1

3D-printed UST_2 stellarator: an overview

Dr. Vicente Queral

National Fusion Laboratory

CIEMAT

Presentation in IPP Max-Planck,

Greifswald, Germany

16 October 2015

2

Manufacturing grooves of the UST_1 stellarator, May 2006.

Personal hints

• Engineer. Previously machinery.

• Estimation of tokamak, but

~10 MW →stellarator (UST_1).

• Later CIEMAT.

• Keen on stellarators (but also work for DEMO, ITER…).

Background

3

Other problem is the high geometrical complexity of the devices, at high accuracy.

Concept of additive manufacturing of continuous structure (Waganer 2008)

Contorted plasma for an advanced stellarator

A problem in stellarator research is the calculation of excellent magnetic configurations.

Problem. Previous solutions

Simple coils. CNT [2]

Plasma ↓ convolu-tion. LHD [1]

Background

4

Independent coils on a ring, W7-X (Wanner 2006) [3]

Structure of bars for the coils (Jaksic 2011)

Modest number of solutions and research

Previous solutions to the problem

Modular frame (Hartwell 2003)

Background

• UST_1 stellarator was designed, built and operated by me from 2005 to 2007 in my personal laboratory.

• The coils were built by an innovative toroidal milling machine.

UST_1 facility

Toroidal milling

machine

Facility

UST_1 stellaratorBackground

6

Compression of conductors in the groove

Finished UST_1

1º. Concept of Monolithic frame

Two main concepts developed

2º. Conductor compressed in groove

UST_1 stellaratorBackground

Main results (such relevant for UST_2)

It has inspired other researchers. SCR-1 coil design and shape is the same as UST_1 (scaled two fold).

SCR-1 stellarator

(Costa Rica)Picture courtesy of

ITCR

◦ The toroidal milling machine is unsuited for very convoluted winding surfaces and,

◦ expensive to build only one device.

• The combination of a monolithic frame with grooves and,

• compression of wire in the groove resulted effective.

UST_1 stellarator

Recorded magnetic surfaces in UST_1

Background

8

UST_2. Objective and means

Engineering experiments (prototypes) are produced.

Only geometrical and integrative aspects are studied (no forces, stresses, …).

Objective of the work.

Contribute to the construction problem of stellarators, particularly by Additive Manufacturing (AM).

Background

Importance. To accelerate the production cycle of stellarators and experiments in stellarators.

9

Background

Means (up to now):

Only private funds (crowdfunding and personal) of 6000 €.

~ one person work, essentially me.

All manufactured and assembled in my personal laboratory (no help of technicians).

CIEMAT codes and computers.

IPP Max-Planck codes.

LCFSs from many centres.

UST_2. Objective and means

10

Development of the work

Concepts and methods explored

Validation

Results

11

QPS

QIPCC3 SELECTED

QIPCC3 is a Quasi-isodynamic stellarator of 3 periods supplied by researchers from here, IPP Max-Planck(Mikhailov 2004)

QIPCC2

Other: NCSX-TU, QIPCC6

QIPCC3

Magnetic configurations studiedConcepts

12

QIPCC3

Modify QIPCC3 to enhance some engineering features?

Modification of QIPCC3

Different concepts and plasma shapes for inspiration

(Imai 2011, Kulygin 2006, Spong 2010, Queral 2010)

? • Space

Concepts still imprecise

• Idea of tilting coils

Wide ports

(Wang 2005) [4]

?

Concepts

13

Calculation process with CASTELL code

NESCOIL, field from planar

coils

Projec-tion

Modification of 3 Fourier coefficients of QIPCC3

• The process is repeated for ~1000 magnetic configurations defined by different parameters.

• The best configuration found is chosen. Neoclassical transport ~3.5 times increase, acceptable.

NESCOIL

Stretch and compression

Concepts

14

UST_2 physics properties

Vacuum magnetic surfaces and

Iota profile (from CASTELL code)

Element Specification

Number of periods 3

Plasma volume (litres) 9.5

R, plasma major radius (mm) 292

a, ave. plasma minor radius (mm) 40.6

Aspect ratio 7.2

Bo Magnetic field at axis (T) ~ 0.1

ι0 , rotational transform at axis 0.74

ιa , rotational transform at edge 0.70

Vacuum max. magnetic well 0.21%

From VMEC and CASTELL codes

15

UST_2 physics properties

Boozer coordinates of QIPCC3 and UST_2

Should be improved

Expansion

Very straight

These calculations performed after the

CASTELL calculation of UST_2.

