Long-term Fusion Vision, Strategy,and Role
M.C. Zarnstorﬀ
PPPL
Presented to the NAS Commi7ee for a
Strategic Plan for US Burning Plasma ResearchApril 11, 2018

Outline
PerspecFves on:
1. Status of US research supporFng burning plasma science
2. PPPL plans that might strengthen or accelerate US research inburning plasma science
3. Strategic elements supporFng a long-term vision for US fusionenergy research and promote leadership in the ﬁeld

Building on the talk by R.J. Hawryluk in Aus9n, TX2

Summary• Strong parFcipaFon in ITER is the best approach to develop burning
plasma research, technology, and understanding- advance to fusion energy research• InnovaFon is required to improve fusion energy prospects in US- reduce size, cost, and increase eﬃciency, reliability ofburning plasma- examples: liquid metals, compact tokamaks (ST) and stellarators,HTS, advanced materials…
- advance towards commercial fusion power• Both provide opportuniFes for US leadership3

US Burning Plasma Research is Centered on ITER
• ITER is the US facility for burning plasma research- ConstrucFon is well along- Beneﬁts from world-wide eﬀort and investment• US parFcipaFon in science and technology development- Training of US personnel in all aspects- Signiﬁcant US leadership• Thru ITER: joint ownership of results, IP rights, experFse-- The science and technology from ITER will inform all
magne9c-conﬁnement approaches

4Status of US Burning Plasma Research AcFviFes• ITER design is largely ﬁxed, candidate Q=10 scenarios idenFﬁed- Steady state Q=5 scenario is sFll being invesFgated• PPPL leading US diagnosFc design and development
CriFcal for ITER’s research capability
Area of US leadership & responsibility, including port design• Develop validated approaches for high-priority topics- DisrupFons and runaway electron beams- Edge instability (ELM) suppression- Power-exhaust width5

DisrupFon & Runaway Electron MiFgaFon• SciDAC - Center for Tokamak Transient SimulaFons (PPPL led collab.)- 3D simulaFon of tokamak disrupFons with conducFng wall
- DisrupFon dynamics, sha7ered pellet miFgaFon, connect to engr.
• SciDAC - SCREAM on runaway electron modeling (PPPL led collab.)- New results: generaFon & sca7ering by Whistler waves- Appears to explain puzzling experimental observaFons- ITER implicaFons not yet evaluated• Deep-learning pre-disrupFon trigger for miFgaFon (Internal funding)• Rail-gun launched pellet miFgaFon, for hot plasma edge (Internalfunding, with U. Washington)
6

Prediction of No Locking Window of ELM Suppression
Validated in Experiment !

Edge Instability Control Window Understood• Building on experiments
at DIII-D and NSTX
• Control of KSTAR edge
stability using 3-rows ofperturbaFon coils atedge

Experimental Validation ofModel

IPEC Prediction of stabilitySpaceSuppression
Suppressio
Lockingnthreshold
thresholdthresholdmet
met
exceeded• Vary amplitude andtoroidal phase of middle
rows of coils• QuanFtaFve validaFonof theoreFcal model foredge instabiliFes control
15

access to“hiddenwindow”
Non-resonant 3D7perturbations

Divertor Heat-Flux
Power exhaust width (mm)

• IniFally understood thru heurisFc
drie-model (PPPL)• PredicFon for ITER: < 1mm heatﬂux width => very high heat ﬂux

2MA
NSTX-U
Range of NSTX-U
projecFons• XGC1 (PPPL) reproduces data
variaFon, but predicts turbulence
broadens ITER. Is this correct?

C-Mod• NSTX-U will test broadening &miFgaFon by ﬂux expansion
8

2. Accelerate PreparaFons forBurning Plasma Science: Integrated Modeling• High ﬁdelity integrated model of burning plasma thru DOE Exascale Proj.
• IniFal focus: core-edge Fght integraFon, building on SciDAC models
Edgemodeltokamaks&stellarators

Core
model

IntegraFon
Framework
Tight / loose
coupling methods

Plasma-MaterialInteracFon
HeaFng & Fueling
Large-scale InstabiliFes
EnergeFc ParFcles

PPPL (lead), ANL, LLNL, ORNL,Rutgers, U.Texas, UC-Boulder

Mul$-scale $me
advance
See talk by A. Bha7acharjee

9Preparing ProducFon Whole-Device Models• Reduced ﬁdelity, faster, integrated models under development- For predicFve modeling of proposed experiments- For rouFne analysis of data
- Veriﬁed with high-ﬁdelity models- Validated on current experiments, including DIII-D and NSTX-U• Especially important for high pressure (β) and bootstrap-current
for long-pulse experiments, due to non-linear evoluFon ofequilibrium• Similar eﬀorts starFng for stellarators

10

Example: NSTX-U is studying α-parFcle
instabiliFes applicable to ITER
64α-heatedSpherical
Tokamaks

2 α-heatedconventional aspectratio tokamaks(ITER, DEMO)

