Conceptual Design Report on JT-60SA DC current of main power supply in the table is determined...

Conceptual Design Report on JT-60SA

3.9 ECRF System Sec.3.9

3.9 ECRF System 3.9.1 Outline The electron cyclotron range of frequency (ECRF) system for JT-60SA is used for electron cyclotron heating (ECH) and electron cyclotron current drive (ECCD) with the maximum pulse duration of 100 s to generate or sustain high performance plasmas, assistance of plasma start-up to reduce the maximum value of loop voltage and cleaning the first wall of the vacuum vessel. It is composed of two different frequency systems, that is, 110GHz and 140GHz systems to be applicable for a wide range of plasma parameters. Main specifications are listed in Table 3.9-1 and a bird’s-eye view of the ECRF system is shown in Fig.3.9-1. The ECRF system consists mainly of high voltage power supplies, high power gyrotron sets, transmission lines, launcher (antenna) systems, evacuating systems for lines and launchers, and cooling systems.

Table 3.9-1 Main Specifications of ECRF System on JT-60SA.

110 GHz System 140 GHz System Frequency 110 GHz 140 GHz Max. Power into plasma 3 MW 4 MW Max. Pulse Duration 100 s 100 s Number of Units 4 5 Number of Launchers 2 2 Duty Cycle 1/18 or 1/40 1/18 Max. Power at Gyrotron Window

1 MW 1 MW

Max. Power at MOU Output ~ 0.94 MW ~ 0.94 MW Transmission Efficiency ~ 81% ~ 86 % Transmission Mode HE11 HE11 Transmission Length ~ 60 m/line ~ 70 m/line Diameter of Waveguides 31.75 mm 63.5 mm

Actual composition of the 110GHz system will be basically similar to the present JT-60U ECRF system (3 MW x 5 s at 110 G Hz with 4 gyrotrons) [3.9-1], which was constructed in 2001 on the basis of the International Thermonuclear Experimental Reactor (ITER) gyrotron development in Japan Atomic Energy Research Institute (JAERI) [3.9-2,3] and has been successfully operated. So far RF energy of 10 MJ (2.8 MW x 3.6 s) was injected into plasmas in JT-60U and high gyrotron output power of 1.2 MW for 4 s were attained [3.9-1,4]. As the frequency is the same in both systems, the components of the JT-60U ECRF system will be reused in the 110GHz system as many as possible. However, the maximum pulse duration is 100 s, quite longer than 5 s in the JT-60U ECRF system. Then four gyrotrons and two main power supplies should be newly fabricated and two main power supplies should be upgraded. Many components of transmission lines in the JT-60U ECRF system will be reused. The transmission lines also will be evacuated around 10-4 Pa to keep voltage stand-off capability for high power transmission at 1 MW levels. However, cooling and evacuating systems will be upgraded for extended pulse duration. Launchers



2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

ITER

JT-60SA

JT-60U

Construction

Construction

Operation

Operation

Operation

System Design

Gyrotron Set

Antenna(Launcher)

System

JT-60SA ECH System Construction / Modification Operation

Fabrication of some parts Basic Design Detailed Design

Design / Calculation First gyrotron : Fabrication / test

Gyrotrons : Fabrication / test

Antennas : Fabrication / test

First antenna : Fabrication / testDesign / Calculation

Commissioning / Conditioning

(R&D Works for the NA Part)


FY 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018

ITER

JT-60SA

JT-60U

Construction

Construction

Operation

Operation

Operation

System Design

Gyrotron Set

Antenna(Launcher)

System

JT-60SA ECH System Construction / Modification Operation

Fabrication of some parts Basic Design Detailed Design

Design / Calculation First gyrotron : Fabrication / test

Gyrotrons : Fabrication / test

Antennas : Fabrication / test

First antenna : Fabrication / testDesign / Calculation

Commissioning / Conditioning



FY

should be developed which can control the injection angle of RF beams both in the poloidal and toroidal directions. On the other hand, most of components of the 140GHz system will be fabricated newly except for the AC power lines. Its composition is the same as the 110GHz system. However, as the transmission lines will be newly fabricated, wider waveguide components with the diameter of 63.5 mm will be used. So higher transmission efficiency from the matching optics unit (MOU) to the antenna input of ~86 % is expected and more stable high power transmission will be carried out at 1 MW levels.

Fig. 3.9-1 Bird’s-eye view of the ECRF system on JT-60SA.

Table 3.9-2 shows a rough construction schedule of the ECRF system. There are two points to strongly affect the construction process. One point is that the JT-60U will be operated until

Table 3.9-2 Construction Schedule of the ECRF System.



FY2010 and the other point is that the operation of the ECRF system on JT-60SA will be started in FY2014. So, basic and detailed design works in both 110GHz and 140GHz systems will becontinued until FY2009 in order to reflect the latest progress in the ECRF heating technology, especially the gyroton and launcher fields. Then the fabrication and modification will be started in FY2010. The installation and test will have to bedone within 3 years to keep the schedule. In this phase, it is supposed that the installation will be complicated in the torus hall because the construction of other components of the JT-60SA will be also at their climax.



3.9.2 Power Supply The power supply system is fed with the large capacity (198 MVA) transformer of the JT-60 power supply. Specifications of the transformer are given in Table 3.9-3. The incoming AC power is at 18 kV with frequency of 50 Hz.

