mission and design requirements on national centralized tokamak (nct)

Mission and Design Requirements on National Centralized Tokamak (NCT)

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

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

* 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.

JT-60

New Minimum Step to Fusion Power NCT

Demonstration of SS operation Demonstration of SS operation

Recent strategyRecent strategy

TFTRJETJT-60

DEMO

ITER

Large Tokamaks

Commercialization

High SS→NCT

ITER

JT-60(JA)JET(EU)TFTR(US)

①Self-sust. burn②Long burn

③SS plasma④Power production

⑤Economical feasibility

Previous StrategyPrevious Strategy

Large Tokamaks

DEMOProto Commercialization

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 (N=3.5(SSTR)-5.5(CREST))• should operate reliably (less than 1 off-normal event in 2 years) at least towards

the end of operating period.

NCT is a domestic research program for advanced tokamak research to succeed JT-60U incorporating Japanese

universities accomplishments

Academic Research Basis

Reactor engineeringPlasma Science

Fusion Science

Realization of Fusion EnergyDevelopmental

Academic

Stratified Structure of Fusion Research

Tokamak Helical Laser

(Academic)

IFMIF

(Developmental)

ITER

Hokkaido U.U. of FukuiNagoya U.Ibaraki U.U. of TsukubaKyushu U.Kanazawa U.Toyama U.Kyushu Tokai U.Tohoku U.Yamaguchi U.Osaka U.The U. of TokushimaChiba U.Hiroshima U.Chubu U.Kyoto U.Shizuoka U.Mie U.The U. of TokyoTokyo Institute of Tech.Tokyo U. of ScienceKeio U.CRIEPINIFS








Hokkai do U.

U. of Fukui

Nagoya U.

I baraki U.

U. of Tsukuba

Kyushu U.

Kanazawa U. Toyama U.

Kyushu Tokai U.

Tohoku U.

Yamaguchi U.Osaka U.

The U. of Tokushi ma

Chi ba U.

Hi roshi ma U.

Chubu U.Kyoto U.

Shi zuoka U.

Mi e U.

The U. of TokyoTokyo I nsti tute of Tech.Tokyo U. of Sci enceKei o U.CRI EPI

NI FS

Collaborating Universities or Institutes in FY2004.

NCT

0

50

100

150

200

2000 2002 2004

The Number of Collaborators

Year

Mission of National Centralized Tokamak

• Establish high steady state operation for DEMO and Contribute to ITER

– Demonstrate high (N=3.5-5.5) 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

NCT

ferritic steel

Requirements of NCT machine capability

• A super-conducting device with break-even-class plasma performance

• Capability of steady state high- (N=3.5-5.5) 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

TFC

PFC

VV

Stabiliser Plate Divertor

Sector Coil

13.5 m

15 m

P-NBI

N-NBI

R F

P-NBI

Present equipment in JT-60 (reuse)

reuse

Cryostat

NCT

best use of existing JT-60 infrastructure

Heating and Current Drive systems for NCT

P-NB: 85 keV Tang.: 4 unitsPerp.: 8 units

N-NB: 350-400 keV Tang.: 2 units

01020304050020406080100duration [s]ëùóÕ44MW41MW30MW25MW15MW

possible upgrade

ECW: 110GHz 4 units

1. P-NB(85keV)/ Co-injection : 4 units Current Profile control2. P-NB(85keV)/ Counter : ??? Rotation control3. P-NB(85keV)/ Perpendicular: 8 units Heating Profile control4. N-NB(350-400keV)Co-inj. : 2 units Current Profile control5. ECW : 110GHz, 4 units NTM suppression

1. P-NB(85keV)/ Co-injection : 4 units Current Profile control2. P-NB(85keV)/ Counter : ??? Rotation control3. P-NB(85keV)/ Perpendicular: 8 units Heating Profile control4. N-NB(350-400keV)Co-inj. : 2 units Current Profile control5. ECW : 110GHz, 4 units NTM suppression

NCT

Presented by T.S. Taylor at DOE/JAERI Technical Planning of Tokamak Experiments and Large Tokamak Workshop in Naka at 7-8 Feb. 2001

Higher Plasma Shape for a High-N

• Extension of the flexibility in the plasma shape is key issue for a high-N 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.

