F usion Reactor Technology I
(459.760, 3 Credits)
Prof. Dr. Yong-Su Na
(32-206, Tel. 880-7204)
Week 1. Magnetic Confinement/Fusion Reactor Energetics (Harms 8) Week 2. Tokamak Operation (I):
Basic Tokamak Plasma Parameters (Wood 1.2-3, Harms 9.2) Week 3. Tokamak Operation (II): H-mode
Week 4. Tokamak Operation (III): Advanced Operation Mode Week 7-8. Tokamak Operation Limits (I):
Plasma Instabilities (Kadomtsev 6, 7, Wood 6) Week 9-10. Tokamak Operation Limits (II):
Plasma Transport (Kadomtsev 8, 9, Wood 3, 4) Week 11. Heating and Current Drive (Kadomtsev 10) Week 12. Divertor and Plasma-Wall Interaction
Week 13-14. How to Build a Tokamak (Dendy 17 by T. N. Todd)
2
Contents
Week 1. Magnetic Confinement/Fusion Reactor Energetics (Harms 8) Week 2. Tokamak Operation (I):
Basic Tokamak Plasma Parameters (Wood 1.2-3, Harms 9.2) Week 3. Tokamak Operation (II): H-mode
Week 4. Tokamak Operation (III): Advanced Operation Mode Week 7-8. Tokamak Operation Limits (I):
Plasma Instabilities (Kadomtsev 6, 7, Wood 6) Week 9-10. Tokamak Operation Limits (II):
Plasma Transport (Kadomtsev 8, 9, Wood 3, 4) Week 11. Heating and Current Drive (Kadomtsev 10) Week 12. Divertor and Plasma-Wall Interaction
Week 13-14. How to Build a Tokamak (Dendy 17 by T. N. Todd)
3
Contents
Tokamak Operation Scenario
4
Current Ramp-up
High Power Phase
Plasma Quench Plasma
Initiation
JET pulse 69905 (BT = 3.1 T)
Tokamak Operation Scenario
5
JT-60U
H-mode
6
• 1982 IAEA F. Wagner et al. (ASDEX, Germany)
- Transition to H-mode: state with reduced turbulence at the plasma edge - Formation of an edge transport barrier: steep pressure gradient at the edge
H-mode
7
• 1982 IAEA F. Wagner et al. (ASDEX, Germany)
- Transition to H-mode: state with reduced turbulence at the plasma edge - Formation of an edge transport barrier: steep pressure gradient at the edge
t c
a
2 E»
H-mode
8
• Established in stellarators as well
Wendelstein 7-AS
V. Erckmann et al, Physical Review Letters 70 2086 (1993)
H-mode
Hoover dam
9• 1982 IAEA F. Wagner et al. (ASDEX, Germany)
- Transition to H-mode: state with reduced turbulence at the plasma edge - Formation of an edge transport barrier: steep pressure gradient at the edge
H-mode
Hoover dam
10• 1982 IAEA F. Wagner et al. (ASDEX, Germany)
- Transition to H-mode: state with reduced turbulence at the plasma edge - Formation of an edge transport barrier: steep pressure gradient at the edge
11
• First H-mode Transition in KSTAR (November 8, 2010)
- B
0= 2.0 T, Heating = 1.5 MW (NBI: 1.3 MW, ECH: 0.2 MW) After Boronization on November 7, 2010
H-mode
H-mode: How to?
12
• Separation of plasma from wall by a limiter and a divertor
• Advantage of the divertor configuration
- First contact with material surface at a distance from plasma boundary - Reducing the influx of ionized impurities into the interior of the plasma
by diverting them into an outer „SOL“
Strike point
Tokamak
13
H-mode: How to?
14
H-mode: How to?
15
• Role of wall condition
16
P
th= 2.84M
-1B
t0.82n
200.58R
1.0a
0.81H-mode: How to?
17
H-mode: How to?
J-W. Ahn, H.-S. Kim et al., “Confinement and ELM characteristics of H-mode plasmas in KSTAR”, Nucl.
Fusion 52 114001 (2012)
019 . 0 941 . 0 032 . 0 803 . 0 035 . 0 717 . 0
20
,
= 0 . 0488 ± 0 . 0028 n
±B
±S
±P
thr scaling e TY. R. Martin et al., “Power requirement for accessing the H-mode in ITER”, J. Phys.: Conf. Ser. 123 012033 (2008)
H-mode: Why?
18
• 1982 IAEA F. Wagner et al. (ASDEX, Germany)
- Transition to H-mode: state with reduced turbulence at the plasma edge - Formation of an edge transport barrier: steep pressure gradient at the edge
H-mode: Why?
19
• 1982 IAEA F. Wagner et al. (ASDEX, Germany)
- Transition to H-mode: state with reduced turbulence at the plasma edge - Formation of an edge transport barrier: steep pressure gradient at the edge
Density fluctuations at r/a = 0.65
G.R. McKee, et al. Plasma Fusion Res. (2007)
20
H-mode: Why?
• 1982 IAEA F. Wagner et al. (ASDEX, Germany)
- Transition to H-mode: state with reduced turbulence at the plasma edge - Formation of an edge transport barrier: steep pressure gradient at the edge
H-mode: Why?
