Plasma and Fusion Research: Regular Articles

Volume 14, 1405163 (2019)

Improved Design of a Cartridge-Type Helical Blanket System for
the Helical Fusion Reactor FFHR-b1
Junichi MIYAZAWA1,2) , Hitoshi TAMURA1) , Teruya TANAKA1,2) , Yukinori HAMAJI1) ,Makoto KOBAYASHI1) , Takanori MURASE1) , Sho NAKAGAWA1) , Takuya GOTO1,2) ,Nagato YANAGI1,2) , Akio SAGARA1,2) and the FFHR Design Group1)

2)

National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu 509-5292, JapanSOKENDAI (The Graduate University for Advanced Studies), 322-6 Oroshi, Toki, Gifu 509-5292, Japan(Received 26 July 2019 / Accepted 24 October 2019)

The cartridge-type helical blanket system called the CARDISTRY-B has been proposed for the helical fusion
reactor FFHR-d1. The CARDISTRY-B is aimed at easy construction and maintenance. However, there remain
many issues in the design. For example, these include a large number of cartridges, no tangential ports, low
compatibility with the helical divertor, and others. To solve these issues, an improved design of the cartridge-typeblanket is proposed and named the CARDISTRY-B2. This is composed of the tritium breeding blanket (BB)filled with the flowing molten salt and the neutron shielding blanket (SB) filled with the tungsten-carbide. The
number of the BB (or, SB) cartridges in the 1/10 section of the full torus are reduced from 32 to 17 (or, from 44 to17). Tangential ports for the neutral beam injection heating are newly equipped together with the multi-purpose
blanket cartridge. Compatibility with the helical divertor is also improved. The BB cartridges are fixed on the
fixing units set on the top of the SB. No other part of the BB is touching the SB except the fixing ribs. The SB
cartridges surround the superconducting magnet coils and work as the cryostat inside the vacuum vessel. This
makes the large bellows for the large maintenance ports unnecessary. Details of the CARDISTRY-B2 designed
for a small helical fusion reactor FFHR-b1 are described in this paper.
c 2019 The Japan Society of Plasma Science and Nuclear Fusion ResearchKeywords: heliotron, fusion reactor, molten salt blanket, neutron shield, thermal shield, LHD, FFHR
DOI: 10.1585/pfr.14.1405163

1. Introduction
The FFHR-d1 is the LHD-type helical fusion reactor
aiming at demonstration of the fusion output, Pfusion , of
∼3 GW and the device lifetime of longer than 30 years[1]. The device size is four times larger than the LHD [2],i.e., the major radius of the helical coils, Rc , is 15.6 m in
the FFHR-d1 and 3.9 m in the LHD. The magnetic fieldstrength at the helical coil center, Bc , is 4.7 T - 5.6 T. The
FFHR-c1 is the compact version of the FFHR-d1 with
0.7 times smaller device size (Rc = 10.92 m) [3]. The
FFHR-c1 is aiming at demonstration of one-year steadystate operation with self-produced fuel and electricity. The
Bc is increased to 7.3 T to achieve a good plasma confinement in the small device. There are 22 important
issues to be solved to realize the FFHR-c1 and d1 [4].
To eﬀectively resolve these issues, a step-by-step strategy has been proposed [4]. In this strategy, the FFHRb1 as the helical volumetric neutron source (HEVNS) andthe FFHR-a1 as the pilot-HEVNS are planned before the
FFHR-c1. The FFHR-b1 has the same device size as the
LHD (Rc = 3.9 m), with Bc = 5.7 T. The main purposeof the FFHR-b1 is to demonstrate new technologies of, forexample, high-temperature superconducting (HTS) mag-net coils, and a cartridge-type blanket system, which is themain topic of this paper, in a reactor-relevant condition.
Tangential neutral beam injection (NBI) is the main plasma
heating method in the FFHR-b1. The neutrons producedby the beam-plasma fusion irradiate the SC magnet coils
and the blankets. From this point of view, the FFHR-b1
plays the role of the component test facility. The FFHR-b1
can also be a commercial neutron source. The FFHR-a1
is the non-nuclear R&D device of 0.7 times smaller device
size (Rc = 2.73 m) than the FFHR-b1, with Bc = 4.0 T.
The blanket is one of the important components comprising the fusion reactor. The blanket has three roles oftritium breeding, neutron shielding, and energy conversion from the 14 MeV neutron energy to the thermal energy. Because of the severe neutron irradiation [5], theblanket should be maintained periodically. At the sametime, RAMI (reliability, availability, maintainability, andinspectability) should be satisfied in the blanket at a highlevel. In the case of the helical reactor, how to construct the complicated structure within a realistic periodof time is also an important issue. To realize easy construction and maintenance, a cartridge-type helical blanket
system named the CARDISTRY-B (cartridges divided andinserted radially - blanket) has been proposed [3, 6] based

