recent progress with high-resolution fm-cw profile ... · e.j. doyle, g. wang, l. zeng, w.a....

UCLAUCLA UCLA

PERSISTENT SURVEILLANCE FORPIPELINE PROTECTION AND THREAT INTERDICTION

Recent Progress with High-resolution FM-CWProfile Reflectometer Measurements on DIII-D

E.J. Doyle, G. Wang, L. Zeng, W.A. Peebles andT.L. Rhodes

University of California,Los Angeles, CA, USA

Presented at the7th International Reflectometry WorkshopMax-Planck-Institut für PlasmaphysikGarching, Germany

May 9-12, 2005

5/8/05 2UCLAUCLA UCLA

OUTLINE

• Overview of recent system improvements

• System hardware upgrades

• Analysis and data acquisition improvements

• Thomson scattering/reflectometer cross-comparisons

• Examples of selected physics applications

– Plasma-wall interaction studies

– ELM dynamics

– L-H transition and pedestal evolution

• Summary


CURRENT SYSTEM EXPANDS AND BUILDS ONPREVIOUS SUCCESSFUL SYSTEM

PREVIOUS NOW

Q-band Solid state Solid state MICROWAVE SOURCE V-band BWO Solid state

Q-band POLARIZATION

V-band O or X O and X

DENSITY COVERAGE

Combined Q- and V-

band

0-~3x1019 m-3 X-mode 1.3-7.2 x1019 m-3 O-mode

0-6.4x1019 m-3

Q-band ≥ 10 µs ≥ 10 µs TIME RESOLUTION V-band

≥ 350 µs, with 2.5 ms dwell time

≥ 10 µs

DATA ACQUISITION

Q- and V-band

2 GaGe 8012/12100 boards (4 Ch), 1 MS on-

board memory each

3 GaGe 12100 boards (6 Ch),

256 MS on-board memory each

AUTOMATED ANALYSIS

Q- and V-band

Offline/overnight Between-shots for X-mode data

• Developments since March, 2003:


SIMULTANEOUS O- AND X-MODEMEASUREMENTS EXPAND DENSITY COVERAGE

• Simultaneous, dualpolarization O- and X-mode launch (45º to B-field). Systemcapabilities are now:– 0–6.4x1019 m-3

density range– ≥10 µs time

resolution– ~4 mm spatial

resolution (at edge)

O-only - curve A

X-only - curve B

O+X - curves A + B


ANTENNA ARRANGEMENT ON DIII-D FORNOVEL DUAL POLARIZATION MEASUREMENTS

• Launch and receive antennas are external to vacuum vessel,launch at 45º to B-field (rotatable to match B-field orientation)

Q-launch Q-X receive

Q-O receive

V-launch V-X receive

V-O receive

Toroidal direction

Toka

mak


DUAL POLARIZATION SYSTEM RETAINS SIMPLEFM-CW REFLECTOMETER HARDWARE

• High performance solid-state sources now used in both Q- andV-band systems, common to both X- and O-mode receivers

Arbitrary

12.5-18 GHz 50-72 GHz (Q)

Launch

X-Receive

Mixer 1

255o port

Fast-tuningOscillator

FrequencyMultiplier Coupler

Directional

WaveformGenerator

Rotatable

Mixer 2

IF signal 1

IF signal 2

x4 10 dB

O-Receive3 dB

45o

DC Amplifier WG Delay

LineAttenuator

8.25-12.5 GHz 33-50 GHz (V)

rf f

req

uen

cy fIFReference Reflection from

a target

Time

Time

Target distance

Time delay/phase shiftrf signal


UPGRADED DATA ACQUISITION SYSTEM PROVIDESHIGH TIME RESOLUTION AND EXPANDED COVERAGE

• Now using 3 high memory-depth GaGe CS12100 PC-based dataacquisition boards– 256 MS/board, maximum total 1.5 GB/shot!– High sampling rate, maximum 50 MHz in dual-channel mode

