Japan-Korea : Workshop on Physics of Wave Heating and Current Drive, NFRI, Daejon, Korea, Jan. 14-15, 2008

Design study for JT-60SA ECRF systemand

the latest results of JT-60U ECRF system

Takayuki KOBAYASHI, Shinichi MORIYAMA, Kenji YOKOKURA, Mitsugu SHIMONO, Koichi HASEGAWA, Masayuki SAWAHATA,

Sadaaki SUZUKI, Masayuki TERAKADO, Shinichi HIRANAI, Koichi IGARASHI, Fumiaki SATO, Kenji WADA, Takashi SUZUKI,

Shinichi SHINOZAKI and Tsuneyuki FUJII

Japan Atomic Energy Agency

Japan Atomic Energy AgencyRR FF-

& ICLHRFRF &EC RF

60JTRR FF

-

& ICLHRFRF &EC RF

60JT

JTJT--60 RF group60 RF group

Contents

I. Design study for JT-60SA ECRF system• Outline of JT-60SA and the ECRF system

• Design study of antennas by a numerical code

II. The latest results of JT-60U ECRF system

• System upgrades

• 1.5 MW for 1 sec oscillation experiment

III. Summary

I. Design study for JT-60 SA ECRF system

1-1. Outline of JT-60Super Advanced (JT-60SA)A Combined project of A Combined project of •• Japanese national project (former JTJapanese national project (former JT--60SC or NCT)60SC or NCT)•• ITER satellite tokamak project.ITER satellite tokamak project.

(Collaboration between EU and Japan)2.59 / 2.72Toroidal Field Bt (T)

4.0 / 6.7 Shape Parameter, S

3.10 / 2.64Aspect Ratio, A

3.5 / 5.5

1.02 / 1.14Minor Radius (m)

4 x 1021Neutron (year)

10 MW/m2PFC wall load

7 MWECRF

34 MWNBI

41 MW x 100 sHeating & CD power

100 sFlattop Duration

3.0 / 3.77Safety Factor q95

0.33 / 0. 57Triangularity, δ95

1.7 / 1. 83Elongation, κ95

3.16 / 3.01Major Radius (m)

Plasma Current Ip(MA)

D2 main plasma + D2 beam injection

ITER similarhigh-S for DEMO

1-2. Overview of JT-60SA ECRF System

Maintenance Space

Torus HallTorus HallTorus Hall

Gyrotron room (4th floor)Gyrotron room (4Gyrotron room (4thth floor)floor)

1.25”x4

P1P1

P4P4

P11P11

P8P8

2.5”x5

Gyrotrons and Power Supplies

110 GHz 4 units : 1 MW / 100 sJT-60U ECRF system will be upgraded

140 GHz 5 units : 1 MW / 100 sIt will be newly fabricated!

3 gyrotrons : provided by EU2 gyrotrons : developed by JA

5 units of power supplies by EUInjection power & pulse duration

3 MW / 100 s @ 110 GHz4 MW / 100 s @ 140 GHz

Total 7 MW /100s

110 GHz 140 GHzAll components of the transmission lines will be developed by JA. Reuse / Upgrade New

2-1. Key Issues of transmission systems

Key Issues !!

• All Gyrotron systems can be operated at 1 MW output powerwith 100 s pulse duration.Transmission lines also enable operation of 1 MW for 100 s.

• Maintenance in JT-60SA Torus Hall is limited owing to high neutron fluence. Only by a remote handling technology is acceptable in vacuum vessel.

I. Cooling systems are required, miter-bends, antennas…

II. High reliability is required, especially in-vessel-components, such as antenna.

Now we are in the phase of basic design study.

• JT-60SA can produce various plasma shapes with toroidal field of 1.5 – 2.7T.(ITER like single null, double null…).

III. Various positions of the electron cyclotron resonance surfaceshould be covered by the same antenna.

2-2. Conceptual Designs of ECRF Antenna

Curved Mirror

Cooling Channel

Driving Mechanism

Straight Moving Mirror

Corrugated Waveguide

Linear Motion Antenna

Corrugated Waveguide

Focusing Mirror(Toroidal angle control)

Flat Mirror(Poloidal angle control)

Straight Moving RodRotating mechanism

Rotating mechanism

Flexible Cooling Unit

2-D Scan Antenna

Two types of antennas are now under consideration.

3-1. Principle of a Linear Motion Antenna

dmax=0.6mdmin=0.2m

φ63.5mm WG

-27deg

58 deg

Side ViewSide View

Upper ViewUpper View

0.48mCannel for coolant (fixed)

The linear movement of the flat mirror change the location of reflection on the curved mirror, and alters the beam angle.

Drive shaft can be used as a “rigid” water-cooling channel. Bellows or flexible parts can be placed outside VV.

