2018, Seminar in Univ. Carlos III of Madrid about high-field ignition stellarators and i-ASTER, 19-11-2018

1
High-field ignition stellarators.
A path to fusion energy?
Vicente Queral
National Fusion Laboratory, CIEMAT, Spain
Seminar offered in University Carlos III of Madrid
Madrid, Spain
19 November 2018

2
● Background (cost, solutions, importance of size)
● Why a stellarator? Why high field for a
experimental (ignition) device?
● Some properties of high-field ignition-capable
stellarators
● Technical features of i-ASTER.v1
● The future
Outline

3
Background
Seminar offered under grant ENE2015-64981-R,
project ‘Study of Additive Manufacturing for the
application to high performance fusion devices of
stellarator type’, funded by the Spanish ‘Ministry of
Economy and Competitiveness’ and ‘FEDER EU’.
• The presentation focusses on the matters in the
paper titled “Initial exploration of high-field
pulsed stellarator approach to ignition
experiments”, V. Queral, F.A. Volpe, D. Spong, S.
Cabrera, and F. Tabarés, Journal of Fusion Energy
1-17 (2018) DOI 10.1007/s10894-018-0199-5
• However, additional matters are included in the
presentation.

4
Problem Previous solutionsBackground
High cost of a (first) fusion
plant or experiment due to:
- First-of-a-kind (FOAK) (there are
examples of cost escalation)
- No typical cost improvements
(no standardization, no large series,…)
- Large and indivisible (few
suppliers~delays~cost escalation)
- Complex (poor management of
complexity results in cost scalation,
sequential~interruptions, exponential
cost?)
-No solution for
FOAK
-Difficult
solution for
cost improv.
- Smaller,
‘detachable’
(ARIES-CS, ARC)
- Simplification
(e.g. AP1000
fission plant,
stellarators)

5
Importance of size
Figure reproduced
from [Bro 17]
- The fusion reactor cells (QAS, K-DEMO, ST) are about an
order of magnitude larger than in a PWR fission plant.
- Large size → huge hot cells for maintenance/storage
and large RHE → High cost
Comparison of size
of buildings
AMF, full of
RHE and
comp. under
radiation
Smaller
Order of magnitude of total AMF cost in
relation to past real hot cells ~ 15000 M€

6
What means high-field?
The term ‘high-field’ means different magnitude
depending on the type of device, the size of the
device, and the preceding real devices. Note Pfus
∝~ β2 B4 V
- For experimental stellarators of the size of W7-X
or larger, high field might be considered in the
range of B ~ 5–10-(15?) T.
- In the other extreme, high field might be deemed
as B ~ 1–2 T for a small table-top stellarator,
since current table-top stellarators reach B ~ 0.3–0.5 T and
fast coil heating.
- For power plants B~7–10T may be a reasonable
high-field for common hE and β.

7
Two types of high-field devices/cases
1. Commercial
power plants
2. Experimental
devices
Not studied in the paper. Study
expected in the future.
In paper only studied DT exp.
devices capable of plasma
ignition, i-ASTER, i≡ignition.
Reason: To have an important
aim, much simpler than power
plants, (high ratio cost/impact?)
π-ASTER (pre-ignition
ASTER) was defined in the
[Unpublished large version of
paper].
i-ASTER special coils

8
Main features
of i-ASTER &
π-ASTER
Element i-ASTER.v1
V 30 m3
B 9.8 T
R 3.8 m
a 0.63 m
A 6
Plasma surface 95 m2
n line 1.1 × 1021 m-3
T0 14.6 keV
Fusion power 1.4 GW
hE (ISS04) 1.5
<> 5%
E 0.4 s
Pulse length 2 s
Load on divertor targets (50%
improvement, factor 2 sweeping, 50%
radiation). Lithium divertors and walls
30 MW/m2
Average neutron wall load 12 MW/m2
Weight of the copper magnet ~ 1000 Ton
Power consumed in the resistive
copper coils
~ 750 MW
Relative thickness of monolithic
coil support Ψ
0.5
Ave. stress on coil support at S 240 MPa
ΔTmax copper coils~insulation,
only Ohmic (QIP3 ~ fc = 5)
100 K
i-ASTER
Only to better
understand next slides
Element π-ASTER.v1
V ~ 2 m3
B ~ 3.7 T
R 1.5 m
a 0.26 m
A 6
Pulse length ~ 2 s
π-ASTER
π-ASTER is only
tentatively defined as few
not definitive
parameters. To be
discussed and studied

9
Why a stellarator?
Why high field for a
experimental (ignition)
device?

10
Why a stellarator?
It seems that a high-field ignition-capable
experimental device of stellarator type has never
been proposed (but a previous high-field reactor study FFHR2
exists, [Sag 08]). This encouraged a proposal based on
a stellarator.
For simplicity. Stellarators are ‘simple’ (operation,
control, power supplies…, not as an object of study) compared
with tokamaks, except for the geometrical
complexity. The later likely could be confronted by
Additive Manufacturing, see Refs [69-71 in paper].