S Ip

aBT

q95

~ A-1{1+2(1+22)}

JT-60 ASDEX-U JET DIII-D

S=2.3-7.4

S=3.0-5.4S=3.1-3.6

S=2.0-2.2

Research target of NCT

No

rmal

ized

N

6

5

4

3

2

DIII-D experiment

ITER

JT-60

2 3 4 5 6 7Shape parameter S

NCT

Two Options of NCT (NCT-1 & NCT-2)NCT

NCT-1 NCT-2

Nb3Sn

Nb3Sn

Nb3Sn

Nb3Sn

NbTi

NbTi

NbTi

NbTi

NbTi

NbTi

NbTi

NbTi

NbTi

NbTi

432 turn

144 turn

168 turn

144 turn

208 turn540 turn

418 turn

400 turn

160 turn

96 turn

144 turn

144 turn

400 turn

294 turn

4m

-4m

6m6m

Ip=5.5MA Bt=2.76TA=2.695=1.84

Ip=4.0MA Bt=3.43TA=2.8595=1.57

Typical Plasma Parameters for 2 Options with SN & DN

Design

Divertor Single Null Double Null Single Null Double Null

PoloidalCross

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

95 / 95 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

1 m1 m

3

1 m

4

1 m

2

NCT

Divertor Pumping is important for long pulse operation- Design Criteria for Divertor Geometry-

For divertor performanceS≥ 100m3/s, ≥ 0.4m

Leg

Pump SCryopanel

Inside divertor

Outside divertor

S. Sakurai et al., Plasma Phys. Cont. Fusion 44 (2002) 749.

A 3.30 2.85 2.85 2.60

x ≤ 1.91 ≤ 1.65 ≤ 2.18 ≤ 1.98

NCT-1 NCT-2

Criteria of is estimated for given A, to ensure the divertor pumping and leg length.

x=0.55

0

50

100

150

200

1.6 1.8 2 2.2

Pumping rate (m

3/s)

Elongation x

-1NCT-2NCT

x=0.55

(a) inside divertor

A=2.6A=2.85

A=3.3

A=2.85

1.6 1.8 2 2.20

50

100

150

200

Elongation x

-1NCT-2NCT

x=0.55

(b) outside divertor

A=2.6

A=2.85

A=3.3

A=2.85Pumping rate (m

3/s)

0

0.2

0.4

0.6

0.8

1.6 1.8 2 2.2

Leg length (m)

Elongation x

-1NCT=2.85A

-2NCT=2.6A

0.550.6

0.5

0.6

x=

(c) inside divertor

0.55

δx=

high-, , and low-A makes divertor narrow

NCT

Optimization of Shape Parameter by A and, Criteria : Divertor pumping speed ≥ 100m3/s -> 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.

NCT

1

2

3

4

5

0

-1

-2

-3

-4

-51 2 3 4 5

Stabilizer for NCT-2 DN

Z (

m)

R (m)

Matsukawa’s presentation

2 3 4 5 6 7 8

2.5

3.0

3.5

å`èÛàˆéq S

1

2

3

4

É_ÉCÉoÅ[É^îrãC(m3/s)

ÅÜ100ÅÉ100NCT-1

NCT-2 DN

JT-60SCNCT-2 SN

Asp

ect

Rat

io A

Shape Parameter S

Divertor Pump

3.5

3.0

2.0

2 3 4 5 6 7 8

Critical N for MHD stability on Plasma Aspect Ratio

- Dependence of critical N on plasma aspect ratio for n=1 and n=2 mode is estimated as a function of the ratio of r

W/a (ERATO-J code).