Table 3.9-3 Specifications of Feeding Transformer of the JT-60SA Power Supply.

Figure 3.9-2 indicates outline of the power supply system. Three gas circuit breakers (GCB) are used for nine high voltage power supplies of existing four GCBs. In detail, GCB#1 is for four power supplies in the 110GHz system, GCB#2 for two power supplies in the 140GHz system and GCB#3 for three power supplies in the 140GHz system. Main specifications of the GCB are the maximum rating voltage 24 kV, maximum rating current 1.2 kA and breaking current 25 kA. Protecting coordination has to be established considering specifications of the transformer and GCB. In the 110GHz system, two DC generators (DCG) will be fabricated and other two DCGs upgraded. Existing smoothing circuits (FCB) will be modified. Fast switching circuits (IGBT switches) and acceleration power supplies will be reused. Most of components of the power supplies will be made in the 140GHz system. The high voltage cables probably can be reused in both systems, indeed depending on their design. The DCGs in both systems will be installed in the transformer yard outside the heating power supply building.

Fig. 3.9-2 Outline of power supply system in the ECRF system.

Specifications of the power supply are listed in Table 3.9-4. The specifications must be matched to the gyrotrons used actually in the system. So it is possible that some specifications will be changed. The DC current of main power supply in the table is determined assuming some reduction of gyrotron efficiency in the series of practical operation. Typical gyrotron efficiency in the best

#1

#2

#3

GCB DCG FCB

300 m Cable

IGBT Switch & Acceleration P/SGyrotron set

110GHz JA

140GHz JA

140GHz EU

Switching device & Acceleration P/S

JT-60SApowersupply

Transformer Capacity 198 MVA % Impedance 18 % at 198 MVAPrimary Voltage 275 kV Secondary Voltage 18 kVFrequency 50 Hz



condition will be ~45 %, however in the experiences of gyrotron operation in JT-60U, the gyrotron parameters are required to be re-adjusted in the series of experiments to refuse termination of the oscillation during the scheduled pulse length. The beam current of the JT-60U gyrotron tends to decrease during the pulse due to cathode cooling by electron emission. To keep the oscillation condition, a delicate adjustment is required with refusing influence of electromagnetic noises from the Tokamak and other heating systems etc. As a result, the practical gyrotron efficiency tends to be less than ~35%. Reasonable margin of the power supply capability will significantly enhance the reliability and availability of the ECH system. Duty cycle is decided for operation where a 100s pulse shot can be repeated in 30 minutes. The acceleration or body power supplies are strongly affected by what type of electron gun will be used in the gyrotron in the 140GHz system. In this conceptual design, some parameters are not fixed. One of plasma instabilities limiting high plasma performances is neoclassical tearing mode (NTM) instability. The NTM instability was suppressed by ECH/ECCD when the EC beam aimed the position of the NTM instability [3.9-5,6]. Recently, the NTM instability seems to be efficiently suppressed when the EC power is modulated with the frequency same as that of the NTM instability. The power Modulation at 2~3 kHz has been achieved by switching the anode voltage in the 110GHz system of JT-60, and the frequency seems to be close to the limit of the power supply circuit which will be used in JT-60SA as it is. In 140 GHz system, the acceleration voltage will be chopped by the newly fabricated voltage modulation circuit and the modulation frequency will possibly be close to 5 kHz. It is preferable that the voltage modulation circuit is composed of solid-state components.

Table 3.9-4 Main Specifications of Power Supply for the gyrotrons

he gyrotron used in the 110GHz system will have a triode electron gun, which seems to be

110 GHz System 140 GHz System Tsimilar to that in the present 110GHz system. So, figure 3.9-3 shows the power supply system with a triode gun gyrotron in the 110GHz system. On the other hand, in the 140GHz system, gyrotrons made in Japan probably will have the triode gun while those made in EU the diode gun. An example of power supply for the 140 GHz triode gun gyrotron by JA is shown in Fig. 3.9-4. The high voltage power supply system can be used for the gyrotron basically adding the anode voltage controller, and also for the JA 110GHz gyrotron. A voltage modulation circuit must be introduced, which modulates the acceleration voltage. A fast switching circuit, such as IGBT switch, must be

Main Power Supply DC Voltage ~ 65 kV * 60 - 70 kV *DC Current 65 A 65 APulse Duration 100 s 100 s or CWVoltage Ripple < 1 % < 1 %*Duty Cycle 1/18 (new product) 1/18 or CW

1/40 (modified) Power Factor > 0.8 > 0.8

Acceleration (Body) Power SupplyDC Voltage 50 - 90 kV * 50 - 90 kV *DC Current 0.3 A < 0.3 APulse Duration CW CWVoltage Ripple < 0.5 % < 0.5 % *

Voltage Modulation Frequency > 1 kHz 5 kHz

* These specifications should be matched to the gyrotrons used

110 GHz System 140 GHz System

Main Power Supply DC Voltage ~ 65 kV * 60 - 70 kV *DC Current 65 A 65 APulse Duration 100 s 100 s or CWVoltage Ripple < 1 % < 1 %*Duty Cycle 1/18 (new product) 1/18 or CW

1/40 (modified) Power Factor > 0.8 > 0.8

Acceleration (Body) Power SupplyDC Voltage 50 - 90 kV * 50 - 90 kV *DC Current 0.3 A < 0.3 APulse Duration CW CWVoltage Ripple < 0.5 % < 0.5 % *

Voltage Modulation Frequency > 1 kHz 5 kHz

* These specifications should be matched to the gyrotrons used



provided to protect the gyrotron when it has electrical breakdown, and therefore no crowbar circuit using tubes is provided. Shut-off speed is less than 10 μs. An example power supply for the 140 GHz diode gun gyrotron by EU is shown in Fig. 3.9-5, the main power supply (driving the beam current) can be designed to be the same as that for the triode gun gyrotron, including the fast switching circuit for protecting the gyrotron. The body power supply can be connected between the body and collector in the 140GHz system if Vkb is regulated at the stability of less than 0.5 %.

