Parametric Wave Coupling and Non-Linear Mixing in Plasma

Lead Research Organisation: University of Strathclyde
Department Name: Physics

Abstract

Plasma is a state of matter that exists when the energy level or temperature become so high that electrons are no longer bound to atoms. This produces at least two species (negative electrons and positive ions) with opposite charge and very different masses (electron mass << ion mass). The charge of both types of particle make them each respond to electromagnetic fields (such as light, microwave and radio waves), but in opposite directions, and at very different rates. They particularly respond to waves at frequencies close those of natural plasma oscillations, determined by complicated combinations of the magnitude and direction of any static magnetic field, the number density and mass of the particles. They can absorb wave energy at frequencies called 'resonances', and reflect wave energy at frequencies called 'cut-offs'. These effects are often used to heat or measure plasmas in important laboratory experiments and applications, such as new techniques for energy production through fusion reactions (magnetically confined) and industrial processing as well as natural plasmas in the Earth's magnetosphere and ionosphere. Both natural ionospheric and magnetospheric plasmas are important to modern communication and navigation systems. In industrial processing, plasma physics underpins semiconductor processing and hence modern digital technology. In fusion energy research the impact potential is to enable an almost unlimited supply of energy, addressing serious environmental concerns surrounding the use of fossil fuel, with no long term radioactive byproducts.

Parametric coupling refers to a multi-wave interaction where two or more waves exchange energy when their frequencies are related by a natural plasma oscillation frequency. Such processes have recently been found to cause difficulties in laser-plasma interactions for inertial confinement fusion, whilst at the same time offering exciting potential for new and more flexible ways of delivering energy into both inertially and magnetically confined fusion plasmas. Indications exist that suggest such new techniques will be increasingly important as such research moves from fundamental experiments to application scale equipment. We therefore propose to undertake fundamental research investigating these interactions in the microwave frequency range. The microwave range is particularly appealing for such research since powerful sources and amplifiers, developed for a range of applications, are readily available, can be very precisely controlled, enhancing the ability to investigate the plasma physics dynamics, whilst groundbreaking research points towards microwave generators achieving very high levels of normalised intensity (a measure of the effective intensity of the wave, affected by the wavelength, meaning that microwave intensities are effectively 'uplifted' compared to optical intensities). This therefore indicates potential in the microwave frequency range to explore the dynamics of extreme ranges of wave-plasma interaction in the near future. The project will be based at the University of Strathclyde where it benefits from co-location within a pre-eminent microwave source research laboratory. A further motivation for investigating the effect of wave coupling using microwaves is its direct application relevance to industrial processing and magnetic confinement fusion plasma physics.

The coupling of two precisely controlled microwave beams (~10cm to 3cm wavelength) in a (weakly to strongly) magnetised helicon plasma by plasma (acoustic-like) oscillations in the electrons and ions, cyclotron oscillation of the electrons and ions and hybrid oscillations including both quasi-acoustic and cyclotron motion will be investigated, as will the effects of stochastic heating where 'quasi-random' motion of particles in high amplitude waves gives very rapid increase in effective temperature.

Planned Impact

The impact of our research can be found primarily through the application of fundamental plasma science research on society, energy, environment, economy and policy.

A primary beneficiary of fundamental plasma science research and this proposed programme is both the inertial and magnetic confinement approaches to fusion energy. Realisation of practical schemes of fusion energy will result in a near limitless supply of energy with minimum environmental consequences, due to the high availability of the input materials and the relatively benign nature of the by-products. Affordable energy sources which do not contribute to the environmental problems associated with fossil fuels, or to the production of the long life radioactive by-products associated with fission energy, whilst avoiding the problems of proliferation, have profound, global sociological and economic benefits. Availability of energy is important in addressing social problems including equality and healthcare, whilst wide distribution of the necessary fusion input materials eliminates a source of competition and potential international tension. Ensuring an adequate energy supply in the face of declining fossil reserves (setting aside for the present environmental misgivings surrounding carbon emissions) is a key problem for government policy with enormous economic consequences. As such the impact of this research programme through its relevance to both mainstream approaches to fusion energy can be very substantial.

Research in the field of plasma science has potential for direct impact on industrial processing of materials. Low pressure industrial processing discharges need to achieve stable, dense and uniform plasma over a wide processing surface, and are usually produced by RF drive, often at two or more frequencies. The plasma source we plan to investigate, the helicon, is particularly attractive for future applications, as it is an effective and efficient approach to produce large volumes of highly ionised gas at relatively low pressures. Our research is on the interaction of a range of RF and microwave signals with plasma. We would anticipate being able to contribute to the understanding of multi-frequency industrial discharges. One of the most economically important industrial applications is in semiconductor processing. Enhancements in this field can have both direct impact on the economy and indirect impact via enhanced digital technology.

