Presentation in TOFE USA 2014 (TOFE Congress, 3D-Printed UST_2 Stellarator)

3D-Printed UST_2 Stellarator Status and First E-Beam Mapping Experiments Vicente Queral, CIEMAT L 1
3D-Printed UST_2 Stellarator Status
and First E-Beam Mapping
Experiments
Vicente Queral
National Fusion Laboratory, CIEMAT
ANS Topical Meeting: Technology of Fusion Energy (TOFE)
Anaheim, CA, USA
10-13 November 2014

Outline
▪ Background
▪ UST_2 conceptual design
▪ Engineering concepts and design
▪ Pictures of UST_2 construction status
▪ E-beam field line mapping experiments
▪ Results
▪ Potential future lines of R&D

Background. Objectives
► The work is carried out with very low funds. Therefore, the
importance of the work resides in the developed manufacturing
methods, not in the size of the device or the plasma performance.
♦ The geometrical complexity of stellarators is one of their main
drawbacks. To try lo lessen such drawback,
the objectives of UST_2 work are:
▪ Contribute to the development of new better (faster, cheaper,
simpler) construction methods for experimental stellarators, and
other fusion devices.
▪ Try to accelerate the R&D cycle of: design → construction →
experiments → results → improved design → construction …

Background. UST_2 essential data
▪ UST_2 is a small three period
stellarator of major radius 0.26 m and
plasma volume 10 litres.
UST_2
design
▪ UST_2 has been designed to
be fabricated by 3D printing
(additive manufacturing).
Construction
status

UST_2 conceptual design

▪ UST_2 is based on a 3 period Quasi-isodynamic stellarator with
poloidal closed contours (QIPCC3) supplied by German researchers,
[Mik 04]. It exhibits high confinement at any β<4%, middle compactness, high iota ~0.7
QIPCC3 LCFS, [Mik 04]
Modification
▪ Complex optimization process using several
codes (CASTELL, NESCOIL and DESCUR codes for
stellarator calculations).
UST_2 based on a 3 period Quasi-isodynamic stellarator
UST_2 Last Closed Flux
Surface (LCFS) showing the
achieved straight section

1) Wide port
1) Wide ports for fast in-
vessel access, maintenance
and remote handling.
2) Potential maintenance of
full (half)periods, i.e. similar
to concepts in [Wan 05].
3) Allocate space for
possible innovative power
extraction systems, i.e.
concepts [Kul 06], [Ima 11]
[Hir 09], [Wer 89], [Hir 97].
Potential advantages of the design (if it were a larger experimental
device or reactor)
2) Independent
module with
splitable
vacuum vessel
3) Space for power
extraction systems
Modification of QIPCC3 for enhanced engineering
~350 mm

Engineering concepts and
design

+
Approach for the coil frame manufacturing method
Resin casting
Concept of 3D-printed light truss structure
covered by a thin shell (internal surface removed
in the figure) formed by two joined halves.
The shell=‘mould’ (700€) remain
attached to the matrix after casting.
The two halves are split after casting.
Combination of 3D printing + casting (→ accurate & low cost)

Coil frame split in two halves
Assembling concept
Introduction of the vacuum
vessel in one half coil frame
Two halves
of the coil
frame after
casting and
splitting
Closure with the second
half coil frame
Concept of fully modular vacuum
vessel and coil frame !!

Approach for the vacuum vessel manufacturing
Central Vacuum Vessel (VV) Section
Cu strip
shaping
on form ↓
Finished VV liner
Concept of modular VV
Metal liner epoxy resin reinforced (→ low cost for large VV)
Finished Curved VV
sector. Copper liner
epoxy reinforced

Slide → contact of 3D-printed
positioning elements on
circular central ring
Assembling and positioning concept
Advantages:
- Accurate, fast and
simple halfperiod
positioning. Slide →
contact → slight final
rotation. Approach similar
to Remote Handling
philosophy.Sliding on horizontal
smooth base
Non-3D-printed
CIRCULAR
central ring
Contact,
accurate
positioning

Pictures of UST_2
construction status

UST_2 status on January 2014

One finished halfperiod and
one ongoing
Status on June 2014
Decision of device to build 
Conceptual design 
Detailed design 
Validation by e-beam mapping
Construction 25%