author’s e-mail: miyazawa.junichi@nifs.ac.jp

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Fig. 1 Schematic view of the CARDISTRY-B2 for the FFHR-b1.

on the T-SHELL blanket concept [7]. The CARDISTRYB is composed of the tritium breeding blanket (BB) filledwith the flowing molten salt and the neutron shielding
blanket (SB) filled with the tungsten carbide (WC). Bothof the BB and SB are toroidally segmented every two degrees. At each toroidal angle, the segmented parts are
divided into several cartridges in order to make it possible to assemble the cartridges after construction of the
SC magnet coils. A detailed maintenance process of the
CARDISTRY-B has been discussed and the availability is
estimated to be ∼70% [3]. The thermal and flow analysis
in a typical cartridge has been performed [8]. The neutrontransport simulation also has begun [9].
Although the CARDISTRY-B has enabled detailed
discussions on the maintenance scenario and numericalsimulations, there remain many unsatisfactory points, as
listed below:(1) a large number of cartridges (32 BB cartridges and 44
SB cartridges in a 1/10 section of the full torus),(2) no tangential ports available for tangential NBI,
(3) low compatibility with the helical divertor,(4) extremely large bellows are indispensable for large
maintenance ports,
and others. To solve these unsatisfactory points, an improved design of the cartridge-type blanket is proposed
and named the CARDISTRY-B2. In this paper, detailsof the CARDISTRY-B2 applied for the FFHR-b1 as the
HEVNS are described. An overview of the CARDISTRY-

B2 is given in the next Section. Detailed explanations on
the BB and SB cartridges are given in Secs. 3 and 4, respectively. Compatibility with the divertor is discussed inSec. 5. Summary and issues remaining for future studies
are given in Sec. 6.

2. Overview of the CARDISTRY-B2
A schematic view of the CARDISTRY-B2 applied to
the FFHR-b1 is shown in Fig. 1. Tangential ports for thetangential NBI are newly equipped. These are inevitableespecially in the case of FFHR-b1 as the HEVNS to produce the beam-plasma fusion neutrons. The CARDISTRYB2 is composed of 17 BB and 17 SB cartridges as shownin Figs. 2 and 3, respectively, in a 1/10 section of the full
torus of the FFHR-b1. In total, 170 BB and 170 SB cartridges are used in the CARDISTRY-B2. Compared withthe former CARDISTRY-B, the total number of the cartridges are largely reduced from 760 to 340. Among these,
14 BB cartridges of B01 - BB13, and BB17, i.e., 140 BB
cartridges in total, need periodical maintenance. These BB
cartridges are equipped with the divertor units, as will be
explained later in Sec. 5. Therefore, the divertor units are
replaced together with the 140 BB cartridges. This number is equivalent to the total number of the componentsthat need periodical maintenance in the tokamak DEMO of
128, which consists of 80 blanket segments and 48 divertor
cassettes [10,11]. The other BB cartridges of BB14 - BB16
can be replaced if necessary. The SB cartridges are basically used during the whole device life. Nine BB cartridges

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Fig. 2 Exploded view of the BB cartridges in a 1/10 section. Assembled view is shown in the box at the upper right-top.

