On the safety of ITER accelerators

Abstract

Three 1 MV/40A accelerators in heating neutral beams (HNB) are on track to be implemented in the International Thermonuclear Experimental Reactor (ITER). ITER may produce 500 MWt of power by 2026 and may serve as a green energy roadmap for the world. They will generate −1 MV 1 h long-pulse ion beams to be neutralised for plasma heating. Due to frequently occurring vacuum sparking in the accelerators, the snubbers are used to limit the fault arc current to improve ITER safety. However, recent analyses of its reference design have raised concerns. General nonlinear transformer theory is developed for the snubber to unify the former snubbers' different design models with a clear mechanism. Satisfactory agreement between theory and tests indicates that scaling up to a 1 MV voltage may be possible. These results confirm the nonlinear process behind transformer theory and map out a reliable snubber design for a safer ITER.

Manipulating multiple order parameters via oxygen vacancies: The case of Eu0.5Ba0.5TiO3Li1, He2, Wang3 et al. 2017Phys. Rev. B15290View full textAdd to dashboardCite

“…Moreover, EBTO is structurally similar to the archetypal TMOs, such as BaTiO3 (BTO) and SrTiO3 (STO), and the introduction of VO has been shown to enhance the ferroelectricity of STO [6,22]. Additionally, our previous results established that the doping of VO shows strong influence on the magnetic ordering of the Eu0.5Ba0.5TiO3-δ (EBTO3-δ) thin films [23].Our present work shows that careful manipulation of VO can improve both magnetic and FE properties in EBTO3-δ. We experimentally observed that the ferroic orders in EBTO3-δ thin films are transformed from AFM-FE to FM-FE, and the FE Curie temperature is enhanced to be over room temperature.…”

“…Moreover, EBTO is structurally similar to the archetypal TMOs, such as BaTiO3 (BTO) and SrTiO3 (STO), and the introduction of VO has been shown to enhance the ferroelectricity of STO [6,22]. Additionally, our previous results established that the doping of VO shows strong influence on the magnetic ordering of the Eu0.5Ba0.5TiO3-δ (EBTO3-δ) thin films [23].…”

Many-body theory of spin-current driven instabilities in magnetic insulators

“…Earlier, a condensate has been realized at room temperature in YIG by other means, namely via parametric pumping [25]. This is an example of a non-equilibrium condensate of quasiparticles [26][27][28][29][30]. Such non-equilibrium BECs have attracted a great deal of attention and occur in different physical systems such as excitons [31][32][33], phonons [34], polaritons [35] and photons [36].…”

Stimulated thermalization of a parametrically driven magnon gas as a prerequisite for Bose-Einstein magnon condensation

“…In addition, this technique fruitfully serves for experimental studies of nonlinear dynamics in multi-mode wave systems as well. One of the greatest achievements in this area was the realization of a Bose-Einstein condensation of magnons [10], where the parametrically pumped magnon gas undergoes a phase transition leading to the spontaneous formation of a coherent state at the bottom of the spin-wave spectrum [11]. Since the moment of this discovery, the physics of the parametrically driven magnon gases is under active theoretical and experimental investigation.…”