NSTX-U will:• assess confinementof fast-ions in highperformance STregimes

Beam-heated
NSTX-U• extend predictive
capabilities forConventional
Beam-heated tokamaks
0energetic particle
0.2
0.3
0.0
0.1
0.4
0.5
β fast/β total
dynamics in burning~ (EP-instability drive)/(EP-instability damping)plasma regime
NSTX-U: Fast-ion dynamic rangespanning ST and conventional A
burning plasma regime

Vary beam pitch angle,
pressure profile à Assess
mode stability as a function ofion phase space3. Long-term Vision toward Fusion Energy• ITER is a physics and technology experimentWill provide knowledge & experiencefor fusion energy research• As in the 2004 NRC Burning Plasma Report,
ITER is not a prototype for a commercialpower reactor in the US- Need higher performance for size and cost
• Next steps based on ITER are larger andlikely more expensive, e.g. EU DEMO

EU DEMOpulsed-ind.
R0 (m)

9.0a (m)2.5

BT (T)

6.5

IP (MA)

16.8

fBoot36%

β2.6%

H98,y2

1.0

Pthermal

2.2 GWNet
Pelectic500 MW
12

US Route to Commercial Fusion• In some countries, fusion will be developed by their government• US: development of commercial fusion will be led by industry- Role of government is to enable by developing underlying science- Enable via public-private partnerships• Interest by start-up companies very important
Sign of success in developing scienFﬁc and technical basis for fusion- Assessment that gaps probably can be closed- Builds on world-wide experiments (all kinds) and ITER
• Focus on prioriFzing and resolving risks- At minimum scale (cost) and on a rapid Fmescale13

Industry Requests• Safety• Long-term economically compeFFve• Rapid construcFon and moderate capital cost per unit
• Licensing simplicity• Reliability, availability, maintainability, inspectability (RAMI)• Steady state, with load-following (quick shutdown/restart)• Public acceptance- No need for wide-area evacuaFon
Aeer EPRI, LIFE Adv. Commi7ee

Not the same approach as some of our interna9onal partners

14ImplicaFons: InnovaFon is Needed• Robust, reliable operaFon – eliminate disrupFons and “oﬀ normal events”- Thin ﬁrst wall for T-breeding• More eﬃcient producFon of energy and use of plant- Higher fusion power density => higher β and/or B- Less recirculaFng power• Smaller unit size than 1 GWe, especially during development• Robust power handling with reduced maintenance• Simplify, probably by eliminaFon of some sub-systems• Need long-lived materials, to reduce maintenance (esp. divertor)

15

InnovaFon OpportuniFes• Liquid-metal boundaries (see M. Jaworski)- High power-ﬂux, eliminate erosion, allows low-Z wall and higher conﬁnement(NSTX-U, EAST?)• Spherical tokamak (see S. Gerhardt)- More compact, high β, higher magneFc ﬁeld uFlizaFon, lower capital cost
(NSTX-U & MAST-U)• Higher eﬃciency current drive- Helicon-wave and inside launch lower-hybrid current-drive (DIII-D & KSTAR)• Compact stellarators / 3D-Tokamaks (commi7ee’s teleconference)- Eliminate disrupFons, eliminate current-drive; high β, high density, high gain
( US led, but ? )16

InnovaFon OpportuniFes II• HTS magnets (see M.Greenwald, S.Prestemon)- Higher B, higher current density, enables compact conﬁguraFons- May allow simpler coil design• Advanced materials- Longer life, higher strength at high temperature- Reduce maintenance, increase availability, increase thermal conv. eﬃciency• Use validated simulaFon to guide extrapolaFon (See A.Bha7acharjee)- Reduce risks• Aim at a “pilot plant” (see J. Menard)- Address integraFon risks at modest scale- Then mature technology and operaFng experience together- If innovaFons achieve high Q, net-power producFon is easier than life-Fme tesFng

PPPL is exploring many of these poten9al innova9ons with the community. 17

Strategy with ITER: Innovate in Parallel• During ITER construcFon and burning plasma operaFon:- Explore and mature innovaFons- A7empt mulF-innovaFon integraFon, increasing TRL- Validate models for simulaFon• Assess combined results from ITER and innovaFons in modeledprojecFons• Go forward when projected systems are compelling, and addresscommercial needs- Pilot Plant as small as credible, to reduce risks, build conﬁdence

18Strategy without ITER: Innovate• US out of ITER: loss of technical experFse, experience, momentum- Missed iteraFon will delay US advance to burning plasma research- Recover by exploring and maturing innovaFons; integraFng• Assess results from innovaFons combined with world’s experiments
in modeled projecFons, but will not have full ITER knowledge• Go forward when projected systems are compelling, moFvate funds- Recover burning plasma experFse and experience- May use innovaFons to partner with other programs post-ITER- Pilot Plant as small as credible, to reduce risks, build conﬁdence 19

Summary• Strong parFcipaFon in ITER is the best approach to develop burning
plasma research, technology, and understanding- advance to fusion energy research• InnovaFon is required to improve fusion energy prospects in US- reduce size, cost, and increase eﬃciency, reliability ofburning plasma- examples: liquid metals, compact tokamaks (ST) and stellarators,HTS, advanced materials…
- advance towards commercial fusion power• Both provide opportuniFes for US leadership20