• Two modes of operation:– Continuous digitization, maximum 2.56 s data coverage at 50 MHz,– “Burst” data acquisition mode, with ~1ms duration data bursts every 5-

10 ms throughout discharge (~40 measurements/burst)


PROFILE ANALYSIS UTILIZES ADVANCED DIGITALRADAR-SYSTEMS BASED APPROACH

• Profile analysiscontinues to useflexible digitalprocessing approachbased on radarsystems analysistechniques (E.J.Doyle, et al., Proc.Varenna Confs.1995/97)

• Profile reconstructionfrom dual-polarizationmeasurementsoutlined in graph

Pha

se

Combine O-mode phase

X-Receive IF signal O-Receive IF signal

Density Profile

Calculated O-mode Phase

Measured O-mode Phase

n e

R

Pha

se

rf (GHz)

0 f1

33 72

33

Pha

se

0 f1

Density Profile

R0R1

n e

R R0R1R3

50

rf (GHz)

7250 rf (GHz)

V-X

V-X

V-X

V-X

Q-X

Q-X

Q-X

Q-X

Q-O

Q-O

Q-O

V-O

V-O

V-O


DENSITY PROFILES NOW AVAILABLE BETWEEN-SHOTS

• Recently implemented between-shotsprofile analysis capability. Use 10processors in two Unix-clusters– Divide up data in time and

distribute among processors– X-mode data only, to-date

• “Star” cluster consists of 12 Dual-Xeon2.66 GHz processors, 2 GB RAM each,Gigabit ethernet

• Analysis of profile every 5-10 ms (eachaveraged over ~15 measurements)throughout discharge takes ~4-5 min.– Analysis starts after 5 min. delay for

between-shots EFIT analysis to complete

• Profiles stored in MDSplus for viewingbetween-shots after ~10 min.


BETWEEN-SHOTS PROFILE ANALYSIS WITH 4 s DATACOVERAGE AND 5 ms TIME RESOLUTION

1.0 2.0 3.0 4.0Time (s)

2.10

2.15

2.20

2.25

2.30

2.35

R (m

)

2.9e+19

0.0

123062

ECCD Onset

Locked mode

0

1

2

3

4

5Line average density (x1019 m-3) Reflectometer density contours

1.0 2.0 3.0 4.0Time (s)


REFLECTOMETER/TS CROSS-COMPARISONSMOTIVATE FURTHER DETAILED WORK

• TS profiles (1 s average) from stationaryL-mode discharges have reproducible spatialstructure (A. Leonard, GA)– Structure is on fixed TS channels– Structure not seen in X-mode reflectometer

profile

• Reflectometer data haveconfirmed central densityand gradient in ITBdischarges

Shot 120055

R (m)

Dens

ity (1

019

m-3

)1.7 2.0 2.1 2.2 2.3 2.40

1

2

3

4

6

1.91.8

7

5

Thomson Scattering at 2975 ms

Reflectometer at 2980 ms (1 ms average)

Reflectometer profile

Thomson scattering data

Den

sity

(x1

019 m

-3)

Persistent structures

in Thomson data

Psi0.4 0.60.2 0.8 1.00. 1.2

2.5

2.0

1.5

1.0

0.5

0.

123310, 2-3 s


REFLECTOMETER MEASUREMENTS HAVE HIGHACCURACY

• Example fromcarbondepositionexperiment withCD4 gas puff– Reflectometer

data with 5 mstime resolution,TS with 12.5 ms


EXCELLENT AGREEMENT FOUND BETWEEN DIAGNOSTICS INPLASMA/WALL INTERACTION, CARBON SOURCE STUDIES

• Detailed plasma parameter measurements required in SOL– Excellent agreement between three independent measurements– Comparison constructed by M. Groth (LLNL), Langmuir probe data from D.

