Overview of diagnostic performance and results for the first operation phase in Wendelstein 7-X (invited).

Wendelstein 7-X, a superconducting optimized stellarator built in Greifswald/Germany, started its first plasmas with the last closed flux surface (LCFS) defined by 5 uncooled graphite limiters in December 2015. At the end of the 10 weeks long experimental campaign (OP1.1) more than 20 independent diagnostic systems were in operation, allowing detailed studies of many interesting plasma phenomena. For example, fast neutral gas manometers supported by video cameras (including one fast-frame camera with frame rates of tens of kHz) as well as visible cameras with different interference filters, with field of views covering all ten half-modules of the stellarator, discovered a MARFE-like radiation zone on the inboard side of machine module 4. This structure is presumably triggered by an inadvertent plasma-wall interaction in module 4 resulting in a high impurity influx that terminates some discharges by radiation cooling. The main plasma parameters achieved in OP1.1 exceeded predicted values in discharges of a length reaching 6 s. Although OP1.1 is characterized by short pulses, many of the diagnostics are already designed for quasi-steady state operation of 30 min discharges heated at 10 MW of ECRH. An overview of diagnostic performance for OP1.1 is given, including some highlights from the physics campaigns.

[1]  G. Pautasso,et al.  Energy flux to the ASDEX-Upgrade diverter plates determined by thermography and calorimetry , 1995 .

[2]  R. König,et al.  Laboratory tests of the Pulse Height Analysis system for Wendelstein 7-X , 2015 .

[3]  R. Burhenn,et al.  High efficiency extreme ultraviolet overview spectrometer: Construction and laboratory testing , 2006 .

[4]  J. Svensson,et al.  Bayesian modelling of a thermal helium beam for measurement of electron density and temperature in the W7-X divertor plasma , 2011 .

[5]  C. Biedermann,et al.  A high resolution IR/visible imaging system for the W7-X limiter. , 2016, The Review of scientific instruments.

[6]  W. Biel,et al.  Compact imaging Bragg spectrometer for fusion devices , 2004 .

[7]  A. Werner,et al.  Diagnostics for steady state plasmas , 2006 .

[8]  S. Lazerson,et al.  Setup and initial results from the magnetic flux surface diagnostics at Wendelstein 7-X , 2016 .

[9]  M. Hirsch,et al.  Design criteria of the bolometer diagnostic for steady-state operation of the W7-X stellarator. , 2010, The Review of scientific instruments.

[10]  Nengchao Wang,et al.  Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000 , 2016, Nature Communications.

[11]  M. Münich,et al.  Bragg Reflection Band Stop Filter for ECE on Wega , 2011, 2011 International Conference on Infrared, Millimeter, and Terahertz Waves.

[12]  M. Preynas,et al.  Plans for the first plasma operation of Wendelstein 7-X , 2014 .

[13]  B. Wiegel,et al.  Monitoring of the neutron production at the Wendelstein 7-X stellarator. , 2014, Radiation protection dosimetry.

[14]  R. König,et al.  Simulation of pulse height analysis soft X-ray spectra expected from W7-X , 2015 .

[15]  A. Werner,et al.  Engineering design for the magnetic diagnostics of Wendelstein 7-X , 2015 .

[16]  S Zoletnik,et al.  Diagnostics development for quasi-steady-state operation of the Wendelstein 7-X stellarator (invited). , 2012, The Review of scientific instruments.

[17]  T. Szabolics,et al.  Overview video diagnostics for the W7-X stellarator , 2015 .

[18]  Torsten Bluhm,et al.  Scientific component framework for W7-X using service oriented GRID middleware , 2010 .

[19]  H. Bosch,et al.  In vessel pressure measurement in nuclear fusion experiments with ASDEX gauges , 1998 .

[20]  O. Schmitz,et al.  Development of miniaturized, spectroscopically assisted Penning gauges for fractional helium and hydrogen neutral pressure measurements. , 2016, The Review of scientific instruments.

[21]  R. König,et al.  Numerical investigation of plasma edge transport and limiter heat fluxes in Wendelstein 7-X startup plasmas with EMC3-EIRENE , 2017 .

[22]  R. König,et al.  Synthetic plasma edge diagnostics for EMC3-EIRENE, highlighted for Wendelstein 7-X. , 2016, The Review of scientific instruments.

[23]  R C Wolf,et al.  The Thomson scattering system at Wendelstein 7-X. , 2016, The Review of scientific instruments.

[24]  J. Svensson,et al.  Forward Modeling of X-Ray Imaging Crystal Spectrometers Within the Minerva Bayesian Analysis Framework , 2016 .

[25]  H P Laqua,et al.  Absolute calibration of sniffer probes on Wendelstein 7-X. , 2016, The Review of scientific instruments.

[26]  R. König,et al.  Design of a high–efficiency extreme ultraviolet overview spectrometer system for plasma impurity studies on the stellarator experiment Wendelstein 7-X , 2004 .

[27]  O. Schmitz,et al.  Fast piezoelectric valve offering controlled gas injection in magnetically confined fusion plasmas for diagnostic and fuelling purposes. , 2017, The Review of scientific instruments.

[28]  B. Vowinkel,et al.  Correlation reflectometry at TEXTOR. , 2010, The Review of scientific instruments.

[29]  R. König.  The Set of Diagnostics for the First Operation Campaign of the Wendelstein 7-X Stellarator , 2015 .