Review of D-T Experiments Relevant
to Burning Plasma Issues
R. J. Hawryluk
Frontiers in Plasma Confinement andRelated Engineering/Plasma ScienceToki, Japan

December 11, 2001

Excellent Technical Progress Has Enabled TFTR
and JET to Begin Studying Burning Plasmas

Fusion(MW)
Fusion PowerPower (MW)104
TFTR (DT)

101
10-2
PLT
PLT-5

10

ASDEX

JET

Ohmic

ALC-C
ATC10-8

JET (DT)
JET (DT)
JT-60UTFTR TFTRJET TFTR
D-IIID
D-III
JET D-IIID
JET
PDX

ORMAK

ALC-A PLT

RFPLT

NBI- DST
T-3A
10-11
1970

NBI-DT

1980

1990
YEAR2000JET and TFTR were Designed to Perform
Deuterium-Tritium Experiments
Joint European Torus(JET)

Tokamak Fusion Test Reactor(TFTR)

Ip(MA)BT(T)
PDT(MW)
PDT/Pin=QDT

4.0
3.6
16.1
0.64

2.7
5.6
10.6
0.27

Fusion Energy (GJ) 0.68
Tritium Proc. (g)
99.3

1.70
99.

How are D-T Experiments
Different from D?
• Isotope Effects– Transport– Wave-particle Interactions• Alpha-particle Physics• Technology

Isotope Effect Studied in a Wide
Variety of Operating Regimes
JET H-ModeTFTR<A>0.85

τEDT - τEDD
τEDD(% )30<A>0.5

20100<A>0.16±.06

Elmy-10<A>0.3-0.5<A>0.3-0.5

OH

ICRF
L-modeNBI
L-modeSupershot/High liReverse
Shear<A>-0.25±.22
Elm-free• Challenge to theoretical interpretation and togyro-Bohm scaling, <A>-0.2• Recent ITER scaling <A>0.19

JET D-T Elmy H-mode Experiments
Consistent with ITER Scaling
NBI

0.7

w

0.5

Core

0.4

Pedestal

0.2
0.1
00

JG98.325/4c

0.3

Cordey
0.1

0.2

0.3

0.4

0.5

τITERH–EPS97(y) (s)• τth ∝ <A>0.16±0.06

0.6

0.7

JG98.305/2aτth (s)

0.6

JETICRH
HDD–TT

Transport barrier

0.80.8r/a1• What is the role ofthe pedestal andthe core?

Stored Energy Associated withPedestal Increases with <A>
BhatnagarCordey• Wped ∝ <A>0.96• Power loss by ELMs decreases

In JET H-mode Discharges Thermal
Conductivity Degrades in the CoreCordey• Confinement scaling in the core consistent withgyro-Bohm.
– τthcore ∝<A> -0.16±0.1
χI ∝ <A>0.73±0.4

Power Threshold Going from L to H-modeShows Favorable Isotope Scaling
8JET

ER98.026Hydrogen
Deuterium
Tritium

6PLOSS (MW)DT

42wall loading series
25:75 DT cryompump off
10:90 DT002Righi
4680.83ne 1.12Bt 0.69R2• Ploss ∝ <A>-1• ELM frequency
decreases with <A>Improvement of χI in Core ofTFTR Supershots in DT
TFTR

Ti
T- NBI30

D- NBI

20mag.
axis
D T

100Te
T- NBID- NBI

5mag.
axis

D0•

2.5

T

SS962040(keV)

10 (b)

χ toti (including convection) (m2/s)(keV)

40 (a)

3.0
3.5
MAJOR RADIUS (m)ni(0)ττETi(0) increased by~55% from D to DT– Some cases up to 80%increase

7DD-T1

factor of 2
PNBI = 18MW
I p= 1.6MA
0.1
0.00.5
Minor Radius / aτEthermal ∝ <A>0.89±0.1
χitot ∝ <A>-1.8 ±0.2
Scott

ITG Model with Radial Electric Field
Reproduces the Ion Temperature
TFTRPinj = 15 MW

30Ti (keV)

Model with Er shear•

Maximum linear growth rate
decreases with ion mass.

•Er shearing rate increases with Ti.

•Radial Electric Field Shear
Reproduces Strong Isotope Effect.

•==> Isotope Effect depends on
Operating RegimeDT20DD

10IFS-PPPL without Er

Effectof Er
Sheardre11119701m

00.0

0.2

0.4

0.6
r/a

Ernst

0.8

1.0

Favorable Isotope Scaling Not Observed inReverse Shear Experiments
4TFTR
Set # 3

Wdia (MJ)3

Set # 2

2

Set # 1

LegendD

NBI ‘Prelude’Scott5101520Pinj (MW)Pco / Pinj
0.60 - 0.65
0.45 - 0.75
0.40 - 0.62
0.45 - 0.55

100DT

253035• Power threshold for internal barrier
formation increased with <A>.

Summary of Isotope Effects onConfinement• H-mode isotope scaling studies on JET, together
with the worldwide physics database, provide agood technical basis for baseline operation ofburning plasma experiments.
– Isotope scaling for τE and power threshold.
• Understanding of isotope scaling is incomplete.
– Variation in different operating regimes.
– What is the role of radial electric field shear?
– What are the implications for advanced
operating modes?

