Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47...

26
1 Results from ICRF Heating and Current Drive on C-Mod * G. Schilling 1 , P. T. Bonoli 2 , A. Hubbard 2 , L. Lin 2 , Y. Lin 2 , A. Parisot 2 , M. Porkolab 2 , J. R. Wilson 1 , S. J. Wukitch 2 , and the C-Mod Team 1 Princeton University Plasma Physics Laboratory, Princeton NJ 08543 2 MIT Plasma Science and Fusion Center, Cambridge, MA 02139 Presented at the 45th Annual Meeting of the Division of Plasma Physics October 27-31, 2003, Albuquerque, NM *Work supported by US DoE Contract DE-AC02-76-CH0-3073 and Cooperative Agreement DE-FC02-99ER54512

Transcript of Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47...

Page 1: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

1

Results from

ICR

F Heating and C

urrent Drive

on C-M

od*

G. Schilling

1, P. T. Bonoli 2, A

. Hubbard

2, L. Lin2, Y

. Lin2,

A. Parisot 2, M

. Porkolab2, J. R

. Wilson

1, S. J. Wukitch

2,and the C

-Mod Team

1Princeton University Plasm

a Physics Laboratory, Princeton NJ 08543

2MIT Plasm

a Science and Fusion Center, C

ambridge, M

A 02139

Presented at the 45th Annual M

eeting of the Division of

Plasma Physics

October 27-31, 2003, A

lbuquerque, NM

*Work supported by U

S DoE C

ontract DE-AC

02-76-CH

0-3073 and Cooperative

Agreement D

E-FC02-99ER54512

Page 2: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

2

Abstract

On C

-Mod, ion cyclotron range of frequencies (IC

RF) is the only

auxiliary heating. To inject high power, the antennas need to be able to

withstand high RF voltages. To m

aximize voltage handling, the antennas

have been modified to avoid or m

inimize the R

F E-field in regions where

the RF E-field is parallel to the tokam

ak B-field. For 0.5 second pulses,the IC

RF antennas have now

delivered up to 5 MW

with m

inimum

densityand im

purity generation in H-m

ode. Furthermore, initial tests of the 4-

strap antenna in non-symm

etric phasing were begun. In m

inority Hheating scenario, the 4-strap antenna has coupled 2.7 M

W w

ith bothcounter and co-current phasing w

ithout significant negative impact on the

plasma. The saw

tooth period was observed to lengthen w

ith co-currentphase and shorten w

ith counter-current phase. In addition, initial mode

conversion current drive experiments w

ere begun. Direct electron heating

was observed, independent of phase, for a D

( 3He) m

ode conversionscenario. A

n analysis of the antenna performance and plasm

a responsew

ill be presented.

Page 3: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

3

Outline

•Physics achievem

ents- M

ode conversion studies- Current drive initiation

•ICRF system

technical achievements

- Power

- Phased operation

•ICRF antenna upgrades- D

and E-port- J-port

Page 4: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

4

C-Mod ICRF resonance location at 78 M

Hz

0 1 2 3 4 5 6 7 80.40.5

0.60.7

0.80.9

B(0.66m) (T)

R(m

)

ΩB

-11,5+Ω

D , ΩH

e-4

ΩH

e-3

ΩH

Page 5: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

5

ICR

F Mode C

onversion

Narrow

deposition may

provide tool for modifying

or controlling pressure andcurrent profiles.

Mode conversion cancom

pete with other

damping m

echanisms.

•D

etailed measurem

entsprovide stringent test forIC

RF code predictions.

•M

ore complicated than

expected.•

Absorption details could

affect current and flow drive

predictions.

n3H

e /ne =

0.14B

T=8 T, Ip=0.8

D(3H

e) discharge

TO

RIC

GPC

expG

PCth

Unique com

bination of diagnostics, codes, andR

F system to study various scenarios D

( 3He),

H( 3H

e), and D(H

).•PC

I measures chord-integrated fluctuation

level.•H

igh resolution (~0.7 cm) EC

E radiometer

measures pow

er deposition profile.•First principle 2-D

full-wave calculation

using ICR

F code TOR

IC.

Page 6: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

6

Phase Contrast Imaging diagnostic m

easureselectron density fluctuations

RF ANTENNAPC

I Chords

Wide spectrum

of wavenum

bers are measured

simultaneously; spatial structure is probed over w

ideareaPoor spatial localization results from

line integration12 vertical chords:

•60 cm < R < 79 cm

(R0 =0.66 m

, a=0.22 m)

•0.5 < |kR | < 10 cm-1

•Effective spacing is set by magnification optics

Utilize 100 W

CO2 laser (λ=10.6 µm

)Sensitivity

•1012 m

-2 Hz -1/2

•2-500 kHz

Planned upgrade:•U

pgrade from 12 to 32 channels.

