Real time neutral beam power control on MAST

Homfray, D.; Benn, Anthony Wedgwood; Ćirić, D.; Day, I.E.; Dunkley, V.; Keeling, D.; Khilar, S.; King, D.; King, R.; Kurutz, U.; Payne, Don M.; Simmonds, M.; Stevenson, P. D.; Tame, Chris R.

doi:10.1016/j.fusengdes.2011.01.124

Cited by 10 publications

(8 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It has been demonstrated that the magnitude of the redistribution effect is related to the plasma electron density and the NBI power. The magnitude of the redistribution effect has additionally been shown to be related to the magnitude of the FB mode growth rate which, in turn, is related to the magnitude of the FI distribution function radial gradient through equation (1). Significantly, a region of the parameter space investigated at high plasma density and relatively low beam power has been demonstrated to be free of FI redistribution by FBs either through the complete absence of FBs or due to the low growth rates of FBs, leaving the FI population relatively unperturbed.…”

Section: Discussionmentioning

confidence: 99%

“…At the injection energy chosen, the neutral power injected by the second beamline (that fitted with the "chequerboard" source) was 1.6MW. Of course, considering the different ion sources in use on the two beamlines a small perturbation to the energy gradient is expected but this was assumed to be small compared to the changes effected in the ⁄ term in equation (1). Motional Stark Effect (MSE) measurements may only be obtained when the "supercusp" beam is injecting power hence the choice of this for the single beam shots resulting in MSE measurements being available for all 8 shots in the parameter scan.…”

Section: 1experimental Basis and Designmentioning

confidence: 99%

“…The neutral-beam injection (NBI) system on MAST consists of two injection devices capable of injecting neutral deuterium with energies up to 75 keV and total power exceeding 2 MW per injector [1]. NBI has been used extensively in recent MAST experimental campaigns to access high performance operational regimes relevant to the operational domain of MAST-Upgrade [2,3], which is currently under construction.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mitigation of MHD induced fast-ion redistribution in MAST and implications for MAST-Upgrade design

et al. 2014

View full text Add to dashboard Cite

The phenomenon of redistribution of neutral beam fast-ions due to MHD activity in plasma has been observed on many tokamaks and more recently has been a focus of research on MAST (Turnyanskiy M. et al, 2011 Nucl. Fusion 53 053016). n=1 fishbone modes are observed to cause a large decrease in the neutron emission rate corresponding to a significant perturbation of the fast-ion population in the plasma. Theoretical work on fishbone modes states that the fast-ion distribution itself acts as the source of free energy driving the modes that cause the redistribution. Therefore a series of experiments have been carried out on MAST to investigate a range of plasma density levels at two neutral beam power levels to determine the region within this parameter space in which MHD activity and consequent fastion redistribution is suppressed. Analysis of these experiments shows complete suppression of MHD activity at high density with increasing activity and fast-ion redistribution at lower densities and higher NB power accompanied by strong evidence for localisation of the redistribution effect to a specific region in the plasma core. The results also indicate correlations between the form of the modelled fast-ion distribution function, the amplitude and growth rate of the fishbone modes, and the magnitude of the redistribution effect. The same analysis has been carried out on models of MAST-Upgrade baseline plasma scenarios to determine whether significant fast-ion redistribution is likely to occur in that device. A simple change to the neutral-beam injector geometry is proposed which is shown to have a significant mitigating effect in terms of the fishbone mode drive and is therefore expected to allow effective plasma heating and current drive over a wider range of plasma conditions in MAST-Upgrade.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: 1experimental Basis and Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mitigation of MHD induced fast-ion redistribution in MAST and implications for MAST-Upgrade design

et al. 2014

View full text Add to dashboard Cite

show abstract

“…As beam divergence is dependent on both beam current and acceleration voltage (through the perveance), ramping the ion beam current will affect the beam cross section, and beamline transmission. The real time control of an arc current of a high perveance MAST PINI allows variations of the neutral beam power by ∼20% with only minimal effect on the beam footprint [9].…”

Section: Nbi Optimisation and Power Controlmentioning

confidence: 99%

Neutral beam heating on the TCV tokamak

Karpushov

Chavan

Coda

et al. 2017

Fusion Engineering and Design

View full text Add to dashboard Cite

The TCV tokamak contributes to physics understanding in fusion reactor research by harnessing a wide experimental tool set: in particular flexible shaping and high power electron cyclotron heating. Plasma regimes with high plasma pressure, a wider range of temperature ratios and significant fast-ion population are now attainable with a TCV heating system upgrade. In a first stage, a 1 MW neutral beam was installed (2015) and is reported in this paper. The installation of the NB injector required modifications of the vacuum vessel and considerable work on the machine infrastructure, resulting in a shutdown from late 2013 to mid-2015. TCV is now operating partly as a European Medium-Size Tokamak (MST) facility under the auspices of the EUROfusion consortium. The NBI was intensively operated in the February-July 2016 phase of the MST campaign. Record ion temperatures of 2.0-2.5 keV and toroidal rotation velocities up to 160 km/s were promptly attained in the first few L-mode discharges with NB injection. Ion temperatures up to 3.5 keV were subsequently achieved in ELMy H-mode. The injector produces a focused deuterium neutral beam with 25 keV energy, 1 MW neutral power and 2 s duration. Highlights: • Installation of 1 MW, 25 keV neutral beam, direct ion heating, access to Ti/Te ≥ 1. • Specific low divergence neutral beam injector with tunable power and energy. • Ion temperature of 2.0 keV, toroidal rotation of 160 km/s attained with NB heating.

show abstract

“…For MAST-U, a real time NB power control system to actively control beam timing and power is currently being developed. This will involve an in-house built FPGA-based master [5] (connected to the SCADA System using Modbus) controlling individual injector based FPGA controllers, which will include controlling beam power by actively controlling arc voltage and current [6]. From initial measurements it can be seen there are associated time lags due to filament thermal effects, the arc notch (causing a small overshoot at beginning of the beam) and the arc controller feedback circuits ( figure 5).…”

Section: Future Implementationmentioning

confidence: 99%

Development of multi-platform control and instrumentation communications to increase operational reliability – Application to MAST

Homfray

Deakin

Khilar

et al. 2013

Fusion Engineering and Design

Self Cite

View full text Add to dashboard Cite

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 that analyses data is one aspect of achieving this. This has been realised on the MAST Neutral Beam Injection system (MNBI) following an extensive upgrade to the C&I, to improve the operational reliability of the neutral beam plant.

show abstract

Real time neutral beam power control on MAST

Cited by 10 publications

References 4 publications

Mitigation of MHD induced fast-ion redistribution in MAST and implications for MAST-Upgrade design

Mitigation of MHD induced fast-ion redistribution in MAST and implications for MAST-Upgrade design

Neutral beam heating on the TCV tokamak

Development of multi-platform control and instrumentation communications to increase operational reliability – Application to MAST

Contact Info

Product

Resources

About