T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 1

T. M. Biewer, R.E. Bell

October 20th, 2003

NSTX Physics Meeting

Princeton Plasma Physics Laboratory

ERD Observations in RF Heated Helium Plasmas

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 2

I got married.

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 3

Outline

• The Edge Rotation Diagnostic

• Ohmic, Helium Plasma– He (majority ion) and C (impurity ion) dynamics

– Calculation of Er from force balance

• RF Heated Helium plasma– Cold component comparison to Ohmic plasma

• RF antenna is a BIG source of C at the edge

– Hot component dynamics and implications

• Summary

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 4

The Edge Rotation Diagnostic

Poloidal Chords

Toroidal Chords

• 10 ms time resolution.• 6 toroidal and 7 poloidal rotation chords covering 140 to

155 cm.• Local Er=vB-p/eZn• Does not require neutral beam.• Sensitive to C III, C IV (impurity ions), and He II.• Cold plasma broadens C III emission shell, resulting in

possible Er measurement.• Edge rotation measurement complements main-CHERS.

Poloidal Chords

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 5

Ohmic He Dischage 110153

• Phil Ryan, et. al RF heating XP

• RF system shut down resulting in an Ohmic, He plasma

• Ip~500 kA, ne~1.2x1019 m-3, Te~800 eV, BT~0.44 T

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 6

Raw ERD data shows strong He, C light

Fit the spectra (He or C)•Amp.*Width

•Line brightness•Emissivity (inversion)

•nz (with ADAS modeling)

•Width•Apparent Ti

•Center shift•Apparent velocity

•Local velocity (inversion)

~

~R

~

C III

He II Poloidalviews

Toroidalviews

Edge most

Edge mostCore most

Core mostFiber 13

121011

987654321

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 7

He II evolution at R=145 cm

+ is co-Ip

Apparent toroidal velocity and temperature

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 8

Modified Abel Inversion

• Inversion process: R.E. Bell, RSI 68, 1273 (1997).• Poloidal radii from sightlines w/ EFIT due to strong plasma shaping• He II peaks further in than C III consistent with its higher ionization

potential (54.4 eV compared to 47.9 eV)• Approximately equal Emissivities suggests that emission is essentially

isotropic on the flux surface (during Ohmic He plasmas).

He II (majority ion) C III (impurity ion)

LCFS LCFS

Tor.Pol.

Tor.Pol.

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 9

He II dynamicsR

(cm

)T

i (eV

)v

(km

/s)

Good pol. & tor. agreement and w/ ionz. potential

Ti isotropic

+ tor. co-Ip

+ pol. down @ outboard mp.

Er (

kV/m

)

He II ion. Pot.

He I ion. Pot.

Time (sec)

Tor., Pol., Te

Er=vxB-p/Zn

LCFS

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 10

C III dynamics

TC<THe~60 eV not surprising

RC>RHe~145 cm not surprisingR

(cm

)T

i (eV

)v

(km

/s)

Er (

kV/m

)

C III ion. Pot.

C II ion. Pot.

Time (sec)

Tor., Pol., Te

LCFS

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 11

Er profile from He II and C III

Er=vxB-p/ZnGood agreement between the Er found from He II and that from C III

q=2 radius

Shape around LCFS similar to simulations for ASDEX-U. Kiviniemi PoP 10 2604 (2003)

Other structure from TM islands?

q=3 radius

q=4 radius

Probably not; no MHD activity.

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 12

Application of RF power

• Two shots from the same day of Phil Ryan’s RF heating XP

• Shot 110144 v. 110153

• Ip 500 kA, 500 kA

• BT 0.41 T, 0.44 T

• PRF 4.3 MW, 0

• Te 1.7 keV, 0.8 keV

• ne 2.0x1019, 1.2 x1019

Ohmic

RF heating

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 13

Two successive time frames clearly show the spectral consequences of 30 MHz HHFW heating (4.3 MW input) on the edge plasma.

This effect is apparent in edge C (impurity) ions and He (bulk) ions.

coun

ts RF off

Toroidal, rtan~146 cm

Pixel # (~)

RF onRF off

Poloidal, rtan~146 cm

Pixel # (~)

RF on

RF power heats edge ions

Data is best fit with 2 Gaussian distribution function (hot and cold components).

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 14

HHFW RF Power heats edge ions

1G fit2G high2G low

Time evolution of NSTX Shot 110144 shows that edge ion heating is well correlated with the application of 30 MHz HHFW power to the plasma.

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 15

He II cold componentR

(cm

)T

i (eV

)v

(km

/s)

Peak emission has moved outward.

