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Inside the Tokamak assembly pit, two small machines are entrusted with a formidable task: faultlessly and seamlessly welding the first two sections of the cryostat. Following the manual welding of feeder stubs and "manways," and the initial manual passes on both sides of the weld joint between the base and the lower cylinder, the time has now come to join both components. The delicate operation, which began on 26 October, will take approximately five months to fully complete. The two machines have been positioned across from one another, on opposite sides of the 30-metre-in-diametre cryostat base. Closely monitored by operators—one observing the weld's quality and progression from a distance of a few centimetres, another monitoring the process on a video screen nearby—each machine covers 8 centimetres per minute.  A pass inside the six-metre-long predefined sections is approximately one millimetre thick ... and it takes close to 80 passes to fill the gap between the two components.Equipped with a flat head that is half-inserted into the gap, the machine uses a welding technique called "gas tungsten welding". A tungsten electrode creates an electrical arc that melts the filler material, which is deposited, pass after pass, inside the gap. All in all, the welding process will require close to one tonne of filler material. To prevent the oxidation of its tungsten electrode, the welding head operates under a local atmosphere of argon. A mere draft in the assembly pit could disrupt the protective cloud and alter the quality of the weld. The weld area and the electrode are protected by a local atmosphere of argon to prevent oxidation. It is therefore essential that no air currents occur within the pit while welding is in progress. A mere draft caused by the opening of a port cell door could dissipate the local argon atmosphere and alter the quality of the weld.As soon as two six-metre-long sections are completed, the quality of the weld is tested using non-destructive ultrasonic test examination. As for helium tests, they will be performed when the whole 90-metre circumference is finalized.With the planned addition of a third welding machine, the operation should take approximately 65 workdays, which amounts to approximatively three-and-a-half months. An additional month-and-a-half will be necessary for tests and documentation after the welding is complete. 

In the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Assembly Hall, the circle of the lower cryostat thermal shield is now complete. A lot of work remains to be done, however, before the silver-plated component is inserted into the assembly pit in about one month. "We need to check the alignment of the 18 panels, tighten the bolts, remove the internal supports, and install the instrumentation and piping," explains Germàn Perez Michel, the mechanical engineer who oversees the operation. Soon, a dedicated circular lifting tool will be assembled to raise the relatively frail component (20 metres in diameter, 50 tonnes) and deliver it to its final position inside the cryostat base. The lower cryostat thermal shield will fit inside the soup-dish-shaped depression of the cryostat base to form a heat barrier protecting the magnets at superconducting temperature. The thin layer of silver (a low-emissivity material) that covers its entire surface raises an obstacle against the thermal radiation, in the form of electromagnetic waves, that a heat source generates.

Plasma is back inside the spherical chamber of the United Kingdom's MAST Upgrade tokamak after a seven-year campaign to upgrade the device. With its renewed capabilities, MAST Upgrade will serve as an important test bench for °ÄÃÅÁùºÏ²Ê¸ßÊÖ; it will also contribute to the body of knowledge that will go into designing a fusion power plant.  In the control room of the Culham Centre for Fusion Energy, on 29 October 2020, the moment may have been brief but the satisfaction was immense.First plasma for any device is the demonstration that the core of the machine has been assembled, that it is capable of sustaining plasma breakdown, and that all systems are working together smoothly.For MAST Upgrade, first plasma marked the culmination of a £55 million, seven-year upgrade project that was undertaken in 2013 to enable higher performance on the original MAST machine—including longer pulses, increased heating power and a stronger magnetic field. Studies carried out on this spherical device will contribute a different spectrum of results to the worldwide base of physics data, which helps to predict °ÄÃÅÁùºÏ²Ê¸ßÊÖ's performance.MAST Upgrade will also investigate the important question of plasma exhaust—or how to remove excess heat from fusion machines in order to preserve materials. Its unique super-X divertor creates a magnetic configuration that spreads the heat loads at the divertor area of the machine, and could be a viable concept for fusion power stations.Finally, MAST Upgrade is the forerunner of the United Kingdom's STEP fusion power plant, scheduled for completion in 2040. This £220 million program funded by the UK government will be based on MAST Upgrade's spherical tokamak concept.You can watch MAST-U's first plasma shot in slow motion on the UKAEA's YouTube channel here.If all goes according to plan, MAST Upgrade will run for 10 experimental days in December, and continue its operation in 2021. Further enhancements are planned in 2023, including extra neutral beam heating, control upgrades, and a cryoplant to manage the heat load on the divertor.The Culham Centre for Fusion Energy is part of the UK Atomic Energy Authority and is based at Culham Science Centre near Oxford, England. MAST Upgrade was financed by the Engineering & Physical Sciences Research Council, part of UK Research & Innovation, and the Department for Business, Energy & Industrial Strategy. Find out more about MAST Upgrade here or watch this video. 

