13 research outputs found
D-Mag: a laboratory for studying plasma physics and diagnostics in strong magnetic fields
We have set up a diagnostic magnet (D-Mag) laboratory for a wide range of
applications in plasma physics. It consists of a superconducting magnet for
field strengths of up to 5.9 T. The main purpose is to provide an experimental
environment for the development of plasma diagnostics for nuclear fusion
studies and the investigation of dusty plasmas in strong magnetic fields. We
describe in the article the setup and operation of the D-Mag. Some applications
are presented for the development of plasma diagnostics, such as neutral
pressure gauges and Langmuir probes that have to be operated in strong magnetic
fields. Among the examples is the test of the long-pulse capability and
stability of the diagnostic pressure gauge (DPG) for the ITER device.Comment: Superconducting Magnet - laboratory for diagnostic development and
tests in strong and variable magnetic fields of up to 6 Tesl
Characterization of the radial electric field and edge velocity shear in Wendelstein 7-X
In this work we present the first measurements obtained by the V-band Doppler
reflectometer during the second operation phase of Wendelstein 7-X to discuss
the influence in the velocity shear layer and the radial electric field, E,
of several plasma parameters such as magnetic configuration, rotational
transform or degree of detachment. In the first place, we carry out a
systematic characterization of the turbulence rotation velocity profile in
order to describe the influence of density and heating power on E under the
four most frequent magnetic configurations. The E value in the edge is
found to increase with configurations featuring higher , although this
does not apply for the high mirror configuration, KJM. As well, the E value
in the SOL and the velocity shear near the separatrix are found to display a
clear dependence on heating power and density for all configurations. For a
number of relevant cases, these results are assessed by comparing them to
neoclassical predictions obtained from the codes DKES and KNOSOS, finding
generally good agreement with experimental results. Finally, the evolution of
E at the edge is evaluated throughout the island-divertor detachment regime
achieved for the first time in the 2018 campaign. After detachment, E
is reduced both at the SOL and edge, and the plasma column shrinks, with the
shear layer seemingly moving radially inwards from the separatrix.Comment: Sent for publication to Nuclear Fusio
First results from an event synchronized-high repetition Thomson scattering system at Wendelstein 7-X
The Wendelstein 7-X (W7-X) Thomson scattering (TS) diagnostic was upgraded to
transiently achieve kilohertz sampling rates combined with adjustable measuring
times. The existing Nd:YAG lasers are employed to repetitively emit "bursts",
i.e. multiple laser pulses in a short time interval. Appropriately timing burst
in the three available lasers, up to twelve evenly spaced consecutive
measurements per burst are possible. The pulse-to-pulse increment within a
burst can be tuned from 2 ms to 33.3 ms (500 kHz - 30 Hz). Additionally, an
event trigger system was developed to synchronize the burst Thomson scattering
measurements to plasma events. Exemplary, a case of fast electron density and
temperature evolution after cryogenic H2 pellet injection is presented in order
to demonstrate the capabilities of the method.Comment: 11 pages, 5 figures, To be published as proceeding to the 3rd
European Conference on Plasma Diagnostics 2019 in Lisbon in the Proceedings
Section of the Journal of Instrumentation (JINST
Towards a 1.5 MW, 140 GHz gyrotron for the upgraded ECRH system at W7-X
For the required upgrades of the Electron Cyclotron Resonance Heating system at the stellarator Wendelstein 7-X, the development of a 1.5 MW 140 GHz Continuous Wave (CW) prototype gyrotron has started. KIT has been responsible to deliver the scientific design of the tube (i.e. the electron optics design and the RF design), with contributions from NKUA and IPP. The prototype gyrotron has been ordered at the industrial partner, Thales, France, and is expected to be delivered in 2021. In parallel, a short-pulse pre-prototype gyrotron has been developed at KIT, to provide the means for a first experimental validation of the scientific design in ms pulses, prior to the construction of the CW prototype. This paper reports on the status of the 1.5 MW CW gyrotron development, focusing on the scientific design and its numerical and experimental validation. © 2021 Konstantinos A. Avramidis, Zisis C. Ioannidis, Gaetano Aiello, Patrick Bénin, Ioannis Chelis, Andreas Dinklage, Gerd Gantenbein, Stefan Illy, John Jelonnek, Jianbo Jin, Heinrich P. Laqua, Alberto Leggieri, François Legrand, Alexander Marek, Stefan Marsen, Ioannis Gr. Pagonakis, Tobias Ruess, Tomasz Rzesnicki, Theo Scherer, Dirk Strauss, Manfred Thumm, Ioannis Tigelis, Dietmar Wagner, Jörg Weggen, Robert C. Wolf, the Wendelstein 7-X Tea