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Neutron emission levels during the ITER zero activation phase
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
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2010 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 50, no 8, 084020- p.Article in journal (Refereed) Published
Abstract [en]

In recent experiments at JET, a contribution to the neutron emission from reactions between beryllium and 3He, 4He and H has been identified. With the beryllium walled planned for ITER, this raises the question of possible neutron activation during the ITER zero activation phase. Here, we estimate the neutron emission rates for various heating scenarios foreseen for this ITER phase using Monte Carlo simulations. The emission is seen to be strongly dependent on the scenario chosen and the assumptions involved. We find that fundamental minority heating can contribute on the scale of low temperature deuterium plasmas, depending on minority concentration and ICRH power applied. Harmonic ICRH leads to production of tails that can give rise to significant neutron emission rates, while rates from hydrogen beams will be near zero. Better knowledge of the zero activation phase conditions, and more sophisticated ICRH codes, would be needed to give exact rate predictions. We conclude that rates from so-called zero activation plasmas will be significantly lower than expected for the DD or DT phases, but far from zero.

Place, publisher, year, edition, pages
2010. Vol. 50, no 8, 084020- p.
Keyword [en]
PACS codes: 29.30.Hs, 29.25.Dz, 52.55.-s, 52.55.Fa, 25.55.-e, 52.55.Pi
National Category
Natural Sciences
Research subject
Applied Nuclear Physics
Identifiers
URN: urn:nbn:se:uu:diva-114041DOI: 10.1088/0029-5515/50/8/084020ISI: 000280505800021OAI: oai:DiVA.org:uu-114041DiVA: diva2:292659
Available from: 2010-02-08 Created: 2010-02-08 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Fusion Plasma Observations at JET with the TOFOR Neutron Spectrometer: Instrumental Challenges and Physics Results
Open this publication in new window or tab >>Fusion Plasma Observations at JET with the TOFOR Neutron Spectrometer: Instrumental Challenges and Physics Results
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The neutron spectrometer TOFOR was installed at JET in 2005 for high-rate observation of neutrons from reactions between two deuterium (D) ions. Neutron spectrometry as a fusion plasma diagnostic technique is invoked to obtain information about the velocity states of fusion fuel ions. Based on neutron spectrometry data, conclusions can be drawn on the efficiency of plasma heating schemes as well as optimization of fuel ion confinement. The quality of TOFOR analysis is found to depend on how well the instrument response function is known; discriminator threshold levels, detector time alignment and electronics broadening are identified as crucial issues.

About 19 percent of the neutrons observed with TOFOR have scattered off the JET vessel wall or other structures in the line-of-sight before reaching the instrument, as established through simulations and measurements. A method has been developed to take these neutrons into account in the analysis. TOFOR measurements of fast deuterium distributions are seen to agree with distributions deduced from NPA data, obtained based on an entirely different principle. This serves as validation of the modeling and analysis.

Extraordinary statistics in the TOFOR measurements from JET pulses heated with 3rd harmonic RF heating on D beams allow for study of instabilities using neutron emission spectrometry. At ITER, similar studies should be possible on a more regular basis due to higher neutron rates.

Observations of neutrons from Be+3He reactions in the TOFOR spectrum from D plasmas heated with fundamental RF tuned to minority 3He raise the question of beryllium neutrons at JET after installation of the ITER-like wall, and at ITER, with beryllium as the plasma facing component. This is especially important for the first few years of ITER operation, where the machine will not yet have been certified as a nuclear facility and should be run in zero-activation mode.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 110 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 715
Keyword
Fusion, Plasma diagnostics, Neutron Spectrometry, TOFOR, JET, ITER, time-of-flight, plasma heating
National Category
Subatomic Physics
Research subject
Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-114077 (URN)978-91-554-7724-0 (ISBN)
Public defence
2010-03-26, Polhemsalen, Ångströmlaboratoriet, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2010-03-04 Created: 2010-02-09 Last updated: 2010-06-08Bibliographically approved

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Publisher's full texthttp://stacks.iop.org/0029-5515/50/i=8/a=084020

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Gatu Johnson, MariaHellesen, CarlCecconello, MarcoConroy, SeanEricsson, GöranWeiszflog, Matthias

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