Fig. 3 Exploded view of the SB cartridges in a 1/10 section. Assembled view is shown in the box on the upper right-top.

of BB01 - BB09 are fixed to the fixing units of SB10 and
SB11 equipped on the top of the SB cartridges (see Fig. 1).
No other part of these BB cartridges touches the SB except
the fixing ribs (see Fig. 6 in the next section, and see also

Figs. B1 - B9 in the Appendix).
The SB cartridges completely enclose the SC magnet
coils. Surfaces of the SB cartridges facing the SC magnet coils are cooled down to ∼80 K by gas He and these1405163-3

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Fig. 4 Sliced views of the CARDISTRY-B2 with the Poincaré plot of the magnetic field lines at the toroidal angle φ = 0, 11, and 18 deg.

works as the thermal shield for the SC magnets. In the
LHD, similar thermal shield is set on the inner surface ofthe cryostat and the main vacuum vessel for plasma confinement is placed inside the cryostat. In this case, largesize bellows are needed to connect the ports on the cryostat
to the main vacuum vessel. In the case of the fusion reactor as the FFHR-b1, c1, and d1, large maintenance ports,
which are relatively larger than the corresponding ports in
the LHD, are equipped. Although these large ports are favorable for easy maintenance, there emerges another problem, i.e., such large bellows that can cover the extremely
large maintenance ports for the FFHR-d1 will not be available. However, if the cryostat is inside the main vacuum
vessel, as in the case of the FFHR-b1 shown in Fig. 1, thelarge bellows become unnecessary except the connecting
ports to the SC magnet coil cooling system, which can bereasonably small.
One of the diﬃcult points in designing a helical fusion reactor is the narrow blanket space at the inboard
side of the torus. Sliced views of the CARDISTRY-B2
at the toroidal angle, φ, of 0, 11, and 18 degrees areshown in Fig. 4. Other sliced views at diﬀerent φ areshown in Figs. A1 - A4 in the Appendix. As seen in thesefigures, the blanket space between the plasma including
the ergodic layer and the helical coils (HC) is quite narrow at the inboard side of the torus. Nevertheless, thethickness of the BB is kept larger than 100 mm even in
the case of the CARDISTRY-B2 for the relatively small
FFHR-b1. To maintain this minimum thickness, the BB
and SB cartridges are designed using the solids definedat 0 - 20 mm from the HC surface, 0 - 40 mm, 40 - 140 mm(not shown), and 140 - 160 mm from the last-closed-fluxsurface (LCFS), as shown in Fig. 5. For example, theplasma side of the BB08 is determined so as to have nointerference with the solid defined at 0 - 40 mm from the
LCFS, and the thickness of the BB08 is determined by using the solid defined at 40 - 140 mm from the LCFS. Sim-ilarly, the BB side of the SB05 is determined so as to haveno interference with the solid defined at 140 - 160 mm fromthe LCFS, and the HC side of the SB05 is determined so as
to have no interference with the solid defined at 0 - 20 mmfrom the HC surface. By applying this drawing rule forall other blankets, the clearances between HC-SB, SB-BB,
and BB-LCFS are kept 20 mm, 20 mm, and 40 mm, respectively, and the minimum thickness of the BB is kept larger
than 100 mm (see Fig. 5 (c)).
At this moment, the clearances between the adjoining
cartridges are set to be ≥ 10 mm for both the BB and the SB(see Fig. 5 (c)), to allow a few mm of manufacturing errors
and the deformation due to the large temperature change
during the operation. These clearances will be reconsidered in the future study, by taking the numerical simulation
results on the neutron streaming into account.

3. The Tritium Breeding Blanket (BB)One of the main roles of the BB is to produce tritiumfrom lithium. In the CARDISTRY-B2, the molten salt including lithium (FLiNaBe, or FLiBe) is used for this. It
is also necessary to increase the molten salt temperaturehigh enough for electricity generation. At the same time,
the first-wall of the BB facing on the plasma suﬀers fromsevere irradiation by charge-exchanged neutrals and neutrons. Therefore, a strong first-wall cooling ability is also
required for the BB. In the former study, the thermal andflow analysis on the CARDISTRY-B applied to the FFHRc1 has been performed [8]. In that study, a flowing channelof 30 mm width is assumed in the plasma facing side ofa BB cartridge. Be pebbles are filled inside the BB cartridge as the neutron multiplier. The metal Be pebbles arealso beneficial to increase the eﬀective thermal conductivity inside the BB cartridge. The molten salt flows in the
SB facing side of the BB at first, and then returns in the
30 mm flowing channel at a higher flow velocity. In this1405163-4

