# Presentation: 506427

## LLNL Collaboration on NCSX

**David N. Hill, Tom Kaiser, Vlad Soukhanovskii, ****Tom Rognlien, and Maxim Umansky**
***Lawrence Livermore National Laboratory***

- _Outline_
- Present work: divertor design (mapping SOL for divertor design)
- Proposed work:
- Boundary physics: divertor measurements + modeling
- MSE internal field measurements: equilibrium, internal currents

- This work performed under the auspices of the US DOE by the University of California, Lawrence Livermore National Laboratory, under contract W-7405-Eng-48

- This work supports high-priority FY11 research tasks

## LLNL began looking at boundary physics for NCSX  in 2000

- Internal funding for three years
- Engaged Greifswald W7-X boundary group to assist with development of 3D SOL model
- Worked with W7-AS group to apply VMEC/MFBE/GOURDON codes to map structure of the proposed NCSX coil set
- Began looking at potential diagnostics for SOL measurements.
- Very modest OFES funding since 2002
- Focus on mapping structure of SOL plasma as equilibrium has evolved
- Focus on mapping SOL to divertor structures to support design activies
- Reduced the scope of our collaboration with Greifswald  to periodic consulting on their 3D SOL code

## Field line tracing using MHD equilibrium from either PIES or VMEC/MFBE determines SOL and divertor geometry

- Extensive benchmarking activity during FY05-06 to compare SOL geometry as determined by PIES and VMEC/MFBE equilibrium codes. Some differences are observed, but within uncertainties.
- Computed SOL geometry used in deriving conceptual design for divertor plates.  SOL transport simulated by magnetic field line diffusion.

## LLNL is supporting design of PFCs

- Heat flux is estimated by mapping LCFS field lines to divertor targets.
- Field lines are a bit short (higher Te at target), but density is higher (lower Te at target). Different than Local Island Divertors.
- Do we need the inner target plates during early low-power operation?

## Infrared and visible TV cameras can provide information on 3D SOL structure provided appropriate viewing geometry.

**Wide-angle tangential views provide outline at single cross section.**
**Inversions possible with model of LCFS (similar to what we do now on DIII-D with recycling and ELMs).**
**Also possible to generate simulated diagnostic images.**
**Imaging through most ports will require re-entrant optics to obtain desired field of view, so most of the cost is related to engineering design activities.**

## Livermore Is Responsible for Divertor IR Imaging on DIII-D and Has Used the Data to Validate 2D SOL models

**IR brightness converted to surface temperature, from which heat flux can be derived.**
**Heat flux profiles mapped to MHD equilibrium.**
**Measurements can be compared with simulations.  Example shows UEDGE 2D simulation.**
**On DIII-D, divertor Thomson (LLNL-GA collaboration) provides 2D temperature and density to compare with simulation.**

- 2d reconstruction of plasma pressure profile in detached divertor plasma in DIII-D.

## LLNL Brings Experience Designing, Building, and Using World-Class DIII-D MSE System to NCSX Internal Current Profile Measurements.

- MSE routinely used to constrain MHD reconstruction of DIII-D plasmas with strong current profile modification (Advanced Tokamak, Hybrid, Negative Central Shear, Current Holes, edge bootstrap currents).  *DIII-D will not run AT experiments without MSE.*
- Calibration for precision polarization measurements, proper line-of-sight, adequate spatial resolution, are key elements to successful MHD reconstruction.
- Existing collaborations with U. Wisconsin and General Atomics complement strengths of the Livermore team.

## B

**Major Radius (m)**

**BES measurements verify strong RSAE localization around q****min**** location**

**B**

**A**

**A**

**B**

**119346**

**119345**

**BES makes radially localized measurements of density fluctuations**
**Combined with MSE, BES data confirm high-n RSAE density fluctuations are localized near q****min****.**** **

**MSE q-profile**

**BES measurements verify strong RSAE localization around q****min**** location**

- Mike Van Zeeland – General Atomics

## Some general comments on collaborations

- Collaborations can bring many benefits to host institution
- Unique skills/experience in personnel, new hardware capability
- Potentially cheaper and/or more flexible workforce
- Free energy and fresh ideas from an external without the “project” perspective
- Collaborations can bring many benefits to the collaborating institution
- New funding for people and equipment (as opposed to more work for same people)
- Opportunity to expand scope of research, applying expertise to new problems
- Increased recognition and invitation to branch out further, tackle bigger challenges.
- Some key elements of successful long-term collaborations in experimental science
- _Fund people + instrumentation + design support _(free energy, safety valve, tangible assets)
- Have clearly defined institutional roles for collaborating institutions (more than individuals)
- Provide professional growth opportunities for collaborators and help advertise role of host institutions