ICRF Successfully Heated DT Supershot
Plasmas in TFTR
TFTR
10with RFwith RF

Te (keV)Ti (keV)30

20no RF

10magneticaxis
2.5

8no RF64magneticaxis

2
3.0

R(m)

3.5

∆ Ti due to 2nd harmonictritium heating

2.5

Wilson3.0R(m)∆ Te due to direct electronand 3He minority ion heating• Power deposition calculations in good
agreement with experiment.

JET Demonstrated Successful Deuterium
Minority Heating of Tritium Plasmas• Record QDT for steadystate operation.
– deuterium energy
optimized– Not optimal for high QDT• Strong ion heating
observed with 3He– Absorption weaker withΩΤ2Ω– Recommended scenario
for ITER
Eriksson, Start•• Studied tritium
minority heating.

Physics of ICRF heating well established.
- Technology challenges remain.

Alpha-particle Physics Studies• MHD Quiescent– Alpha-particle heating• MHD Affects Alpha Confinement• Alpha Particle Induced MHD Activity• Diagnostic Development Critical for these Studies

Alpha-Particle Parameters in TFTR/JET
Sufficient to Begin Study ofAlpha-Particle Physics
TFTR
10.6
Pfusion(MW)pα(0) (MW/m3) 0.28
βα(0) %
0.30βα)% 2.0–R••grad(βVα(0)/VAlfvén(0) 1.72
0.03
Pα/PheatJET
16.1
0.08
0.4
2.3
2.52
0.09

ITER400
0.430.84.0
1.76
0.66

Budny

beam-thermal10(1018 s–1)

Thermal106Budny,
Keilhacker

2.5

3.0

ƒth

2.0

TRANSP
dWdia
dt

Measured

DT neutron rate

Measured

4TRANSP

20
0.8

0.0

PIN

200

1.0

MeasuredDα + Tα (a.u.)

5030

beam-beam
P (MW)

2.0

TRANSP

15

Thermonuclear fraction

0.4

JG98.703/6c

MeasuredTotal(neutroncollimator)

JET
Wdia (MJ)

TFTR

3.0

(1017/m2/sec)

Chordal DT neutron emission

D-T Neutron Emission is Consistent withCalculations Based on Plasma Parameters

Radius (m)012.4

12.8Time (s)•Alpha birth rate and profile are adequately
modeled.

13.2

Escaping Alpha Flux at 90o Detector isConsistent with Classical First Orbit Losses

Alpha collection fraction (x10-9)30TFTR90° detector

Escaping AlphaDetectors∇B

Normalized
here

108
620°
45°
CL

90°

60°

First-orbit
loss model

4Zweben

200.5

1
1.5
2Plasma current (MA)2.53

• At 2.5 MA in TFTR , first orbit loss ≈ 3% globallyConfined Alphas in the Plasma CoreShow Classical Slowing Down Spectrum
TFTR

dn/dE (a.u.)

106nr≈0nn105

normalization

nnn

104

Double Charge Exchange
Technique
He++ + Li+ ⇒ He0 + Li3+nVpellet

nTRANSP/FPPT

Li

103

0

1234
Alpha energy (MeV)

5• TRANSP calculation includes:– orbit trajectories– classical slowing down
– time dependence of alpha production

He0CloudHe++
Alpha Particles

Fisher, Petrov, MedleyStochastic Ripple Diffusion Affects
Confinement of Deeply Trapped Particles
TFTR
100

Eα = 1.21 MeVAlpha Density (a. u.)

Alpha Density (a. u.)

100

Without ripple
10-1

Normalization

With ripple
10-2
2.52.6

2.7

2.8

2.9

Major Radius (m)

3.0

3.1

Eα = 0.64 MeV

Without ripple

Normalization
10-1

With ripple

10-2
2.5

Medley, Redi
2.6

2.7

2.8

2.9

Major Radius (m)• FPPT includes modeling of stochastic ripple
diffusion.
• Heat deposition due to ripple loss of fast ionsimaged on JT60U.

3.0

3.1

Intensity (1010 ph/s-cm2-ster)

Alpha Particles Are Well Confined
3.5
3.0

PlasmaSurface

Data
TRANSP:Dα =0 (w/error band)

2.5

TFTR

22.0

Dα =0.03 m /s

1.5
1.0

DetectOpticalEmission

Neutral
Beam

0.5 E

α = 0.15-0.6 MeV

0.00.0

0.1

0.2

0.3

0.4

0.5

Minor Radius (r/a)• 0 ≤Dα≤ 0.03 m2/s

0.60.7

Charge exchange
between fast beam
neutrals andnonthermal alphas

McKeeRapid Ash Transport from theCore to the Edge in Supershots
TFTR

16

Helium Density (x10 m-3 )25
NoTransport

20

4.75 sConsistent with τ p*He/τE = 8,
acceptable for a reactor

15
DHe, VHe
from gas puff

10DataDHe / χD ~ 15000.2

0.4

0.6r/a0.81• Confinement of ash consistent with impurity
transport and edge conditions.