- Critical N 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 Kurita’s talk.3

4

5

6

7

8

9

1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6

A=2.5 (n=1)A=2.5 (n=2)A=3.0 (n=1)A=3.0 (n=2)C

riti

cal N

rw/a

Double null95 = 1.8Negative shearqmin= 2.4Parabolic P(r)

NCT design

NCT

Kurita’s presentation

High N together with large QDTequ.

• NCT should have a potential to investigate high N at large QDTequ

• conditions: q95~3.5, PNB=25MW, HHy2=1.5, fGW=0.5-1

• In the case of N~5.5, QDTequ <0.2

• In the case of QDTequ~1 with fGW ~0.6-0.8,

N ~2.6-3(NCT-1), N ~2.9~3.3(NCT-2)

NCT

2

3

4

5

6

0 0.5 1 1.5 2

N

QDT

eq

2.01 /1.82 MA T

2.5 /2.27 MA T

3 /2.72 MA T

3.5 /3.18 MA T

4 /3.63 MA T

-1, =3.2NCT A

1.7 /1.54 MA T

2

3

4

5

6

0 0.5 1 1.5 2

N

QDT

eq

3 /1.5 MA T3.5 /1.8 MA T

4 /2 MA T4.5 /2.3 MA T

5 /2.5 MA T

-2, =2.6NCT A

2.5 /1.25 MA T

2.3 /1.15 MA T

Parameters of * and * for two optionsNCT

• In the regime of

N=2.5-5.5, *<0.01

for fGW=0.5-1.0.

• Conditions:– q95~3.5,

– PNB=25 MW,

– HH(y,2)=1.5,

– fGW=0.5-1.0ITER

ITER

High N with full non-inductive scenario

-0.200.20.40.60.8100.20.40.60.81012345602468101200.20.40.60.81qTiTeneëSìdó¨ÉrÅ[ÉÄãÏìÆÉuÅ[ÉgÉXÉgÉâÉbÉvOH-0.200.20.40.60.8100.20.40.60.81q012345602468101200.20.40.60.81TiTeneëSìdó¨ÉuÅ[ÉgÉXÉgÉâÉbÉvÉrÅ[ÉÄãÏìÆOH

A=3.3, 1.5MA, 1.8T, q95=5.1, N=3.7, HHy2=1.51, fGW=0.50

A=2.6, 1.7MA, 1.5T, q95=8.8, N=3.6, HHy2=1.64, fGW=0.63

NNB

NNB

PNB

PNB

PNB

PNB

fBS=0.68

fBS=0.60

• 15MW with HHy2=1.5-1.6(25MW with HHy2=1.2-1.3), It is possible to have 1.5-1.7MA plasma with high N and full CD conditions

• For q(0)>1, it is necessary to increase q95 (because of the central CD).

jBD

jBS

jTOTALjBD

jBS

jTOTAL

NCT

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.• A=2.6, Ip=3.0MA, Bt=2.1T,

q95=6.1, qmin=2.0, N=4.0,

HHy2=1.99, fGW=0.50, N-NB

(3MW, 400keV),

P-NB (22MW, 85keV)

N-NB

P-NB

fBS=0.69

jBD jBS

jTOTAL

NCT

NCT-2

Controllability of ECCD for NTM suppression

m/n ρS

ICD/PEC (kA/MW)

Resonance

width EC

PECmin

(MW)

NCT-1

mid-A

3/2 0.53 20.5 0.049 2.2

2/1 0.73 12.1 0.028 2.2

NCT-2

low-A

3/2 0.51 40.0 0.098 3.2

2/1 0.71 21.0 0.038 2.0

Controllability of ECCD is estimated by ray-tracing and Rutherford equation to deduce the required power.

normal shear with qo=1 fECE= 110 GHz

For m/n=3/2 mode in low-A, slightly high power is required due to the bload resonance width.