Rudakov (UCSD)

1019

-0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1

120350 - 4150ms (EFIT03)

Thomson ScatteringLangmuir ProbeReflectometer

Elec

tron

dens

ity (m

-3)

R-Rsep, OMP (m)

1018

1017


ELM DYNAMICS: UNPRECEDENTED SPATIAL ANDTEMPORAL RESOLUTION THROUGH ELM CYCLES

• 25 µs time resolution throughELM cycles, high spatialresolution

• Can derive many physicsquantities, L. Zeng, et al., J.Nucl. Mater. p.742-746 (2005)– Radial expansion velocity– Density rise at wall– Particle flux to wall– Time evolution of pedestal

widths and gradients– Scaling with plasma

parameters– Precursor activity

3120 3140 3160 31801.90

2.00

2.10

2.20

2.30

2.40

2.50

Dα (

a.u.

)

R ( m

)

Time ( ms )

4.5 0

ne (10 19 m-3)

17

65

43

28

3

1

7

6542

8

1 2 3

Separatrix

Precursor

118219

ne=4.5

ne=0.1


SPATIAL AND TEMPORAL RESOLUTION ISSUFFICIENT TO DETECT ELM PRECURSORS

• Some (not all) Type I ELMs have precursors– Precursors seen on density profile data and fluctuation

measurements


DETAILED DENSITY PROFILE EVOLUTION CANNOW BE OBTAINED THROUGH A SINGLE ELM



• Rapid profileexpansion tooutermidplane wallat Type I ELMonset– Up to

2x1018 m-3,~6% of thedensitypedestal


PROFILE EVOLUTION AT L-H TRANSITION VARIESWITH ∇B DRIFT DIRECTION

• Density profiles with 25 µs time resolution through L-H transitions– G. Wang et al., Plasma Phys. Control. Fusion 46, A363 (2004)

2.5 MW NBI 10 MW NBI

Dα

116048

R (

m)

a.u

.

Time (ms)

2.20

2.25

2.40

2.35

2.30

0.1

0.2

0.3

1430 1435 1440 1445

Ion ∇B Drift Toward X-point

sep

arat

rix

Dα

114551

R (

m)

a.u

.

Time (ms)

2.20

2.25

2.40

2.35

2.30

0.1

0.2

0.3

0.4

1480 1485 1490 1495 1500

sep

arat

rix

Ion ∇B Drift Away From

X-point

0.1,0.8,1.8,3,6,11.5,18.5,21.5,24e18 m-3

Density contour

Contour plot for 0.1,0.8,1.8,3,6,13,20,23,26,28e18 m-3


PEDESTAL DENSITY GRADIENT BUILDS, THENSATURATES DURING ELM-FREE H-MODE PHASE

• Density profileswith 25 µs timeresolution from L-Htransition to first ELM– Pedestal

evolution varieswith plasmaconditions

Dα118874

0.3

0.5

0.1

R (

m)

2.1

2.3

2.2a.

u.

0

0

1

(x10

21m

-4)

sep

arat

rix

Maximum density gradient

0.5

1220 1240 1250Time (ms)

1230

L-H transition1st ELM

Contour plot for density layers 0.01,0.2,0.8,2,2.5,2.9x1019 m-3

Pedestal width

(cm

)

4

12

8

2.4


SUMMARY

• Hardware and software upgrades continue to be incorporated inthe DIII-D FM-CW density profile reflectometer system– Expanded density coverage range using simultaneous dual

polarization measurements, now 0-6.4x1019 m-3 density range– Full density range now measured with ≥10 µs time, ~4 mm spatial

resolution, using solid state microwave sources– New between-shots profile analysis capability– Performance is now such that reflectometer/TS spatial cross-

calibration is underway• Increased system capability has expanded range of physics

issues which can be addressed, e.g:– Plasma-wall interaction studies– RF propagation/loading studies– ELM dynamics– L-H transition, pedestal evolution, etc.

• Demonstrated DIII-D performance levels are encouraging forreflectometer profile measurements on ITER

recent progress with high-resolution fm-cw profile ... · e.j. doyle, g. wang, l. zeng, w.a....

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