Our experience shows that research in plasma physics has further potential for economic impact through the UK high technology electronics industry. Plasma-wave interactions are relevant to 'free-electron' technology. Two of the project partners are industrial companies within this community. In addition to direct support of this specific project through the provision of key aspects of hardware, both firms sponsor and engage in knowledge exchange (KE) projects at Strathclyde building on prior fundamental plasma physics research. One potential impact of our project will be novel schemes for heating of magnetically confined fusion plasmas. One of our partners (TMD) is a leading UK designer and manufacturer of high power microwave sources and amplifiers whose sales have doubled in the last 5 years. They are well placed to take advantage of developments in novel heating schemes in fusion science, with the potential for new products and markets.

Strathclyde has a leading reputation for research in novel microwave sources and has a strong track record of KE with two of the leading UK-based manufacturers in the field of free-electron technology (e2v and TMD) which resulted in a highly ranked impact case study in the last REF. As an example of this type of impact, previous EPSRC fundamental research recently enabled Strathclyde (via the present PI Ronald) to form and lead a UK academic-industrial partnership (also featuring RAL and TMD) to secure international funding (from ESA) for research into space communication.

Publications

10 25 50
 
Description The project is ongoing and these findings should be viewed as ongoing and preliminary.

A novel scheme of lightweight magnet coils have been designed as part of the apparatus design. These coils are potentially of wider interest beyond this project.

Modern microwave amplifiers and oscillators have been assessed and in some cases tested. These combined with suitable optics are capable of achieving normalised power levels well above those required to initiate a range of plasma instabilities.

These findings will be updated in due course.
Exploitation Route It is anticipated that this research will be of use to both magnetically and inertially confined fusion plasma researchers, and to researchers in materials processing.
Sectors Electronics,Energy,Other

 
Title Data for Large-scale Numerical Simulation of Ionospheric Langmuir Turbulence Excited by a Radio Frequency Electromagnetic Wave 
Description "This dataset contains simulation data generated by the simulation of an ionospheric heating experiment described in the article ""Data for Large-scale Numerical Simulation of Ionospheric Langmuir Turbulence Excited by a Radio Frequency Electromagnetic Wave"" published in the journal ""Plasma Physics and Controlled Fusion"". The data consists of periodic snapshots in time of the simulation variables stored in hdf5 format. MATLAB scripts to read and analyze the data are also included. See the README file for a detailed description. " 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
Impact
 
Description Research collaboration with Prof. Mark Koepke, University of West Virginia, USA 
Organisation West Virginia University
Country United States 
Sector Academic/University 
PI Contribution Host : Hosting academic visitor : Research collaborations during visits of Prof. Mark Koepke, University of West Virginia, USA to University of Strathclyde
Collaborator Contribution Prof. Mark Koepke contributed his extensive expertise in plasma physics, especially in the interpretation of experimental results.
Impact Several joint research publications in international refereed research journals with Prof. Mark Koepke as a co-author
Start Year 2007
 
Description Research collaboration with Prof. R. Alan Cairns, University of St Andrews 
Organisation University of St Andrews
Country United Kingdom 
Sector Academic/University 
PI Contribution Host : Hosting academic visitor : Collaboration in plasma physics research with Prof. R. Alan Cairns of the University of St. Andrews
Collaborator Contribution Prof. R. Alan Cairns contributed his theoretical plasma physics knowledge and expertise gained from over 40 years of active research.
Impact Many joint research papers in refereed international research journals have been published with Prof. R. Alan Cairns as a co-author. Prof R. Alan Cairns has been appointed as a Visiting Professor to our research group at the University of Strathclyde.
 
Description Design and measurement of a Penning discharge plasma 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Poster presentation at the 71st GEC 2018
Year(s) Of Engagement Activity 2018
 
Description A magnetized plasma apparatus for non-linear microwave interaction experiments 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Poster presentation at the 71st GEC conference 2018
Year(s) Of Engagement Activity 2018
 
Description A magnetized plasma experiment to study non-linear microwave interactions 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Poster presentation at the 60th APS DPP Meeting
Year(s) Of Engagement Activity 2018
 
Description An apparatus for investigating micorwave interactions in magnetized plasmas 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Poster paper at the 19th International Congress on Plasma Physics (ICPP)
Year(s) Of Engagement Activity 2018
 
Description Development of an apparatus to study nonlinear microwave coupling in magnetised plasma 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Poster paper at the 24th Europhysics Conference on the Atomic and Molecular Physics of Ionized Gases (ESCAMPIG)
Year(s) Of Engagement Activity 2018
 
Description Experimental concept for investigating nonlinear microwave interactions in magnetised plasma 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Poster presentation at 45th IoP Annual Spring Plasma Physics Conference
Year(s) Of Engagement Activity 2018
 
Description Laboratory Open Evening during ESCAMPIG 2018 conference (hosted at Glasgow University) 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact As part of the ESCAMPIG 2018 leading international practitioners were present in the city of Glasgow. An evening event was hosted where the visitors came to Strathclyde University and were able to review the facilities and research.
Year(s) Of Engagement Activity 2018
 
Description Magnetized plasma appartus for investigating non-linear interactions at microwave frequencies 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Poster paper at IEEE ICOPS 2018 conference
Year(s) Of Engagement Activity 2018
 
Description Maser radiation from electrons accelerated by magnetised collisionless shock waves 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Poster presentation at 60th APS DPP conference
Year(s) Of Engagement Activity 2018