Synakowski

Alpha Density (x1016 m-3)

Sawteeth Cause a Large Radial
Redistribution of Alpha Particles
beforesawtooth

6Eα=0.15-0.6 MeV

TFTR

model

4(reconnection)
2AfterStratton

q=1

000.2

0.4

0.6

r/a

• Alpha heating profile in a burning plasma
will depend upon sawtooth activity,
although only transiently

MHD Activity can Cause Enhanced Lossof Alpha Particles
TFTR• Strong toroidal anisotropy
in loss apparent as NTM
mode is rotating• Enhanced loss observed
due to:- disruptions- kinetic ballooning modes
Mode locks• Concern for plasma-facing
components.

Zweben, Darrow

Observation of TAE Instability
Driven by Fusion Alphasβα(0)TFTR103101“Drive”

n=40PNBI(MW)
25-2 “Damping”

3x10β(0)02.0-96 x10

Neutral Beam Injection

2.5TIME(s)“Response”

n=4~
B wallBT

3.0

n=2
n=3

n=50

2.8
NBI off

2.9TIME(s)0Mode Amplitude

10-3-1.00

1.0r/a• TAE primarily damped
Radialmodebyradiativeandstructure
beamviaion
microwave
reflectometry.
Landau damping

3.0Nazikian

TAE Modes Redistribute Deeply
Trapped Alpha-Particles
10 -1

TFTR

Alpha Signal (a.u.)

0.53 MeV and 1.71 MeV

with TAE
10 -2Observed
q(0) ~ 2

10 -3
0.53 MeV and 1.71 MeV

no TAE

10 -4

Medley
10 -5
0

0.1

0.2

0.3

0.4

0.5

0.6

r/a

• Further work required to benchmark models.
• NNBI experiments on JT60U have observed
strong radial redistribution.

Sawtooth Frequency Decreases withIsotopic MassJETNave••

Change in sawtooth period attributed to increase in slowingdown time and beam ion perpendicular energy density.
Calculations imply that alpha particles had a stabilizing
effect in highest performance D-T discharges.

Initial Evidence of Alpha-Particle Heating

Te(DT) - Te(D) (keV)

Te(R) (keV)

105TFTR

D-T, Pfus ≈ 5 MW
(6 Plasmas)•Alpha heating ~15% ofpower through electronchannel•

Plasmas matched fordominant Te scaling in D
only plasmas.
- Te(0) ∝ τE0.5- account for theisotope effect onconfinement•No sawteeth or adverseMHD.

D Only(17 Plasmas)

01Measurement
0.5TRANSP
Prediction
02.6

3.0
2.8
Major Radius (m)Taylor, Strachan

3.2

Alpha Heating Observed in JETJET•

Palpha/Pheat ~12%-•30-40% through theelectron channel

Larger range in T
concentration- analyze the effects
associated with isotopes•
ThomasSawteeth variability-limited number of pulses• Alpha heating observed on both TFTR and JET.
• Comprehensive study of alpha heating requires
higher values of Palpha/Pheat .

Can Alpha Particles Be Harnessed toFurther Improve Reactor Potential?
•Theoretical work on alpha channeling, frequency sweepingof waves, and stochastic ion heating raise the prospects of:– Increased ion heating– Alpha ash control– Modify alpha heating profile– Reduce alpha pressure to decrease instability drive– Current drive•

Need for experimental study– Fundamental wave-particle physics studies begun on TFTR.
– D. Gates et al. predicted the role of stochastic ion heating in
NSTX discharges when VNBI >> VAlfven– P. Thomas at EPS suggested possibility of increased ion
heating due to alpha particles.
• Limited dataSummary Alpha-Particle Physics• Alpha-particle confinement, transport, andslowing down well understood in MHD quiescent
discharges.
– Not as extensively studied in reversed shearexperiments.

• Alpha-particle confinement affected by MHD.
• Alpha particle driven instabilities studied– Nonlinear consequences remain to be studied.

• Alpha-particle heating observed.
– Higher power alpha particle heating experiments arerequired.

Tritium Processing Safely
Performed• On-site tritium
processing successful.
• Tritium retention ingraphite is a serious
concern.
– TFTR tiles 16% retention– JET 12% retention– One year after extensive
removal efforts• Need for in-situ removal– Alternative materials

PPPL-JAERI Collaboration
Gentile,Skinner (PPPL)
Shu (JAERI)

In-vessel Remote Handling
Demonstrated on JET
JET• Critical technology
for future burning
plasma experiments– Fluence ~ 104 greater

Telescopic Articulated ManipulatorSuccessful Demonstration ofDecommissioning of a Fusion Facility
TFTR• Machine activation in future burning plasma
experiments will require remote disassembly.

Summary• Results from TFTR and JET:
– Provided solid design basis for a burning
plasma experiment.
– Identified opportunities to learn new scienceand technology.

• Critical aspects of the technology for aburning plasma experiment were utilized– Burning plasma experiment will be far moredemanding due to the higher fluence, tritium
retention and processing requirements.
• Full potential and consequences of alpha heating
have not been explored!