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UKAEA-CCFE-PR(20)1382020
The electron runaway phenomenon in plasmas depends sensitively on the momentum space dynamics. However, efficient simulation of the global evolution of systems involving runaway electrons typically requires a reduced fluid description. This is needed for example in the design of essential runaway mitigation methods for tokamaks. In this paper, we p…
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UKAEA-CCFE-PR(20)1352020
The poloidal harmonics of the toroidal normal modes of an unstable axisymmetric tokamak plasma are employed as basis functions for the minimisation of the 3D energy functional. This approach presents a natural extension of the perturbative method considered in [M.S. Anastopoulos Tzanis et al, Nuclear Fusion 59:126028, 2019]. This variational formul…
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UKAEA-CCFE-CP(20)1242020
During ITER operations the water coolant flowing through components such as the first wall, blanket modules, divertor cassettes and vacuum vessel will become activated by high energy neutrons. Two key neutron-induced reactions will occur with oxygen in the water producing the radioactive isotopes, N-16 and N-17, which have relatively short half-liv…
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UKAEA-CCFE-CP(20)1232020
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UKAEA-CCFE-CP(20)1202020
The divertor component is subject to some of the most extreme loading conditions in a fusion environment and the safety design window is relatively narrow. Variation in mechanical properties of the same material throughout a component is common place in practice and can be caused by both local effects of processing and joining, and local variations…
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UKAEA-CCFE-CP(20)1212020
While current tokamak experiments are beginning to utilise real-time feedback control systems to manage the plasma exhaust, future tokamaks still require validation of theoretical models used to predict the threshold impurity concentration required to facilitate stationary divertor operation. This work exploits new spectroscopic measurements of …
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UKAEA-CCFE-CP(20)1222020
A thorough physics and engineering analysis of alternative divertor configurations is carried out by examining benefits and problems by comparing the baseline single null solution with a Snowflake, an X- and a Super-X divertor. It is observed that alternative configurations can provide margin and resilience against large power fluctuations, but the…
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UKAEA-CCFE-PR(20)1172020
A discrepancy between predicted and measured neutron rates on MAST using TRANSP/NUBEAM was observed. Further causes of this discrepancy are here studied by means of TRANSP/NUBEAM and ASCOT/BBNBI simulations. Gyro-Orbit simulations resulted in an approximately 20 % reduction of the fast ion density compare to the Guiding Center with TRANSP/NUBEAM…
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UKAEA-CCFE-CP(20)1062020
The measurement of the fusion neutron yield provides a direct relationship with fusion power and is hence an important measure of experimental performance. In pulsed neutron emission scenarios, such as those experienced in dense plasma focus devices, inertial confinement fusion and even in short-pulse tokamak experiments, considerations of the dyna…
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UKAEA-CCFE-PR(20)1202019
A Doppler coherence imaging spectroscopy diagnostic has been developed on the HL- 2A tokamak for scrape-off-layer impurity plasma flow measurements. Two- dimensional imaging of line-averaged C2+ flow in the high-field-side scrape off layer with time resolution up to 1 ms, has been achieved successfully by this system. The spatial angular resolut…
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