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- Murari, A., et al.
(författare)
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A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors
- 2024
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Ingår i: Nature Communications. - 2041-1723 .- 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied configuration is the tokamak. Disruptions are catastrophic collapses affecting all tokamak devices and one of the main potential showstoppers on the route to a commercial reactor. In this work we report how, deploying innovative analysis methods on thousands of JET experiments covering the isotopic compositions from hydrogen to full tritium and including the major D-T campaign, the nature of the various forms of collapse is investigated in all phases of the discharges. An original approach to proximity detection has been developed, which allows determining both the probability of and the time interval remaining before an incoming disruption, with adaptive, from scratch, real time compatible techniques. The results indicate that physics based prediction and control tools can be developed, to deploy realistic strategies of disruption avoidance and prevention, meeting the requirements of the next generation of devices.
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| 6. |
- Tortora, P., et al.
(författare)
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AWARDS: Advanced microwave radiometers for deep space stations
- 2013
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Ingår i: Space Communications. - 0924-8625 .- 1875-9211. ; 22:2-4, s. 159-170
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study, named AWARDS (Advanced microWAve Radiometers in Deep space Stations), is the preliminary design of a transmission Media Calibration System (MCS) to be located at an ESA Deep Space Antenna (DSA) site. The crucial aspect is the capability to accurately retrieve the tropospheric path delay along the line-of-sight of the deep space probe in order to allow precise tropospheric calibration of deep space observables (range and range-rate) with particular reference to the BepiColombo spacecraft and its primary DSA at Cebreros (ES). The study focuses on two main aspects which lead to the preliminary design of the Mercury Orbiter Radioscience Experiment (MORE) MCS: the characterization of current microwave radiometers (MWRs) available at ESA/ESTEC and the atmospheric fluctuation effects on the MCS error budget, in terms of the Allan standard deviation (ASD). In the course of the study, further critical aspects have been identified (effects of Sun contamination, effects of ground noise emission), and mitigation strategies have been proposed. The final outcome is a preliminary design of the MWR (and the entire MCS) to be deployed at the ESA/ESTRACK (ESA Tracking station network) sites and being compliant with MORE requirements.
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| 7. |
- Graziani, A., et al.
(författare)
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Assessment of Ground-Based Microwave Radiometry for Calibration of Atmospheric Variability in Spacecraft Tracking
- 2014
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 62:5, s. 2634-2641
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Tidskriftsartikel (refereegranskat)abstract
- In a suggested radio propagation experiment using a deep space antenna, accurate calibration of the propagation delay through the Earth’s atmosphere is essential. One or two microwave radiometers can be used for this purpose. Differences in precise locations of the radiometer(s) and antenna to be calibrated leave a residual wet path delay value. We computed the Allan Standard Deviation (ASD) of this residual, as well as the one resulting from different pointing positions in the plane of the sky, by simulations.Pointing offsets, e.g., to avoid solar radiation into the radiometer beam, lead in general to an increased ASD. However, for many observation geometries a deliberate pointing offset can compensate for the location differences. In the case studied we found a reduction of the ASD with up to 45% compared to the ASD obtained for a zero pointing offset. The size of the calculated ASD depends strongly on the model parameters used, e.g., the turbulence strength parameter C_n^2, which has a significant natural variation over a year.
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| 10. |
- Tortora, P., et al.
(författare)
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Instruments, data and techniques for the assessment of tropospheric noise in deep space tracking
- 2012
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Ingår i: Proceedings of 6th European Conference on Antennas and Propagation, EuCAP 2012. Prague, 26-30 March 2012. - 9781457709180 ; , s. 106-110
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Konferensbidrag (refereegranskat)abstract
- This paper describes the techniques currently in use and those proposed for a precise estimation of the Earth troposphere path delay for Deep Space probe tracking purposes. The different proposed techniques could be selected according to the to the mission goals and tracking accuracy requirements. In this paper, they are sorted by an increasing accuracy but also level of complexity.
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