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Contribution to fusion research from IAEA coordinated research projects and joint experiments
The paper presents objectives and activities of IAEA Coordinated Research Projects 'Conceptual development of steady-state compact fusion neutron sources' and 'Utilisation of a network of small magnetic confinement fusion devices for mainstream fusion research'. The background and main projects of the CRP on FNS are described in detail, as this is a new activity at IAEA. Recent activities of the second CRP, which continues activities of previous CRPs, are overviewed
Transitions to improved confinement regimes induced by changes in heating in zero-dimensional models for tokamak plasmas
It is shown that rapid substantial changes in heating rate can induce
transitions to improved energy confinement regimes in zero-dimensional models
for tokamak plasma phenomenology. We examine for the first time the effect of
step changes in heating rate in the models of E-J.Kim and P.H.Diamond,
Phys.Rev.Lett. 90, 185006 (2003) and M.A.Malkov and P.H.Diamond, Phys.Plasmas
16, 012504 (2009) which nonlinearly couple the evolving temperature gradient,
micro-turbulence and a mesoscale flow; and in the extension of H.Zhu,
S.C.Chapman and R.O.Dendy, Phys.Plasmas 20, 042302 (2013), which couples to a
second mesoscale flow component. The temperature gradient rises, as does the
confinement time defined by analogy with the fusion context, while
micro-turbulence is suppressed. This outcome is robust against variation of
heating rise time and against introduction of an additional variable into the
model. It is also demonstrated that oscillating changes in heating rate can
drive the level of micro-turbulence through a period-doubling path to chaos,
where the amplitude of the oscillatory component of the heating rate is the
control parameter.Comment: 8 pages, 14 figure
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