11
We aim at avoiding many elements by utilizing
stellarators. But geometric complexity of coils, VV, divertors,
supports is a DRAWBACK and has to be overcome.
Why a stellarator?

12
Why high field for a experimental
(ignition) device?
- Smaller, lower cost: Case ignition: Estimated/
calculated lower cost of the reactor core. Lower cost of
buildings and RHE. Case π-ASTER: probably lower cost,
not estimated yet.
Order of magnitude of costs
expected for only the coils and
coil support structures. Valid for
copper coils and highly stressed
superconducting coils. Source of figure
[Unpublished large version of paper]
Cost (M€) ~= Kc 0.92 [ B2 / (2 0) ξ2 V 10-6 ]0.6
Currently Kc ~ 3 ; ξ ~ 2
Of coils+coil structures Based on [Gre 08]
π-ASTER & i-ASTER as starting point of
the high-field path to fusion energy

13
- Investigate new high pressure plasma regimes. Thus,
it might find new advanced plasma regimes (as many
significant results emerged from Alcator program).
- Testing and optimizing high power extraction systems
(e.g. lithium-based), since high power density plasmas are
possible at high fields.
- Would complement the stellarator research line and
database in the high plasma pressure range and high
plasma pressure gradients.
- Advance technologies for the manufacturing of strong
(stellarator) magnets.
Why high field for a experimental (ignit) device?
π-ASTER & i-ASTER as starting point

14
- Case ignition: Rapidly and at modest cost achieving
and understanding ignition, and studying alpha-
particle physics.
- High-field is related to DD (3He-catalised) plants, that
much reduce large hot cells and RHE, so such costs.
- (why, locally in Spain) Be pioneers in this, to try to
be leaders when the future high-field fusion power
plants arrive.
π-ASTER & i-ASTER as starting point

15
- Why to start with a high-field ignition
(experimental) device and not a high-field power
plant directly?
- Why IGNITOR and FIRE tokamaks are not built
yet? Might this imply high-field is not a
satisfactory path for ignition studies?
- Please, ask more awkward questions at the end
Extra tricky questions

16
Some properties of high-field
ignition-capable stellarators

17
(two) Physics properties of high-field ig. stell.
Note, for all cases : A = 6 , ι = 0.7, fd = plasma dilution
factor = 0.84
Minimum magnetic field
B0 for ignition for various
parameters
Line-averaged electron
density nL and Sudo
density limit nS
T0.ig = 14.6 keV

18
Other properties of high-field ignition stell
Fusion power
generated for
combinations
of hE, βlim
Heat power load on
divertor targets
(improved divertors,
sweeping, Kd = 20,
50% radiated power
at edge
Von Mises stress in the
monolithic support structure

19
Technical features of
i-ASTER.v1

20
i-ASTER mission
• i-ASTER aims at, rapidly and at modest cost,
achieving and understanding ignition, and
studying alpha-particle physics in ignited or near-
ignited plasmas in a small fusion device. This
physics will be only partially investigated in ITER.
• High power-density  additional goal of testing
and optimizing power extraction systems (e.g.
lithium-based) and studying the plasma-wall
interaction.
• Indirectly, it would complement the stellarator
research line in the high plasma pressure range,
advance technologies for high field fusion devices
and for the manufacturing of strong stellarator
magnets.

21
Massive resistive coils
Illustration of the concept of massive resistive coils of
variable cross-section in poloidal direction (variable-
width). One turn per coil depicted but several turns may be necessary.
• Variable cross-section coils important to reduce ~ 3-5
times the power required to try to avoid cryocooled
Cu coils (as in IGNITOR and FIRE).
• Still 750 MW of electric power needed to feed the
coils.

22
Massive resistive coils
Future:
• New calculation methodologies for magnetic
surfaces are required (~ heat-ΔT-resistivity,
current paths), it represent a novel field of study
~ For a CIII student as master work?
• Stress in insulation is not calculated yet.
• No concept for feedthroughs yet.