Functional tests on the "sector lifting tool" have demonstrated that the tool's controller and actuators are ready to implement operator commands during the delicate lifting operations of vacuum vessel sectors, toroidal field coils, and the finalized sector sub-assemblies. The sector lifting tool is a purpose-built assembly tool designed and manufactured by the Korean Domestic Agency to lift and transfer some of °ÄÃÅÁùºÏ²Ê¸ßÊÖ's heaviest components—vacuum vessel sectors and D-shaped toroidal field coils—as well as the nine sector sub-assemblies that will be created on °ÄÃÅÁùºÏ²Ê¸ßÊÖ's tallest assembly tools. The overhead travelling cranes cannot "grasp" these major loads directly; instead, several layers of attachments intervene between the cranes and the components to be lifted. First, a 90-tonne beam attached to the four hooks of the double crane provides a single connection for the next-layer of lifting attachment. This "dual crane heavy lifting beam," which allows the cranes to work in tandem and lift loads of up to 1,500 tonnes, has been procured (along with the cranes) by the European Domestic Agency. (It does not appear in the image below.) The tool is equipped to perform horizontal-plane adjustments along the X and Y axis (longitudinal and transverse) in order to balance the loads before each lift. Through a pin attachment at the top, the sector lifting tool connects to the dual crane heavy lifting beam. For the components that must be mounted on the sector sub-assembly tool, the next in order is the sector lifting tool, which attaches to the dual crane heavy lifting beam through a pin connection. The tool will interface at three points in two places with toroidal field coil lifting beam to lift the coils from the upending tool to the sector assembly tools. For the nine vacuum vessel sectors, the sector lift tool's direct interface will be the nine radial beams, which are part of the in-pit assembly tools. These radial beams are transported from the pit to connect to each sector in its upended (vertical) orientation, and they remain attached to the sector through transport (under the sector lifting tool) to the sub-assembly tool, throughout the sub-assembly operation, and through delivery and installation in the Tokamak pit. Considering the importance of the centre of gravity when lifting such heavy loads, the sector lifting tool has been designed with a balancing control system that can be activated through controllers and electrically driven actuators. The tool is equipped to perform horizontal-plane adjustments along the X and Y axis (longitudinal and transverse) in order to balance the loads before the lift. This system, which was first confirmed during testing at °ÄÃÅÁùºÏ²Ê¸ßÊÖ Korea, has been verified through functional site tests this month at °ÄÃÅÁùºÏ²Ê¸ßÊÖ.Early next year, the fully tested sector lifting tool will enter into activity—playing an important role in transferring the first toroidal field coils and the first vacuum vessel sector to the standing tools in the Assembly Hall.