•Increase digitizing rate from 1 to 10 M

Hz w

ithincreased m

emory.

»May allow

direct measure of w

ave damping rate.

•Utilize field alignm

ent of scattered wave to

provide localization.

Page 7: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

7

Detected m

ode converted Ion Cyclotron wave

Contour Plot of Fourier Analyzed PCI D

ata

-10-5

05

10k

R , cm-1

320

340

360

380

Df [kHz]

80.47

80.50

80.53

fRF [MHz]

ph

ase velocity

tow

ards

anten

na

ph

ase velocity

away fro

man

tenn

a

Dispersion curves near M

C Region

FW ICW

IBW

FW

-6 -4 -2 0 2 4 6

PCI chords

5< k <

10 cm-1

PCI Signal Structure

~

Noise Floor

MC

surface•M

easured wavenum

bers are ingood agreem

ent with dispersion

relation.•Fluctuations are m

easured to thelow

field side of the mode

conversion surface.E. N

elson-Melby et. al., PRL 90 155004-1 (2003).

Page 8: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

8 Experimental observation of D

(H) m

ode conversion

.4

1.4

1.6

1.5

2 2.5

2 2.4

1.61.821.21 1.6

1.2

1.4

1.6

0.7

0.9

1.1

0.5

0.6

0.180.2

0.220.24

H/D

0.60.8

10 0.5

1 1.5

PRF (M

W)

1.62 2.42.8

1.6

2 2.4

1.61.71.81.9

1.4

1.5

1.6

1.21.3

1.4

0.80.91 1.1

0.5

0.55

0.6

0.22

0.24

0.26H

/D

0.970.98

0 0.5

1 1.5

PRF (M

W)

Te [keV]

R=0.68 m

1020911026 B

T=5.26 T

, Ip =1.0 MA

, ne0 =1.8x10 20 m-3

Tim

e (sec)

R=0.70 m

R=0.73 m

R=0.75 m

R=0.78 m

R=0.8 m

R=0.83 m

Experim

ent

TO

RIC

S (MW/m^3/MW_inc)

r/a

Com

parison of measured and predicted pow

erdeposition profiles during D

(H) M

Cexperim

ents.

First experimental observation of D

(H) m

ode conversion.Experim

ental fraction of absorbed power is 0.16 and TO

RIC

predicts 0.14.

Y. Lin et al., PPC

F (accepted) 2003.

Page 9: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

9

Off-axis D

(H) m

ode conversion

D(H

) mode conversion is

an opportunity tocom

pare simulation

with experim

ent.•

Direct m

onitor of Hm

inority is routine.•

Experimental

absorbed power is 0.2

and TOR

IC predicts

0.18.Sim

ulation indicates acom

plicated mode

conversion region.•

IBW

and ICW

areboth present.

Y. Lin et al., PPCF (accepted) 2003.

-20 -10 0 10 20

Z (cm)40

200-20

-40Z (cm)

50-5

-10

-15

ICW

IBW

R - R

0 (cm)

R - R

0 (cm)

-14 -12 -10 -8 -6 -4 -2

0.19

0.85

3.74

72.2

16.4

MA

X: 144

S_eld

FW

Data

TO

RIC

r/a

S (MW/m3/MWinc)

Page 10: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

10

On-axis current drive initiation

0 0.51 1.52 2.53

P_R

F (M

W) 1030710005

0.04

0.06

0.08W

_MH

D (M

J)

1.52 2.53

Te0

0 2 4H

E3 N

RA

TE

0.70.8

0.9

1nl_04

0.5

1 1.52P

I foil (MW

)

1.5

2 2.5Z

_eff (z_ave)

0.60.8

11.2

1.44 6

D_alpha m

ain (AU

)

0 0 .51 1.52 2.53

P_R

F (M

W) 1030710006

0.04

0.06

0.08W

_MH

D (M

J)

1.52 2.53

Te0

0 2 4H

E3 N

RA

TE

0.70.8

0.9

1nl_04

0.5

1 1.52P

I foil (MW

)

1 1.5

2 2.5Z

_eff (z_ave)

0.60.8

11.2

1.44 6

D_alpha m

ain (AU

)

co-currentcounter-current

heatingheating

•S

awtooth

period increased x3 (co vscounter phasing)

RF

pow

er

stored energy

electron tem

p.

neutron rate

density

radiated pow

er

Zeff

Tim

e (s)

Page 11: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

11

Off-axis current drive initiation

•F

irst off-axis current drive experim

ents

•O

bserved both shortening and lengthening of the saw

tooth period depending upon phase, deposition location, and pow

er level.