23
Detachable (half)periods
In power plants it is
also critical for coil
replacement and fast
blankets maintenance.
Concept of detachable
(half)periods. The depicted
large coils and interfaces are
only a reference to understand
the concept, not i-ASTER design.
Detachable periods in
i-ASTER as validation
of the concept.
Dispensable in π-ASTER &
i-ASTER.
Issues:
- Accurate positioning.
- Interfaces, flanges.
- Closure of rad-materials
during movement.
Detachable (half)periods also
studied in Ref. [Wan 05]
DetachableARC,butequatorialsplit…

24
Liquid lithium CPS and other advanced Li
CPS : Capillary Porous System
Power on divertor target critical for i-ASTER,
and for competitive fusion plants [Abd 99] ~ plant
size ~ hot cell size and RHE size ~ …
First-wall almost
entirely covered with
low temperature liquid
lithium (low recycling of
particles)
Advantages:
• Increased plasma confinement.
• Higher plasma purity Zeff~1.3
• No erosion.
• Less hot spots ~ self-shielding.
• Low Z.
Drawbacks:
• Safety ~ fires.
• Difficult management
(possible oxidation,
reactive).
• Little developed.

25
Concept of beams of high speed
(>100 m/s) Li droplets as in Ref.
[Wer 89]. Figure reproduced from [Wer
89]
One of the next advanced Li-based systems
required at divertor areas (~ 30MW/m2):
Concept of shower
jets as in Ref. [Sag
17]. Figure reproduced
from [Sag 17]

26
Dry (tungsten or CFC)
divertor targets ~30
MW/m2 load may help,
but currently not
preferred due to
impurities, erosion,
radioactive powders.
One of the next advanced Li-based systems
required at divertor areas (~ 30MW/m2):
Photograph of a real jet droplet
curtain in the T-3M tokamak.
Figure reproduced from [Kar 89]
Concept of jet-drop
curtain. Figure
reproduced from [Mir 92]

27
Pulse length, heating & diagnostics strategy
Pulse length:
• 5 E
• Low duty-cycle (~ 1000 pulses during a ~ 10 year
lifetime)
Plasma heating strategy:
• B = 9.8 T  high frequency (275 GHz) even at first
harmonic.
• Slightly overdense plasma  may require EBW
heating.
Diagnostics strategy :
• Fully integrated in small few ports.
• Initially for plasma operation and machine
protection. In a 2nd stage, study energetic particle
dynamics.

28
Elements not cited in this presentation
• Calculation and geometry of island divertors.
Geometry and calculation of advanced Li
systems for divertor areas.
• Ports: number, size, location…
• Neutronics.
• Selection of best type of quasi-symmetry
and number of periods and aspect ratio.
• Cost of stellarator core and systems.
• Many details of each element.
Also, some of the next elements are not
studied in the paper

30
How to build the monolithic structure?
Characteristics:
• Coils wound on (in grooves/
casings) an additively manufac-
tured part filled with short-fibre-
reinforced epoxy resin.
• Coils wound from the outside ~
simpler than from the inside as
in ARIES-CS.
• A layer of long-fibre-reinforced
epoxy resin generates the
toroidal monolithic support.
• Coils fabricated from water-jet
cut Cu sheets.
Additive manufacturing plus
fibre-reinforced resin
Additively manufactured
halfperiod of (scaled)
UST_3 stellarator
Toroidal
monolithic
support
Data beyond
[Que 18]

31
• Built the first time: Variable
thickness in toroidal and
poloidal is designed, and cited
in [Wan 08] and [Que 18].
• Optimization of thickness not
produced, only approximate
thickness.
Additive manufacturing plus
fibre-reinforced resin
Lower field + centering
forces  δ 
intermediate thickness
Higher field + centering
forces  δ  larger
thickness
Higher field +
expanding forces  δ 
intermediate thickness
How to build the monolithic structure?Data beyond
[Que 18]

32
Approximate electric
power consumed in
the resistive copper
coils for ε = 1 [Que 18]
Ratio between the electrical
power generated Pe (if a power
plant, Pe = Pfusion / 3 ) to the
electrical power consumed in
resistive coils for ε = 1
A (DEMO) power plant with Cu coils?
It has some advantages and drawbacks
This question is not answered in the accepted paper. It was
contemplated in a previous version.
Data beyond
[Que 18]
ε and other
terminology
Plot from [Unpublished large version of paper]

