Development of the first ITER gyrotron in QST

This paper presents a summary of recent progress pertaining to the manufacturing and inspection of ITER gyrotrons and the operation system in QST. Major achievements are as follows. (i) The final design of the ITER gyrotron was accomplished and manufacturing of two ITER gyrotrons was completed. Then operation test in QST prior the shipment to ITER has started with ITER relevant high voltage power supply configuration. The 1st ITER gyrotron has achieved 1.05 MW operation for 300 s with 51% efficiency. Measured cooling channel waveform of 300 s pulse demonstrated thermally stable condition representing sufficient cooling performance for 1 MW CW operation; (ii) 5 kHz modulation operation was demonstrated up to 200 s at with >0.8 MW at flat top of pulses; (iii) 300 s/1 MW operation was repeated for 20 shots with successful 19 shots which demonstrating >95% of reliability requirement. These results lead to success of ITER EC H&CD system construction and commissioning toward first plasma

Recent activities of ITER gyrotron development in QST

ITER Gyrotron: An electron cyclotron heating and current drive system in ITER is designed to inject RF power of 20 MW to control actively plasmas. The RF power is supplied by 24 gyrotrons. QST procures to supply 8 gyrotrons which produce 170 GHz / 1 MW each and 1 equatorial launcher for ITER.The specification of ITER gyrotron is 170 GHz / 1MW output / 50% efficiency / 3600s pulse duration. The oscillation mode in the cavity is TE31,11 mode to keep marginal heat load on the cavity surface . The internal mode converter was optimized for 170 GHz single frequency operation. The triode electron gun is utilized and the operation of high frequency power modulation up to 5 kHz is achieved by control of anode voltage.The final design review of the gyrotron was held in 2015 and the gyrotron design was approved for manufacturing. Manufacturing of auxiliary components for gyrotron operation system, for example the super conducting magnets (SCM), started in 2015 and first two sets of SCMs were delivered to QST test stand in the beginning of 2016. In 2016, the first set of two gyrotrons was manufactured in Toshiba Electron Tube & Devices(TETD) and they were delivered to QST Naka Fusion Institute.The short pulse test of the first ITER gyrotron has started since 2017 April after preparation of test stand. A new anode and body power supply system which has the same configuration with ITER high voltage power supply (HVPS) system was installed into the gyrotron test stand. The new power supply system consists of DC HVPS devices which generate high voltage and HV switch components which control HV injection into gyrotrons. The ITER gyrotron was installed into the test stand with ITER SCM. The conditioning for long pulse operation follows after short pulse test. Preliminary results of shot pulse tests and long pulse conditioning will be presented in the meeting.Development of multi frequency gyrotron: In QST, the experiment of the multi frequency operation of high power gyrotron was carried out. This gyrotron was designed to produce RF beam of 203 GHz (TE37,13), 170 GHz (TE31,11), 137 GHz (TE25,9) and 104 GHz (TE19,7). These combination of cavity modes for multi frequency operation were selected to adjust the transparent frequency of the output window and to keep the similar radiation angle in the internal mode converter design. This gyrotron was operated with 8T SCM for operation of 203 GHz and its long pulse operation was examined. The output power, the oscillation efficiency and the electric efficiency for 203 GHz, 170 GHz, 137 GHz, and 104 GHz oscillation are 1.0 MW / 30% / 50%, 1.2 MW / 27 % / 43 %, 1.0 MW / 25 % / 40 % and 1.0 MW / 25 % / 38 % at 2 s pulse, respectively. In long pulse experiment of 170 GHz oscillation, the pulse length reached 100 s with 870 kW output power and 1000 s with 500 kW. For other frequency operation, 250 s with 330 kW at 137 GHz, 20 s with 260 kW at 104 GHz, 9.8 s with 590 kW at 203 GHz were achieved

Completion of 1st ITER gyrotron manufacturing and 1 MW test result

This paper presents a summary of recent progress pertaining to the manufacturing and inspection of ITER gyrotrons and their operation system in QST. Major achievements are as follows: (i) The final design of ITER gyrotron was accomplished and manufacturing of 2 ITER gyrotrons was finished. Then their factory acceptance test (FAT) in QST has started with ITER relevant high voltage power supply configuration. The 1st ITER gyrotron has achieved 1 MW output power for 10 s pulse and 200 kW operation for 300 s which suggests thermally stable condition and sufficient cooling performance for 1 MW long pulse operation; (ii) The coupling function of gyrotron power into the transmission line (TL) waveguide was improved and calculation result of coupling efficiency was increased as high as 96.9% for the fundamental mode purity in waveguide inlet which could produce the sufficient LP01 mode purity in whole EC H&CD system. These results lead to success of ITER EC H&CD system construction toward first plasma.27th IAEA Fusion Energy Conferenc

Demonstration of synchronous control of EC TL switch and gyrotron for ITER EC system

The ITER EC system includes both an equatorial port launcher and upper port launchers as RF power injection devices, The waveguide switch in the transmission line (TL) is used to select the operating launcher. Its operation is required even during plasma operation, primarily for the mid-pulse switch operation. Changing the waveguide switch requires that the gyrotron stop RF power during the switch operation since the direction is changed by mechanical movement of the mirror position which takes a few seconds. Since the ITER EC system is based on a multi-subsystem concept, each subsystem has its own subsystem control unit (SCU). The EC main controller supervises all subsystem controllers. Hence, cooperative operation requires the sharing of the information of both RF power status and switch status between the gyrotron SCU and TL SCU via the main controller. Since the design of the inter-subsystem control scheme is a key issue for ITER EC system control, its evaluation is required. At QST, the gyrotron and ITER-relevant TL test stand were utilized for demonstration of mid-pulse switch operation. For this purpose, SCUs for each subsystem and the main controller were developed using the ITER-relevant control system. The operation of the mechanical switch during gyrotron pulse was demonstrated. During the 150 s operation of the high power gyrotron at 400 kW level, the waveguide switch in the TL was operated to change the direction of RF power. The time duration for the switch operation with inter-subsystem control scheme took 1.5 s in total. The synchronizing of RF power suspend and resume with switch motion has therefore been realized, and RF power direction control during the gyrotron operation was successfully demonstrated