•F

urther analysis required to determ

ine driven current.

3 3.4

3 3.4

3 3.4

2.4

2.8

0.9850.995

1.005

1 2

Tim

e [sec]

PRF (M

W)

Rm

aj =0.66 m

Rm

aj =0.69 m

Rm

aj =0.72 m

Rm

aj =0.75 m

1030716016 IP =0.8 M

A, B

T=8.0 T

Te [keV] Te [keV] Te [keV] Te [keV]

Page 12: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

12

ICRF system technical achievem

ents

•O

perated ICRF antennas to maxim

um achievable voltage in their

12/2002 configurations and evaluated voltage and power lim

its.

•Evaluated and im

plemented changes to increase the voltage and pow

erhandling capabilities of all three antennas.

•Began high-pow

er heating experiments w

ith the modified antenna

systems and identified candidate target plasm

a conditions likely to leadto high tem

perature and low collisionality.

•Produced high tem

perature plasma w

ith 5 MW

ICRF power for 0.5

sec.

Page 13: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

13

5 MW

ICRF H-m

ode discharges

•A

ntenna modifications significantly

improved pow

er handling of D, E

, and J-port antennas.

-D

and E-port pow

er limit

increased to 1.5 MW

in H-

mode.

-J-port pow

er limit increased to

3 MW

.

•F

ull assessment requires m

ore operation tim

e and an inspection (Jan 2004)

2 4

PRF (M

W)

WM

HD

(MJ)

2 4

Te0 (keV

)

2 4

RD

D (x10 13 s -1)

1 1.5

nline_04 (x10 20 m-2)

1.5

2 0.15

0.05

1030605030 IP =0.8 M

A, B

T=5.4 T

0.81.0

1.2T

ime [sec]

Zeff

Page 14: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

14

Dem

onstrated flexible antenna phasing

•In L-m

ode discharge, 2.7 MW

is coupled through J-port in co-current phasing for ~

0.4 sec.

•C

omparable plasm

a response to D

and E-port antennas (heating

phasing)

-A

ntenna heating efficiencies are independent of phase.

-Im

purity and density production are sim

ilar.

•V

ery encouraging results for future F

WC

D and M

CC

D

experiments

-A

lso use for flow drive

1 20.04

0.06

2 32 40.8

10.5

1 1.5

Prad (M

W)

1.5

2 2.5

0.60.8

1.21.4

4 6D

main (A

U)

PRF (M

W)

WM

HD

(MJ)

Te0 (keV

)R

DD

(x10 13 s -1)

nline_04 (x10 20 m-2)

1030710005 IP =0.8 M

A, B

T=5.2 T

Zeff

1.0

J-portD

and E-port

Tim

e [sec]

Page 15: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

15

Antenna perform

ance

•V

oltage limits in 12/2002 w

ere ~30, 30, 35 kV for D

, E, and J-port.

•Pow

er limits in 12/2002 w

ere ~1.0, 1.0, 1.5 MW

for D, E, and J-port.

•Further antenna upgrades w

ere carried out 12/2002 - 3/2003.

•H

ave now achieved 35 kV

on all antennas.

•Pow

er limits now

up to ~1.5, 1.5, 3.0 MW

for D, E, and J-port.

Page 16: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

16

ICR

F antenna upgrades

•Perform

ance limits dom

inated by antenna voltageholding lim

its and antenna front surface - plasma

interactions.

•The em

pirical rf voltage holding limit of ~15 kV

/cmw

here E||B

has required redesign of internal antennaelem

ents to reduce local rf electric fields.

•A

ntenna front surface - plasma interactions have been

largely eliminated by covering exposed m

etal with

boron nitride.

Page 17: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

17

D- and E-port fast w

ave ICRF antennas

D-port:

Arc dam

age on feedthrough centerconductors at 20 ohm

section on#2, #3, and #4.•

replaced feedthroughs #2, #3,and #4

•m

odified center conductordiam

eter to 50 ohm dim

ensionA

rc damage w

as found on the air sideof #4.

Upper left therm

ocouple was m

elted.

E-port:A

rc damage on #4 feedthrough center conductor at 20 ohm

section.•replaced feedthroughs #2 and #4•A

nd modified center conductor diam

eter to 50 ohm dim

ensionD

amaged feedthroughs on #4 cannot be repaired.