In describing the R&D program of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ device, the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan also identifies the top R&D issues requiring consolidation or refinement. In the interest of making these R&D support needs more widely accessible to the fusion research community, scientists at the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization have just released a consolidated list as an °ÄÃÅÁùºÏ²Ê¸ßÊÖ Technical Report. Published in 2018, the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan was elaborated with the support of experts from the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Members. It is now the key document describing the R&D program of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ device.   The document defines the plan for the exploitation of the facility necessary to meet the °ÄÃÅÁùºÏ²Ê¸ßÊÖ mission goals. Following the demonstration of First Plasma, operation is divided into two main phases: operation in hydrogen/helium plasmas (Pre-Fusion Power Operation, PFPO) and operation in deuterium and deuterium-tritium plasmas (Fusion Power Operation, FPO) to demonstrate the project's fusion production goals (see Figure 2). This is namely a fusion gain (Q) of Q = 10 for 300-500 s, and Q = 5 for 1000 s and 3000 s (corresponding to steady-state operation). The °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan describes the objectives of each operational campaign consistent with the available systems according to the Staged Approach. It also details the experimental plan to achieve the objectives (including options), and identifies the main risks of the experimental plan and the corresponding mitigation actions. In addition, the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan identifies a series of issues for which R&D is required to support their refinement or consolidation. These issues cover a wide range of areas—such as the refinement of designs (particularly for the disruption mitigation system and some diagnostics), and the optimization of operational scenarios in the various phases.   Figure 2. Schematic of the timeline for the first years of °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan operations. Now, the Science Division and the Port Plugs & Diagnostics Division have categorized these issues according to their impact on the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan and have selected a set of issues with high impact, which warrant priority focus in ongoing R&D at the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Member fusion research institutes over the next few years. The selected set includes: a) issues related to completion of system designs; b) specific choices and options to be explored in the early stages of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan; and c) strategic assumptions on the development of the experimental program towards high Q operation. The set of issues and their categorization by the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization have been provided to the International Tokamak Physics Activities (ITPA), which coordinates the research done by the fusion research institutes of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Members to support °ÄÃÅÁùºÏ²Ê¸ßÊÖ needs, and has been used to focus the ITPA R&D program. In the interest of making these °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan R&D support needs more widely accessible to the fusion research community—and following the recommendation of the ITPA Coordinating Committee—the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization is making them publicly available as an °ÄÃÅÁùºÏ²Ê¸ßÊÖ Technical Report (ITR-20-008). The support from °ÄÃÅÁùºÏ²Ê¸ßÊÖ Member fusion research institutes provides an essential contribution to the further refinement of the Research Plan; making these R&D needs publicly available is intended to strengthen this support. "The key work carried out by the fusion community has been already instrumental in guiding the development of plasma scenarios (see Figure 1) and the tokamak systems—in particular plasma diagnostics—required for °ÄÃÅÁùºÏ²Ê¸ßÊÖ to achieve its goals," says Alberto Loarte, Head of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Science Division. "We are hoping that the publication of our consolidated R&D priorities leads to a more effective collaboration between the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization and the fusion community to further improve the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan." Download "Required R&D in Existing Fusion Facilities to Support the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Research Plan" from the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Technical Reports page here.  

The list of °ÄÃÅÁùºÏ²Ê¸ßÊÖ Technical Reports available on the public website continues to grow. These reports, freely downloadable, aim to make the results of scientific and technical activities carried out under the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Agreement widely available. Typically, they are versions of internal reports that have been deemed of interest for the wider scientific and technical community, but that have not been submitted for conventional publication in scientific journals or books. View the growing list here : /technical-reports

Whether in person or virtual, the world's largest fusion conference will forge ahead: FEC 2020 will be maintained for 10-15 May 2021 with the now-finalized scientific program. The International Atomic Energy Agency (IAEA), together with the Local Organizing Committee, is currently reviewing the evolving COVID-19 situation and its impact on the conference.  A decision whether to maintain a physical conference or move to a virtual event will be taken in early 2021. You will be kept informed. So be ready to join us at the 28th IAEA Fusion Energy Conference (FEC 2020) whatever its format, as the fusion show must go on. We look forward to seeing you there! For more information about the conference and updates regarding the program, please visit the website.