# Presentation: 806704

## XP743: Island-induced neoclassical toroidal viscosity and dependence on i

- _XP743: Island-induced neoclassical toroidal viscosity and dependence on ____i_

***Columbia U***
***Comp-X***
***General Atomics***
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***Johns Hopkins U***
***LANL***
***LLNL***
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***MIT***
***Nova Photonics***
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***Culham Sci Ctr***
***Hiroshima U***
***HIST***
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***JAERI***
***Ioffe Inst***
***TRINITI***
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***KAIST***
***ENEA, Frascati***
***CEA, Cadarache***
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***U Quebec***

**NSTX Team XP Review Meeting**
- May 8, 2007
- Princeton Plasma Physics Laboratory

*1**Department of Applied Physics and Applied Mathematics, **	**Columbia University, New York, NY*
*2**University of Wisconsin, Madison, WI*

- V1.1

## Investigate the role of islands and i in neoclassical toroidal viscosity rotation damping physics

- Goals
- Test theory of island-induced neoclassical toroidal viscosity (INTV)
- Compare to theory of drag due to electromagnetic torque
- Investigate damping over range of ion collisionality and island width to determine affect on rotation damping and to distinguish theories
- Examine 1/i dependence of NTV without internal rotating modes
- Determine percentage of torque from non-resonant NTV vs. INTV vs. electromagnetic
- Addresses
- Rotation aspect of R(07-2) milestone, leverages ST geometry
- ITPA experiments MDC-4, MDC-12
- ITER issue card AUX-1

- Note: this XP was combined from two XPs presented at last NSTX Forum

## Rotating modes significantly alter rotation damping

- In absence of internal rotating modes
- global rotation damping observed
- non-resonant NTV theory describes toroidal rotation damping (W. Zhu, et al., PRL **96** (2006) 225002.)
- Appearance of internal rotating modes
- local rotation damping near key rational surfaces; outward momentum transfer; evolution to rigid rotor core observed
- qualitative evolution described by electromagnetic torque applied at rational surface (M. Yokoyama, *et al*., Nucl. Fusion **36** (1996) 1307.)

- 0.365s
- 0.375s
- 0.385s
- 0.395s
- 0.405s
- 0.425s

-  (kHz)

- 40

- 30

- 20

- 10

- 0

- R (m)

-  (kHz)

- 40

- 30

- 20

- 10

- 0

- Global
- damping

- Outward
- momentum
- transfer

## INTV theory to be compared to experiment

- Leading theories can be distinguished
- Non-resonant NTV theory
- Scales as ***B**2**(p**i**/****i**)(1/A)**1.5*, yields distinct rotation profile evolution
- Electromagnetic torque at rational surface (R. Fitzpatrick, Nucl. Fusion **33** (1993) 1049.)
- Scales as ***B**2* (not ***i*), rotation profile evolution consistent with observation
- Island-induced NTV (K.C. Shaing, PRL **87** (2001) 245003.)
- Scales as ***B (island width ****w**2**) due to toroidicity*, depends on ***i*
- Theory can be evaluated quantitatively (as done for NTV)
- Experiment to vary key parameters to test theory
- n = 1 mode most significant
- Change ***i* at constant *q* (done successfully in XP619 - gas puffing / BT and Ip variation); consider transitioning out of H-mode
- Change ***B* by changing applied *n* = 1 field
- Change rotating mode onset time by small change in elongation

## XP743: INTV and dependence on i - Run plan

- _	__Task__	__	__	__	__	__	__             Number of Shots_
- 1) Create target plasma near, but not well above the ideal no-wall beta limit (control shot)
- 	(use recent 123866 as setup shot, reduce *I**p* flat-top to 0.9 MA, 2 or 3 NBI sources and
- 	NO step-down of NBI power)
- 	A) Determine time of steady **** and *n* = 1 tearing mode onset			1
- 	B) Reduce elongation to 1.9 (increase PF1A current) if earlier *n* = 1 TM onset desired	1
- 2) Establish applied non-axisymmetric field scenarios (control shots)
- 	A) Apply *n* = 1 field at TM mode onset (t ~ 0.700s) (*n* = 1 setup from (2B))		2
- 	B) Apply *n* = 1 field at steady **** from (1A) (t ~ 0.490s) (*n* = 3 setup: 116939, 0.7 kA)	2
- 	C) Apply *n* = 3 field at steady **** from (1A) (t ~ 0.490s) (*n* = 1 setup: 123889, 0.8 kA)	2
- 3) Ion collisionality scan
- 	A) Vary ***i* for *n* = 1 applied field, with tearing mode (setup from (2A)		3
- 	B) Vary ***i* for *n* = 1 applied field, no rotating modes (setup from (2B))		3
- 	C) Vary ***i* for *n* = 3 applied field, no rotating modes (setup from (2C))		3
- 4) Applied field scan / vary island width (pick most favorable ***i* setup from part (1A)
- _	__A) Vary __*n*__ = 1 applied field (est. range 200A – 1200A)__	__	__	__	__5_
- 								       Total:    22

## INTV XP743: Required / Desired Diagnostics

- Required diagnostics
- Internal RWM sensors
- CHERS toroidal rotation measurement
- Thomson scattering (30 point)
- USXR
- MSE
- Toroidal Mirnov array / between-shots spectrogram with toroidal mode number analysis
- Diamagnetic loop
- Desired diagnostics
- FIReTip
- Fast camera

## XP743: diagnosis of magnetic islands as in XP739/740

- USXR
- appearance of phase inversions
- matching to simple island models to estimate island width
- Thomson scattering: appearance / width of flat spot near rational surfaces
- CHERS
- Radially-localized momentum transfer across key rational surfaces
- Radially-localized rotating mode locking
- NOTE: internal, localized electromagnetic torque cannot be responsible for rotation damping for an ideal plasma perturbation
- MSE: equilibrium reconstructions to accurately determine position of key rational surfaces
- Coordinate with other diagnostics

## Island appears in Te, Ti, and plasma rotation – XP739

- Island evident in kinetic profiles and plasma rotation
- Flat-spot in profiles appears just inside the q = 2 surface
- Rotation evolution shows outward momentum transfer across rational surface and core rotation decay
- Island disappears as mode restabilizes due to beta ramp-down