Spectroscopic “key” to nuclear fusion

Scientists at the UK Atomic Energy Authority’s Culham Science Centre are investigating spectroscopic techniques that could be crucial to the eventual commercialisation of nuclear fusion as an energy source.

Spectroscopic diagnostic techniques developed at Culham are an important ingredient in actively influencing the stability of the plasma required for nuclear fusion. Head of the spectroscopic diagnostics research, Dr Patrick Carolan, says: “The outcome of our research will lead to spectroscopic diagnostics being incorporated into a feedback system designed to “tune” the magnetic structure and density, and so increasing the stability and performance of the plasma.” The eventual commercialisation of nuclear fusion will depend on being able to maintain a stable, self-sustaining plasma capable of producing power continuously.

In fusion research spectroscopic diagnostics are used in two ways: passive and active. The passive techniques, for example, include monitoring spectral lines from neutral to highly ionised elements that are used to measure impurity concentrations, distributions, transport and sources. The presence of impurities affects plasma performance through radiation losses, for example, but also influence stability by altering the current distribution in the plasma. These impurities include iron, carbon, oxygen and nickel from the walls of the reactor vessel, diluting the plasma and so reducing its efficiency.

The photograph shows a deuterium plasma, heated by Neutral Beam Injection of hydrogen. It was taken (using a conventional 35 mm camera) in plasma visible light and is dominated by the red Balmer alpha line (Da: 656.1 nm), emitted at the plasma boundary by the deuterium gas refuelling the discharge. Plasma power and particles flow to graphite plates at the top and bottom, where intense Da together with carbon (neutral and ionised) line radiation is locally emitted.

As Carolan observes the effect of impurities is not be underestimated. “The more impurities you have the more energy you need to put into the fusion chamber to combat them, effectively reducing the energy productivity of the plasma. Diluting the plasma by as much as 20% can reduce the reaction rate dramatically by up to 40%,” he says.

Spectroscopic diagnostics have been fundamental to selecting materials for the chamber walls. “Given the extreme temperatures generated during fusion the reactor wall has to be protected. We used to carbonise the walls, producing a hard diamond-like layer, but by switching to boronisation instead there’s been a dramatic effect on the level of impurities. Oxygen contamination has been reduced by a factor of five and metallics (iron/nickel/chromium/chlorine) by a factor of ten or more,” notes Carolan. However, it is from the area of “active” spectroscopy that the greatest advances in plasma stability have been made recently.

For example, by injecting neutral atoms such as hydrogen in a high-energy beam of 50–100 kV into the fusion chamber, it is possible to measure the plasma’s magnetic field and direction. Using this technique it was demonstrated experimentally that the pitch of the magnetic field is an important parameter in plasma stability. Carolan explains: “If the sheer in the pitch of magnetic field lines is increased the confinement time is improved, allowing the plasma performance to be “tuned”. As a result a doubling of the plasma confinement time has been achieved.

Optimising the sheer allows plasma physicists to obtain an internal transport barrier (ITB), a phenomenon only made possible by the development of this spectroscopic technique. The ITB substantially increases the thermal insulation of the hot plasma core. The ITB has a certain spectroscopic signature—a Doppler shift in the ITB region of the plasma.

Similarly there is an Edge Transport Barrier which supports steep thermal gradients. Here neutral hydrogen, or deuterium, transported inwards from the plasma periphery, may play an additional role, in contrast to the ITB where the neutral density is insignificant. Nonetheless, the spectroscopic technology is similar in both cases and there is with much in common in the underlying physics and research goals.

Carolan and his team are now looking at the ETB and ITB in different fusion chambers at Culham. “Our focus is on observing, and actively “tuning”, the ETBs and ITBs in a range of different fusion chambers to arrive eventually at a way of optimising their roles in stabilising and improving the thermal insulation of the plasma. The technology developed and the understanding gleaned from these experiments may be important in operating future fusion control systems,” he concluded.

For further information on the spectroscopic diagnostic techniques used by Patrick Carolan and his team contact Christopher Carpenter, Public Affairs Manager, UKAEA Fusion, on +44-1235-464190.

15th IMSC

The 15th International Mass Spectrometry Conference (IMSC) will be held from 27 August to 1 September in Barcelona, Spain. The Conference programme will cover all fundamental aspects and applications of Mass Spectrometry in the fields of Instrumental, Organic, Inorganic, Biological, Pharmaceutical and Industrial Mass Spectrometry. The most positive aspects of the previous successful Barcelona MS Symposia will be implemented, ensuring ample poster space and time for relaxed scientific interaction and discussion amongst participants. A key feature of the 15th IMSC will be the International Technical Exhibition of equipment, accessories, literature, software and services. The Exhibition will be integrated with the Scientific Programme in the Exhibition Hall at the Conference Centre, together with the Poster Sessions and coffee-break area. The Conference will be organised at Barcelona’s Palau de Congressos, located in the city centre within the Barcelona Fair grounds and ten minutes from the International airport.