Fig. 3.9-3 Power supply system for a 110GHz triode gun gyrotron.

Fig. 3.9-4 Example of power supply system for a 140GHz triode gun gyrotron.

Fast Switching Device of Solid-State ComponentsMain DC

Generator

B

C

K

Body PS

Anode Voltage Controller

JA 140GHz Gyrotron(triode electron gun)

Surge Absorber

60 - 70 kV *65 A

< ~ 50 kV *< 0.3 A *

Smoothing Circuits

100 kV, 100 A*On/Off speed

< 10 μs

* These values should be optimized

A

Fast Switching Device of Solid-State ComponentsMain DC

Generator

B

C

K

Body PS

Anode Voltage Controller

JA 140GHz Gyrotron(triode electron gun)

Surge Absorber

60 - 70 kV *65 A

< ~ 50 kV *< 0.3 A *

Smoothing Circuits


< 10 μs

* These values should be optimized

A

RF PowerAC DC

100kV, 300mA

C

H

A

B

K

Gyrotron

OpticalSignal

Controller

Functional Generator

Heater P/S

AnodeVoltageController

Body P/SDC Generator

IGBTSwitch

100 kV, 100 A

Electron Beam

Heater Controller

Main P/S

DC Break

IC

JT-60USA Control System

Local Control(sequencer)

Timing Generator

1 MW

#1

#8#9

••

•••

GCB #1

GCB#3

18 kV / 60-70 kV65 A

•

RF PowerAC DC

100kV, 300mA

C

H

A

B

K

Gyrotron

OpticalSignal

Controller

Functional Generator

Heater P/S

AnodeVoltageController

Body P/SDC Generator

IGBTSwitch

100 kV, 100 A

Electron Beam

Heater Controller

Main P/S

DC Break

IC

JT-60USA Control System

Local Control(sequencer)

Timing Generator

1 MW

#1

#8#9

••

•••

GCB #1

GCB#3

18 kV / 60-70 kV65 A

•



Fig. 3.9-5 Example of power supply sy tem for a 140GHz diode gun gyrotron.

.9.3 Gyrotron System

gyrotron is only a high power oscillator in the millimeter wave frequency range. High power

Fig. 3.9-6 yrotron. A diamond cond pulse

s

3 Agyrotron development aiming 1 MW for tens seconds above 100 GHz was progressed very much by the ITER gyrotron development activity in 1990s [3.9-2,3]. Figure 3.9-4 indicates a conceptual view of such a high power and long pulse gyrotron. There are several strong points in such a gyrotron. An oscillation mode in the cavity is quite higher mode, for example TE31,8, which reduce the dissipation on the cavity wall so as to obtain 1 MW output power.

Conceptual view of a high power and long pulse gwidow can transmit a Gaussian mode of the output power for tens se

RF

CavitySCM

Electron gun

Quasi-optical mode converter

DC Break

Acceleration voltage

Main DC voltage

Diamond Window

Deceleration voltage

CPD

Diamond Window

CPD

Fast Switching Device of Solid-State Components

Main DC Generator B

C

K

Body PS

~ 1 MΩ

EU 140GHz Gyrotron(diode electron gun)

60 - 70 kV *65 A

< ~ 50 kV *< 0.3 A *

Smoothing Circuits


< 10 μs

* These alues should be optimized

Surge Absorber

v

VkbFast Switching Device of Solid-State Components

Main DC Generator B

C

K

Body PS

~ 1 MΩ

EU 140GHz Gyrotron(diode electron gun)

60 - 70 kV *65 A

< ~ 50 kV *< 0.3 A *

Smoothing Circuits


< 10 μs

* These alues should be optimized

Surge Absorber

v

Vkb



duration because of its quite high heat conductivity and low dielectric loss tangent. Insulation between collector and body enables collector potential depressed (CPD) operation which leads to higher efficiency. Direct cooling of a superconducting magnet with a cryo-refrigerator and without a liquid helium system, makes it easier operating.

Table 3.9-5 Specifications of Gyrotron and Super Conducting Magnet for JT-60SA.