Low risk of water leakage, low frequency of maintenance inside VV

Cannel for coolant (linearly movable)

Flexible tube

3-2. First Design and Numerical AnalysisFirst design of a linear motion antenna was done in 2006 based onthe geometrical-optics, in which an ideal lens and para-axial beam were assumed*.Portheight : 480 mmwidth : 480 mmangle : 35.5 degreeCurved Mirror (M2)surface : cylindricalcurvature : 700 mm

In actual, the cylindrical mirror dose not work as an ideal lens and beam into the curved mirror is not para-axial beam.

x (m

m)

z (mm)y (

mm)

Waveguide end Linearly moved mirror : M1

Fixed cylindrical mirror : M2

Plasma

* S. Moriyama et al., Fusion Engineering and Design, Volume 82, Issues 5-14, October 2007, Pages 785-790** Y. Tatematsu et al., Japanese Journal of Applied Physics 44, No. 9A, 6791-6795, 2005.

Expected injection angleangle : -27 ~ 58 degree

( from port axis)

To clarify the property of RF propagation, radiation power profiles were evaluated bya numerical code** based on the Huygens-Fresnel formula.

Large curvature Similar to a flat mirror on each reflecting position.Small curvature Is there an undesirable deformation of beam profile?

3-3. RF Profile at Resonance Surface

40 deg 20 deg

0 deg

-20 deg

Toroidal direction

Pol

oida

l dire

ctio

n

Radiation power profiles in this design were evaluated around the resonance surface.

Profile is almost bi-Gaussian and the significant deformation was not found.

Vertical Expansion of profile on the lower side owing to…

2) Effect of mirror curvature

1) Incident angle into the surface(~ 1/sin θ)

Can it be minimized by adjustments of the mirror curvature?Does the adjustment conflict with wide range incident angle?

This can not be avoided. Injection to lower position from the upper inclined port causes large vertical expansion.

1500 mm

40

20

0

-20

θ

3-4. Optimization of the Mirror Curvature

z (mm)

x (m

m)

Geometry of curve mirrors

Mirror shapes having various curvatures fit into the JT-60SA port.

Incident Angle (degree)

Larger curvature makes narrower profile.In the case of R=1000mm, vertical expansion is relatively small, wvertical/whorizontal ~ 1.3Upper half range (0 ~ 58 deg) is available

Optimization and clarification of the antenna performance will be continued.

0

50

100

150

200

500 600 700 800 900 10001100

Wvertical

Whorizontal

1/e

radi

us o

f ele

ctric

fiel

d [m

m]

Curvature of cyrindrical mirror [mm]

Expected radius with an ideal lens assumption

Smaller curvature makes wider incident angle.Expected Full range incident angle (-27 ~ 58 deg) is available at R < 700 mm.In that case, wvertical/whorizontal ~ 2.0

0.8

0.9

1

1.1

-30 -20 -10 0 10 20 30 40 50 60

R 600mmR 700mmR 800mmR 900mmR1000mmTr

ansm

issi

on E

ffici

ency

Ptota

l -P

spill

over

on m

irror

s

Ptota

l

4-1. 2D-scan Antenna

How to cool the antenna? Flexible spiral tube? Other flexible materials?

Toroidal and poloidal cross sectional views of the 110 GHz antenna

Toroidal Sectional View

Poloidal Sectional View

Straight Moving Rods for Rotating and Steering

Converging Mirror

480

Steering Mirror

Rotating Mechanism

Steering Mechanism

0 0.5 1 m

Bellows

480

Corrugated Waveguide CasingAntenna Support

Stabilizing Baffle Plate Cryostat WallVacuum Vessel Wall

ECRF

ECRF

Schematic view of the antenna installed into the NCT upper port

RF Gate Valve

Supports for the Antenna System

Cryostat

Vacuum Vessel

Stabilizing Baffle Plate

ECRF Antenna

Torus Window

Mirror Driving System

0 1 2 3 m

+25(58) deg

-60(-27)-43(-10)

-33(0)

Beam angle (from the antenna axis)

Toroidal and poloidal cross sectional views of the 110 GHz antenna

Toroidal Sectional View

Poloidal Sectional View

Straight Moving Rods for Rotating and Steering

Converging Mirror

480

Steering Mirror

Rotating Mechanism

Steering Mechanism

0 0.5 1 m

Bellows

480

Corrugated Waveguide CasingAntenna Support

Stabilizing Baffle Plate Cryostat WallVacuum Vessel Wall

ECRF

ECRF

Schematic view of the antenna installed into the NCT upper port

RF Gate Valve

Supports for the Antenna System

Cryostat

Vacuum Vessel

Stabilizing Baffle Plate

ECRF Antenna

Torus Window

Mirror Driving System

0 1 2 3 m

+25(58) deg

-60(-27)-43(-10)

-33(0)

Beam angle (from the antenna axis)

The antenna needs water-cooling system in long pulse operation, 1MW x 100 s.