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Fig. 5 (a) The plasma and cartridges of SB04, SB05, BB08,
BB09, BB10, and the molten salt pool sliced at φ = 0 deg.
(b) Solids used to cut the cartridges defined at 0 - 20 mmfrom the HC surface, 0 - 40 mm and 140 - 160 mm fromthe LCFS, respectively. (c) Top view of the equatorialslice.

study, we also assume a 30 mm width flowing channel inthe plasma facing side (front-side) of each BB cartridge,
instead of 2.8 times smaller width, to maintain the similar
flow condition with the former study. An exploded viewof the BB01 is shown in Fig. 6. See also Figs. B1 - B19 in
the Appendix for other BB blankets. The BB cartridges
are basically composed of a main case, a separating plate,
and a front panel. The molten salt flows in two flow chan-nels in the front-side and in the back-side of the separatingplate. As was discussed above, the thickness of the frontside molten salt is basically fixed to 30 mm, while the backside molten salt flows through the entire area between theseparating plate and the main case. One of the largest differences compared with the former study is that the molten
salt flows from the top to the bottom of a BB cartridge in aonce-through manner. The molten salt is then released into
to the molten salt pool (see Figs. 4 and 5 (a)) from the exhaust pipes equipped on the bottom of each BB cartridge(Fig. 7). Although a quantitative evaluation of the influence of the molten salt vaper, which is lower than 0.1 Pa
in the case of FLiBe at 550◦ C [12], to the plasma remains
for future study, we assume that there will be no criticalinfluence since the molten salt consists of the only lightweight atoms of F, Li, Na, and Be. When the molten salt
containing tritium is released to a vacuum, a part of tritiumis also expected to be released into the vacuum because of
the low hydrogen solubility of molten salt. This should bealso investigated in the future study.
In the CARDISTRY-B2, a multi-purpose blanket(BB17) is prepared in the outer port. The outer port
equipped with two tangential ports is composed of three
BB blankets, BB11, BB12, and BB13. The BB17 is a plugblanket to be put into a large hole of the BB11, as shownin Fig. 8. It is relatively easy to remove and reinstall theBB17. One can use this as the test blanket module to testother types of blanket using, for example, ceramic pebbles, or liquid metals. It is also possible to use this BB17
for reprocessing of spent nuclear fuel and/or isotope production, for example. By opening a hole on the BB17 as
in Fig. 8, it becomes possible to extract neutron beams to
distant rooms for medical use, for example.
The coverage is one of the important properties ofthe blanket. The coverage can be given by the averageof the poloidal angle covered by the blanket measured atevery toroidal angle. In the case of the CARDISTRYB2, the poloidal angles that are not covered by the BB
cartridges are ∼80, ∼75, ∼72, ∼70, and ∼50 degrees at
φ = 16, 17, 18, 19, and 20 degrees, respectively, as shownin Figs. A2 (h), A2 (i), A3 (a), A3 (b), and A3 (c) in the
Appendix. At the toroidal angle other than φ = 16 - 20
degrees, the poloidal angle that is not covered by the BB
cartridges is zero. Therefore, the coverage is estimated as
1.0 − (80 + 75 + 72 + 70 + 50)/360/36 ∼ 0.973. Notethat this estimation does not include the opening area ofthe tangential ports, the spaces between the adjoining BB
cartridges, the thickness of walls and ribs, which are diﬃcult to measure in the toroidal slices as seen in Figs. A1 A4 in the appendix. Nevertheless, this rough estimation isstill acceptable since the tangential ports are located at relatively separated positions, and the number of them will belimited to 4 in the FFHR-b1. Because of the limited spacearound the FFHR-b1, it is diﬃcult to place many large NBI
devices more than 4. Detailed estimation of the tritium
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Fig. 6 An exploded view of BB01. The assembled form, the main case, the molten salt in the back-side, the separating plate, the molten
salt in the front-side, the front panel, and the divertor are depicted from left to right.