110 GHz

System(JA) 140 GHz

System (JA) 140 GHz System

(EU) Gyrotorn Frequency 110 GHz 140 GHz 140 GHz Max. Power at Gyrotron Window 1 MW 1 MW 1 MW Output Mode Gaussian Gaussian Gaussian Max. Power at MOU Output 0.94 MW 0.94 MW 0.94 MW Max.Pulse Duration 100 s 100 s 100 s

Operation Mode Depressed Depressed Depressed Collector Collector Collector

Efficiency > 40 % > 40 % > 40 % Super Conducting Magnet Max. Magnetic Field ~ 4.5 T ~ 7.0 T 5.7 ~ 7.0 T (TBD) Bore Diameter > 0.24 m > 0.24 m > 0.22 m Cooling Method Direct Cooling Direct Cooling Direct Cooling

(No Liquid He

System) (No Liquid He

System) (No Liquid He

System)

gyrotron for JT-60SA should fulfill specifications shown in Table 3.9-5. In this year of 2006, a Agyrotron has been developed with 0.6 MW for 1000 s at 170 GHz for ITER, based on this concept in Japan Atomic Energy Agency (JAEA) [3.9-7]. Then the gyrotron for JT-60SA becomes quite realistic. Set of a gyrotron, a super conducting magnet (SCM) system including its power supply, a heater power supply, an ion-pump power supply, a matching optics unit (MOU), and local control units for these parts is defined as “gyrotron set”. Three of the gyrotron sets for 140 GHz will be provided by EU and the rest of the gyrotron sets will be by JA. When the gyrotron requires special additional equipments near by gyrotron for cooling, e.g., a heat exchanger, a pump for pressurize, or chiller for special coolant, in addition to the usual water cooling supply system, these equipments are included to the gyrotron set. The detailed specifications of gyrotron system are determined after further discussions between EU and JA. The maximum SCM field strength of 7 T for the 140 GHz system will enhance the flexibility of output frequency expecting future improvement of gyrotron. Japanese manufacturer developed direct cooling SCM of 10 T in 1995 and provided a direct cooling SCM up to 7 T for gyrotron. When no expansion of the frequency range in future is expected for the EU gyrotrons, the maximum field strength will be ~ 5.7 T for these gyrotrons. The MOU converts the Gaussian mode of gyrotron output to the HE11 mode of the transmission mode with high conversion efficiency of 94 % in JT-60U and the similar efficiency will be expected for the new 140 GHz system.



3.9.4 Transmission Line

he gyrotron room is located in the 4th floor of the JT-60SA building adjacent to the torus hall. TThe layout of the transmission lines between the gyrotrons and the antennas is briefly designed as shown in Fig.3.9-5. JAEA has a responsibility of fabrication and setting up all the nine transmission lines for 110GHz and 140 GHz systems. The average of the transmission line length is roughly 70 m. A large part of JT-60U waveguides and transmission components for 110 GHz system will be reused for JT-60SA with some modifications especially for extension of the pulse length from 5 sec to 100 sec at 1MW/line. The corrugated waveguides have inner diameter of 31.75 mm (1.25”) and the transmission mode is HE11 and they will be evacuated < 10-3 Pa to avoid arcing in high power transmission of 1 MW / line. Because the antennas of JT-60U are located port-17 and 18 (P-17 and 18), the part of the waveguides close to the antenna for P-1 and 4 in JT-60SA should be set up newly. Five 140GHz waveguide lines will be newly fabricated and the inner diameter will be enlarged to 63.5 mm (2.5”) to enhance the transmission reliability by improving the vacuum conductance and reducing transmission power density.

Fig. 3.9-7 Layout of the transmission lines between the gyrotron hall and the torus hall.

he composition of the transmission line and the summary of the transmission loss of the

Tcomponents are shown in Fig. 3.9.7. A pair of polarizers with grooved rotating mirrors is used to optimize polarization. Vacuum pumping waveguides will be used to keep the pressure in the transmission line < 10-3 Pa. The location of the vacuum pumping waveguides should be designed carefully because the conductance of the waveguide itself is small. Two directional couplers will be equipped at MOU output and close to the antenna as RF monitors. A torus window featuring a



synthetic diamond disk will separate the vacuum regions of the vacuum vessel of JT-60SA and the waveguide with small transmission loss. The temperature rise of the torus window will be monitored by an infrared thermometer or very thin thermo couple for a real time power monitor. A DC break waveguide will separate the electric potential of JT-60SA and the ECRF transmission line system. An RF gate valve is used to keep the surface of the torus window clean when the vacuum vessel pressure is high, and also act as double shield when ECRF system is not in operation. An arc detector watching at visible light is used to protect the torus window from arcing. Many of the transmission components in JT-60U are water-cooled but some of the components including all the waveguides have to be improved to enable cooling for longer pulse operation up to 100 s. A short pulse (< 200 ms) dummy load is installed for tuning and initial conditioning of the gyrotron as well as calorimetric power measurement. A waveguide dummy load is used to test, tune and condition the gyrotrons for longer pulses. The special internal corrugations of the 31.75 mm waveguide made of nickel plated strengthened copper convert incident HE11 mode to an EH11 surface wave which absorbs about 80 % of the input power, and a tank dummy load attached at the outlet of the waveguide dummy load as a termination absorbs the rest of the power. The waveguide dummy load absorbs 1MW of continuous wave (CW) with 4 liters/sec water cooling at ~500 kPa pressure drop. A waveguide network with some waveguide switch enables connection to a waveguide dummy load from 3 ~ 5 gyrotrons.

windowDC break

RF gate valve

Antenna #1

unit 1 · · ·

unit 2 · · ·

unit 8 · · ·

unit 9 · · · ·

torus window

arc detector

vacuum pumping W/Gpolarizer-2

polarizer-1

W/G exchangerdirectionalcoupler

MOU

calorimetricdummy

1MW-cw W/Gdummy load

insertion mirrorwindow

corrugated W/G(63.5 mm diam)