Page 18: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

18

Arc dam

age in D and E feedthroughs

Dam

age suggests arcing is where E||B.

•D-port had dam

age on feedthrough #2, #3, and #4.•E-port had heavy dam

age localized to #4 with m

inor damage to #2.

Modified FS resulted in longer antenna electrical length.

•Moved higher voltage to this section of transm

ission line.Estim

ated impedance is ~20 ohm

s.•50 ohm

line has maxim

um voltage handling capability.

B

Page 19: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

19

D and E feedthrough m

odifications

Modification w

ill lower electric field by ~30%

.•

Should require about 2 times the circulating pow

er to reachbreakdow

n.•

Coupled power should also double but w

ill be limited by

transmitter to a m

aximum

of 2 MW

.

Page 20: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

20

J-port fast wave antenna

Installed new nose tiles replacing the

failed BN cover tiles.

Replaced septum spine because of

severe damage.

Refurbished feedthroughs:•

#4 vacuum side ceram

ic was

cleaned before re-installation.•

refurbished #2 and #4feedthrough center conductors.

Modified antenna m

ounting plate to improve contact and reduce E-fields

Center conductor connection to vacuum strip line and spool piece contact w

ith strip lineand current strap w

ere improved.

Did not install RF contact along side plate (capacitors).

Found arc damage across field lines on #4 near back plate feedthrough. V

acuumcoaxial line center conductors w

ere damaged.

Page 21: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

21

BN

cover tiles failed

Tiles top #2 and #3 and bottom #7 failed

completely.

Tile bottom #5 partially failed.

Disruption force results in a torque

applied to the BN

tile.•

The plate the BN

tile rests uponand the rail experience thistorque.

•The B

N experiences both

compressive and tensile stress.

•B

N perform

s poorly undertensile stress.

Fastening system m

oved with the B

Ntile instead of being hard fastened.

Disruption induced torque

Page 22: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

22

BN

tile redesign

Replace front and cover tiles w

ith singlefront tile.

•Previous nose tiles have not failed todate.

»Test indicates the tile fails ~1000 G

Failed tiles suggests ~200 G loads.

•Shield fasteners from

plasma.

»Preload bevel w

ashers to ~ 200 G so

the BN

tile moves w

ith metal tile.

•M

aterial under the fastener increased to0.5”.

•Increase front m

aterial by removing

metal.»

Alleviate over heating.

Mo tile m

odified to accomm

odate thickerB

N tile.•

Tile strength is not comprom

ised.

Page 23: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

23

Septum sustained significant dam

age

Observations:

•M

elt damage is m

ost severe where

there is no probe.•

Probes appeared to weld to the spine.

•Injections from

J-port ~ at cross overbegan 1020723.

•A

ntenna ran in (0,0,0,0) phasing from1020628-1020802.

»H

igh power for ~ 8 discharges.

Mechanism

:•

For (0,0,0,0) phasing, large fluxthrough slots results in voltage acrossslot.

•B

N tile facilitates breakdow

n.M

ade new spine w

ithout slots.

Top

Bottom

Page 24: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

24

Mounting plate m

odifications

Address arc dam

age found invacuum

coax.B

asic problem is reliable contact.

•Possible to have poor contactdue to m

ultiple connections.To im

prove reliable contact andreduce E-fields.•

Increased diameter of opening

and added full radius.•

Increased the bolt pattern from4 bolts to 8 bolts.

•R

elieved the plate to allow the

plate to rest only around theopenings.

•Plated the flange face w

ithcopper to im

prove contact.

Page 25: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

25

Modified all junctions to im

prove contact

Num

ber of junctions showed signs of series arcing.

Improved contact by relieving the flat section leaving ashoulder.

Page 26: Princeton University Plasma Physics Laboratory, Princeton ... · -1 320 340 360 380 Df [kHz] 80.47 80.50 80.53 fRF [MHz] phase velocity towards antenna phase velocity away from antenna

26

Antenna perform

ance summ

ary

•C

-Mod has presented a challenge to install high pow

er (~4 MW

) 4-strap and (~2 M

W) 2-strap IC

RF antennas in a tight space.

•plasm

a - front surface interactions•

empirical voltage holding lim

it•

high neutral edge pressure, 0.1-1 mTorr

•C

areful analysis of antenna fault modes together w

ith thoroughantenna inspection follow

ing each run period have allowed us to raise

antenna performance system

atically during use on C-M

od.

•W

e have been able to bring the total antenna power up to above 5

MW

, with good heating efficiency and no deleterious effects on the

plasma.

•Im

provements w

ill continue as we learn m

ore about antenna behavior.