By Drs. Joachim Geiger (Boozer

coordinates) and V. Tribaldos

(Neoclassical transport calculations)

UST_2

QIPCC3

UST_2

plasma shape

16

2) Large planar tilting coils → Wide ports

1) Separation in modules.

2) Wide ports for fast in-vessel access.

3) Space for possible innovative power extraction systems.

Potential engineering advantages of the concept (some only applicable to large stellarators)

3) Space

1)

UST_2 engineering propertiesConcepts

17

UST_2 engineering design

Sketch showing the elements and geometrical concept of UST_2

Elevation view

Concepts

Concept of AM ofARIES-CS reactor

Independent coils

Modular frame (Hartwell 2003)

Monolithic frameCurved formwork [5]

Metal AM, permeator(Sacristan 2014)

Other manufac-turing methods

What method to choose?The c

onstr

uction p

roble

m

AM

Concepts & methods

19

Design for proof of concept

Combination of a sector of the winding surface, a sector of the vacuum vessel (double hull), and structural beams.

Interior filled with a material able to cure or settle.

Initially selected:

1st explored method, Hull Concept

Main results: • Robust and accurate. ◦ Perhaps, too expensive

(80€) if scaled. ◦ Improvable strength of

the bar structure.

Concepts & methods

20

Detail ‘A’ of the truss structure

CAD Automation

Additive manufactu-ring

After fabrication, the truss structure is covered by a plastic sheet, and the interior is cast with resin or other.

Hull Concept

Truss

Curved truss structure

2nd explored method, Truss Concept Concepts & methods

One half-sector after hard plaster

casting

Main results: • Low 3D-printing material

consumption (only 168 cm3

200 €).◦ Long set-up time (4h).◦ Thermal warping (2 mm).

Test of assembling of a Coil frame sector

Process previous to casting

Frame structure as received. Selective Laser Sintering.

Results of Trust Concept

22

+

Resin casting, or other material, in the internal volume. The ‘mould’ remains attached to the resin.

Light truss structure covered by a thin cover, all fabricated by AM (internal surface removed in the figure).

Results from Hull Concept

Results from Trust Concept

3rd explored method, 3DformworkConcepts & methods

3Dformwork structure, 800-1100 €

~ 350 mm

24

The Coil frame is split in two halves (after casting)

Vacuum vessel inside half Coil frame

Two halves of the Coil frame

Closure with the second half Coil frame. Modular vacuum vessel.

Assembling of a halfperiodConcepts & methods

25Central Vacuum Vessel (VV) section

Cu strip shaping on form ↓

Finished VV liner

Concept of modular VV

Sectors joined by flanges | Approach 1 Resin reinforced liner

Finished Curved VV sector. Epoxy-reinforced copper liner.

Modular vacuum vesselConcepts & methods

~ 3

00

mm

26

Slide → contact of 3D-

printed positioning elements on circularcentral ring

Advantages:Accurate, fast and simple halfperiod positioning. Approach similar to Remote Handling philosophy.

Sliding on horizontal smooth base

Non-3D-printed CIRCULAR central ring

Contact, accurate positioning

Assembling and positioning concept Concepts & methods

27

Coil winding and crossover

Conductor pass through opening

Results:

• Reasonable pressure of conductor on walls.

• The crossover was feasible and satisfactory.

• 14 coils wound in 3 hours.

Finished crossover

Test coil

Concept of one turn/layer compressed in groove to allow fast winding and many coils (thus, small curvature radius)

Compression in groove and special crossover

Concepts & methods

28

Validation Half period finished and assembled

29

Overlapping of consecutive frames

Agreement of experimental points (cyan)

and calculated points (blue

line)

Sketch of the experimental set-up

Agreement experiments-calculationsValidation

30

Thus, the experiment proved that major mistakes have not been produced during the development of the work and that the UST_2 stellarator likely will result satisfactory.

