desirable goal in respect of global warming. The key to practical fusion power lies in maintaining the correct plasma conditions for the fusion burn; this relies on ensuring fresh fuel reaches the burning region, and that the plasma stability and power exhaust systems are optimised appropriately. An advanced understanding of injected pellet/plasma interaction processes is paramount to delivering these milestones.
The UK is a major player in the commercial use of plasma technology, from gas remediation to surface processing. The fresh insight into plasma ablation that will result from this proposed research will help not only maintain the UK economic and technological lead in existing surface plasma interaction applications (including textile processing to produce tailored hydrophilic or hydrophobic coatings, laser ablation of thin targets to produce beams for therapeutic applications and ion implantation for surface hardening or improved coatings) but may offer new routes to novel applications. Indeed it may be that the ablation of a volumetric suspension of microscopic solid or liquid particulates may be a preferable alternative to the 2-D conventional sputtering or catalytic processes, in terms of access to greater surface area, more sensitive content control, and superior flexibility in geometric terms.
Just as one topical example, plasma medicine involves a detailed, complex interaction between tissue, activated neutral gas and charged plasma species, generally involving escape/creation of volatiles from the tissue surface, which could be chemically altered in the plasma environment and exploited advantageously to maximise the efficacy of such treatments.
Fusion as a clean energy source will reduce our dependence on fossil fuels, and consequently our national carbon footprint - clearly a highly desirable goal in respect of global warming. The key to practical fusion power lies in maintaining the correct plasma conditions for the fusion burn; this relies on ensuring fresh fuel reaches the burning region, and that the plasma stability and power exhaust systems are optimised appropriately. An advanced understanding of injected pellet/plasma interaction processes is paramount to delivering these milestones.
The UK is a major player in the commercial use of plasma technology, from gas remediation to surface processing. The fresh insight into plasma ablation that will result from this proposed research will help not only maintain the UK economic and technological lead in existing surface plasma interaction applications (including textile processing to produce tailored hydrophilic or hydrophobic coatings, laser ablation of thin targets to produce beams for therapeutic applications and ion implantation for surface hardening or improved coatings) but may offer new routes to novel applications. Indeed it may be that the ablation of a volumetric suspension of microscopic solid or liquid particulates may be a preferable alternative to the 2-D conventional sputtering or catalytic processes, in terms of access to greater surface area, more sensitive content control, and superior flexibility in geometric terms.
Just as one topical example, plasma medicine involves a detailed, complex interaction between tissue, activated neutral gas and charged plasma species, generally involving escape/creation of volatiles from the tissue surface, which could be chemically altered in the plasma environment and exploited advantageously to maximise the efficacy of such treatments.
Publications
Bennet E
(2016)
Precision charging of microparticles in plasma via the Rayleigh instability for evaporating charged liquid droplets
in Journal of Aerosol Science
Diver D
(2016)
Modelling nonlinear electrostatic oscillations in plasmas
in Physics of Plasmas
Helling C
(2016)
Atmospheric Electrification in Dusty, Reactive Gases in the Solar System and Beyond
in Surveys in Geophysics
Martin Frederick Kyle
(2021)
Cryogenic pellet ablation modelling in a hot, magnetised plasma
Stark C
(2018)
Dust cloud evolution in sub-stellar atmospheres via plasma deposition and plasma sputtering
in Astronomy & Astrophysics
Stark C
(2020)
Evolution of spheroidal dust in electrically active sub-stellar atmospheres
in Astronomy & Astrophysics
Wilson A
(2016)
Alfvén ionization in an MHD-gas interactions code
in Physics of Plasmas
Wilson A
(2017)
Ionization fronts in coupled MHD-gas simulations
in Physics of Plasmas
Wilson A
(2019)
Critical Velocity Ionization in Substellar Atmospheres
in The Astrophysical Journal
Description | We are exploring a new underlying mechanism for pellet ablation, that naturally allows for striations in diagnostic light curves to occur. We are particularly interested in the role of in-site generated positive ions in the ablation process. |
Exploitation Route | fully developed modelling and simulation is currently underway- Kyle Martin's PhD work has revealed significant aspects meriting further study, but his funded period is now ended. |
Sectors | Energy |
Description | Fusion Forward Ardeer Consortium |
Geographic Reach | National |
Policy Influence Type | Contribution to a national consultation/review |
Impact | Raised awareness of fusion, as opposed to fission, as a possible electrical power supply - not just in the broader community, but also with local and national politicians, decision makers and influencers. We have also created a new policy of cooperation between HE, FE, SDS (Skills Development Scotland) and industry to ensure optimum workforce training, spanning apprenticeships to PhDs - the advisory panel will review the needs of industry, and help education providers plan appropriate training in such a way that a comprehensive offer is available to the local population that will allow them to participate in any developments, rather than have a non-local workforce commute in to help with construction and operation, thereby diminishing the socio-economic impact of investment locally. |
