Mission and Design Requirements on National Centralized Tokamak (NCT)

1
Mission and Design Requirements on National
Centralized Tokamak (NCT)
IEA/LT Workshop (W59) combined with DOE/JAERI
Technical Planning of Tokamak Experiments (FP1-2)
'Shape and Aspect Ratio Optimization for High
Beta Steady-State Tokamak 14-15 Feb. 2005 at San
Diego, GA
JT-60

• Y.Miura and the National Centralized Tokamak
  Facility Design Team
• 1)Naka Fusion Research Establishment, Japan
  Atomic Energy Research Institute, Mukoyama, Naka,
  Ibaraki, 311-0193 Japan

• the National Centralized Tokamak Facility
  Design Team
• M. Akiba1), H. Azechi2), T. Fujita1), K.
  Hamamatsu1), H. Hashizume3), N. Hayashi1), H.
  Horiike2),
• N. Hosogane1), M. Ichimura4), K. Ida5), T.
  Imai4), S. Ishida1), Y. Kamada1), H. Kawashima1),
  M. Kikuchi1),
• A. Kimura6), K. Kizu1), H. Kubo1), Y. Kudo1), K.
  Kurihara1), G. Kurita1), M. Kuriyama1), K.
  Masaki1),
• M. Matsukawa1), M. Matsuoka7), Y. M. Miura2), N.
  Miya1), A. Morioka1), K. Nakamura8),
• H. Ninomiya1), A. Nishimura5), K. Okano9), K.
  Okuno1), A. Sagara5), M. Sakamoto8), S.
  Sakurai1), K. Sato8),
• R. Shimada10), A. Shimizu8), T. Suzuki1), H.
  Tamai1), H. Takahashi1), Y. Takase11), M.
  Takechi1), S. Tanaka11),
• K. Tsuchiya1), H. Tsutsui10), Y. Uesugi12), and
  N. Yoshida8)
• 2)Osaka Univ., 3)Tohoku Univ., 4)Univ. of
  Tsukuba, 5)National Institute for Fusion Science,
  6)Kyoto Univ.,
• 7)Mie Univ., 8)Kyushu Univ., 9)Central Research
  Institute of Electric Power Industry,
• 10)Tokyo Institute of Technology, 11)Univ of
  Tokyo, 12)Kanazawa Univ.

2
New Minimum Step to Fusion Power
Recent strategy
ITER
Commercialization
DEMO
Large Tokamaks
Demonstration of SS operation

• To establish vision for commercialization
• for a period of 2030-2050, it
• should operate in steady state
• (for example, continuously for 1year)
• should achieve high beta
• (?N3.5(SSTR)-5.5(CREST))
• should operate reliably (less than 1
• off-normal event in 2 years) at least
  towards the end of operating period.

High b SS
JT-60
TFTR
?NCT
JET
3
NCT is a domestic research program for advanced
tokamak research to succeed JT-60U incorporating
Japanese universities accomplishments
Collaborating Universities or Institutes in
FY2004.
Stratified Structure of Fusion Research
Realization of Fusion Energy
Developmental
ITER
Tokamak
IFMIF
Helical Laser
(Developmental)
(Academic)
Fusion Science
Reactor engineering
Plasma Science
Academic Research Basis
Academic
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Mission of National Centralized Tokamak

• Establish high ? steady state operation for DEMO
  and Contribute to ITER
• Demonstrate high ? (?N3.5-5.5) non-inductive
  operation for more than 100 s in collision-less
  regime
• Test compatibility of reduced activation ferritic
  steel
• Demonstration of ultra-long (8 hours) steady
  state operation

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Requirements of NCT machine capability

• A super-conducting device with break-even-class
  plasma performance
• Capability of steady state high-? (?N3.5-5.5)
  plasma with full non-inductive current drive,
• required for the DEMO for
• more than 100 s
• Flexibility in terms of
• plasma aspect ratio,
• plasma shaping control,
• and feedback control

best use of existing JT-60 infrastructure
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Heating and Current Drive systems for NCT
1. P-NB(85keV)/ Co-injection 4 units Current
Profile control 2. P-NB(85keV)/ Counter
??? Rotation control 3. P-NB(85keV)/
Perpendicular 8 units Heating Profile control 4.
N-NB(350-400keV)Co-inj. 2 units Current Profile
control 5. ECW 110GHz, 4 units NTM suppression
P-NB 85 keV Tang. 4 units Perp. 8 units
ECW 110GHz 4 units
possible upgrade
N-NB 350-400 keV Tang. 2 units
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Higher Plasma Shape for a High-?N

• Extension of the flexibility in the plasma shape
  is key issue for a high-bN plasma operation where
  the research target of NCT is addressed.
• Observed in DIII-D experiment M.R. Wade et al.,
  PoP 8 (2001) 2208
• In order to improve a shape parameter, low aspect
  ratio as well as high elongation and high
  triangularity is considered in NCT design.

Presented by T.S. Taylor at DOE/JAERI Technical
Planning of Tokamak Experiments and Large Tokamak
Workshop in Naka at 7-8 Feb. 2001
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Two Options of NCT (NCT-1 NCT-2)
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Typical Plasma Parameters for 2 Options with SN
DN
Design
Divertor Single Null Double Null Single Null Double Null
Poloidal Cross Section
Ip (MA) / BT (T) 4.00 / 3.63 4.00 / 3.43 4.00 / 2.96 5.5 / 2.76
Rp (m) / ap (m) 2.94 / 0.90 3.11 / 1.09 2.77 / 0.89 2.97 / 1.13
k95 / d95 1.82 / 0.39 1.57 / 0.53 1.83 / 0.45 1.84 / 0.52
A / S 3.27 / 4.16 2.85 / 4.41 3.10 / 5.26 2.62 / 6.81
Vp (m3) / q95 80.9 / 3.39 106.9 / 4.12 77.7 / 3.48 132.4 / 3.87
NCT-1
NCT-2
1 m
1 m
1 m
1 m
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Divertor Pumping is important for long pulse
operation- Design Criteria for Divertor Geometry-
For divertor performance S 100m3/s, l 0.4m
S. Sakurai et al., Plasma Phys. Cont. Fusion 44
(2002) 749.
Criteria of k is estimated for given A, d to
ensure the divertor pumping and leg length.