21
Theoretical physics
H-mode: Why?
22
Theoretical physics
Experimental physics
Basic Tokamak Variables
• Safety factor q = number of toroidal orbits per poloidal orbit
23
q-profile
3
0 0.5 0.95
Normalised radius 1
5
2
Advanced scenario Baseline scenario
q
954 Hybrid scenario
Magnetic field lines Magnetic flux surfaces
q-profiles
0 1 2 3 4 5
0 0.5 1
r/a
ELMy H-mode
Tokamak Operation Modes
24
Conventional Operation Mode – H-mode
25
plasma radiusa
plasma pressure
0
core
pedestal
plasma radiusa
plasma pressure
0
core
pedestal
• Naturally peaked current profile
• Mild pressure gradient with steep edge pedestal
• Monotonic q-profile
• Positive magnetic shear
q
0< 1: Sawtooth instability, periodic flattening of the pressure in the core Stability of H-mode plasmas related safety factor profile: q(r)
H-mode: Limitations
0 1 2 3 4 5
0.5 1
r/a
H-mode, q-profile
q = 1
0
Sawtooth
27
time (s)
0 2 4 6 8
8 6 1 10 1
Ip(MA)
PNBI (MW) PRF (MW)
WMHD(MJ)
Nel x1.1019
Ti(keV) Te (keV)
pulse 20438
- nonlinear low-n internal mode - internal (minor) disruption - enhanced energy transport
in the plasma centre
q
0< 1: Sawtooth instability, periodic flattening of the pressure in the core Stability of H-mode plasmas related safety factor profile: q(r)
q = 3/2 and q = 2:
Neoclassical Tearing Modes (NTMs):
• limit the achievable β ≡ 2µ
0p/B
2• degrade confinement (+ disruptions)
• often triggered by sawteeth.
H-mode: Limitations
0 1 2 3 4 5
0.5 1
r/a
H-mode, q-profile
q = 1
0
q = 3/2
q = 2
• ITER work point is chosen
conservatively: b
N£1.8 !
Neoclassical Tearing Mode (NTM)
29
ASDEX Upgrade
f
b f
b aB
I
N t(%)=
Neoclassical Tearing Mode (NTM)
30
• Pressure flattening across magnetic islands due to large transport coefficients along magnetic field lines
p
Neoclassical Tearing Mode (NTM)
31
0.4 0.8 1.2
Pressure(kPa)
6620
Temperature(keV)
Radius (m) 0.7
0.6 0.5 0.4 0.3 0.2 0.1 0.8 0.6 0.4 0.2 0
EFIT q=2 surface magnetic estimate
12cm inboard 2/1 island
• Pressure flattening across magnetic islands due to large transport
coefficients along magnetic field lines
Neoclassical Tearing Mode (NTM)
32
q
0< 1: Sawtooth instability, periodic flattening of the pressure in the core Stability of H-mode plasmas related safety factor profile: q(r)
q = 3/2 and q = 2:
Neoclassical Tearing Modes (NTMs):
• limit the achievable β ≡ 2µ
0p/B
2• degrade confinement (+ disruptions)
• often triggered by sawteeth.
H-mode: Limitations
0 1 2 3 4 5
0.5 1
r/a
H-mode, q-profile
q = 1
0
q = 3/2
q = 2
• ITER work point is chosen conservatively: b
N£1.8 !
K. Miyamoto, “Controlled Fusion and Plasma Physics” Taylor & Francis (2007)
q
0< 1: Sawtooth instability, periodic flattening of the pressure in the core Stability of H-mode plasmas related safety factor profile: q(r)
q = 3/2 and q = 2:
Neoclassical Tearing Modes (NTMs):
• limit the achievable β ≡ 2µ
0p/B
2• degrade confinement (+ disruptions)
• often triggered by sawteeth.
H-mode: Limitations
0 1 2 3 4 5
0.5 1
r/a
H-mode, q-profile
q = 1
0
q = 3/2
q = 2
• ITER work point is chosen conservatively: b
N£1.8 !
q
95(µ 1/I
p) = 3: Safe operation at max. I
PPeriodic collapses of
the ETB (ELMs)
q
95=3
35
Edge Localised Mode (ELM)
• Example of sawteeth and ELMs
JET, Pulse 52022
36
Edge Localised Mode
Disruption
Edge Localised Mode (ELM)
37
Edge Localised Mode (ELM)
t(s)
t(s)
Power Supply Limit
Inherent drawback of Tokamak!
Faraday‘s law
ds dt B
v d
S
× -
= ò
H-mode: Limitation
38
Plasma Current
PF Coil Flux [Wb]
[MA]
Faraday‘s law
ds dt B
v d
S
× -
= ò
H-mode: Limitation
39
I
CB
TB
PI
PI
OHdt
dI
CBy
induction
I
P= I
OH+
INIStandard inductive operation
steady state scenario: producing continuous fusion power in a tokamak reactor.
I
P= 0 + I
NINon-inductive operation
40
References
- E. Joffrin, “Advanced tokamak scenario developments for the next step”, 34th EPS Conference, Warsaw 2007
- A. C. C. Sips, Seminars