Achievement of ion temperatures in excess of 100 million degrees Kelvin in the compact high-field spherical tokamak ST40

McNamara, Steven; Asunta, O.; Bland, James Robert; Buxton, P.F.; Colgan, Cary; Dnestrovskii, Aleksei; Gemmell, M. A.; Gryaznevich, M.; Hoffman, David J.; Janky, F.; Lister, J.B.; Lowe, Hazel; Mirfayzi, Reza; Naylor, Graham; Nemytov, Vadim; Njau, John; Pyragius, Tadas; Rengle, A.; Romanelli, M.; Romero, Cristian; Sertoli, M.; Shevchenko, V.; Sinha, Joyeeta; Sladkomedova, A D; Sridhar, S.; Takase, Y.; Thomas, Paul R; Varje, J.; Vincent, Benjamin G.; Willett, H.V.; Wood, J. S.; Zakhar, David; Battaglia, D. J.; Kaye, S. M.; Delgado‐Aparicio, L.; Maingi, R.; Mueller, D.; Podestà, M.; Delabie, E.; Lomanowski, B.; Marchuk, O.

doi:10.1088/1741-4326/acbec8

Cited by 20 publications

(27 citation statements)

References 18 publications

(21 reference statements)

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“…The modelling confirms that there are negligible temperature or rotation shear effects, and that the measurements are well localised. Results for #10009 find that central carbon impurity temperatures of above 9 keV match well with other diagnostics [1], as shown in figure 5. TRANSP was used to derive the hydrogenic temperature for #10009, finding that T D is 0.2 keV lower than the measured carbon impurity temperature T CVI [8].…”

Section: Jinst 18 C03019supporting

confidence: 75%

“…We present recent ion temperature and toroidal velocity results from the ST40 2021-22 experimental campaign, and consider comparisons between diagnostics measuring the same plasma properties, profile estimates using an integrated analysis methodology [1] and correlation of ω tor with the frequency of magneto-hydro-dynamic (MHD) instabilities.…”

Section: Introductionmentioning

confidence: 99%

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Characterisation of ion temperature and toroidal rotation on the ST40 tokamak

et al. 2023

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ST40 is a high field low-aspect ratio spherical tokamak built and operated by Tokamak Energy Ltd. Recent plasma operations were aimed at exploring operational scenarios to maximise the central plasma temperature and have culminated in the achievement of thermal ion temperatures of over 9 keV. This paper presents ion temperature and toroidal rotation measurements performed on ST40 during the 2021–22 campaign for a range of different scenarios. Several independent diagnostic systems are used, analysing their correlation and interpreting their differences using new diagnostic forward models.

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Section: Jinst 18 C03019supporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Characterisation of ion temperature and toroidal rotation on the ST40 tokamak

et al. 2023

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“…Figure 3(a) shows the T i time evolution measured during an ST40 pulse by the TriWaSp, PI and XRCS diagnostics. The PI and XRCS results are further discussed elsewhere [2,3]; here we focus on the TriWaSp performance. The three systems have high consistency in their temporal evolution behaviour, and the differences in the measured T i values can be attributed to the differing measurement locations.…”

Section: Commissioning Resultsmentioning

confidence: 99%

TriWaSp: a multi-faceted visible spectroscopy diagnostic on the ST40 tokamak

et al. 2023

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We present a new state-of-the-art Triple Wavelength Spectrometer (TriWaSp), recently deployed on ST40, a high field low aspect ratio spherical tokamak. The TriWaSp has a range of possible applications due to its flexible design; the current configuration focuses on charge exchange recombination spectroscopy from carbon and neon impurities in the ST40 plasma. This paper discusses the detailed setup of the system and presents initial charge exchange ion temperature measurements using a single line of sight, which show good agreement with other ion temperature diagnostics. Building on these commissioning results and forward modelling of the system, a new observation geometry has been implemented for the next experimental campaign which will considerably improve the localisation of ion temperature and velocity profile measurements.

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“…The line integrated electron density was obtained from interferometry. The plasma profiles were inferred using an integrated analysis workflow [23] that incorporated the line-ofsight integrated and profile measurements of the electron and ion temperatures and toroidal rotation, the line-of-sight integrated density measurements, as well as equilibrium constraints given by NUBEAM [31]. The TRANSP transport code [32] was then used to determine the temperature of the main hydrogenic species, as well as the fast ion density profile.…”

Section: Experimental Set Upmentioning

confidence: 99%

“…ST40, depicted in figure 1, is a high toroidal field and high beta ST [22] that was built and is owned and operated by Tokamak Energy Ltd UK, a private company whose mission it is to develop the ST for commercial power generation. ST40's most recent period of operation has achieved its goal of producing plasmas with central ion temperatures in excess of 100 million Kelvin (8.6 keV) [23], values considered to be near those required to produce net fusion power.…”

Section: Introductionmentioning

confidence: 99%

Perturbative analysis of low-frequency instabilities in high-field ST40 experiments

et al. 2023

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Linear and nonlinear perturbative analyses of low-frequency instabilities are presented for ST40 spherical torus high field plasmas, with simultaneous neutral beam heating due to two tangential sources at 25keV and 55keV. Initial plasma profiles on which the TRANSP and NUBEAM codes were based were obtained using an integrated analysis of several diagnostics including line-of-sight integrated and volume average measurements, as well as limited profile information from a charge-exchange-recombination spectrometer. MHD analysis using the NOVA/NOVA-K codes suggests that the modes in the experiments are core-localized n=1 eigenmodes with mixed acoustic and electromagnetic Alfvénic polarization. The global transport combined with the perturbative mode analysis indicates that there is greater tendency for bursty chirping response as the level of background micro-turbulence decreases in time and those predictions are shown to be consistent with the experimental data. This finding is interpreted in terms of the suppression of coherent phase-space structures that support chirping when the resonant fast ion dynamics is dominated by frequent stochastic, orbit-decorrelating events.

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Achievement of ion temperatures in excess of 100 million degrees Kelvin in the compact high-field spherical tokamak ST40

Cited by 20 publications

References 18 publications

Characterisation of ion temperature and toroidal rotation on the ST40 tokamak

Characterisation of ion temperature and toroidal rotation on the ST40 tokamak

TriWaSp: a multi-faceted visible spectroscopy diagnostic on the ST40 tokamak

Perturbative analysis of low-frequency instabilities in high-field ST40 experiments

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