Ti lower (but ne=2ne), and is anisotropic (Tpol=1.5Ttor)

Tor. velocity appears more negative (anti-Ip)

Er (

kV/m

)

He II ion. Pot.

He I ion. Pot.

Time (sec)

Tor., Pol., Te

Er slightly more negative

Rel. to Ohmic

Ohmic

Ohmic

Tor. Ohmic

Pol. Ohmic

Ohmic

End of RF power

LCFS

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 16

He II dynamicsR

(cm

)T

i (eV

)v

(km

/s)

Good pol. & tor. agreement and w/ ionz. potential

Ti isotropic

+ tor. co-Ip+ pol. up @ outboard mp.

Er (

kV/m

)

He II ion. Pot.

He I ion. Pot.

Time (sec)

Tor., Pol., Te

Er=vxB-p/Zn

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 17

Er from He II and C III (cold)

Ohmic v. RF heated

The Er at the edge most region of the plasma (R>146 cm) is more negative during RF heated plasmas than during Ohmic.

For R<146 cm the Er is similar (for the region measured)

Implies that RF leads to ion loss at the edge of the plasma.

Er~-5 kV/m

RF on

Ohmic

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 18

RF antenna sources C?

• EHe for cold comp. of RF plasma ≈ EHe of Ohmic• EHe for c.c. is balanced (tor~pol), as for EHe of Ohmic• EC of cold comp. of RF plasma >> EC of Ohmic• Tor. EC >> Pol. EC for c.c. of RF plasma• Collisions with edge C neutrals responsible for ion loss?

He II (majority ion) C III (impurity ion)

LCFS LCFSTor.Pol.

Tor.Pol.

Ohmic

Ohmic

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 19

• What about the Hot component?

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 20

Hot component of 110144

• Hot component has an unequal distribution for both He and C, i. e. Epol >> Etor

• Epol: He h.c. >> c.c. ~ Ohmic, C h.c. ~ c.c. >> Ohmic

• Etor: He h.c. ~ c.c. ~ Ohmic, C h.c. ~ c.c. > Ohmic

He II (majority ion) C III (impurity ion)

LCFSLCFSTor.

Pol.

Tor.Pol.

Ohmic Ohmic

cold pol

cold

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 21

A plasma dissected by Charge Exchange

He+

~54 eVHe2+

~max Ti

C+

~24 eVC2+

~48 eVC3+

~65 eVC4+

~392 eVC5+

~490 eVC6+

~max Ti

He II C III C VICHERS bkgnd

C0

~11 eV

C2+

~11 eV

He0

~max Ti

C2+

~11 eV

C0

~48 eV

C2+

~11 eV

C+

~65 eV

C2+

~11 eV

C2+

~392 eV

C2+

~11 eV

C3+

~490 eV

C2+

~11 eV

C4+

~max Ti

C+

~11 eV

He0

~54 eV

C+

~11 eV

He+

~max Ti

C+

~11 eV

C0

~24 eV

C+

~11 eV

C+

~48 eV

C+

~11 eV

C2+

~65 eV

C+

~11 eV

C3+

~392 eV

C+

~11 eV

C4+

~490 eV

C+

~11 eV

C5+

~max TiCHERS signl

C3+

~11 eV

C0

~65 eV

C3+

~11 eV

C+

~392 eV

C3+

~11 eV

C2+

~490 eV

C3+

~11 eV

C3+

~max Ti• Epol: He h.c. >> c.c. ~ Ohmic, C h.c. ~ c.c. >> Ohmic

• Etor: He h.c. ~ c.c. ~ Ohmic, C h.c. ~ c.c. > Ohmic

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 22

More power leads to more heating

From NSTX Shot 110133 to 110145 the applied RF power was increased. Empirically, Ti increases as PRF

0.47.

Negative poloidal velocity is upwards on the outboard midplane.Negative toroidal velocity is opposite to the direction of Ip.

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 23

Summary

• Applying power to the RF antenna coincides with large amounts of Carbon in NSTX– Antenna direct source?

• Effect greater near antenna (poloidal view).

– Surface waves scouring the walls?• Or why do we see anything in the toroidal view?

• This Carbon is useful as a Charge Exchange Diagnostic– There are hot ions in the edge.– Parametric decay of HHFW on He2+ majority as heating mech.

• How does Carbon get hot? Collisions?

• Does running the antenna clean itself up?• Need experiments with CHERS and antenna camera.• Need modeling of edge plasma (CRM, MIST?).

T.M. Biewer, Oct. 20th, 2003 NSTX Physics Meeting 24

Er from He II and CIII hot