seminar given in ucsd, usa, 2014 (univ. california san diego, california)

3D printed UST_2 stellarator, a small innovative fusion device Vicente Queral, CIEMAT L 1

3D printed UST_2 stellarator,

a small innovative fusion device

Vicente QueralNational Fusion Laboratory, CIEMAT, Spain

TM

Seminar given in

UC San Diego, CA, USA

17 November 2014


This is not a sculpture or fine art presentation !

It deals with fusion…

Perhaps, you might apply the developed

techniques for your work or projects,

think on it during the presentation!


Outline

▪ Two stellarator issues. Previous conceptual solutions.

▪ Hints about the previous UST_1 stellarator.

▪ UST_2

∙ Devising, test and selection of concepts.

∙ Engineering concepts and design.

∙ Pictures of UST_2 construction status.

∙ E-beam field line mapping experiments.

∙ Results.

▪ Potential future lines of R&D.


Two stellarator issues.

Previous conceptual

solutions


There are many different fusion approaches. Source

of figure [Woo 04]

We are going to

talk about these

devices, named

stellarators.

Fusion approaches

▪ Each type of

device has its

own advantages

and drawbacks (no time to discuss

about it).


Comparative plasma size and shape of real stellarators. Again, each one has

advantages and drawbacks. Source of figure [Tri 11], modified.

Some real stellarators in the world

Working in brief Construction

halted. No

plasmas

UST_1

Somewhat

similar to

several

linked

mirrors

UST_2

~10 m


♦ 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]


Main objectives of the work

♦ The geometrical complexity of stellarators is one of their main

drawbacks. To try lo lessen such drawback,

the main objectives of UST_2 work:

▪ Contribute to the development of new better (faster, cheaper,

simpler) construction methods for experimental stellarators,

and other fusion devices.

▪ Accelerate the R&D cycle of: design → construction →

experiments → results → improved design → construction …

Other objective: Build a small stellarator to prove the results of

the R&D, and able to be used by a university (formation, basic

experiments, etc.).


Background


► Currently I work in CIEMAT in Remote Maintenance for DEMO.

Previously in RM for IFMIF (International Fusion Materials Irradiation

Facility) and ITER.

I developed UST_2 work majorly on my own, with low personal and

crowdfunding funds, in my personal laboratory (~garage), during a

leave of absence period, with some help and contribution from

CIEMAT (codes, help from fusion expert colleagues,…).

► The work is R&D and innovation in engineering, focused in

new construction methods for stellarators (small stellarators now,

larger ones in a future!). It is not focused on physics and plasma

experiments.

Background


Background. UST_2 essential data

▪ UST_2 is a small three period

stellarator of major radius 0.26 m and

plasma volume 10 liters

UST_2

design

▪ UST_2 has been designed to

be fabricated by 3D printing

(additive manufacturing)

Construction

status


• UST_1 stellarator was designed,

built and operated from 2005 to

2007 in my personal laboratory.

• Cost of the whole facility ~ 3000 €

(many 2nd hand pieces).

• The coils were built by a new

toroidal milling machine.

• Motivation: Develop innovative

construction methods for stellarators,

edification and generation of

demonstration effect. UST_1

stellarator

UST_1

facility

UST_1 modular stellarator

Background. There is a previous UST_1


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. Patented.

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

2) 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.

E-beam field mapping experiments

Recorded magnetic surfaces. Comparison calculation-experiment


• The toroidal milling machine is unsuited for very convoluted winding

surfaces and expensive to build only one device. Additive rapid

manufacturing methods might be better.

► The combination of a single monolithic frame with grooves and

compression of wire in the groove resulted effective and fast.

Essential experiences learned and results

► Inspiration has been generated in

other researches and countries, i.e.

the SCR-1 stellarator being built

in Costa Rica is based on the

UST_1 design.

Status of

SCR-1

Status of SCR-1


Devising, test and selection

of concepts


Hull concept and Truss concept developed

Hints about the development of engineering concepts

Assembling of the test

coil frame sector

Truss concept: 3D printed truss structure. Nylon.

Results: Long casting process, too inaccurate (250 €)

Hull concept: 3D printed

piece conceived as a

double hull structure.

Nylon. Results: Accurate,

slightly expensive (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


UST_2 is based on QIPCC3, [Mik 04].

High confinement at any β<4%,

middle compactness, high iota ~0.7

QIPCC3

Modification

Complex CASTELL code optimization process

using integrated NESCOIL and DESCUR codes

(codes for stellarator calculations).

UST_2 Last Closed Flux

Surface showing the achieved

straight section

Why not to modify QIPCC3 for enhanced engineering?


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 [Wan 05].

3) Allocate space for

potential 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


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=‘mold’ (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 !!


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

Central Vacuum Vessel (VV) Section

Cu strip

forming

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 ~ CIRCULAR

central ring and 3D-printed

positioning elements

Assembling and positioning concept

Advantages :

- Accurate, fast and

simple halfperiod

positioning (slide +

contact + slight rotation

~ Remote Handling

philosophy).