Description | Membership of UK Tokamak Science Council |
Geographic Reach | National |
Policy Influence Type | Membership of a guideline committee |
Impact | UK Tokamak Science Council advises on the best practice for fusion power research. |
Title | Critical Velocity Ionisation in Substellar Atmospheres |
Description | This dataset includes the global circulation model snapshot and ionisation/recombination data as well as necessary read codes from the associated article. |
Type Of Material | Database/Collection of data |
Year Produced | 2019 |
Provided To Others? | Yes |
URL | http://researchdata.gla.ac.uk/id/eprint/910 |
Title | gas-plasma envelope |
Description | We are building a holistic model of the evolution of ablation from cryogenic pellets exposed to fusion-energy magnetised plasma. Although there have been ablation models created in the past, none have our combination of extreme parameters. We propose to create a new comprehensive and consistent model of ablation, ionization and feed-back on solid surfaces encountering energetic magnetised plasma. Such a model will deepen under-standing how to maximise the effectiveness of pellet injection in tokamaks for refuelling, and quan-tify the effect of dust behaviour at the tokamak edge, as well as providing new insight into the fun-damental behaviour of gas-plasma-dust systems for industrial applications such as plasma catalysis, and astrophysical contexts such as star-grazing comets. This research is timely, since ITER is depend-ent on pellet injection as a refuelling strategy, and the complexity of this new device demands greater understanding of the underlying physics and engineering. |
Type Of Material | Computer model/algorithm |
Year Produced | 2018 |
Provided To Others? | No |
Impact | The model - which is under construction, and not yet complete - will allow investigation of tailored pellet injection to achieve particular refuelling profiles or density structures for suppression of instablities. The physical model will have wider application than just pellet injection - for example, comet-star encounters. |
Description | CCFE Pellet Injection Group |
Organisation | EURATOM/CCFE Fusion Association |
Country | United Kingdom |
Sector | Academic/University |
PI Contribution | With Dr M Valovic, access to pellet diagnostic data from MAST, along with CCFE simulation codes. |
Collaborator Contribution | This collaboration is at an early stage, given the recent start of the funding. |
Impact | Outputs are still being generated at his early stage. |
Start Year | 2016 |
Title | Ionization simulation in fluid plasmas |
Description | Novel method of modelling ionization processes in fluid plasmas |
Type Of Technology | New/Improved Technique/Technology |
Year Produced | 2018 |
Impact | First combined holistic treatment of flow ionization in magnetofluid plasmas, published and cited. |
Description | Address to local politicians and community organisations |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Policymakers/politicians |
Results and Impact | An address to the elected members of North Ayrshire Council, as well as selected community organisations and government agencies (such as Scottish Enterprise, SCDI, SDS). There were two such meetings: one in August 2021 (attended by UKAEA to pitch the project) and one in January 2022, which was essentially an update meeting relating progress since the last one (UKAEA did not attend the Jan meeting). I spoke at both meetings, and was involved in the Questions and Answers panel at each. |
Year(s) Of Engagement Activity | 2021,2022 |
Description | Direct engagement with UKAEA Technical Teams |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Policymakers/politicians |
Results and Impact | As part of the STEP Siting competition, the UKAEA technical site assessment team visited the Ardeer site on 3 occasions, the latter two involving me. These last two visits occurred on Nov 2021 and again on Jan 2022, with the January visit including politicians, local authority specialists (planning, investment) and members of the UKAEA Board. A third private visit by UKAEA CEO Ian Chapman took place in March 2022 - Ian had missed the full visit on Jan because he tested positive for Covid. The November visit included technical project staff from UKAEA and their consultants, Atkins; the January visit involved senior board members from UKAEA, the local MP, North Ayrshire Council officials (including the CEO) and the elected head of the council, plus consortium members (me representing University of Glasgow, the landowner NPL) and Scottish Enterprise. The purpose of these visits was to explore all technical and socio-economic aspects of the Ardeer site (land practicalities, utilities, transport and access, jobs and worforce training). There was significant interaction (discussion, exploration of strategy and implications for the local and regional economies) and the UKAEA team pronounced themselves very satisfied with the visit, have had all their questions answered, and achieved a thorough understanding of the nature of the site. |
Year(s) Of Engagement Activity | 2021,2022 |
URL | https://www.thisisnorthayrshire.co.uk/invest/step-spherical-tokamak-for-energy-production/step-ardee... |
Description | Fusion: Power for the Future |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Professional Practitioners |
Results and Impact | Public lecture to members of Royal Scottish Society of the Arts (RSSA) in Edinburgh, on ITER and the development of fusion power. About 45 professionals attended (some retired). |
Year(s) Of Engagement Activity | 2017 |
URL | https://www.rssa.org.uk/ |
Description | Governmental briefings |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Policymakers/politicians |