A 3.30 2.85 2.85 2.60
kx 1.91 1.65 2.18 1.98
NCT-1
NCT-2
high-k, d, and low-A makes divertor narrow
dx0.55
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Optimization of Shape Parameter by A and, ?
Criteria Divertor pumping speed 100m3/s -gt
X-point height limit Leg length limit

• - With the trade-off of divertor pumping,
  S-parameter goes up to 8 at A 2.6 in NCT-2
  design.
• With the divertor pumping of 100 m3/s,
  S-parameter 7 is expected.
• - Restrict of ? causes the decrease of S in low A.

Flexibility in plasma shape and aspect ratio is
extended in consistent with the sufficient
divertor performance.
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Critical ?N for MHD stability on Plasma Aspect
Ratio
Kuritas presentation

• Dependence of critical bN on plasma aspect ratio
  for n1 and n2 mode is estimated as a function
  of the ratio of rW/a (ERATO-J code).
• Critical bN increases in lower aspect ratio,
  which suggests the advantage of low aspect ration
  on ?N.
• optimization of pressure profile is being
  studied.
• Critical ?N dependence on shape factor S will be
  presented by Kuritas talk.

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High ?N together with large QDTequ.

• NCT should have a potential to investigate high
  ?N at large QDTequ
• conditions q953.5, PNB25MW, HHy21.5,
  fGW0.5-1
• In the case of ?N5.5, QDTequ lt0.2
• In the case of QDTequ1 with fGW 0.6-0.8,
• ?N 2.6-3(NCT-1), ?N 2.93.3(NCT-2)

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Parameters of ? and ? for two options

• In the regime of
• ?N2.5-5.5, ?lt0.01
• for fGW0.5-1.0.
• Conditions
• q953.5,
• PNB25 MW,
• HH(y,2)1.5,
• fGW0.5-1.0

ITER
ITER
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High ?N with full non-inductive scenario

• 15MW with HHy21.5-1.6(25MW with HHy21.2-1.3),
  It is possible to have 1.5-1.7MA plasma with high
  ?N and full CD conditions
• For q(0)gt1, it is necessary to increase q95
  (because of the central CD).

A2.6, 1.7MA, 1.5T, q958.8, bN3.6, HHy21.64,
fGW0.63
PNB
A3.3, 1.5MA, 1.8T, q955.1, bN3.7, HHy21.51,
fGW0.50
NNB
PNB
PNB
jTOTAL
fBS0.68
jTOTAL
jBD
jBD
fBS0.60
jBS
NNB
jBS
PNB
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For a high performance, off axis N-NB is a
candidate

• By a modification of N-NB beam line, it is
  possible to increase performance of high-?N with
  full CD.
• The modification increases the capability of the
• current profile controllability.
• A2.6, Ip3.0MA, Bt2.1T,
• q956.1, qmin2.0, ?N4.0,
• HHy21.99, fGW0.50, N-NB
• (3MW, 400keV),
• P-NB (22MW, 85keV)

NCT-2
jTOTAL
jBD
jBS
fBS0.69
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Controllability of ECCD for NTM suppression
1 0.5 0
Controllability of ECCD is estimated by
ray-tracing and Rutherford equation to deduce the
required power. normal shear with qo1
fECE 110 GHz For m/n3/2 mode in low-A,
slightly high power is required due to the bload
resonance width. Required power is available for
30 s
r
6 4 2 0
Drive current density (MA/m2)
m/n ?S ICD/PEC (kA/MW) Resonance width DEC PECmin (MW)
NCT-1 mid-A 3/2 0.53 20.5 0.049 2.2
NCT-1 mid-A 2/1 0.73 12.1 0.028 2.2
NCT-2 low-A 3/2 0.51 40.0 0.098 3.2
NCT-2 low-A 2/1 0.71 21.0 0.038 2.0
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Heat and Particle Control

• high pumping capability is set on NCT
• To reduce divertor heat load and to keep plasma
  clean, the higher density is better

Radiation Power
Zeff
Zeff, Radiation Power
required radiation power imput power - 10MW
Density
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Assessment of Two options
There is a strong probability that NCT-2 option
will be National Centralized Tokamak
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Day long operation
Plasma-wall-interaction with a long time scale
(8 hours) Avoidance of disruption against the
external perturbation
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Example of Day-long operation

• Demonstration of controllability for ultra-long
  time scale

Example simulation for day-long
operation available both in NCT-1 and NCT-2
BT1.3T IP1MA Rp2.85m ap0.85m q955 k951.76 d9
50.46 Vp70.7 m3 bN3.66 W2.36 MJ tE0.236
sec HHy21.6 Zeff1.5 (O2) PNBabs7.73
MW neav3.36e19m-3 fGW76 fBS56 QDTeq0.143 Pfu
sion1.1 MW Full CD
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Summary

• Design of NCT is in progress to establish high ?
  steady state operation for DEMO and to contribute
  to ITER
• The shape and aspect ratio are important
  parameters for NCT.
• Recent evaluation for the designs, there is a
  strong probability that NCT-2 option which has
  A2.6, ?2, S7 and BT3T will be selected as
  National Centralized Tokamak.