Solid tungsten Divertor-III for ASDEX Upgrade and contributions to ITER

Abstract

ASDEX Upgrade became a full tungsten experiment in 2007 by coating its graphite plasma facing components with tungsten. In 2013 a redesigned solid tungsten divertor, Div-III, was installed and came into operation in 2014. The redesign of the outer divertor geometry provided the opportunity to increase the pumping efficiency in the lower divertor by increasing the gap between divertor and vessel. In parallel, a by-pass was installed into the cryo-pump in the divertor region allowing adapting the pumping speed to the required edge density.Safe divertor operation and heat removal becomes more and more significant for future fusion devices. This requires developing 'tools' for divertor heat load control and to optimize the divertor design. The new divertor manipulator, DIM-II, allows retracting a relevant part of the outer divertor into a target exchange box without venting ASDEX Upgrade. Different frontends can be installed and exposed to the plasma. At present, front-ends for probe exposition, gas puffing, electrical probes and actively cooled prototype targets are under construction.The installation of solid tungsten, the control of the pumping speed and the flexibility for testing divertor modifications on a weekly base is a unique feature of ASDEX Upgrade and offers together with the extended set of diagnostics the possibility to investigate dedicated questions for a future divertor design.

On the detection and classification of material defects in crystalline solids after energetic particle impact simulations

“…The simulation box is initially prepared as a pristine singlecrystalline W lattice sample with 48778 W atoms based on a bcc unit cell. The box has a dimension of (28a, 28a, 28a) with a = 0.316 nm as the W lattice constant [15], for a sample temperature of 300K due to the majority of the experiments of tungsten damaging are done at room temperature [16,17]. The deuterated W lattice is created by introducing 0.1 at % D (53 deuterium atoms) randomly distributed in the whole sample at tetrahedral interstitial positions, Fig.…”

Feedback controlled, reactor relevant, high-density, high-confinement scenarios at ASDEX Upgrade

“…The versatile auxiliary heating system is comprised of 20 MW neutral-beam injection (NI), up to 6 MW ion cyclotron resonance heating (ICRH), and 5 MW electron cyclotron resonance heating (ECRH). The investigations reported here were done in operations with the bulk tungsten divertor III configuration [6].…”

Cracks avoidance with a modified solid tungsten divertor in ASDEX Upgrade

“…According to the 'EFDA roadmap for the realization of fusion energy' the material portfolio for DEMO will consist of consolidated developments of EUROFER as a structural material and tungsten as plasma facing material. Bearing that in mind, AUG is presently equipped with ferromagnetic tiles in the inner column [1] and massive tungsten tiles in the strike line region of the lower outer divertor [2]. The remaining wall elements are made of tungsten coated graphite.…”