Set-up for the e-beam
mapping experiments
Status on July 2014
Oscillating e-gun

E-beam field line mapping
experiments

E-beam experimental set-up
Free oscillating e-gun
Video frame of the fluorescent ZnO
lines on screen, and mirror image
of the oscillating e-gun
Sketch of the
experimental set-up
E-gun arc (black) and
e-orbits (red) of 60 eV
electrons, calculated
by CASTELL code

Overlapping of the consecutive frames shown above
Detail of the series of frames containing
fluorescent points for pulse #15 Overlapping of
perspective-
transformed
experimental
fluorescent
points (in cyan)
and calculated
intersection of
oscillating e-
beam with the
screen (blue line)
Comparison calculations-experiments

Video recording of pulse #15
Video recording

Results

♦ Manufacturing the twisted UST_2 vacuum vessel was time consuming
and needs further R&D, i.e. using electrodeposition, electroforming, etc.
♦ ±0.3% dimensional accuracy has been achieved, still excessive.
Thermal warping seems the reason.
► The positioning strategy for the coil frames resulted satisfactory.
► A construction method for stellarators based on 3D printing + casting
has been developed.
► A method to fabricate a liner epoxy-reinforced twisted vacuum vessel
has been advanced.
► The low cost of this small device (2400 € in materials up to now)
suggests reasonable cost for larger devices.
Experiences learned and results

Potential future lines of R&D

1) Either Combination of metal 3D printing + metal casting
+
Metal (Zn, Al
…) casting in
the Titanium
shell ?
Titanium
shell ?
2) Or Use of large direct
metal laser 3D printers
Titanium piece 3D-printed by
AVIC Laser, China. Presented
in a Beijing fair [AVI 13].
Source of picture [3de 14]

A) A hybrid stellarator/tokamak
(with two coil-sets, ∞
intermediate configurations?)
For example the
compact A=3
Quasi-
axisymmetric
stellarator being
developed in
China/PPPL,
[Zhe 14]
3D printing of low or high aspect ratio stellarators by 1) or 2)
method (previous slide)
B) A high <β>lim large
aspect ratio stellarator,
thick copper coils
<β>lim ~10% A=10 [LKu 10]
<β>lim ~ 9% A=12 [Sub 06]
Quasi-isodynamic stellarator, 6
periods, [Sub 06]
QA-LAx stellarator, Source of figure [Zhe 14]
Perhaps
<β>lim
~15% ??

Acknowledgement
I would like to give thanks to all the people and researchers helping
in the development, in particular:
Jefrey Harris, Donald Spong and team (ORNL, QPS LCFS and coils)
Juergen Nueremberg and team (IPP Max-Planck, QIPCCs LCFS)
H. E. Mynick (PPPL, NCSX-TU LCFS)
Jesús Romero (NESCOIL teaching, other)
Antonio Lopez-Fraguas (DESCUR code update and teaching)
Gerardo Veredas (CAD teaching)
Juan A. Jiménez (VMEC teaching)
Víctor Tribaldos (stellarators)
Jose A. Ferreira (vacuum)
Cristobal Bellés (I. T. help)
Other

[3de 14] Web site, http://www.3ders.org/articles/20130529-china-shows-off-world-largest-3d-
printed-titanium-fighter-component.html, 2014.
[AVI 13] AVIC Laser (AVIC Heavy Machinery subsidiary), ‘16th China International High-tech
Expo’, Beijing, 21-26 May 2013, web site www.france-metallurgie.com, August 2014.
[Hir 97] ‘Steady state impurity control, heat removal and tritium recovery by moving-belt plasma-
facing components’, Hirooka et al., Proc. 17th IEEE-SOFE, San Diego, Oct. 6th-10th, 906, 1997.
[Hir 09] ‘Active particle control in the CPD compact spherical tokamak by a lithium-gettered
rotating drum limiter’, Y. Hirooka, et al., Journal of Nuclear Materials 390–391, 502–506, 2009.
[Ima 11] ‘Status and plan of gamma 10 tandem mirror program’, T. Imai, et al., Transactions of
Fusion Science and Technology vol. 59 Jan. 2011.
[Kul 06] ‘Project EPSILON – a way to steady state high b fusion reactor’, V.M. Kulygin, V.V.
Arsenin, V.A. Zhil’tsov, et al., IAEA XXI Fusion Energy Conference, 16 -21 October 2006,
Chengdu, China.
[LKu 10] ‘New Classes of Quasi-helically Symmetric Stellarators’, Report PPPL 4540, L.P. Ku
and A.H. Boozer, August, 2010.
[Mik 04] ‘Comparison of the properties of Quasi-isodynamic configurations for Different
Number of Periods’, M. J. Mikhailov et al., 31st EPS Conference on Plasma Phys. London,
28 June - 2 July 2004 ECA Vol.28G, P-4.166 (2004).
References