An idea of using a carbon sheet is now under consideration.

4-2. First Design of Focusing Mirror

First design of the focusing (ellipsoidal) and the flat mirror was done by using the numerical code.

Long distance from the WG end to the focusing mirror will make good focusing property.On the other hand, the size of the focusing mirror is limited due to the port size.Here, the distance is set to 800 mm.Focusing property will be adjusted by the focus point of ellipsoidal plane which is shown as D.

Calculation parameter.D : position of one of

the focus points (fa).

WG(φ63.5mm)

800mm

10 °

370mmDistance from the flat mirror (L)

Dfa

fb

480mm

3000 mm

160mm

The port has relatively wide area compared with that of JT-60U.Good focusing performance is expected.

JT-60U antenna

0

20

40

60

80

100

-200 0 200 400 600 800 1000

5001000150020002500

1/e

elec

tric

field

radi

us [m

m]

D : Distance between WG-end and one of the focus points (fa) [mm]

4-3. Focusing Property

Narrow beam radius in wide region will be favored in JT-60SA due to various positions of the resonance surface.

5001000

15002000

2500Good focusing performance!

In this parameter, D ~ 600 mm, beam radius less than 60 mm in wide region!Therefore, this antenna will produce narrow EC driven current profile for various plasma shapes!

Distance from flat mirror (L)

L

5. Summary of Present Antenna Design

Linear motion antenna

Advantage

Higher reliability of cooling system with wide poloidal injection angle.

Disadvantage

Relatively wider beam width for lower side.

2-D scan antenna

Advantage

Good performance of beam focusing in wide region.

Disadvantage

Require an idea of a flexible cooling structure with high reliability.

Two types of antennas were evaluated by the numerical code.

II. The latest results of JT-60U ECRF system

0.1

1

1 10

3

0.3

3 30 80

Inje

cted

Pow

er (

MW

)

Pulse Duration (s)

2002

Objectives

2006

Construction : 1998 Full operation : 2001

4 high power gyrotrons4 transmission lines (HE11 mode)2 antennas (launchers)

Injected RF energy10 MJ (2.8 MW x 3.6 s) by 2002

Long Pulse Operation45 s (0.35 MW) by 2004

JT-60U Tokamak(cross sectional view of vacuum vessel)

Antenna A & B

Transmission Lines 1 MW, 5 s at 110 GHz each

#1

#2

#4

#3

Gyrotrons

1. Status of ECRF system in JT-60U

2. The latest upgrades of the system in 2007

Tank Load

Main-WG Load by GA

RF from gyrotron1.88m

Sliding support

Vacuum Pumping

Vacuum Pumping

Pre-WG Load by GA

Vacuum Pumping

High power dummy load system

1.5MW,CW,Att:50%

1.0MW,CW,Att:75%

1.0MW,5s

EH11 HE11

Si3N4 DC break Some improvements of gyrotron were carried out to achieve the longer pulse and the higher power.

Si3N4 DC break was installed instead of alumina.

Cavity cooling water flux was increased about 20 %.

Some minor modifications.

High power dummy load system was installed in gyrotron room, it enables gyrotron aging up to 1 MW - 40 s (40 MJ).

3. 1.5MW for 1s at 110 GHz by JT-60U gyrotron

NEXT step:Improvement of the mode converter planned in this year will enable longer pulse test for JT-60SA.

020406080

100120140160180200

0 2 4 6 8 10

Temperature on 1.5MW 1sec oscillation

Tem

pera

ture

(deg

)

Time (s)

Collector (middle part)

Cooling water for DC break

RF

Boiling temperature at 3-5 atmCavity

JT-60U (@110GHz, 2007)

JT-60U (@110GHz, ~2006)

JAEA for ITER (@170GHz, ~2007)

Effective pulse length for present Tokamak experiments

Pulse length for ITER

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0.1 1 10 100 1000 10000

Gyr

otro

n ou

tput

pow

er (M

W)

Pulse length (s)

Longer pulse trial, such as 2 sec, will be done with detailed temperature measurements of some components.

Ref. “State-of-the-Art of High Power Gyro-Devices and Free Electron Masers Update 2006” by Dr. M. Thumm

Current status of Design study for JT-60SA ECRF system was shown.

Until now,

・Conceptual specification of ECRF system was shown.

・Two types of antenna have been considered.

・Numerical studies for RF propagation by a linear motion antennaand a conventional 2-D scan antenna were carried out.

・Heat transport by a carbon sheet is now under consideration. (not presented today)

Those design study will be continued until 2010.

The latest results of JT-60U ECRF system was shown.

・ Some improvements of the system were carried out.

・ High power trial was done and 1.5 MW/ 1 sec oscillation was successfully achieved.

III. Summary