Gaussianbeam

pumping

pumping

directionalcoupler

miter bend

gyrotron1 MW x 100 s

Antenna #4····

Gyrotron set

110 GHz 140 GHzCorrugated wave guide ~ 60m / ~ 70m ~4 % ~1 %Miter bend 5 5% 5%Directional coupler 2 2% 2%Polarizer 1 ~3 % ~3 %RF gate valve 1 1% 1%Others (window, DC break, etc) - ~3 % ~1 %

~18 % ~ 13 %

MOU (in gyrotron set) 1 6% ~ 6%(TBD)

Total RF dissipation / line

Components in transmission line Number / length RF dissipation

windowDC break

RF gate valve

Antenna #1

unit 1 · · ·

unit 2 · · ·

unit 8 · · ·

unit 9 · · · ·

torus window

arc detector

vacuum pumping W/Gpolarizer-2

polarizer-1

W/G exchangerdirectionalcoupler

MOU

calorimetricdummy

1MW-cw W/Gdummy load

insertion mirrorwindow

corrugated W/G(63.5 mm diam)

Gaussianbeam

pumping

pumping

directionalcoupler

miter bend

gyrotron1 MW x 100 s

Antenna #4····

Gyrotron set

110 GHz 140 GHzCorrugated wave guide ~ 60m / ~ 70m ~4 % ~1 %Miter bend 5 5% 5%Directional coupler 2 2% 2%Polarizer 1 ~3 % ~3 %RF gate valve 1 1% 1%Others (window, DC break, etc) - ~3 % ~1 %

~18 % ~ 13 %

MOU (in gyrotron set) 1 6% ~ 6%(TBD)

Total RF dissipation / line

Components in transmission line Number / length RF dissipation

Fig. 3.9-8 Transmission components and their RF losses.

he transmission loss highly depends on the number of the corner components in the design of the

Hz and 140 GHz systems are shown in Figs. 3.9-9 and 3.9-10

Ttransmission line layout as shown in the table of the losses in Fig. 3.9.8. The total RF losses from the MOU output to the antenna input are estimated to be 18 % for 110 GHz and 13 % for 140 GHz in the present plan of the layout. The waveguide layouts for 110 Grespectively. For 110 GHz transmission lines, present maintenance stages and waveguide support



close to P-1 will be reused. To reduce the corner components, the waveguides to P-4 antenna is designed to be a direct route rather than taking detour. They will be located over the beam line of the tangential NBI, and the maintenance stage for the waveguide close to the antenna should be carefully designed considering NBI maintenance. For 140 GHz transmission lines to P-11 and P-8, stages for JT-60 LHRF system will be reused and additional stage will be needed near antennas.

Fig. 3.9-9 Layout of the transmission lines for 110 GHz system in th orus hall. e T

Fig. 3.9-10 Layout of the transmission lines for 140 GHz system in the Torus hall.



The te utput mperature rises of the components by the RF losses measured in JT-60U at gyrotron opower of 0.5 MW for up to 21 s are shown in Fig. 3.9-11. The corner components were cooled by water, and waveguides themselves were not cooled directly. The temperature rise was not saturated completely at 21 s but is estimated to be saturated < 30s. Some methods to cool the waveguides are under consideration.

0

5

10

15

0 5000 10000 15000 20000 25000

Tem

pera

ture

rise

(deg

)

Pulse length (ms)

Polarizers

Miter bends

Directional couplersArc detector

0

5

10

15

0 5000 10000 15000 20000 25000

Tem

pera

ture

rise

(deg

)

Pulse length (ms)

Polarizers

Miter bends

Directional couplersArc detector

Fig. 3.9-11 Temperature rise of the components in JT-60U at 0.5 MW for up to 21 s

.9.5 Launcher System

our ECRF antennas will be installed to JT-60-SA. Two antennas for 110 GHz have to launch two

3 Fbeams from two waveguides per an antenna. One of the two antennas for 140 GHz has to launch two beams from two waveguides, and the other has to launch 3 beams from three waveguides as shown in Fig.3.9-12 and -13.

Fig. 3.9-12 Reference antenna design which enables two dimensional beam scan with two

steerable mirrors per line for the 110 GHz system.



The reference design at has proved good adopts the 2 directional beam scan mechanism thperformance and reliability in JT-60U. The mechanism consists of one rotary focusing (or flat) mirror at the end of the waveguide and one steerable flat mirror.

Fig. 3.9-13 Reference antenna design which enables two dimensional beam scan with two

this reference design, the ranges of beam angle are -60 to 25 deg in the poloidal direction and

be discussed. A water cooling for the antenna

concept with a mirror driven in the linear motion [3.9-8]

steerable mirrors per line for the 140 GHz system.