Sliding on horizontal

smooth base

Non-3D-printed

CIRCULAR

central ring

Contact, accurate

positioning


Pictures of UST_2

construction status


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%


Finished

halfperiod

assembled

in position

Status on June 2014


Set-up for

the e-beam

mapping

experiments

Status on July 2014 and future work

Oscillating e-gun

Future work (undefined term ~ funding)

▪ Fabricate the remaining 5 VV

sectors and 4 coil frames.

▪ Assembling.


E-beam field line mapping

experiments


E-beam experimental set-up

Free oscillatiing e-gun

Picture 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


♦ ±0.3% dimensional accuracy has been achieved, still excessive.

► A suitable 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 enhanced.

► The positioning strategy for the coil frames resulted satisfactory.

► 1/3 of a fusion device has been produced with low budget. It was

possible since integrated innovations have been devised and

developed.

► The low cost of this small device (2400 € in materials up to now)

suggests reasonable cost for larger devices.

► Other types of fusion devices might be built by similar techniques.

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 photo [3de 14]

http://imageshack.us/photo/my-images/809/3dprintedpartsfighter2.png/

http://imageshack.us/photo/my-images/809/3dprintedpartsfighter2.png/


A) A hybrid stellarator/tokamak

For example the

compact A=3

Quasi-

axisymmetric

stellarator being

developed in

China/PPPL. Source of figure

[Zhe 14]


3D printing of low or high aspect ratio stellarators by 1) or 2)

(previous slide) with liquid Li walls

QA-LAx stellarator, Source of figure [Zhe 14]

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]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


The list does not include the references in extra slides.

[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.

[Bei 00] ‘The Helias Reactor’, C.D. Beidler, G. Grieger, E. Harmeyer, et al., Presentation, ~ 2000.

[Hei 06] ‘Design of Narrow Support Elements for Non Planar Coils of Wendelstein 7-X’ B. Heinemann, 1-4244-0150-X

IEEE, 2006.

[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.

[Jak 11] ‘Alternative conceptual design of a magnet support structure for plasma fusion devices of stellarator type’, Nikola

Jaksic, Boris Mendelevitch, Jörg Tretter, Fus. Eng. and Des. 86 689–693, 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, Chengdu, China,16 -21 October 2006.

[LKu 10] “New Classes of Quasi-helically Symmetric Stellarators”, Report PPPL 4540, L.P. Ku and A.H. Boozer, August,

2010.

[Men 11] ‘Prospects for pilot plants based on the tokamak, spherical tokamak and Stellarator’, J.E. Menard, et al.,

Nuclear Fusion 51 103014, 2011.

[Mik 04] “Comparison of the properties of Quasi-isodynamic configurations for Different Number of Periods”, M. J.

Mikhailov et al., 31st EPS Conf. on Plasma Phys, 28 June - 2 July 2004 ECA Vol.28G, P-4.166 (2004).

[Myn 10] ‘Reducing turbulent transport in toroidal configurations via shaping’, H. E. Mynick, N. Pomphrey and P.

Xanthopoulos, Physics of Plasmas 18 056101, 2011.

References


[Naj 06] ‘Recent progress in the ARIES compact stellarator study’, Farrokh Najmabadi, A. Rene Raffray, and the ARIES

Team, Fusion Engineering and Design 81 2679–2693, 2006.

[Naj 05] ‘Recent Progress in ARIES Compact Stellarator Study’ ,Farrokh Najmabadi and the ARIES Team, Presentation

in 15th International Toki Conference 6-9 December 2005, Toki, Japan, 2005.

[Que 10] ‘High-field pulsed Allure Ignition Stellarator’, Stellarator News, n. 125, 2010.

[Que 13] V. Queral, Coil fabrication of the UST 1 modular stellarator and potential enhancements, Fusion Engineering

and Design 88 683-686, 2013.

[Spo 10] ‘New QP/QI Symmetric Stellarator Configurations’, Donald A. Spong and Jeffrey H. Harris, Plasma and Fusion

Research: Regular Articles, Volume 5, S2039, 2010.

[Sub 06] A.A. Subbotin, et al., Integrated physics optimization of a quasi-isodynamic stellarator with poloidally closed

contours of the magnetic field strength, Nuclear Fusion 46 921–927, 2006.

[Tri 11] ‘Stellarators & Stellarator Reactors’, V. Tribaldos, University Carlos III lecture pres., Spain, 2011.

[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.

[Woo 04] S. Woodruff, An Overview of Tokamak Alternatives in the US Fusion Program with the Aim of Fostering

Concept Innovation, Journal of Fusion Energy 23 n. 1, March 2004.

[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.

[Wag 08] ‘ARIES-CS COIL STRUCTURE ADVANCED FABRICATION APPROACH’, Lester M. Waganer, Kevin T.

Slattery, John C. Waldrop iii, and ARIES Team, Fusion Science and Technology Vol. 54, 2008.

[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.

[Wan 07] ‘CONFIGURATION DESIGN AND MAINTENANCE APPROACH FOR THE ARIES-CS STELLARATOR

POWER PLANT’ X.R. Wang, et al., Fusion Science and Technology Vol. 52, 2007.

References

seminar given in ucsd, usa, 2014 (univ. california san diego, california)

Science

d printed ust

previous ust

pictures of ust

plasmas ust

stellarator issues

type of device

different fusion approaches

linked mirrors ust