Referred to as ‘plasma starters’ for their role in initiating plasma pulses or ‘wave generators’ for their efficiency at generating high-frequency waves to match the resonant frequency of electrons in the plasma (170 GHz), gyrotrons are a critical part of auxiliary heating at the International Thermonuclear Experimental Reactor (ITER). Electron cyclotron resonance heating (ECRH) heats the electrons in the plasma; the electrons in turn transfer the absorbed energy to the ions by collision.
The original baseline plan for ITER called for 24 gyrotron devices (8 from Japan, 8 from Russia, 6 from Europe and 2 from India). The first sixteen from Japan and Russia have passed all factory acceptance testing and been delivered to ITER. One by one, teams will install them in the Radiofrequency Building’s ‘gyrotron floor’.
Installation of the first 2.7-metre-tall ITER gyrotron, procured by the Japanese Domestic Agency, has now been completed. It has been connected to its power supply and commissioning is expected to begin later this month.
“One of the highlights of commissioning will be the generation of the first radiofrequency waves,” the ITER Organisation said.
ITER is a major international project to build a tokamak fusion device designed to prove the feasibility of fusion as a large-scale and carbon-free source of energy. The goal of ITER is to operate at 500 MW (for at least 400 seconds continuously) with 50 MW of plasma heating power input. It appears that an additional 300 MWe of electricity input may be required in operation. No electricity will be generated at ITER.
Thirty-five nations are collaborating to build ITER – the European Union is contributing almost half of the cost of its construction, while the other six members (China, India, Japan, South Korea, Russia and the USA) are contributing equally to the rest. Construction began in 2010 and the original 2018 first plasma target date was put back to 2025 by the ITER council in 2016. However, in June last year, a revamped project plan was announced which aims for “a scientifically and technically robust initial phase of operations, including deuterium-deuterium fusion operation in 2035 followed by full magnetic energy and plasma current operation”.
The new baseline for ITER, which demands more powerful radiowave plasma heating, has modified plans both for gyrotron procurement and for the Radiofrequency Building. Forty-eight gyrotrons will now be required at the start of ITER operation and another 24 for the first phase of deuterium-tritium plasma operation (DT-1). This requires additional procurement, an annex to the Radiofrequency Building, and an entirely separate building for equipment for the ion cyclotron resonance heating system.
Central solenoid
General Atomics announced that it had successfully completed the central solenoid modules that make up the largest and most powerful pulsed superconducting magnet ever built. ITER’s central solenoid will generate most of the magnetic flux charge of the plasma, initiating the initial plasma current and contributing to its maintenance.
(Image: General Atomics)
The central solenoid magnet consists of six individual sections, or modules, each weighing more than 270,000 pounds (122.5 tonnes). Each module required over two years to fabricate, followed by testing, and then shipment to France, where they will be stacked to form a colossal system more than 18 metres tall, 4.25 metres wide, and weighing more than 1,000 tonnes.
The 15-year-long project to produce the modules was completed inside General Atomics’ Magnet Technologies Center in Poway, California.
“This project signified a watershed moment for the US and for General Atomics,” said Wayne Solomon, vice president of Magnetic Fusion Energy for the General Atomics Energy Group. “As the first private company to take on the challenge of building fusion magnets at this scale, GA is proud to be leading the way in developing the technologies needed to make fusion power a reality.”
