NOVIMIR A. PABLANT

M. BITTER, L.F. DELGADO-APARICIO, M. GOTO, K.W. HILL, S. LAZERSON, S. MORITA, L. ROQUEMORE

HIGH RESOLUTION X-RAY IMAGING CRYSTAL

SPECTROMETER (XICS) ON LHD

2011-10-06

XICS HAS BECOME AN IMPORTANT PART OF THE LHD EXPERIMENTAL PROGRAM.

XICS has been routinely obtaining ion and electron temperatures since the first shot of the the 2011 LHD experimental campaign.

● XICS analysis is now routinely requested.● Can provide ion temperature profiles in situation where charge

exchange is unavailable.

Diagnostic is extremely reliable.● Provides measurements on every other LHD shot.● For shots with high argon emissivity, time and spatial resolution

can be better than existing Te and Ti diagnostics.

PRELIMINARY RESULTS SHOW THE HIGH TEMPORAL AND SPATIAL RESOLUTION OF THE XICS SYSTEMComparisons between the single chord XCS and Thomson scattering systems show good agreement.

TIME HISTORY PROFILES

XICS SHOT 107612 20ms INTEGRATION 2cm RESOLUTION

NEWLY INSTALLED SYSTEM IS ROUTINELY MAKING LINE-INTEGRATED TEMPERATURE MEASUREMENTS

BRIGH

TNESS

ION

TEMPERATU

RE

ELECTRON

TEMPERATU

RE

Inversion routines currently under development.

XICS is a valuable addition tothe LHD experimental program.

XICS MEASUREMENTS COMPARE WELL TO XCS AND THOMSON

Thorough validation of the XICS diagnostic is under way.● Complete validation of inverted Te and Ti profiles is desired.

● Electron temperature comparison with Thomson.● Ion temperature comparison with Charge Exchange Spectroscopy.

● These type of through comparisons have not been done previously!

So far XICS -- Thomson comparisons at LHD have been done only for central chords:

● Agreement is excellent when argon emissivity is centrally peaked.● Profile comparisons require equilibrium reconstructions to map the

real space measurements to flux space.● Accurate comparisons require inversion of the XICS measurements.

SPATIAL CALIBRATION OF THE XICS DIAGNOSTIC HAS BEEN COMPLETED

XICS spatial calibration consists of three parts:1. Measurements of crystal and detector position after installation.2. In-vessel calibration showing actual viewing volume.3. Fit of the detector position based on recorded spectra.

After integrating measurements and in-vessel results, the detector position matched the observed spectra to better than 2 mm.

Final detector location and orientation are found using a least-squares technique.

● Provides an extremely accurate determination of the dispersion.

MANY SPECTRAL FITTING AND XICS ANALYSIS ADVANCEMENTS HAVE BEEN COMPLETEDShot analysis (line-integrated) is now routinely performed.

High resolution of the LHD XICS system allows for insight into the accuracy of our atomic physics models.

RESULTS FROM STELLOPT HAVE BEEN INTEGRATED INTO THE XICS ANALYSIS

Mapping of XICS sightline to flux space can now be performed given a VMEC output file.

INVERSION OF XICS MEASUREMENTS HAS BEEN PERFORMED

Preliminary inversion of XICS data has been performed.● Integration with STELLOPT is still underway.

AN INVITED TALK WAS GIVEN AT THE SPIE CONFERENCE IN SAN DIEGO

SPIE: Advances in Computational Methods for X-Ray Optics II

Accompanying paper was recently published in the conference proceedings:

X-ray imaging diagnostics for magnetically confined and

laser-produced fusion plasmas • http://dx.doi.org/10.1117/12.893651

Presentation was well received and a collaboration was formed to create an advanced x-ray ray-tracing simulation of the LHD XICS system.

● Simulation will allow characterization of the accuracy of our inversion procedures using actual stellarator and diagnostic geometry.

● Simulation will be based on the ray-tracing package McXtrace.

A DEDICATED EXPERIMENT WAS PERFORMED ON LHD IN COLLABORATION WITH PPPL SCIENTISTS.Measurement of Ti and Te profiles with ne scan (0.5-3.0 x 1019m-3). 

Equi-partition from centrally peaked Te (including suprathermal electrons) to Ti

● Experiment lead by Novimir Pablant and Shigeru Morita.

Goal: Examine the evolution of ion and electron temperatureprofiles under ECH and neutral beam heating.

● Experiment done at low densities and magnetic fieldBT = 1.3Tesla, ne = 1 x 1019m-3

● XICS allows measurements of the ion temperature profile without the injection of the perpendicular neutral beam.

FUTURE PLANS

October:● Completion of diagnostic hardware paper to be submitted to RSI.● Further work on STELLOPT integration and profile inversion.● Support of LHD experimental campaign with XICS measurements.

November:● Poster at APS.● Continued work on STELLOPT integration.● Analysis of LHD plasma shots using inverted XICS measurements.● Begin development of XICS simulation code.

December:● Draft of analysis/XICS validation paper.

Ongoing/Future:● Work on developing ability to perform transport analysis on LHD.● Work on XICS upgrade for 2012.