N202_F70-135.mpg

Recording of e-beam experimentValidation

31

Developed the 3Dformwork method Results

• I have conceived, developed and satisfactorilyproved a manufacturing method named3Dformwork, based on additive manufacturingcombined with non-metal casting.

• It uses little expensive 3D printingmaterial and, an inexpensive and strongresin matrix (fibres).

• The measured dimensional deviationsare <±0.3 %, still excessive.

32

• I have developed a fast manufacturing method for certain stellarators (3Dformwork).

• The 3Dformwork structure is producedby AM (rapid method).

• Proved that casting is fast.

Fast manufacturing and assembling Results

• The proved assembling me-thodology and positioningcontributes to an agileassembling. Besides, AM of allthe complex elements on a solepiece (integration).

33

Any magnetic configuration possible, built fast and at moderate cost, based on ‘special’ AM.

It may be important for the advance of plasma physics.

• Numerous coils,• of small curvature

radius,• of high complexity.

Thus,

Any magnetic configurationResults

Proved that it is possible:

Development of the work

Concepts and methods explored

Validation

Results

Current and Future work

35End has been cut

Electroformed liner for vacuum vessel

1. Flange attachment. 2. Optionally, external epoxy reinforcement, similarly to Approach 1.

Curved VV test sector produced by electroforming or electrodeposition

Cu electrodeposition (0.3-0.5 mm thick Cu layer)

Conductive paint (graphite

and silver)

Moulded wax mandrel

Approach 2 Electroformation on painted wax mandrel

~ 150 mm (scale 1/2)

Current work

36

Assembled sector of vacuum vessel under vacuum test

SLA 3D-printed internal surface of shell

Current work

SLS 3D-printed mould for external resin reinforcement

Internal metallic film deposition (PVD, electro-deposition, electrolessor …)

3D-printed shell and internal metallic film

3.2

3.1

Internal metal film for vacuum vessel

Approach 3. Internal metallic film deposition

~ 3

00 m

m

37

Different combinations of metallic materials for the 3Dformwork structure and the filler material are conjectured.

It might have application to devices with radiation.

Same 3Dformwork concept but for AM in titanium

Application to metallic structures

Titanium piece produced by AM. Cost?. (AVIC 2013) [6]

Future work

A) Stellarator of low aspect ratio with potential to reach a second stability regime of high beta

R&D and construction of a stellarator of Vp = 0.1 m3

by similar methods. Two options A or B.

B) A high <β>lim large aspect ratio stellarator

<β>lim ~10% A=10 (Ku 2010)

<β>lim ~ 9% A=12 (Subbotin 2006)

E.g. Quasi-isodynamic stellarator of 6 periods

In the line of QPS. 3 periods?

Future work Application to certain configurations

39

Long term aims

Notes: - Cost and performance is only a coarse value for rough comparison among devices.- PIGNITRON = Pre-IGNITRON

Ultimate aim: High-field pulsed Allure Ignition Stellarator (AIS). (Queral 10). High-field, thick copper, few ignition pulses. Somewhat similar to the IGNITOR or FIRE, but for a stellarator.

Sequential ‘low-cost’ ‘rapid manufacturing’ of larger devices

Future work

Speculative devices

40

Conclusions

3Dformwork was proved as a moderate cost fabri-cation method for high strength complex pieces.

Engineering designs conceived particularly for AM may give extra advantages (simpler assembling ~

complexity on one piece, ↓ modular ripple ~ many coils, etc.).

Additive manufacturing (combined with traditional

fabrication methods) appears promising to build, already today, certain geometrically complex stellarators, fast and at moderate cost.

It may be important to accelerate the production and experimental cycle for stellarators.

41

42

More information in

www.fusionvic.org

(AVIC 2013) AVIC Laser (AVIC Heavy Machinery subsidiary), ‘16th China International High-tech

Expo’, Beijing, 21-26 May 2013, web site www.france-metallurgie.com.

(Hartwell 2003) G.J. Hartwell, S.F. Knowlton, J. Armstrong, J. Peterson, C. Montgomery, et al.,

‘Construction Progress of the Compact Toroidal Hybrid’, Poster presentation in ANS 45th Annual

Meeting of the Division of Plasma Physics, Albuquerque, New Mexico (USA), 27-31 October

2003.

