Engineers at the UK Atomic Energy Authority (UKAEA) have achieved a technological milestone, having manoeuvred a massive 12-tonne component into position for the UK’s flagship fusion machine, MAST Upgrade, at UKAEA’s Culham Campus.
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The double beam box features a double-decker layout designed to house two neutral beam injectors (NBIs). A neutral beam injector plays a vital role in fusion research by firing high-energy neutral atoms into the plasma, raising its temperature to more than 30 million degrees Celsius.
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By adding two more injectors to MAST Upgrade’s existing setup, the new double beam box will double the machine’s neutral beam heating power from 4.4 megawatts (MW) to 8.8 MW.
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The hotter plasma conditions – expected to double from 30 million to 60 million degrees Celsius – will enable researchers to investigate the technologies and physics needed for future fusion power plants, including the UK’s prototype fusion power plant, STEP.
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Andrew Thornton, Head of MAST Upgrade Operations at UKAEA, said:
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\n The lift of the double beam box is a huge step forward for MAST Upgrade. By doubling our heating power, we will explore plasma conditions we simply couldn’t reach before. We will be able to study the stability of higher-pressure plasmas while testing how the MAST Upgrade exhaust system copes with these hotter, higher-performance plasmas.
\n\n These are crucial questions for STEP and future fusion power plants. It’s also a great example of the engineering skill and collaboration across UKAEA’s science and engineering teams.
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Giant 12-tonne box lowered into place for fusion upgrade
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The double beam box lift took place as part of wider MAST Upgrade engineering work, currently underway, including the installation of a new electron Bernstein wave (EBW) microwave heating system. Other engineering upgrades underway include:
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\n - the transfer and repurposing of power supply equipment from the Joint European Torus (JET)
\n - fabrication and installation of the beam line module, which will allow the neutral beam to be formed and injected into the plasma
\n - manufacture and assembly of a cryopump, shortly to be installed inside the double beam box vessel, which will control the pressure in the double beam box
\n - installation of the positive ion neutral injectors (PINIs)
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About the double beam box vessel
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The completed double beam box vessel, including its lid, will weigh around 15 tonnes, roughly equivalent to two and a half African elephants. It has a volume of 20 cubic metres, about the same as 130 bathtubs, and is made from 316L stainless steel, a grade widely used in offshore infrastructure and medical implants for its strength, durability and resistance to corrosion. The material also offers good vacuum compatibility, essential for the ultra-high vacuum conditions required inside the vessel.
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All major hardware is expected to be manufactured and fitted inside the double beam box vessel by the end of autumn 2027. The vacuum-tight vessel will then be commissioned for use in scientific experiments due to begin in 2028.
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