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- Fenstermacher, M.E., et al.
(author)
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DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
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In: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
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Journal article (peer-reviewed)abstract
- DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
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- Gustavsson, S., et al.
(author)
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Driven dynamics and rotary echo of a qubit tunably coupled to a harmonic oscillator
- 2012
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In: Physical Review Letters. - 1079-7114 .- 0031-9007. ; 108:17, s. 170503-
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Journal article (peer-reviewed)abstract
- We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence. © 2012 American Physical Society.
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- De Leon, AP, et al.
(author)
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Differences in child injury hospitalizations in Sweden: the use of time-trend analysis to compare various community injury-prevention approaches
- 2007
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In: Scandinavian journal of public health. - : SAGE Publications. - 1403-4948 .- 1651-1905. ; 35:6, s. 623-630
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Journal article (peer-reviewed)abstract
- Aim: Sweden's child injury fatality rates are among the lowest in the world. The country has engaged in a number of community injury-prevention programmes. The purpose of this study was to compare child injury hospitalization rates from the Skaraborg District with the rest of Sweden. Our study hypothesis was that municipalities that offered comprehensive child injury-prevention programmes would see significant decreases in their child injury hospitalization rates, compared with other areas. Methods: The study areas comprised three groups, consisting of municipalities in Skaraborg that had adapted the Safe Communities approach to injury prevention programmes, other municipalities in the District, and the rest of Sweden. The aim of the analysis was twofold: (1) to fit time trends for children's injuries in various areas in an integrated manner; and (2) to compare time trends across locations between community safety-promotion programmes as well as with the control areas. Panel data models and parametric splines were used. Results: There were differences between incidence rates in the study areas and with regard to gender. There was a steep decrease in injury rates in one of the Safe Communities study areas for both genders. Conclusions: The methods applied in this analysis reveal more detailed and sophisticated time trends than the usual simple linear regression approach. The model provided a clearer view of the interactions of gender, area, and time as they impacted on children's injuries, and allowed for better insight into the impact of safety programmes.
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