Fig. 7 Bottom view of the exhaust pipes equipped on the BB
blankets.

and the thickness of walls and ribs will be performed infuture by considering the complicated 3D structures of theBB cartridges.

Fig. 8 (a) The front view and (b) the back view of the BB cartridges consisting of the outer port including two tangential ports.

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Table 1 List of volumes and weights of the structure and molten salt in the BB cartridges.

Volumes and weights of the structure and the molten
salt in the BB cartridges are listed in Table 1. Here, thedensities of structure material and molten salt are assumed
to be 8 ton/m3 and 2 ton/m3 , respectively. At maintenance,
one should remove and reinstall the empty BB cartridges.
Note that the molten salt is basically drained from the BB
cartridges at maintenance. The heaviest cartridge is theBB09 of ∼2 tons without molten salt. The total weight of
170 empty BB cartridges at all 10 sections is ∼1,580 tons.
When these are filled with the molten salt, the total weightof 170 BB cartridges increase to 2,750 tons.

4. The Neutron Shielding Blanket(SB)
Similar to the BB, the SB is also divided into several
cartridges, as was already shown in Fig. 3. This makes
it possible to shorten the construction period. All the SB
cartridges except the SB01 are manufactured and tested in
the factory. These are then transported to the construction
site and assembled after the construction of the SC magnet coils is completed on the SB01. The CARDISTRY-B2
is composed of only 160 SB cartridges in total except theSB01. Therefore, even if it takes two days to install one
SB cartridge, the total period for assembly can be shorter
than one year.
Each SB cartridge is basically a box consisting ofa main case and a back panel, as shown in Fig. 9 (andFigs. C1 - C8 in the Appendix). This box is filled with pebbles or small blocks of WC. The back panel is cooled
to ∼80 K by gas He. At the same time, the WC is alsocooled by gas He to maintain the BB side of the main caseat around room-temperature. The filling rate of WC is assumed to be 40% to keep enough space for the coolant gas.
Detailed estimations of the temperature profile of each SB
cartridges, the resultant deformation and neutron streaming are remained for the future studies.
Volumes and weights of the structure and the WC in
the SB cartridges are listed in Table 2. Here, the densitiesof structure material and WC are assumed to be 8 ton/m3
and 16 ton/m3 , respectively. The weight of the WC is estimated by multiplying the volume, the density, and thefilling rate of 40%. Note that the cartridges SB01, SB08,
SB09, SB10, SB11, SB16, and SB17 (Fig. C1 in the Appendix) do not include the WC, since these are mainly
used to form the outer structure of the SB that encloses
the HTS magnet coils and forms a cryostat. Other SB cartridges surrounding the BB and the plasma contain the WC
to enhance the neutron shielding rate. The total weight of
the SB cartridges including the WC in all 10 sections is∼8,560 tons. Then, the sum of this and all BB cartridges is
11,310 tons.

5. Compatibility with the Divertor
The CARDISTRY-B2 is designed to be consistent
with the liquid metal ergodic limiter/divertor named the
REVOLVER-D (reactor-oriented eﬀectively volumetricvertical divertor) [13], which is installed on each of theten inner ports. Recently, we have changed the basic concept of the REVOLVER-D by replacing the molten tin
shower with the solid tin pebbles, and renamed it as the1405163-7

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Fig. 9 An exploded view of SB04. The assembled form, the back panel, the tungsten-carbide of 40% filling rate, and the main case are
depicted from left to right.

Table 2 List of volumes and weights of the structure and molten salt in the SB cartridges.