33
A (DEMO) power plant with Cu coils?
Data beyond
[Que 18]
Advantages
• Plant faster to build.
• Higher coil accuracy at same
cost of superc. coils (SC).
• No cryo-isolated legs and
supports. No cryostat ~
maintenance. No Cryogenics.
• No cooldown period. Time≡$
• Cu easier to recycle than SC.
• Larger space for plasma ~
shielding thickness ~ A
stell ~ size.
Drawbacks
• Large recirculated
power (see plot).
• For a power plant ε=1
is rather large (~ coil
cooling pipes for
steady-state).
• Either high beta or
large size is
compulsory ~ [Woo
98] concept.
• Cu only for first(s)
plants. Low cost HTS
for long term.
It has some advantages and drawbacks

34
Why high fields in future power plants
Already and in the future, human beings have to
replace fossil fuels and (if needed/possible/wanted)
increase energy consumption.
(Large) powerful high-field (say 20-50GWth , Pfus
∝~ β2 B4 V ) power plants may act as multifunctional
plants producing one or more of:
synthetic fuels, electricity, freshwater (irrigation,
tap water) by desalination, electrolytic metal
refining, heating (domestic and industrial).
And more speculative functions like elimination of
atmospheric CO2 , air-conditioning of full cities,
mining space trips. (related, read e.g. [She 00])
Much energy needed

35
controlled
Chemical ignition
10000000
times more
powerful
[1] https://www.uv.es/jgpausas/he.htm. Origin A. Busetto from www.ibc.regione.emilia-romagna.it/paleo/index.htm and
www.kheper.net/evolution/ascentofman.html
controlled
Fusion ignition
We need modern energy for modern needs
[1]

38
[Abd 99] Mohamed A. Abdou, The APEX Team, Exploring novel high power density concepts for
attractive fusion systems, Fusion Eng. Des. 45 (1999) 145–167.
[Bro 17] T. G. Brown, Three Confinement Systems—Spherical Tokamak, Standard Tokamak, and
Stellarator: A Comparison of Key Component Cost Elements, IEEE TRANSACTIONS ON
PLASMA SCIENCE, DOI 10.1109/TPS.2018.2832457 (2017).
[Gre 08] M.A. Green, B.P. Strauss, The Cost of Superconducting Magnets as a Function of
stored energy and…, IEEE Trans. Appl. Supercond. 18(2) (2008) 248–251.
[Kar 89] B.G. Karasev, I.V. Lavrentjev, A.F. Kolesnichenko, et al., Research and development of
liquid metal systems for a tokamak reactor, Fusion Eng. Des. 8 (1989) 283-288.
[Mir 92] S.V. Mirnov, V.N. Demyanenko and E.V. Muravev, Liquid-metal tokamak divertors,
Journal of Nuclear Materials 45–49 (1992) 196-198.
[Nyg 16] R.E. Nygren, F.L. Tabarés, Liquid surfaces for fusion plasma facing components–A
critical review. Part I: Physics and PSI, Nuclear Materials and Energy 9 (2016) 6–21.
[Que 18] V. Queral, F.A. Volpe, D. Spong, S. Cabrera, and F. Tabarés, Initial exploration of high-
field pulsed stellarator approach to ignition experiments, Journal of Fusion Energy 1-17 (2018)
DOI 10.1007/s10894-018-0199-5.
[Sag 08] A. Sagara, O. Mitarai, T. Tanaka, S. Imagawa, Y. Kozaki, M. Kobayashi, T. Morisaki, et
al., Optimization activities on design studies of LHD-type reactor FFHR, Fusion Eng. Des. 83
(2008) 1690–1695.
[Sag 17] A. Sagara, J. Miyazawa, H. Tamura, T. Tanaka, T. Goto, N. Yanagi, et al., Two
conceptual designs of helical fusion reactor FFHR-d1 based on ITER technologies and
challenging ideas, Nucl. Fusion 57 (2017) 086046.
References

39
[She 00] STUDY OF OPTIONS FOR THE DEPLOYMENT OF LARGE FUSION POWER
PLANTS, John Sheffield et al., 2000.
[Wan 05] X.R. Wang, et al., Maintenance approaches for ARIES-CS compact stellarator power
core, Fusion Sci. Tech. 47(4) (2005) 1074–1078.
[Wan 08] X. R. Wang, A. R. Raffray, L. Bromberg, J. H. Schultz, L. P. Ku, J. F. Lyon, et al., Aries-
CS magnet conductor and structure evaluation, Fusion Sci. Tech. 54 (2008) 818-837.
[Wer 89] K. A. Werley, ‘A high-speed beam of lithium droplets for collecting diverted energy and
particles in ITER’, Los Alamos N. L. report LA-UR--89-3268, 1989.
[Woo 98] Robert D. Woolley, Improved Magnetic Fusion Energy Economics Via Massive
Resistive Electromagnets, Report PPPL-3312, 1998.
[Unpublished large version of paper] This is a larger version of the paper Ref. [Que 18]. The
manuscript was not accepted in a fusion journal and it is not publically available.
ISS04 : International Stellarator Scaling 2004
ARC : Affordable, robust, compact
References

