Real Time Control of Plasma Boundary In JET

Puppin, S.; Angoletta, M.E.; Campbell, D.J.; Ellis, J.; Garribba, M.; Lennholm, M.; Milani, F.; O’Brien, Dennis P.; Sartori, F.; Sartori, R.

doi:10.1016/b978-0-444-82762-3.50206-8

Cited by 11 publications

(3 citation statements)

References 3 publications

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“…A PF control system similar to the ITER requirements has already been successfully implemented on all presently operating tokamaks with shaped plasma cross-sections and independently controlled PF coils: JET [49], JT-60U [50], DIII-D [44], ASDEX-Upgrade [43], Alcator C-MOD [51] and TCV [52]. While none of these experiments has a PF coil configuration with the exact coil number, position and relative coil to plasma separation of ITER, all of these experiments are able to control 'ITER like' single null diverted plasmas with separatrix elongations about 1.8.…”

Section: Magnetic Control In Present Tokamaks and Itermentioning

confidence: 99%

Chapter 8: Plasma operation and control

MHD¹,

Drive²,

Diagnostics³

et al. 1999

Nucl. Fusion

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Wall conditioning of fusion devices involves removal of desorbable hydrogen isotopes and impurities from interior device surfaces to permit reliable plasma operation. Techniques used in present devices include baking, metal film gettering, deposition of thin films of low-Z material, pulse discharge cleaning, glow discharge cleaning, radio frequency discharge cleaning, and in situ limiter and divertor pumping. Although wall conditioning techniques have become increasingly sophisticated, a reactor scale facility will involve significant new challenges, including the development of techniques applicable in the presence of a magnetic field and of methods for efficient removal of tritium incorporated into co-deposited layers on plasma facing components and their support structures. The current status of various approaches is reviewed, and the implications for reactor scale devices are summarized. Creation and magnetic control of shaped and vertically unstable elongated plasmas have been mastered in many present tokamaks. The physics of equilibrium control for reactor scale plasmas will rely on the same principles, but will face additional challenges, exemplified by the ITER/FDR design. The absolute positioning of outermost flux surface and divertor strike points will have to be precise and reliable in view of the high heat fluxes at the separatrix. Long pulses will require minimal control actions, to reduce accumulation of AC losses in superconducting PF and TF coils. To this end, more complex feedback controllers are envisaged, and the experimental validation of the plasma equilibrium response models on which such controllers are designed is encouraging. Present simulation codes provide an adequate platform on which equilibrium response techniques can be validated. Burning plasmas require kinetic control in addition to traditional magnetic shape and position control. Kinetic control refers to measures controlling density, rotation and temperature in the plasma core as well as in plasma periphery and divertor. The planned diagnostics (Chapter 7) serve as sensors for kinetic control, while gas and pellet fuelling, auxiliary power and angular momentum input, impurity injection, and non-inductive current drive constitute the control actuators. For example, in an ignited plasma, core density controls fusion power output. Kinetic control algorithms vary according to the plasma state, e.g. H-or L-mode. Generally, present facilities have demonstrated the kinetic control methods required for a reactor scale device. Plasma initiation -breakdown, burnthrough and initial current ramp -in reactor scale tokamaks will not involve physics differing from that found in present day devices. For ITER, the induced electric field in the chamber will be ∼0.3 V• m −1 -comparable to that required by breakdown theory but somewhat smaller than in present devices. Thus, a start-up 3 MW electron cyclotron heating system will be employed to assure burnthrough. Simulations show that plasma current ramp up and termination in a reactor scale device ...

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Section: Magnetic Control In Present Tokamaks and Itermentioning

confidence: 99%

Chapter 8: Plasma operation and control

MHD¹,

Drive²,

Diagnostics³

et al. 1999

Nucl. Fusion

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show abstract

“…JET tokamak (Wesson, 2000), though it was built more than twenty years ago, is still the world's biggest pulsed operated fusion experiment, where several computers interact in order to perform real-time control and monitoring services (Lennholm et al (1999), Puppin et al (1996) and Sartori et al (2003)). Tokamaks are the most promising confinement devices in the field of controlled nuclear fusion: their principal object is the containment of a thermonuclear plasma by means of strong magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

A Flexible Software for Real-Time Control Applications in Fusion Experiments

Tommasi

Piccolo

Pironti

et al. 2005

IFAC Proceedings Volumes

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“…Experience has shown that the real-time reconstruction algorithm yields good accuracy compared with the offline full equilibrium reconstruction, and, by accurately placing the flux control points, the system provides sufficient flexibility to explore a wide range of different shapes and configurations. The gap approach was used at JET to develop a robust multi-input, multi-output feedback control system (see [16] October 2005 and [17]). Several gap lines were chosen on a geometric basis in accordance with operational needs.…”

Section: Flux and Gap Descriptions For Shape Controlmentioning

confidence: 99%

IEEE Control Systems Magazine

2005

IEEE Control Syst.

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he efficient and safe operation of large fusion devices relies on accurate knowledge of the position and shape of the plasma column inside the vacuum chamber. There are several reasons for optimizing plasma shape and position, namely, to maintain adequate clearance from the chamber wall to avoid high densities of power and particle deposition, to be sufficiently close to the wall to ensure adequate passive stabilization, to achieve efficient radio frequency (RF) heating by maximizing antenna coupling (see "Tutorial 9"), and finally, to reduce magnetohydrodynamic (MHD) activity (see "Tutorial 2" in [1]).Unfortunately, plasma shape is not a directly measurable quantity and thus can only be evaluated using diagnostic data, such as the magnetic measurements of flux and field. Current trends in existing fusion plants, as well as operating scenarios envisioned for future tokamaks, present the control engineer with the challenge of regulating highly unstable, strongly shaped plasmas with precision and reliability. Therefore, whether to improve fusion performance or to protect the machine components, the problem of reconstructing the plasma boundary is critical for both diagnostic and control purposes. In this respect, shape estimation assumes a key role in fulfilling the requirements for real-time applications.

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Real Time Control of Plasma Boundary In JET

Cited by 11 publications

References 3 publications

Chapter 8: Plasma operation and control

Chapter 8: Plasma operation and control

A Flexible Software for Real-Time Control Applications in Fusion Experiments

IEEE Control Systems Magazine

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