Demonstration of Synchronous Control of EC TL Switch and Gyrotron for ITER EC System

ITER EC system includes equatorial port launcher and upper port launchers as RF power injection device. To select the operating launcher, the waveguide switch in transmission line (TL) is used and its operation is required even during plasma operation also, namely mid-pulse switch operation. To change the waveguide switch the gyrotron has to stop RF power during the switch operation since the direction is changed by mechanical movement of mirror position which takes a few seconds. Since ITER EC system is based on multi-subsystem concept, each subsystem has its own subsystem control unit (SCU) and EC main controller supervises all subsystem controllers. Hence cooperative operation requires to share the information of both RF power status and switch status between gyrotron SCU and TL SCU via main controller. The design of inter-subsystem control scheme is key issue for ITER EC system control and its evaluation is required. In QST, gyrotron and ITER relevant TL test stand were utilized for demonstration of mid-pulse switch operation. For this purpose, SCUs for each subsystem and main controller were developed using ITER relevant control system. The operation of mechanical switch during gyrotron pulse was demonstrated. During the 150 sec operation of high power gyrotron at 400 kW level, waveguide switch in TL was operated to change the direction of RF power. The time duration for switch operation with inter subsystem control scheme took 1.5 sec in total. The synchronizing of RF power suspend and resume with switch motion has been realized and RF power direction control during the gyrotron operation was successfully demonstrated.29th Symposium on Fusion Technology (SOFT2016

Progress in the ITER electron cyclotron heating and current drive system design

An electron cyclotron system is one of the four auxiliary plasma heating systems to be installed on the ITER tokamak. The ITER EC system consists of 24 gyrotrons with associated 12 high voltage power supplies, a set of evacuated transmission lines and two types of launchers. The whole system is designed to inject 20 MW of microwave power at 170 GHz into the plasma. The primary functions of the system include plasma start-up, central heating and current drive, and magneto-hydrodynamic instabilities control. The design takes present day technology and extends towards high power CW operation, which represents a large step forward as compared to the present state of the art. The ITER EC system will be a stepping stone to future EC systems for DEMO and beyond. The EC system is faced with significant challenges, which not only includes an advanced microwave system for plasma heating and current drive applications but also has to comply with stringent requirements associated with nuclear safety as ITER became the first fusion device licensed as basic nuclear installations as of 9 November 2012. Since conceptual design of the EC system established in 2007, the EC system has progressed to a preliminary design stage in 2012, and is now moving forward towards a final design. The majority of the subsystems have completed the detailed design and now advancing towards the final design completion. (C) 2014 Elsevier B.V. All rights reserved

Status of the ITER Electron Cyclotron Heating and Current Drive System

The electron cyclotron (EC) heating and current drive (H&CD) system developed for the ITER is made of 12 sets of high-voltage power supplies feeding 24 gyrotrons connected through 24 transmission lines (TL), to five launchers, four located in upper ports and one at the equatorial level. Nearly all procurements are in-kind, following general ITER philosophy, and will come from Europe, India, Japan, Russia and the USA. The full system is designed to couple to the plasma 20 MW among the 24 MW generated power, at the frequency of 170 GHz, for various physics applications such as plasma start-up, central H&CD and magnetohydrodynamic (MHD) activity control. The design takes present day technology and extends toward high-power continuous operation, which represents a large step forward as compared to the present state of the art. The ITER EC system will be a stepping stone to future EC systems for DEMO and beyond. The development of the EC system is facing significant challenges, which includes not only an advanced microwave system but also compliance with stringent requirements associated with nuclear safety as ITER became the first fusion device licensed as basic nuclear installations as of 9 November 2012. Since the conceptual design of the EC system was established in 2007, the EC system has progressed to a preliminary design stage in 2012 and is now moving forward toward a final design

Status of the ITER Electron Cyclotron Heating and Current Drive System

The electron cyclotron (EC) heating and current drive (H&CD) system developed for the ITER is made of 12 sets of high-voltage power supplies feeding 24 gyrotrons connected through 24 transmission lines (TL), to five launchers, four located in upper ports and one at the equatorial level. Nearly all procurements are in-kind, following general ITER philosophy, and will come from Europe, India, Japan, Russia and the USA. The full system is designed to couple to the plasma 20 MW among the 24 MW generated power, at the frequency of 170 GHz, for various physics applications such as plasma start-up, central H&CD and magnetohydrodynamic (MHD) activity control. The design takes present day technology and extends toward high-power continuous operation, which represents a large step forward as compared to the present state of the art. The ITER EC system will be a stepping stone to future EC systems for DEMO and beyond.The development of the EC system is facing significant challenges, which includes not only an advanced microwave system but also compliance with stringent requirements associated with nuclear safety as ITER became the first fusion device licensed as basic nuclear installations as of 9 November 2012.Since the conceptual design of the EC system was established in 2007, the EC system has progressed to a preliminary design stage in 2012 and is now moving forward toward a final design