REVOLVER-D2 [14]. The CARDISTRY-B2 is compatible with both the REVOLVER-D and the REVOLVER-D2.
Furthermore, the helical divertor, which was not includedin the former CARDISTRY-B, is now included in the design of the CARDISTRY-B2.
A schematic view of the tin pebble flow of the
REVOLVER-D2 is depicted in Fig. 10. Tin pebbles transported to the top of the device by a vibratory spiral elevator fall through the BB14 and hit the plasma at the ergodic layer. The plasma becomes neutralized and evac-

uated through the BB16. After that, tin pebbles further
fall into the lower unit of the REVOLVER-D2, through theBB15. Some pebbles irradiated by the hot plasma may
be damaged or melted. These damaged pebbles together
with the pebbles without damage are melted in the pool ofmolten tin on the lower unit of the REVOLVER-D2. Thismolten tin pool absorbs the large impact of falling pebbles. The molten tin is introduced to the Si oil pool througha shower nozzle unit. Then, the molten tin droplets arecooled in the Si oil pool and become solid tin pebbles. The

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Fig. 11 A bird’s eye view of the entire helical divertor equippedon the CARDISTRY-B2.

cording to the results of magnetic line trace calculation in
the future. The divertor units are replaced together with the
BB cartridges. Therefore, the lifetime of the divertor units
determines the maintenance frequency of the BB. The divertor units are basically installed to the shaded regionswith respect to the core plasma, where the direct 14 MeV
DT neutron irradiation is small. This may help to realize
a long-life divertor unit. A neutron transport simulation
currently being prepared will clarify the lifetime of the divertor unit and therefore the maintenance schedule of theBB.

6. SummaryFig. 10 (a) A bird’s eye view of the REVOLVER-D2, where arrows denote the tin pebble flow, and (b) a close-up viewof region enclosed by a broken square in (a).

solid tin pebbles are transported to the top of the device by
the vibratory spiral elevator again and then repeat the same
scenario.
Although the REVOLVER-D2 is expected to receive∼90% of the total divertor heat load [13], the remaining∼10% will hit the divertor foot prints determined by themagnetic field configuration. In the CARDISTRY-B2,
water-cooled tungsten divertor units are equipped on each
BB cartridge. A bird’s eye view of the helical divertor units
is shown in Fig. 11. Note that the detailed position of thedivertor unit is not fixed yet. It should be determined ac-

An improved design of the cartridge-type blanket system CARDISTRY-B2 has been proposed. This is based on
the former design of the CARDISTRY-B. Similar to theformer design, the CARDISTRY-B2 consists of BB and SB
blanket cartridges that can be installed after the SC magnet coils are constructed. The CARDISTRY-B2 has solved
several issues found in the former design as listed below:(1) the total number of the cartridges are largely reduced
from 760 to 340,(2) tangential ports are equipped for the tangential NBI
heating,(3) the helical divertor unit is set on each BB cartridge,and(4) extremely large bellows become unnecessary because
the cryostat for the SC magnet coils is formed by the
SB cartridges inside the vacuum vessel.
In the case of the CARDISTRY-B2 designed for the
FFHR-b1, the total weight of the empty BB cartridges is
1,580 tons, which increases to 2,750 tons after the molten
salt is filled. As for the SB cartridges, the total weightis 8,560 tons with WC of 40% filling rate. Then, the1405163-9

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tridges at removal and reinstallation are also needed to determine the maintenance scenario. As in the former study
on the CARDISTRY-B [6], a small 3D model of 28/625(= 0.0448) ∼1/20 scale is made by using the 3D printing technology, as shown in Fig. 12. Although 3D motion
is needed to install/remove the SB and BB cartridges, it
has been already confirmed to be possible using this 3Dmodel. However, compared with the former CARDISTRYB, where the SB and BB cartridges can be installed or removed with the 2D motion alone, it becomes diﬃcult to describe the mechanical motion of robots or cranes for maintenance in the case of the CARDISTRY-B2. How to fix
the BB blankets to the fixing units also remains for future
study.

Acknowledgments
This work was supported by JSPS KAKENHI Grant
Number 16K14530, and the budgets of NIFS15UFFF038
and NIFS17UFFF040 of the National Institute for Fusion
Science.