Results and Impact | This is to record briefings given by me to 4 senior politicians and ministers: Michael Matheson, Scottish Government Cabinet Secretary for Energy (Jan 26 - coincided with a stakeholders briefing on the same day, recorded separately in researchfish); Scotland Office minister Ian Stewart (10/2/22); Scottish Labour Party Leader Anas Sarwar (23/2/22) and Scotland Office under secretary of state Lord Offord ( 2/3/22). In each briefing I played a key technical role, laying out the science and the nomination process and progress. In the last two meetings I was accompanied by local government officials and elected members to explain socio-economic; the first two meetings were essentially University led policy briefings. |
Year(s) Of Engagement Activity | 2022 |
Description | Public Engagement on STEP |
Form Of Engagement Activity | A formal working group, expert panel or dialogue |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Public/other audiences |
Results and Impact | This was a companion engagement exercise to the stakeholders' briefing earlier -- both on Jan 26, stakeholders in morning, general community in evening - all by teams. There were formal presentations by me and the local authority, followed by an extensive question and answer session. Many opionions were expressed, including a small number of dissenting voices. Generally, the opinions were positive, and there was a significant expression of support for the initiative, particularly when questions were answered that allayed fears or addressed specific topics about which there was no previous knowledge on the community's part. It was particularly gratifying to create a specialised FAQ for this meeting, and see the range and depth of questions that were addressed, and having been addressed, subsequently elicited messages of support. |
Year(s) Of Engagement Activity | 2022 |
URL | https://www.thisisnorthayrshire.co.uk/invest/step-spherical-tokamak-for-energy-production/step-ardee... |
Description | Radio interview with BBC Radio Scotland |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Public/other audiences |
Results and Impact | A live radio interview on the topic of STEP (Spherical Tokamak for Energy Production) fusion power station, and the candidacy of Ardeer as a host for this facility. The intended purpose was to raise awareness generally about the project, and the prospect of this new type of power station coming to Scotland. Anecdotal evidence was that this interview came across well, and had a positive influence on opinions. |
Year(s) Of Engagement Activity | 2022 |
URL | https://www.thisisnorthayrshire.co.uk/invest/step-spherical-tokamak-for-energy-production/step-ardee... |
Description | STEP Ardeer stakeholder engagement |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Industry/Business |
Results and Impact | A major engagement with local and regional and national organisations in order to publicise Ardeer as a possible host for STEP - the new fusion power station. The stakeholders were significant industrialists, policy makers, government organisations (such as SDS, SE), education and training organisations (SCSI, RSE, universities, colleges). UKAEA were hosts, and I was a key speaker, representing the Fusion Forward Ardeer consortium, the nominating organisation for Ardeer's candidacy. There was a formal question and answer session, but I was unable to attend this since I was called away to brief a government minister (see separate entry). I did participate in the creating a FAQ for the website (see below). |
Year(s) Of Engagement Activity | 2022 |
URL | https://www.thisisnorthayrshire.co.uk/invest/step-spherical-tokamak-for-energy-production/step-ardee... |
Description | School engagement (Ardeer Primary School) |
Form Of Engagement Activity | A talk or presentation |
Part Of Official Scheme? | No |
Geographic Reach | Regional |
Primary Audience | Schools |
Results and Impact | A question and answer session with primary 6 at Ardeer Primary School, on the topic of siting the STEP fusion power station at Ardeer. This meeting was done by teams. The pupils sent me a list of questions before the meeting, and the discussion sparked a significant amount of project work on their part, culminating in set of drawings by the children of how STEP might look in Ardeer, a narrated powerpoint presentation of the history of Ardeer and why it's a great site for a new kind of energy production, and a movie of the children expressing their enthusiasm for the project. All these materials have been supplied to UKAEA (respecting GDPR) as evidence of community engagement |
Year(s) Of Engagement Activity | 2022 |
URL | https://www.thisisnorthayrshire.co.uk/invest/step-spherical-tokamak-for-energy-production/step-ardee... |
Description | Television interviews |
Form Of Engagement Activity | A broadcast e.g. TV/radio/film/podcast (other than news/press) |
Part Of Official Scheme? | No |
Geographic Reach | National |
Primary Audience | Media (as a channel to the public) |
Results and Impact | There were two TV interviews: (i) interview with STV on the topic of Ardeer's candidacy to be the host for STEP (Spherical Tokamak for Energy Production), a fusion power station. The intention was to publicise the concept and application more widely to the general public, to elicit wide support for the initiative. This interview did attract attention, though this is only anecdotal. (ii) a second TV interview with BBC News South (Oxford), on more general topic of fusion power, given the recent results from JET and Tokamak Energy. This second interview (on March 14) came as a result of a radio interview I had done earlier with the BBC. |
Year(s) Of Engagement Activity | 2022 |
URL | https://www.thisisnorthayrshire.co.uk/invest/step-spherical-tokamak-for-energy-production/step-ardee... |