[Que 10] ‘High-field pulsed Allure Ignition Stellarator’, Stellarator News, n. 125, 2010.
[Sub 06] ‘Integrated physics optimization of a quasi-isodynamic stellarator with poloidally closed
contours of the magnetic field strength’, A.A. Subbotin, M.I. Mikhailov, V.D. Shafranov, M.Yu. Isaev,
C. Nührenberg, J. Nührenberg, et al., Nuclear Fusion 46 921–927, 2006.
[Wer 89] ‘A high-speed beam of lithium droplets for collecting diverted energy and particles in
ITER’, K. A. Werley, Los Alamos N. L. report LA-UR--89-3268, 1989.
[Wan 05] ‘MAINTENANCE APPROACHES FOR ARIES-CS COMPACT STELLARATOR POWER
CORE’, X.R. Wang, et al. and the ARIES Team, Fusion Science and Technology 47(4) 1074-1078,
2005.
[Zhe 14] ‘Systematic study of modular coil characteristics for 2-field periods quasi-axisymmetric
stellarator QAS-LA’, Jinxing Zheng, Yuntao Song, Joshua Breslau, G. H. Neilson, Fusion
Engineering and Design 89 (4), 487–501, 2014.
References

Extra slides intended
for the questions

Hints about the previous
UST_1 stellarator

Toroidal milling machine
Method to build the modular coils
Concept of toroidal milling
machine
The milling head of this special milling
machine moves in toroidal and poloidal
coordinates → simplicity and reduced field
errors.
Concept of a toroidal
milling machine for
stellarators

Compressing
conductors in the groove
Winding process and result
12 coils finished
1 ) Concept and implementation
of single monolithic frame
Two main concepts developed
Concept of conductor
compressed in groove

Pulse #202. Overlapping of
calculated (numbered circles) and
experimental points (cyan). Notable
agreement is observed.
Pulse #202. Video recording of
experimental fluorescent points
on a oscillating rod. 94 eV
beam.
Field mapping experiments
Recorded magnetic surfaces. Comparison calculation-experiment

Overview of the facility
CODAC systems
Power supplies. 20 kW
ECRH
1kW
More information in www.fusionvic.org and [Que 13]

• The toroidal milling machine is unsuited for very convoluted winding
surfaces and expensive if building only one device. Additive rapid
manufacturing methods might be better.
• Winding one turn per layer may be simpler and faster than two turns.
► The combination of a single monolithic frame with grooves and
compression of wire in the groove resulted effective and fast.
Experiences learned and results
► A construction method for stellarator
coils based on a new toroidal milling
machine was developed.
► Inspiration has been generated in
other researches and countries.
Formation. i.e., the SCR-1 stellarator
being built in Costa Rica is based on
the UST_1 design.
Status of
SCR-1

UST_2 stellarator

♦ The geometrical complexity of
stellarators is one of their main drawbacks
Coils and supports are shaped and
have to be very accurate (relative
errors ~<10-3). Source of W7-X figure,
http://lecad.fs.uni-
lj.si/research/fusion/W7X/index
One issue of stellarators. Previous proposed solutions
Beam truss
structure to support
the coils, [Jak 11]
Continuous structure and coils
wound in grooves, [Naj 05] [Naj 06]
Concept of 3D-
printed structure and
internally wound
coils, [Wag 08]

♦ In-vessel remote maintenance
(for reactors) is very complex and
downtime-expensive
Small maintenance ports in the
named Helias reactor. Source of figure,
[Bei 00] → slow (expensive
downtime). And, what if a
superconducting coil fails?
Other issue of stellarators. Previous proposed solutions
Vertical maintenance approach. Even
more difficult coil design [Wan 07]
Tokamak Stellarator
Full period disassembly concept,
[Wan 05]. Source of figure [Naj 05]

Hull concept and Truss concept developed
Hints about the development of engineering concepts
Assembling of the test
coil frame sector
Truss concept: 3D printed frame structure.
Nylon. 250 €. From company ‘Shapeways’.
Hull concept: 3D printed
piece conceived as a
double hull structure.
Nylon. Was test filled with
dental plaster. 80 €.