Appendix

Fig. 12 A small model of the CARDISTRY-B2 for the FFHRb1 of ∼1/20 scale made by the 3D printing technology.

total weight of the CARDISTRY-B2 during operation is
11,310 tons.
It should be noted the detailed design of the
CARDISTRY-B2 is not yet fixed. Further studies on theflow and thermal analyses together with the mechanicalstress analysis are needed to determine the thickness of thestructure material of the BB and SB blankets. The designof the separating plate in the BB cartridge should be reexamined after these analyses. The neutron transport should
be carried out to evaluate the TBR and the neutron shielding rate. Although the CARDISTRY-B2 has a large coverage of ∼97%, the thickness of the BB is not necessarily
large enough, which is 10 cm at the smallest. It is quite
important to clarify whether TBR > 1 is possible or not in
the CARDISTRY-B2 for the FFHR-b1. A numerical simulation on magnetic field line tracing is needed to determine the divertor position. Motion analyses of the BB car-Figures that are not included in the main body ofthis article are summarized in this appendix, where sideviews of the assembled SB and BB with Poincaré plotsof the ergodic layer and closed magnetic surfaces inside the LCFS (Figs. A1 - A4), exploded views of BB cartridges (Figs. B1 - B12) and SB cartridges (Figs. C1 - C8)
are shown.
[1] A. Sagara et al., Nucl. Fusion 57, 086046 (2017).
[2] A. Komori et al., Fusion Sci. Technol. 58, 1 (2010).
[3] J. Miyazawa et al., Fusion Eng. Des. 136, 1278 (2018).
[4] J. Miyazawa et al., Fusion Eng. Des. 146, 2233 (2019).
[5] Y. Someya et al., Fusion Eng. Des. 124, 615 (2017).
[6] J. Miyazawa et al., Plasma Fusion Res. 12, 1405017(2017).
[7] T. Goto et al., Plasma Fusion Res. 11, 2405047 (2016).
[8] T. Murase et al., Fusion Eng. Des. 136, 106 (2018).
[9] S. Hong et al., 13th ISFNT (25-29 Sep., 2017, Kyoto,
Japan), P3-107.
[10] A. Loving et al., Fusion Eng. Des. 89, 2246 (2014).
[11] H. Utoh et al., Fusion Eng. Des. 124, 596 (2017).
[12] D.A. Petti et al., Summary Report of Japan-US Joint
Project (JUPITER-II) (FuY 2001-2006) NIFS-PROC-71,
74 (2008). http://www.nifs.ac.jp/report/nifs-proc71.html[13] J. Miyazawa et al., Fusion Eng. Des. 125, 227 (2017).
[14] T. Ohgo et al., Plasma Fusion Res. 14, 3405050 (2019).

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Fig. A1 Side views of the Poincaré plots of the magnetic field lines with the SB and the BB cartridges of the CARDISTRY-B2 sliced at
the toroidal angle φ = 0 - 8 deg.

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Fig. A2 Side views of the Poincaré plots of the magnetic field lines with the SB and the BB cartridges of the CARDISTRY-B2 sliced at
the toroidal angle φ = 9 - 17 deg.

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Fig. A3 Side views of the Poincaré plots of the magnetic field lines with the SB and the BB cartridges of the CARDISTRY-B2 sliced at
the toroidal angle φ = 18 - 26 deg.

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Fig. A4 Side views of the Poincaré plots of the magnetic field lines with the SB and the BB cartridges of the CARDISTRY-B2 sliced at
the toroidal angle φ = 27 - 35 deg.

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Fig. B1 An exploded view of BB01 (same as Fig. 6).

Fig. B2 An exploded view of BB02.

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Fig. B3 An exploded view of BB03.

Fig. B4 An exploded view of BB04.

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Fig. B5 An exploded view of BB05.

Fig. B6 An exploded view of BB06.

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Fig. B7 An exploded view of BB07.

Fig. B8 An exploded view of BB08.

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Fig. B9 An exploded view of BB09.

Fig. B10 An exploded view of BB10.

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Fig. B11 Exploded views of BB11, BB12, and BB13.

Fig. B12 An exploded view of BB17.

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Fig. C1 An exploded view of SB01, SB08, SB09, SB10, SB11, SB16, and SB17.

Fig. C2 An exploded view of SB02.

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Fig. C3 An exploded view of SB03.

Fig. C4 An exploded view of SB04 (same as Fig. 9).

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Fig. C5 An exploded view of SB05.

Fig. C6 An exploded view of SB06.

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Fig. C7 An exploded view of SB07.

Fig. C8 Exploded views of SB12, SB13, SB14, and SB15.

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