Status of Resonant Diplexer Development for high-power ECRH Applications

Kasparek, W.; Plaum, B.; Lechte, C.; Filipovic, E.; Erckmann, V.; Grunwald, Gerhard; Hollmann, Frank; Maraschek, M.; Michel, G.; Monaco, F.; Müller, Stefan; Noke, F.; Purps, F.; Schubert, M.; Schütz, H.; Stober, J.; Wágner, D.; Braber, R. van den; Doelman, Niek; Fritz, Erik; Bongers, W.A.; Krijger, B.; Petelin, M. I.; Lubyako, L. V.; Bruschi, A.; Sakamoto, K.

doi:10.1051/epjconf/20123204008

Cited by 5 publications

(6 citation statements)

References 10 publications

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“…with the Wendelstein 7-X (W7-X) ECRH system at IPP Greifswald and at the ASDEX Upgrade tokamak (AUG) at IPP Garching. A selection of these experiments has been reported in previous publications [7], [8], [9], [10], in which the emphasis was put on the impact a controlled FADIS resonator may have in ECRH applications. Here we report on two fundamental high-power experiments with the adaptively controlled mirror, both of which cases deal with controlling the resonator to resonance.…”

Section: Resultsmentioning

confidence: 99%

“…The functional applications include (a) the tunable distribution of mm-wave power over the output ports, (b) mode purification, (c) a narrow band-pass filter to discriminate between low power Electron Cyclotron Emission (ECE) signals and high power ECRH in a line-of-sight ECE sensing configuration and (d) the combination of gyrotron power from two input ports into a single transmission line. Further details of the versatile application field can be found in [2], [7], [8]. The transmission properties of the FADIS resonator diplexer are similar to those of the Fabry-Perot resonator (1) and (2), in which -in the terminology of Section I and Fig.…”

Section: A Description Of the Resonatormentioning

confidence: 86%

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Adaptive mirror control for an optical resonator cavity

Doelman¹,

Braber²,

Kasparek

et al. 2013

52nd IEEE Conference on Decision and Control

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An adaptive mirror control strategy for tuning an optical resonator is described. The control approach is modelfree and uses a small-amplitude perturbation signal to enable real-time estimation of the cost function gradient. The strategy has similarities with the approaches of 'stochastic approximation' and 'extremum seeking control', which are well-known methods in the control community. Particular fine-tuning of the algorithm, such as perturbation filtering, cost function shaping and disturbance feedforward are discussed. The control strategy has been validated on a (quasi-optical) millimetre wave resonator system. A significant disturbance acting on this set-up is the non-stationary frequency of the wave source (gyrotron). In various experiments it has been demonstrated that the control approach is well capable of keeping the optical cavity in resonance, to track wavelength variations and to reject disturbances in the low and mid-frequency range. The only performance limitation of the approach occurs in cases which require fast disturbance tracking. This is due to the bandwidth restrictions in the underlying mirror motion system.

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Section: Resultsmentioning

confidence: 99%

Section: A Description Of the Resonatormentioning

confidence: 86%

Adaptive mirror control for an optical resonator cavity

Doelman¹,

Braber²,

Kasparek

et al. 2013

52nd IEEE Conference on Decision and Control

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“…undesired) modes in the waveguides distorting the launched beam pattern predominantly exit the diplexer at the non-resonant output port. Very-high-order modes are absorbed in the (absorber-loaded) resonator casing; this filtering reduces the thermal loading of the sensitive cuffs of the vacuum windows in the transmission lines as well as in the launcher components [30]. A stray radiation detector in the diplexer can serve as a monitor for mode purity.…”

Section: Outlook: Options For Applications In Large-scale Ecrh Systemsmentioning

confidence: 99%

NTM stabilization by alternating O-point EC current drive using a high-power diplexer

et al. 2016

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At the tokamak ASDEX Upgrade, experiments to stabilize neoclassical tearing modes (NTMs) by electron cyclotron (EC) heating and current drive in the O-points of the magnetic islands were performed. For the first time, injection into the O-points of the revolving islands was performed via a fast directional switch, which toggled the EC power between two launchers synchronously to the island rotation. The switching was performed by a resonant diplexer employing a sharp resonance in the transfer function, and a small frequency modulation of the feeding gyrotron around the slope of the resonance. Thus, toggling of the power between the two outputs of the diplexer connected to two articulating launchers was possible. Phasing and control of the modulation were performed via a set of Mirnov coils and appropriate signal processing. In the paper, technological issues, the design of the diplexer, the tracking of the diplexer resonance to the gyrotron frequency, the generation and processing of control signals for the gyrotron, and the typical performance concerning switching contrast and efficiency are discussed. The plasma scenario is described, and plasma experiments are presented, where the launchers scanned the region of the resonant surface continuously and also where the launchers were at a fixed position near to the q = 1.5-surface. In the second case, complete stabilization of a 3/2 NTM could be reached. These experiments are also seen as a technical demonstration for the applicability of diplexers in large-scale ECRH systems.

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“…For completeness, it is mentioned here that first plasma experiments have started using a fast directional switch (FADIS) on AUG [10], which, in a second step, shall also be used for in-line ECE [11]. Crucial for this application is a feedback-control of the FADIS resonator to compensate thermal drifts [12].…”

Section: System Statusmentioning

confidence: 99%

ECRH on ASDEX Upgrade - System Status, Feed-Back Control, Plasma Physics Results -

Stober

Bock

Höhnle

et al. 2012

EPJ Web of Conferences

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Abstract. The ASDEX Upgrade (AUG) ECRH system now delivers a total of 3.9 MW to the plasma at 140 GHz. Three new units are capable of 2-frequency operation and may heat the plasma alternatively with 2.1 MW at 105 GHz. The system is routinely used with X2, O2, and X3 schemes. For B t = 3.2 T also an ITER-like O1-scheme can be run using 105 GHz. The new launchers are capable of fast poloidal movements necessary for real-time control of the location of power deposition. Here real-time control of NTMs is summarized, which requires a fast analysis of massive data streams (ECE and Mirnov correlation) and extensive calculations (equilibria, ray-tracing). These were implemented at AUG using a modular concept of standardized real-time diagnostics. The new realtime capabilities have also been used during O2 heating to keep the first reflection of the non-absorbed beam fraction on the holographic reflector tile which ensures a well defined second pass of the beam through the central plasma. Sensors for the beam position are fast thermocouples at the edge of the reflector tile. The enhanced ECRH power was used for several physics studies related to the unique feature of pure electron heating without fueling and without momentum input. As an example the effect of the variation of the heating mix in moderately heated H-modes is demonstrated using the three available heating systems, i.e. ECRH, ICRH and NBI. Keeping the total input power constant, strong effects are seen on the rotation, but none on the pedestal parameters. Also global quantities as the stored energy are hardly modified. Still it is found that the central ion temperature drops as the ECRH fraction exceeds a certain threshold.

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Status of Resonant Diplexer Development for high-power ECRH Applications

Cited by 5 publications

References 10 publications

Adaptive mirror control for an optical resonator cavity

Adaptive mirror control for an optical resonator cavity

NTM stabilization by alternating O-point EC current drive using a high-power diplexer

ECRH on ASDEX Upgrade - System Status, Feed-Back Control, Plasma Physics Results -

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