(Imai 2011) T. Imai, M. Ichimura, Y. Nakashima, I. Katanuma, M. Yoshikawa, et al., ‘Status and

plan of GAMMA 10 tandem mirror program’, Transactions of Fusion Science and Technology 59

1–8, 2011.

(Jaksic 2011) Nikola Jaksic, ‘Alternative conceptual design of a magnet support structure for

plasma fusion devices of stellarator type’, Boris Mendelevitch, Jörg Tretter, Fus. Eng. and Des. 86

689–693, 2011.

(Ku 2010) L.P. Ku and A.H. Boozer, ‘New Classes of Quasi-helically Symmetric Stellarators’,

Report PPPL 4540, August, 2010.

(Kulygin 2006) V.M. Kulygin, V.V. Arsenin, V.A. Zhiltsov, A.V. Zvonkov, A.A. Skovoroda, A.V.

Timofeev, Project EPSILON – the way to steady state high β fusion reactor, Ref. IC/P7-1,

Proceedings of the IAEA XXI Fusion Energy Conference (Chengdu, China), 16-21 October 2006.

(Mikhailov 2004) M. I. Mikhailov et al., ‘Comparison of the properties of Quasi-isodynamic

configurations for Different Number of Periods’, 31st EPS Conference on Plasma Phys. London,

28 June - 2 July 2004 ECA Vol.28G, P-4.166, 2004.

Bibliography

44

Bibliography(Parra 2015) Felix I. Parra, Ivan Calvo, Per Helander, Matt Landreman, Less constrained omnigeneous

stellarators, Nuclear Fusion 55 033005, 2015.

(Queral 2010) V. Queral, ‘High-field pulsed Allure Ignition Stellarator’, Stellarator News, n. 125,

2010.

(Sacristán 2014) R. Sacristán, G. Veredas, I. Bonjoch, I. Peñalva, E. Calderón, et al., ‘Fuskite®

preliminary experimental tests based on permeation against vacuum for hydrogen recovery as a

potential application in Pb15.7Li loop systems’, Fus. Eng. Des. 89 1551–1556, 2014.

(Spong 2010) Donald A. Spong and Jeffrey H. Harris, ‘New QP/QI Symmetric Stellarator

Configurations’, Plasma and Fusion Research: Regular Articles 5 S2039, 2010.

(Subbotin 2006) A.A. Subbotin, M.I. Mikhailov, V.D. Shafranov, M.Yu. Isaev, C. Nührenberg, J.

Nührenberg, 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.

(Waganer 2008) Lester M. Waganer, Kevin T. Slattery, John C. Waldrop iii, and ARIES Team,

‘ARIES-CS COIL STRUCTURE ADVANCED FABRICATION APPROACH’, Fusion Science and

Technology Vol. 54, 2008.

(Wang 2005) X.R. Wang, et al. and the ARIES Team,‘MAINTENANCE APPROACHES FOR

ARIES-CS COMPACT STELLARATOR POWER CORE’, Fusion Science and Technology 47(4)

1074-1078, 2005.

(Wanner 2006) M. Wanner and the W7-X Team, ‘Construction and assembly of WENDELSTEIN

7-X’, Fusion Engineering and Design 81 2305–2313, 2006.

References for pictures

[1] Web site, http://tokamaktales.blogspot.com.es/2014_07_01_archive.html, 2015

[2] Thomas S. Pedersen, et al., ‘First results from CNT’, Presentation from the Columbia

University In the City of New York’.

[3] J. Duhovnik, B. Jerman, T. Kolšek , J. Kramar J., N. Mole et al. (University of Ljubljana),

Analysis of Narrow Support Element of The W7-X Magnet System under Design Loads, Annual

Report 2005 – Fusion Physics Programme, Slovenian Fusion Association (EURATOM-MHEST), 21–27, 2005.

[4] Farrokh Najmabadi and the ARIES Team, ‘Recent Progress in ARIES Compact Stellarator

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

[5] Sitio web www.peri.es/proyectos.cfm/fuseaction/diashow/reference_ID/459/

referencecategory_ID/25/currentimage/2.cfm, fotografía nº 2, 2015.

[6] Web site, http://www.3ders.org/articles/20130529-china-shows-off-world-largest-3d-printed-

titanium-fighter-component.html, 2014.

46