41
Extra slides for discussion

42
“π-ASTER stellarator of high field (high for its size)
and V ~ 2 m3 , R = 1.5 m , a = 0.26 m, would be built
before i-ASTER. Initially it would be aimed essentially
at exploring lower cost and effective techniques to build
the next i-ASTER and at experimenting with the ABIL
divertor-wall concept. The magnetic field B is selected in
order to give a similar current density and increase of
temperature in the coils as i-ASTER for the same pulse
length. This results in B = 3.7 T. The proportion of all
the elements would be kept and scaled down. All the
other properties of i-ASTER defined in Sec. 9.1 and Sec.
9.2 would be kept except for the ignition condition,
tritium use and heating power”
π-ASTER

43
Extra slides for discussion
Some data on
superconductive materials
and coils

45
Fig.: YBCO critical current density
Jc (T, B) Ref. [Kyushu Univ., JP] , [Type of
manufacturing?]
SC properties

46
YBCO properties
Fig.: YBCO critical current density
Jc (T, B) Ref. [Kyushu Univ., JP] , [Type of
manufacturing?]
Ic values range from 80 –110 Amps
at 77 K, self-field, in 4 mm width,
for the SuperpowerYBCO wire on
hand

48
Extrapolation to future
Past data
Source of data [Sar 09]
Source of data [Flu 08]
Source of data [Sar 09]
Technology ‘S’ Curves
Source of data [Sar 09]]
Future cost of YBCO superconductor
YBCO :
Four-fold
cost
reduction in
the next 6
years

49
Price SC in kAm for B and T
NiTi wire $1/kA/m. (4.2 K, 4 T) (2018 data, QUENCH
PROTECTION STUDIES OF MAGNESIUM..)
Nb3Sn around $8, (4.2K B?)(year 2000) [Gra 02].
The price of
coated [YBCO]
conductor (CC) as
of this date
[2012] about
$400/kAm [Mat
12] [T, B?]
year 2000?

50
YBCO Magnets :
The new record -- 26.8 tesla -- was reached in late July at the
magnet lab’s High Field Test Facility
The world-record magnet’s test coil was wound by Schenectady,
N.Y.-based SuperPower
(www.superpower-inc.com) with a well-known, high-temperature
superconductor called yttrium barium
copper oxide, or YBCO.
High-field SC coils

51
High-field SC coils
Stephen Bilenky
Successfully tested in 2017, this magnet is the world's
most powerful superconducting magnet — by a long shot.
Before this new magnet reached full field in December
2017, the world's strongest superconducting user magnet
had a field strength of 23.5 teslas. At 32 teslas, this new
record-holder is a whopping 8.5 teslas stronger than the
previous record – a giant leap in a technology that, since
the 1960s, has seen only baby steps of 0.5 to 1 tesla.
https://nationalmaglab.org/magnet-
development/magnet-science-
technology/magnet-projects/32-tesla-
scm

53
[Flu 08] René Flükiger, “Implementing Agreement on High Temperature Superconductivity
(HTS)”, Presentation in FASI FASI-IEA NEET WORKSHOP, Moscow, 30-09-2008.
[Gra 02] Paul M. Grant and Thomas P. Sheahen, Cost Projections for High Temperature
Superconductors, arXiv:cond-mat/0202386 [cond-mat.supr-con], (2002).
[Mat 12] V. Matias and R. H. Hammond YBCO superconductor wire based on IBAD-textured
templates and RCE of YBCO: Process economics, Physics Procedia 36 ( 2012 ) 1440 – 1444.
[Sar 09] Dr. Philip Sargent, “Commercial superconductors, Cryogenics and Transformers”,
Diboride Conductors Ltd. ; 2009?
References

2018, Seminar in Univ. Carlos III of Madrid about high-field ignition stellarators and i-ASTER, 19-11-2018

Recommended

Recommended

More Related Content

Similar to 2018, Seminar in Univ. Carlos III of Madrid about high-field ignition stellarators and i-ASTER, 19-11-2018

Similar to 2018, Seminar in Univ. Carlos III of Madrid about high-field ignition stellarators and i-ASTER, 19-11-2018 (20)

Recently uploaded

Recently uploaded (20)

2018, Seminar in Univ. Carlos III of Madrid about high-field ignition stellarators and i-ASTER, 19-11-2018