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CCFE-PR(15)092015
The replacement of the JET carbon wall (C-wall) by a Be/W ITER-like wall (ILW) has affected the plasma energy confinement. To investigate this, experiments have been performed with both the C-wall and ILW to vary the heating power over a wide range for plasmas with different shapes. It was found that the power degradation of thermal energy confinem…
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2014
There is an increasing need to model plasma inter- action with complex engineered surfaces, notably to verify that power deposition rates are acceptable. The SMARDDA algorithm has been developed to meet this requirement, with particular reference to the neutral beam ducts that feed into the vacuum vessels of tokamaks. Application to limiters and di…
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2014
The major aspects linked to the use of the JET auxiliary heating systems: NBI, ICRF and LHCD, in the new JET ITER-like wall (JET-ILW) are presented. We show that although there were issues related to the operation of each system, efficient and safe plasma heating was obtained with room for higher power. For the NBI up to 25.7MW was safely injected;…
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2013
Improving the reliability and reducing the maintenance time to give increased availability is a key feature of developing control & instrumentation (C&I) systems relevant to future fusion devices such as DEMO and to fusion power plants. Standardising access to the multiple platforms comprising C&I systems on working plant including software tha…
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2013
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2013
A one dimensional model of the sheath between the plasma and the wall in a negative ion source has been expanded to include the effects of a variable wall surface work function and fast positive ion species. The plasma consists of positive ions, electrons and negative ions. The model also includes the emission of negative ions from the wall into th…
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2012
In fusion negative ion sources, the negative ions are formed on the caesiated plasma grid predominantly by hydrogen atoms from the plasma. The space charge of the negative ions leaving the wall is not fully compensated by incoming positive ions and at high enough emission a virtual cathode is formed. This virtual cathode limits the flux of negative…
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2011
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2011
A 1d analytical model of the sheath in a negative ion source, such as those proposed for heating and diagnostic beams on present and future fusion devices, has been developed. The model describes the transport of surface produced negative ions from a cathode, across the sheath to a plasma containing electrons, positive ions and negative ions. It ac…
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2005
Operation of the JET Neutral Beam Injectors with tritium is described. Supplying the tritium feed via the special electrically grounded gas feed compromised the performance of the up-graded high current triode Positive Ion Neutral Injectors (PINI) due to gas starvation of the source and the methods adopted to ameliorate this effect are described. A…
Showing 51 - 60 of 65 UKAEA Paper Results