In-20 to 20 deg in the toroidal direction and it enables localized current drive and heating in the wide range of plasma shapes expected in JT-60SA. A casing of 3 m in length will be needed to locate the steerable mirror near the stabilizing baffle plate and connect to the flange outside the cryostat with a bellow. The casing lodges the wave guides, the drive shaft for the mirror and pipes for water cooling. The casing consists of a firm angle frame, thin plates having some holes to reduce the weight. Though the length of the antenna is long (~3.6m), the estimated weight is relatively light (0.8 ton), it thus will be supported by a firm stage outside the cryostat as a cantilever, adopting the same method as LHRF and ICRF antennas in JT-60 and JT-60U. Precise stress analysis is needed after the determination of the antenna structure, but the performance of the upper inclined LHRF antenna (3.37m, > 1 ton) in JT-60 encourages this supporting method. The mirror surface is copper plate attached to the stainless steel base by the diffusion bonding, and the other parts of the antenna will be made by stainless steel. Oil free bearings using ceramic ball etc. will be used at the rotation axes and the supports for the drive shaft. However the reference design has some points tomirror will be needed in JT-60SA unlike the JT-60U antenna, because of 100 s pulse duration, the mechanical buffer in the coolant feeder using bellow or flexible spiral tube have to be developed for this reference design. It is possible that the buffer mechanism limits the range or the speed of the mirror rotation. Moreover careful design will especially be needed for the cooling pipe joint to avoid the crack by repeated stresses. In addition, because the mirror will be steered using a link mechanism to convert linear motion of the drive shaft to the rotation, it is inevitable that the speed and accuracy of the steering is limited. As an alternative antenna design, a newhas been started to study. The new antenna eliminates the flexible tube for coolant supply or the link mechanism and will reduce the risk of water leakage and maintenance frequency.



The idea uses a simple principle that the reflection angle at the curved mirror can be changed by

space of the drive shaft is suitable for the coolant channel for the mirror cooling. The

the location of reflection by linear movement of the first flat mirror at the waveguide output or the second curved mirror along the port axis. The principle is shown in the Fig.3.9-14 taking the example of curved mirror movable case. Because the linear motion introduced from outside of the vacuum vessel can directly and simply drive the mirror, the risks of the trouble in the drive mechanism will be reduced and precision of the mirror angle will be improved by reducing backlash. The inner rotation mirror in the conventional antenna requires mechanical buffer structure with bellows or spiral flexible tubes, and has a risk of water leakage by repeated stress especially at the joint. Because the mechanical buffer locates outside the vacuum vessel and the cryostat in the new antenna concept, in the event of the water leakage, the influence is much smaller than in the vacuum vessel and the repair is easier.

Curved MirrorDrive Shaft

Cooling Channel

Driving Mechanism

Bellows Supports

Bellows for Cooling ChannelVacuum VesselPort

Fixed Plane MirrorWaveguide

FootingPlasma

Curved MirrorDrive Shaft

Cooling Channel

Driving Mechanism

Bellows Supports

Bellows for Cooling ChannelVacuum VesselPort

Fixed Plane MirrorWaveguide

FootingPlasma

Fig. 3.9-14 New antenna concept featuring a curved mirror driven in the linear motion.

the antenna with a mirror driven in the linear motion, the mirror size is determined by the

Inrequired beam angle range and the beam radius at the electron cyclotron resonance. The definition of the parameters and the polar coordinate (r, θ) for the beam angle analysis are shown in the Fig.3.9-15. The simplest case involves a spherical mirror having a curvature R that is assumed as the curved mirror. The origin of the coordinates O (0, 0) coincides with the center of the mirror curvature. The incident beam to the spherical mirror from the first flat mirror is assumed as perpendicular to the major radius of the torus (d/r = cos θ because the axis of a waveguide is usually oriented in the direction of the major radius and the launched beam is reflected by π/2 at the flat mirror. The concave mirror moves in the direction of the major radius. The incident (and reflection) angle to (and from) the normal direction of the spherical mirror surface, π/2 – φ, and the incident beam angle to the torus, α = 2φ – π/2, are functions of d, where d is the distance of the incident beam from (0, 0).



Fig. 3.9-15 Coordinate for design study of the antenna with linearly driven mirror.

The incident beam angle to the torus α = 2cos–1(d/R) – π/2 versus d/R is shown in Fig.3.9-16, where the ranges of the incident angle are used as an example for the JT-60SA, JT-60U, and ITER equatorial port antenna designs. Referring Fig.3.9-16, the required range of linear motion can be estimated for the required α. The spherical mirror with R = 1 m, e.g. gives the range of d from ~0.25 m to ~0.85 m, or one with R = 0.75 m gives ~0.2 m to 0.6 m.

Fig. 3.9-16 Incident beam angle to the torus α = 2 versus mirror parameter d/R.

Next, the beam radius at the EC resonance in the plasma was examined as a function of R. A

Gaussian-distributed millimeter-wave beam is assumed; this is described in the following equations [3.9-9].



I(r,z) = I0exp[–ip(z) – (w(z)–2 + ik/2R(z))r2], ip(z) = ln[w(z)/w0] – i(kz – ϕ), (eq. 3.9-1) ϕ= arctan(λz/πw0

2), (eq. 3.9-2) where I(r,z) is the intensity of the beam, R(z) is the radius of the wavefront curvature at z = z1, and w(z) is the beam radius, which is the e-folding length of the intensity of the Gaussian beam at z on the extension of the waveguide axis; k the wavenumber; λ the wave length; and w0 the beam radius at the waveguide end.

Fig. 3.9-17 Beam divergence and convergence toward the electron cyclotron resonance.

