Rapid prototyping of advanced control schemes in ASDEX Upgrade

Sieglin, B.; Maraschek, M.; Kudláček, O.; Gude, A.; Treutterer, W.; Kölbl, Martin; Lenz, Alexander

doi:10.1016/j.fusengdes.2020.111958

Cited by 10 publications

(10 citation statements)

References 10 publications

(9 reference statements)

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“…At high densities, however, back transition to a stable L-mode regime is not possible as this region is not accessible due to the L-mode density limit (red line in figure 7). After H-L back transition at high densities, the plasma is in a regime of strongly enhanced transport (the electromagnetic RBM regime) leading inevitably to a disruption if not avoided by active means [46]. As can be seen in figure 7, H-L transitions at high densities are also accompanied by the transition from the drift-wave regime of turbulence (α t < 1) to the RBM regime of turbulence (α t > 1).…”

Section: Disruptive Limit At Low Temperatures In H-modesmentioning

confidence: 96%

The separatrix operational space of ASDEX Upgrade due to interchange-drift-Alfvén turbulence

Eich

Mänz

2021

Nucl. Fusion

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The efficient operation of a tokamak is limited by several constraints, such as the transition to high confinement or the density limits occurring in both confinement regimes. These particular boundaries of operation are derived in terms of a combination of dimensionless parameters describing interchange-drift-Alfvén turbulence without any free adjustable parameter. The derived boundaries describe the operational space at the separatrix of the ASDEX Upgrade tokamak, which is presented in terms of an electron density and temperature existence diagram. The derived density limits are compared against Greenwald scaling. The power threshold and role of ion heat flux for the transition to high confinement are discussed.

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Section: Disruptive Limit At Low Temperatures In H-modesmentioning

confidence: 96%

The separatrix operational space of ASDEX Upgrade due to interchange-drift-Alfvén turbulence

Eich

Mänz

2021

Nucl. Fusion

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“…Further developments may include the extension to other seeding gases and coupling to other existing controllers, such as the Tdiv controller [16], or the integration into schemes for disruption avoidance (e.g. at the H-mode density limit [22]).…”

Section: Outlook and Future Workmentioning

confidence: 99%

X-point radiation, its control and an ELM suppressed radiating regime at the ASDEX Upgrade tokamak

et al. 2020

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“…These capabilities enable disruption avoidance using continuous control as well as exception handling. Previous papers demonstrated disruption avoidance using proximity control for the HDL on TCV [8] and ASDEX Upgrade [20] based on the so-called HDL state space [21].…”

Section: Control: Requirements and Capabilitiesmentioning

confidence: 99%

“…Exception handling in this context describes a coordinated action of the control system to react on a detected event [18]. A discussion of disruption avoidance for the HDL using continuous control and auxiliary heating is presented in [20]. Using the observations discussed in section 4 disruption avoidance using the upper triangularity δ top is studied.…”

Section: Disruption Avoidancementioning

confidence: 99%

Disruption avoidance and investigation of the H-Mode density limit in ASDEX Upgrade

Sieglin,

Maraschek,

Gude

et al. 2023

Plasma Phys. Control. Fusion

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In recent years a strong effort has been made to investigate disruption avoidance schemes in order to aid the development of integrated operational scenarios for ITER. Within the EUROfusion programme the disruptive H-mode density limit (HDL) has been studied on the WPTE (Work Package Tokamak Exploitation) devices ASDEX Upgrade, TCV and JET. Advanced real-time control coupled with improved real-time diagnostics has enabled the routine disruption avoidance of the HDL. This allowed the systematic study of the influence of various plasma parameters on the onset and behavior of the HDL in regimes not easily accessible otherwise. The upper triangularity δ t o p is found to have a significant influence on the x-point radiator (XPR), which plays a major role for the evolution of the disruptive HDL. At high δ t o p the gas flow rate at which the onset of the XPR occurs is strongly reduced compared to low δ t o p . The reduction of δ t o p has proven to be an effective actuator for the HDL disruption avoidance on ASDEX Upgrade for highly shaped scenarios ( δ t o p > 0.25 ). It is observed that the occurrence of the XPR and the H–L transition at the density limit are two separate events, the order of which depends on the applied auxiliary heating power. At sufficiently high heating power the XPR occurs before the H–L transition. Impurity seeding, used for divertor detachment, influences the onset and the dynamics of the XPR and the behavior of the HDL. The stable existence of the XPR, which is thought to be a requirement for detachment control in future devices, has also been observed without impurity seeding. The implementation of a robust and sustainable operational scenario, e.g. for ITER, requires the combination of continuous control and exception handling. For each disruption path the appropriate observers and actuators have to be validated in present devices. Automation of the dynamic pulse schedule has proven successful to scan the operational space of the HDL without disruption. Applying such a technique to ITER could reduce the machine risk induced by disruptions during commissioning. The methodology to develop physics-based observers, which indicate the entry into a disruption path well in time, and applying the appropriate action before the discharge becomes unstable has proven successful.

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Rapid prototyping of advanced control schemes in ASDEX Upgrade

Cited by 10 publications

References 10 publications

The separatrix operational space of ASDEX Upgrade due to interchange-drift-Alfvén turbulence

The separatrix operational space of ASDEX Upgrade due to interchange-drift-Alfvén turbulence

X-point radiation, its control and an ELM suppressed radiating regime at the ASDEX Upgrade tokamak

Disruption avoidance and investigation of the H-Mode density limit in ASDEX Upgrade

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