Hints about the assessed magnetic configurations
QPS, QIPCC2,
QIPCC3, NCSX-TU,
other, assessed
QPS (Quasi-
poloidal
stellarator)
Last Closed Flux Surfaces supplied by J. Harris & D. Spong, Nühremberg and team [Mik 04] and H. Mynick [Myn 10]
QIPCC2 (Quasi-isodynamic
stellarator with poloidal
closed contours) 2 periods
QIPCC3, three periods.
Selected
LCFS for NCSX, NCSX-
Turbulence Improved
and Mixed
▪ Calcula-
tions by
CASTELL
code (Java
code
developed
by me
during
several
years)

UST_2 essential properties
Element Specification
Number of periods 3
Plasma volume (litres) 10
R, plasma major radius (mm) 260
a, ave. plasma minor radius (mm) ~ 37
Aspect ratio ~ 7
Type of coils
Modular
coils
Number of pancakes = coils 90
Number of non-planar coils 84 (14 x 6)
N. of large planar non-circular
coils
6 (1 x 6)
Vacuum magnetic surfaces at φ = 0

Concept and test of coil winding and crossover
Testing the crossover
performance
Compression in groove
and special crossover
• Results :
- Reasonable pressure of
conductor on groove walls.
- One coil was wound in
about 30 minutes, OK.
- The conceived crossover
was feasible and
satisfactory.
Finished crossover
Test
coil
Concept. One
turn/layer compressed
in groove to allow fast
winding and many
coils (low curvature
radius)

Approach for the vacuum vessel manufacturing
Curious picture of the 3D-printed
mold for epoxy resin casting
Soldering external
claws (brass ball chain)
Finished Curved VV sector.
Copper liner epoxy reinforced
Electrodeposition, electroforming, metal 3D
printing and other methods will be also tested

Modification of QIPCC3
Why not to modify QIPCC3 to enhance some
engineering features of UST_2?
Insight came from,
►Initially:
9/13? = 0.692
Planned divertor for the
GAMMA 10 Tandem mirror.
Source of figure [Ima 11]
Linked mirrors. Source [Kul 06]
New QI configurations.
Source [Spo 10]
► Later, after searching, from:

Process of modification of QIPCC3
The straight section is stretched by CASTELL code,
plus re-optimization
• Automatic CASTELL code processes: The
QIPCC3 straight section is stretched (addition of
poloidal cuts and compression of QIPCC3 sections),
CASTELL DESCUR-like code application, two
NESCOIL runs, confinement, iota and magnetic well
profiles calculated by Monte Carlo method.
• Only about 500 configurations have been
compared. Long lasting computations.
• Increasing elongation of the straight section gave
decreasing confinement for the best configuration.
• The re-optimization is poor (about 3 times less
confinement than the original QIPCC3). However,
the main objective is engineering.
Stretched and
compressed
poloidal cuts

A mix of the Hull Concept and Truss Concept is chosen
Perspective and top view of the first 3 coils being 3D printed. A test
3D printed
thin cover
surfaces
and
internal
truss
structure
UST_2 engineering design

Internals of the coil frame

Sequential low-cost rapid manufacturing of larger devices
Cost and performance is only a coarse value
for rough comparison among devices
Concept : High-field
pulsed Allure Ignition
Stellarator (AIS) (2010).
[Que 10] High-field,
few ignition pulses.
Somewhat similar to
the IGNITOR, FIRE and
FAST concepts, but for
a stellarator.
Possible long term activities

Presentation in TOFE USA 2014 (TOFE Congress, 3D-Printed UST_2 Stellarator)

Recommended

Recommended

More Related Content

Similar to Presentation in TOFE USA 2014 (TOFE Congress, 3D-Printed UST_2 Stellarator)

Similar to Presentation in TOFE USA 2014 (TOFE Congress, 3D-Printed UST_2 Stellarator) (20)

Recently uploaded

Recently uploaded (20)

Presentation in TOFE USA 2014 (TOFE Congress, 3D-Printed UST_2 Stellarator)