Required power is available for 30 s

Focusing mirror

Steerable mirror

Drive current density (MA/m2)6 4 2 0

1

0.5

0

NCT

Heat and Particle Control• high pumping capability is set on NCT• To reduce divertor heat load and to keep plasma clean, the higher d

ensity is better

Density

Radiation Power

Zeff

required radiation power～ imput power　 -　10MW

Zef

f, R

adia

tion

Pow

er

NCT

aÅÜ0.7m, q95ÅÜ3.5, Divertor Region:0.5m

0.0

0.5

1.0

1.5

2.0

2.0 3.0 4.0 5.0

Aspect Ratio R/a

Greenwald Density(10

20

m-

3)

NCT-2NCT-1

TFC

VV First wall + SOL width

Divertor Region

Stabilizer

・ a=0.7m : constant・ Plasma moves to

inside -> higher IP -> higher BT -> higher density

・ FW + SOL widthlimit

・ a and IP is increasing

・Constant I

P

Density window for NCT-1 & 2 ~ same

Assessment of Two options Items NCT-1 NCT-2

Break-even class performance fGW=0.7: HH=1.25Ç≈Q=1 fGW=0.7: HH=1.1Ç≈Q=1

Volt second capability 4MA, 100s is possible 5.5MA, 100s is possible at low density

Simultaneous achievement of

Q~1 and high NN=2.6-3(25 ) ~1MW at Q N=2.9-3.3(25 ) =1MW DN at Q

* and * *~0.005, *~0.1(25 )MW *~0.005, *~0.06(25 )MW

&Flexibility of Aspect RatioShape

2.85, AÅÜ x 1.6, 5ÅÖ SÅÖ 2.6, AÅÜ x 2.0, 7ÅÖ SÅÖ

N dependence on Aspect

Current profile Control

High density for divertor

, Feed back control of RWM NTM ~ same

Nlimit( =2.5) - A N

limit( =3) ~0.5A

~ same

~ same

NCT

There is a strong probability that NCT-2 option will be National Centralized Tokamak

Day long operation

1101 0 01 0 0 0104105t i me ( sec)non- steadymany variations

variation of profile reducesProfile depends on the initial condition

profile depends on self and external heatingÅEno new time constant. The

important point to keep plasma constant from the external purturbation

ÅEHow can we reduce external purturbations?

ÅEHow can we control?

Burning with out He Ash pumping

He ash problem,current diffusion

time

a few s Change of Material a few tens s a few hundred s a few days?

• Plasma-wall-interaction with a long time scale (~8 hours) • Avoidance of disruption against the external perturbation

NCT

Example of Day-long operation• Demonstration of controllability for ultra-long time scale

012(MJ) WS

0

5

10

(MW) PNNB (3MW)PPNB (5MW)

0

0.5

1

(MA)Ip IBS

INNB IPNB IOH

0

1

2

0 50 100 150Time (sec)

HHy2

0

2

4

6

0 0.20.40.60.8 1

(keV)

r/a

Ti

Te

1

2

3

4

5

0 0.20.40.60.8 1

q

r/a

0

2

4

6

0 0.20.40.60.8 1

(1019 m-3)

r/a

ne

ni

0

0.2

0.4

0.6

0.8

0 0.20.40.60.8 1

(MA/m2)

r/a

jNB+jBS

jBS

jOH

jNNB

jPNB

BT=1.3TIP=1MARp=2.85map=0.85mq95=5 95=1.76 95=0.46Vp=70.7 m3

N=3.66W=2.36 MJE=0.236 secHHy2=1.6Zeff=1.5 (O2)PNB

abs=7.73 MWne

av=3.36e19m-3

fGW=76%fBS=56%QDT

eq=0.143Pfusion=1.1 MWFull CD

Example simulation for day-long operation

available both in NCT-1 and NCT-2

NCT

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 A≥2.6, ≤2, S≤7 and BT≤3T will be selected as National Centralized Tokamak.

NCT

mission and design requirements on national centralized tokamak (nct)

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