# Presentation: 536288

## Direct Measurement of MHD-induced Fast-ion  Redistribution in Space and Energy by NPA Vertical Scanning

***Columbia U***
***Comp-X***
***General Atomics***
***INEL***
***Johns Hopkins U***
***LANL***
***LLNL***
***Lodestar***
***MIT***
***Nova Photonics***
***NYU***
***ORNL***
***PPPL***
***PSI***
***SNL***
***UC Davis***
***UC Irvine***
***UCLA***
***UCSD***
***U Maryland***
***U New Mexico***
***U Rochester***
***U Washington***
***U Wisconsin***
***Culham Sci Ctr***
***Hiroshima U***
***HIST***
***Kyushu Tokai U***
***Niigata U***
***Tsukuba U***
***U Tokyo***
***JAERI***
***Ioffe Inst***
***TRINITI***
***KBSI***
***KAIST***
***ENEA, Frascati***
***CEA, Cadarache***
***IPP, J******ü******lich***
***IPP, Garching***
***U Quebec***

**S. S. Medley**

**Energetic Particle Science Focus Group Meeting**
*PPPL, November 15, 2006*

## The Neutral Particle Analyzer (NPA) on NSTX ScansVertically

**The Neutral Particle Analyzer (NPA) on NSTX ScansVertically**
** ****Over a Wide Range of Angles on a Shot-to-Shot Basis**

**The elevation minor radius at the intersection of the NPA sightline with a given neutral beam line depends on the NPA horizontal tangency radius.**

## •  TRANSP simulation of NPA vertical scan without anomalous fast ion diffusion (left) and with core-weighted anomalous fast ion diffusion (right).

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**NPA Vertical Scan Can Measure MHD-induced**
**Spatial Redistribution of Energetic Ions**

- •  **TRANSP simulation of NPA vertical scan without anomalous fast ion diffusion (left) and with core-weighted anomalous fast ion diffusion (right).**

**Without AFID**

**With AFID**

## Comparison of Simulated Vertical Scan Spectra

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**Comparison of Simulated Vertical Scan Spectra**
**With and Without Anomalous Fast Ion Diffusion **

**Without AFID**

**With AFID**

**21 Degrees**

**21 Degrees**

**0 Degrees**

**0 Degrees**

## •  Perform NPA vertical scan for a long-pulse, H-mode discharge (e.g. 1175449)

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**Overview: NPA 2007 Experimental Activities**

**•****  ****Perform NPA vertical scan for a long-pulse, H-mode discharge (e.g. 1175449)**
**    ****under a dedicated XP (~ 1 day).**
**•  ****Support Eric’s proposed XPs with 10x  faster NPA data acquisition **
**    ****(e.g. 0.1 ms sampling for 800 ms)**
**•****   ****Advocate a counter-injection run...a regime offering rich new effects**
**     ****for energetic ion and MHD effects.**

## TRANSP Uses Anomalous Fast Ion Diffusion (AFID)

**TRANSP Uses Anomalous Fast Ion Diffusion (AFID)**
** ****to Emulate MHD-induced Redistribution/Loss**

**• ****In TRANSP, anomalous fast ion diffusion can be specified in time, space and fast-ion energy****.**
**• ****Core-weighted anomalous fast ion diffusion is appropriate for MHD-induced redistribution. In H-mode discharges, outwardly displaced NB ions remain confined  in a region of comparable n****e****, T****e ****so neutron yield is minimally affected.**
** **
**• ****Outboard-weighted AFID favors ion loss and significantly reduces the neutron yield.**
**• ****Energy dependence is chosen to emulate the measured NPA spectrum distribution.**

## TRANSP Anomalous Fast Ion Diffusion (AFID)

**TRANSP Anomalous Fast Ion Diffusion (AFID)**
**Can Simultaneously Match S****n****(t), S****npa****(t) and f****npa****(E) **

**• ****In this TRANSP analysis, the AFID model was optimized for a time of interest (TOI) period t = 0.6-1.0 s during n=1, f = 5-10 kHz kink-type MHD.**
**• ****In the TOI,  good matching of neutron rate and the NPA efflux evolution and energy spectra are obtained.**

**Notes:**
Halos contribute 50-100% to Snpa (Akers), but TRANSP averages halo neutrals (poloidally and toroidally) which dilutes their contribution to the calculated NPA signal.
2. It is conceivable that proper inclusion of halo neutrals could alter both the magnitude and time evolution of the calculated NPA signal.
3. Energy dependence of AFID affects spectrum outside of the selected energy range because the source of slowing down ions feeding lower energies is depleted.

## MHD-induced Current Redistribution is Confirmed

**MHD-induced Current Redistribution is Confirmed**
**using MSE-constrained Current Reconstruction**

**• ****An equilibrium code is used to calculate the inductive (orange) and bootstrap (red) current profile components.**
**• ****The profile of the  neutral beam injection current drive (NBICD, blue) is calculated in TRANSP.  Summation of the above components yields the calculated total current density (black).**
**• ****As shown in panel (a), the calculated total (black) exceeds the MSE-reconstructed value (gray) by 20-30% when NBICD redistribution is neglected.**
**• ****In panel (b), including core anomalous fast ion diffusion of ~ 5-6 m****2****/s in the TRANSP-calculated NBICD component yields good agreement between the calculated total and MSE-constrained reconstruction current profiles. **

## •  The spectra at small tangency radii drop off naturally because this region corresponds to trapped orbits not populated by tangential NB injection in NSTX.

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**NPA Horizontal Scan at 180 ms**
**Preceeding H-mode Onset: No Spectrum Depletion**

- •  **The spectra at small tangency radii drop off naturally because this region corresponds to trapped orbits not populated by tangential NB injection in NSTX.**

## •  Following H-mode onset, a clear depletion of the NPA horizontal scan spectrum is observed at E  > Eb/3 and Rtan < 50 cm (encircled region).

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**NPA Horizontal Scan at 400 ms**
**Following H-mode Onset: Spectrum Depletion**

- •  **Following H-mode onset, a clear depletion of the NPA horizontal scan spectrum is observed at E  > E****b****/3 and R****tan**** < 50 cm (encircled region).**

## The Neutral Particle Analyzer (NPA) on NSTX Scans Horizontally

**The Neutral Particle Analyzer (NPA) on NSTX Scans Horizontally**
** ****Over a Wide Range of Tangency Angles on a Shot-to-Shot Basis**

**• ****Covers thermal (0.1 - 20 keV) and energetic Ion (≤ 150 keV) ranges**
**• ****Capability exists to simultaneously scan vertically through 26****o **

## Line-integrated NPA Measurements are ‘Localized’ 

**• ****Dominance of charge exchange emissivity by beam neutrals results in **
**   ****both field pitch and spatial localization of NPA measurements.**

**Line-integrated NPA Measurements are ‘Localized’ **
** ****in Pitch and Space by Beam Injected Neutrals**