Thus, w(z) and R(z) are expressed as: w(z)2 = w0

2[1 + (λz/πw02)2], R(z) = z[1 + (πw0

2/λz)2]. (eq. 3.9-3) The coordinate is independent of Fig. 3.9-15, and the reflection at the first flat mirror is omitted in this examination. Therefore, the radius of the beam initially increases with z and is converged toward the beam waist following the spherical mirror, as shown in Fig. 3.9-17, and w1 at the spherical mirror, w2 at the beam waist, and w3 at the EC resonance in the plasma are expressed as shown in the figure. The antenna size was estimated by using these formulae. The assumed beam angle range is from α = - 27° to 58°. In Fig.3.9-18, the required range of d is plotted as a function of R in order to achieve a range of α which is estimated using Fig. 3.9.4-16. Here, dmin and dmax are the minimum and maximum of d, respectively, and Δd = dmax – dmin. Δd is the main parameter that determines the size of the spherical mirror, and the size in the direction of the major radius of the torus is estimated from Δd + 4w1 including a margin. Fig.3.9-18 also shows the beam radius at the EC resonance, w3, for various z1, which is the waveguide end–spherical mirror distance. Here we assumed the waveguide inner diameter as 0.06 m and beam radius at the waveguide end w0 as 0.02 m. We also assumed the distance between the antenna and the EC resonance as 2 m, and z3 is chosen as z2 + z3 = 2 m. In Fig.3.9-18, w3 decreases with R; however, the declination for R > 0.75 m is small. This shows that a reasonably small antenna having Δd of ~0.4 m and w3 < 0.07 m will be achieved with R of 0.75 m. Although smaller w3 is obviously suitable and preferable for the localized ECH/ECCD, w3 < 0.07 m is reasonable in comparison with that of the JT-60U antenna, ~0.04 m [3.9-10].



Fig. 3.9-18 Range of linear motion of the mirror which determines the mirror size depends on the beam radius at the EC resonance.

Larger z1 induces a decrease in w3 and an increase in w1, indicating that the heat density on the spherical mirror lessens. Accordingly, large z1 is preferable within permissible geometrical conditions of the antenna. Therefore, a linear motion antenna with an adequate beam steering angle range and a reasonably small beam radius at the EC resonance can be designed with a realistic size.

Fig. 3.9-19 Preliminary antenna design featuring a flat mirror driven in the linear motion and fixed curved mirror.



As a result of the design study, a preliminary antenna design compatible with the JT-60SA upper inclined port having cross section of 0.48 m square is shown in Fig.3.9-19. For the large range of the beam angle, the antenna needs relatively large mirror. In this case it is better way to drive the first flat mirror at the output of the waveguide instead of the large curved mirror. The beam radius at the curved mirror is a little larger than the case of curved mirror driven, but the change in the beam radius at the EC resonance is negligible. The beam scan of this alternative antenna design will be only in the poloidal direction to achieve full beam angle range as a return for the benefits of low risk for water leakage and low maintenance frequency. Two possible methods to enable both toroidal and poloidal beam scan with the alternative antenna design are under discussion. One is a combination with the remote steering concept [3.9-11] which enables full poloidal scan and ~±15° of toloidal scan. Another is adding toroidaly tilted flat mirrors with smaller curved mirror which enables 2/3 of the full poloidal angle range and ~±20° of toroidal scan. The type of the antenna should be chosen shortly and the antenna design will be finalized in 2010. 3.9.6 General site conditions General site conditions are described in this section to contribute to the detailed design especially for the power supply system and the gyrotron system. Some of these conditions will be able to modify as a result of further discussions between EU and JA. The table 3.9.6, 3.9.7 and 3.9.8 are condition of the primary cooling water at the gyrotron room, capacity of the low voltage power supply at the gyrotron room, and the environmental conditions of the transformer yard, the power supply building and the gyrotron room respectively. The table 3.9.9 shows the load conditions of these rooms. The Fig. 3.9.20-22 shows spaces for the power supply system on the geometry of the buildings. Though the original plan of the gyrotrons layout is shown in Fig.3.9.7, an alternative plan when the space for 140 GHz gyrotrons is too narrow is shown in Fig. 3.9.23.

Table 3.9.6 Condition of the primary cooling water at the gyrotron room

Pressure Temperature Electrical conductivity Supply 0.8~1 MPa ≤ 35 ˚C* ≤ 1 μΩ/cm

Return 0.15 Mpa ≤ 70 ˚C? - * Temperature of the secondary cooling water is strongly depends on the atmosphere temperature. Usually, Twater is lower than Tatmosphere by ~2˚C.

Flow rate Capacity of heat exchanger 110GHz 4.8 m3/min 420 kW 140GHz ≤ 17.2 m3/min* ≤ 2140 kW

Total 22 m3/min* 2560 kW * After possible modification of the water tubing between the cooling building and the gyrotron room.