For further information, contact Ana Costejà, Palacio de Congresos, Departament de Convencions, Av. Reina Ma Cristina, s/n, E-08004 Barcelona, Spain. 15imsc@website.es, www.website.es/15imsc.

Major awards at IMSC

The International Mass Spectrometry Society and the National Organising Committee of the 15th International Mass Spectrometry Society (IMSS) announce the 2000 Thomson Medals to be presented at the 15th International Mass Spectrometry Conference (IMSC). Awards will be made to three individuals for outstanding achievements in mass spectrometry and for distinguished service to international mass spectrometry. Nominations, which must be made by national representatives to the Governing Committee of the IMSS, are due by 31 December 1999. They should be sent to: Dr Alison Ashcroft, Thomson Medal, The Centre for Biomolecular Science, Dept. of Biochemistry & Molecular Biology, The University of Leeds, Leeds, LS2 9JT, UK. a.e.ashcroft@leeds.ac.uk.

Previous winners: J.H. Beynon, K. Biemann, M.T. Bowers, C. Brunnée, R.G. Cooks, C. Djerassi, D.E. Games, K.R. Jennings, H. Matsuda, F.W. McLafferty, N.M.M. Nibbering, A.O.C. Nier, H. Schwarz and J.F.J. Todd.

The IMSS and the National Organizing Committee of the 15th IMSC invite nominations for the year 2000 Curt Brunnée Prize to be made on the occasion of the 15th IMSC. The prize, in the amount of $5,000 (US) is generously sponsored by ThermoQuest, Inc., and will be made to an individual for “outstanding contributions to the development of instrumentation for mass spectrometry by a person under the age of 45 at the time of the award”. Nominations may be made by individuals or mass spectrometry societies and are due by 31 December 1999. They should be sent to: Dr Yuzo Nakagawa, Curt Brunnée Prize, 5-18-20 Takenodai Nishi-ku, Kobe, 651-22 Japan. fkonishi@ hi-ho.ne.jp.

Name for HP’s new company

We reported previously that Hewlett-Packard were splitting the company into two, one to concentrate on computing and imaging and the other on measurement and components, which includes the Chemical Analysis Group. The name for the new company has now been announced: Agilent Technologies. The name has been developed from the word “agile”, which is intended to indicate the company’s focus on providing products and services with agility, speed and commitment to its customers. www.hp.com.

Pure water research award

USF Elga and the journal Nature have launched a Scientific Research Award to promote further understanding of the importance of ultra-pure water in many laboratory applications. Entry is by writing a short paper, of no more than 3000 words, outlining research in either water purification technologies or a project or application where purified water plays a key role. Entries can be submitted from any country and will be accepted in either English, French, German or Spanish. All entries will be judged by an international panel of experts who will announce their decision at Analytica 2000.

There are runner-up prizes of a year’s personal subscription to Nature, with the overall winner receiving a research grant of £5000 for their organisation. Alternatively, they can choose to receive up to £7500 of USF Elga water purification equipment to support their research activities.

USF Elga and Nature’s Research Award to promote ultra-pure water.

Enquiries about entries should be directed to Scientific Research Award, Laboratory Water Group, USF Elga, High Street, Lane End, High Wycombe, Bucks HP14 3JH, UK.

ICOFTS and AIRS unite

The International Conference on Fourier Transform Spectroscopy (ICOFTS) has been a very successful conference for 29 years. The meeting in Tokyo this August was the 12th in the series, evidence that it has served the community well. In recent years the orientation of the participants has tended more towards applications than the advancement of fundamental principles and development of FT-IR. In the meantime, AIRS (Advanced Infrared Spectroscopy) was started in 1994 to meet the rapidly growing interest in IR measurements of time-dependent phenomena. As the 3rd International Symposium on Advanced Infrared and Raman Spectroscopy last year in Vienna, AIRS III widened very successfully the original focus by adding Raman to infrared techniques, evidence of the need to target advancements in vibrational spectroscopy in general, rather than limiting the theme to FT methods. At the same time and in today’s funding climate, few members of the community can afford to participate in both international conferences, one or the other each year.

At the conclusion of AIRS III, members of ICOFTS’ International Steering Committee who were present and the AIRS organisers began exploring the feasibility of merging the two conferences. The discussions that followed culminated in a meeting of organisers of both conferences during Pittcon 99 in March where the merger was concluded. The two series of conferences will be replaced by the International Conference on Advanced Vibrational Spectroscopy, to be known as ICAVS and to take place in alternating years beginning with Turku, Finland, in 2001. The principal purpose of these conferences will be “to promote and present research at the advancing edge of vibrational spectroscopy”.

The International Steering Committee will be: J.A. deHaseth (Vice Chair), J.K. Kauppinen (General Chair of ICAVS I), B. Lendl, J. Mink, Y. Ozaki, R.A. Palmer (Chair), H. Siesler and M. Tasumi, plus two new members from ICAVS II in 2003.

For more information, please contact H. Wieser, Department of Chemistry, University of Calgary, Calgary, AB, Canada, T2N 1N4, hwieser@ucalgary.ca).