Table 3.9.7 Capacity of the low voltage power supply at the gyrotron room

Distribution panel

PC10D PC10B

Total capacity 750 kVA 700kVA

Purpose For 140GHz system (Originally for ICRF)

For 140GHz system (Originally for LHRF)

For 110 GHz system

Voltage 420 V 210 V 210 V 105 V 210 V 105 V Individual capacity

700 kVA 50 kVA 300 kVA 40 kVA 325 kVA 30 kVA

Table 3.9.8 Environmental conditions

Temperature Humidity Transformer yard (out side) -13 ~ 42 ˚C 0 ~ 100 %

Heating power supply building (with ventilation, W/O air conditioning)

-5 ~ 42 ˚C 45 ~ 90 %

Gyrotron room (with air conditioning) 20 ~ 30 ˚C 30 ~ 75 %

Table 3.9.9 Load conditions of rooms

Load limitation

Building / room Floor kg/m2

Pump room (for heating systems)

B1F 5000

RF amplifier room #1 B1F 3000 RF amplifier room #2 (gyrotron room)

4F 500

Rooftop RF 500 Areaway Out side(B1) TBD RF adjustment room 1F 250

ＪＴー６０ experiment building (Tokamak building)

hallway (passageway) B1F~4F 1000 Central control room 1F 400 ＪＴ−６０ control and

computer building Computer room 1F 400 ＪＴ−６０ primary cooling

building

Aria for RF cooling system

1F 1500

ＲF heating power supply room #1

1F 2000

ＲF heating power supply room #2

2F 1000 ＪＴ−６０ heating power

supply building

Transformer yard Out side(1) 5000



Fig. 3.9.20 Spaces for the power supply system in the transformer yard.

Fig. 3.9.21 Spaces for the power supply system in the power supply building 1F.

MC1

MC2

MC3A

MC3B

MC3C

MC3D

MC4A

MC4B

MC4C

MC4D

MC11

MC12

MC13

MC14

MC15 PC

10

DCG1A

DCG2A

for upgraded JA-DCGs

20000

MC20

5503

0

space for EU DCGs

for JA DCGs

DCGs of the present system

preparatory spacefor EU

406012

370

6500

2400

5030

DCG11D

DCG12D

48912

7125

1060

0

20000

for JADCGs

for EUDCGs

(need of the foundation works)

(DCGs for LH system at present)

LP10A

LP100

LP200

DP11

support

22270

PSS for EU

3500

29735

9000

3046

0

2240

0

pit

pit

pit

pit

pit

pit

pit

pit

for JAPSS(FCB)

for JAPSS(FCB)

for JAPSS(FCB)

FCB11D

CWS11D

FCB12D

CWS12D

FCB13D

LP12D

LP10D LP11D

for JAPSS(FCB)



Fig. 3.9.22 Spaces for the power supply system in the power supply building 2F.

Fig. 3.9.23 Spaces for the gyrotron systems in the gyrotron room (alternative plan).

74000

1000

1000

4000

3750375052005400490013800150004200

400

3200

18750

74000

1000

1000

4000

3750375052005400490013800150004200

400

3200

18750

Original layout for JT-60U

Aria of traveling crane


140GHz3 gyrotrons

by EU

140GHz 2 gyrotrons

by JA

110GHz4 gyrotrons

by JA

110GHz4 gyrotrons LHRFICRF

Maintenance space /

Local operation panels

Maintenance space

New layout for JT-60SA

74000

1000

1000

4000

3750375052005400490013800150004200

400

3200

18750

74000

1000

1000

4000

3750375052005400490013800150004200

400

3200

18750

Original layout for JT-60U



140GHz 2 gyrotrons

by JA

140GHz3 gyrotrons

by EU

110GHz4 gyrotrons

by JA

110GHz4 gyrotrons LHRFICRF

Maintenance space /

Local operation panels

Maintenance space

New layout for JT-60SA

partition

wave guide

cran

e

support

partition

LP10CLP10B

DP21DP22

guide light

for EUPSS

guide light

guide light

guide light

FCB1B

CWS1B

FCB2B

CWS2B

FCB3B

FCB4B

CWS3B

CWS4B

650023

295

44770

3480

3480

3046

0



References [3.9-1] Y. Ikeda, A. Kasugai, S. Moriyama, et al., Fusion Science Technology 42, 435 (2002). [3.9-2] A. Kasugai, K. Sakamoto, K. Takahashi, et al., Fusion Engineering Design 53, 399 (2001). [3.9-3] K. Sakamoto, A. Kasugai, Y. Ikeda, et al., Nuclear Fusion 43, 729 (2003). [3.9-4] K. Kajiwara, Y. Ikeda, K. Sakamoto, et al., Fusion Engineering Design 65, 439 (2003). [3.9-5] H. Zohm, G. Gantenbein, G. Giruzzi, et al., Nuclear Fusion 39, 577 (1999). [3.9-6] A. Isayama, K. Kamada, N. Hayashi, et al., Nuclear Fusion 43, 1272 (2003). [3.9-7] A. Kasugai, K. Takahashi, N. Kobayashi, K. Sakamoto, et al., Conf. Digest of 2006 Joint

31th Inter. Conf. Infrared Millimeter waves and 14th Inter. Conf. Terahertz Electronics, Sept. 18-22, Shanghai, 202 (2006).

[3.9-8] S. Moriyama et al., 24th Symposium on Fusion Technology (SOFT 2006), Warsaw, to be published in Fusion Eng. Des.

[3.9-9] H. Kogelnik et al., Appl. Opt. 5, 1550 (1966). [3.9-10] S. Moriyama et al., Rev. Sci. Instrum. 76, No.11, 113504-1 (2005). [3.9-11] K. Takahashi, C.P. Moeller, K. Sakamoto, K. Hayashi, T. Imai, Fusion Engineering

Design 65, 589 (2003).

Conceptual Design Report on JT-60SA DC current of main power supply in the table is determined...

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