It was 8:00 p.m. on Tuesday 6 April and something quite unusual happened in the ITER Assembly Hall: applause spontaneously erupted from the teams that had been at work since early afternoon. Specialists do not usually clap for their own accomplishments but this was a unique circumstance: the lifting of the 440-tonne vacuum vessel sector and its positioning in the sector sub-assembly tool was a masterpiece of coordination and precision. Concluding five hours of tension, the applause was both an expression of relief and a tribute to the teams' competence. Over the past 11 months, there have been both heavier and larger loads. The cryostat base, lower cylinder and lower cryostat thermal shield are without contest spectacular components, but none of them is part of the torus-shaped core of the machine; rather, they are large, sophisticated steel structures designed to envelop and insulate the machine. Vacuum vessel sector #6 is something else: it is the first element of the tokamak itself, a 40-degree segment of the vast toroidal chamber hosting the burning plasma— a state of matter that only exists at the core of the stars. Steps to transfer a 440-tonne vacuum vessel sector from its horizontal orientation on the shop floor to the V-shaped sector sub-assembly tool: The upending tool is used to raise the sector from horizontal to vertical. (See this article.)  Because the overhead travelling cranes cannot "grasp" these major vertical loads directly, several layers of attachment are installed between crane and component. These adaptive devices are brought together before the lift operation. (Next bullet.) The 90-tonne dual crane heavy lifting beam (attaches to the four hooks of the double crane to allow the cranes to work in tandem) is connected to the sector lifting tool (equipped with a balance control system that can be activated to perform horizontal-plane load adjustments along the X and Y axis), and a radial beam (which will remain attached to the vacuum vessel sector through to its final position in the assembly pit). The assembled lift attachments are brought above the vacuum vessel sector in its vertical position. The support and alignment units of the sector lifting tool are connected to two lifting hooks on the vacuum vessel sector. This is a tricky step due to the position and angle of the lifting hooks, which have been welded to the sector. Through controllers and actuators, the sector lift tool adjusts its balancing cross beam to match the calculated centre of gravity of the vacuum vessel sector. The sector is lifted to verify that the pre-set centre of gravity is satisfactorily aligned, and that the pins in the upending tool line up with the "guiding pins" on the vacuum vessel sector. If alignment is confirmed, the pins slowly disengage and the vacuum vessel sector is fully lifted and transported in front of the sector sub-assembly tool. The dual crane heavy lifting beam rotates the load 90° for mounting on the V-shaped tool. The load is raised more than 20 metres above the shop floor and brought above the sector sub-assembly tool. The load is lowered into the tool. From the top, the sector is supported by the radial beam, which is braced on the tool. At the bottom, a temporary pillar supports the lower port extension. Two hydraulic jacks in the pillar help to adjust the vertical angle of the sector through a "push and pull" movement until the required position is achieved. The sector lifting tool performs a final balancing adjustment operation before disengaging from the radial beam. The sector sub-assembly operation can proceed: panels of thermal shielding and two toroidal field coils are rotated in to the sector and assembled. On 20 March, sector #6 was transferred from the laydown area to upending tool. On 26 March, bolted and strapped in the upending tool, the component was lifted and tilted from horizontal to vertical. Ten days later, it was time to perform the third stage of the operation and position it inside the sector sub-assembly tool. This was the culmination of an eight-month preparatory campaign since the arrival of sector #6 at ITER. Following site acceptances tests (including a leak test in September), months were spent fully instrumenting the component, first by welding bosses and other attachments onto its outer shell, then by welding magnetic sensors and other instrumentation onto the bosses. On Tuesday 6 April, attached to a complex rigging system (see box below) and delicately pulled out of its berth, vacuum vessel sector #6 travelled a few dozen metres to face sub-assembly tool #2 and made a right angle turn. The last phase of the operation was the most spectacular: lifted by the double overhead crane, the component rose above the 20-metre high sub-assembly tool, before slowly descending through the tool's V-shaped opening to eventually settle, hanging from the radial beam that finds a home on supporting blocks at the top of the tool. The central and most massive element of the first pre-assembly is now in place. In the coming months, it will be encased in thermal shield panels and associated to two toroidal field coils. Before the end of the year, the 1,200-tonne pre-assembly will be lowered into the pit, marking the first step in creating the tokamak's toroidal chamber. Watch a time-lapse video of the transfer operation here.

One of the main deliverables of ITER is the data itself—and there will be a tremendous amount of it to store and analyze. During First Plasma, the highest producer of data will be the magnetic diagnostics, with an aggregate output of 20 gigabytes per second. Researchers will use the information collected during a pulse for near term analysis—but also for analysis well into the future, even beyond the expected 30-year lifetime of ITER. Archiving data at this rate is challenging and so is data preservation—making sure the information can be used for decades to come. Scaling storage capacity well into the future The 20-gigabytes-per-second requirement only takes into account First Plasma. Magnetic diagnostics will produce even more data after First Plasma and other systems, including bolometers, will add significantly to the total amount. Whatever decisions are made today have to work well into the future, scaling up to the ever-increasing storage needs. All of the data will be stored in the Scientific Data and Computing Center, which is scheduled to be operational in 2024. The ITER group responsible for meeting the archiving and retrieval requirements—the Data, Connectivity & Software Section—has begun the process of choosing a file system that can swallow at least 20 gigabytes per second, with an architecture that scales beyond that. Working with colleagues in the Information Technology Division, the team is testing IBM's Spectrum Scale, a high-performance clustered file system that allows parallel access to several nodes in a cluster. "Over the next six months we will host a few IBM experts to make sure we can archive 20 gigabytes per second, and access it simultaneously using data visualization tools," says Lana Abadie, Data Service and Visualization Engineer. "Reading and writing at the same time puts a tremendous load on a file system." One of the challenges is storing complex data structures. The data is heavily nested and its format is highly variable from one case to another. For example, data from magnetic diagnostics will be structured in completely different ways from data originating from heating systems. In addition to finding the right file system, the team needs to make sure the operating system and all applications involved can handle the volume. "We need to profile our software and hardware to find out where the bottlenecks are, and then tune those parts to speed them up," says Abadie. "We look to companies like Google, Netflix and Facebook for inspiration. We also follow the HPC (high-performance computing) community to see what works for them." One tool the team relies on is the extended Berkeley Packet Filter (eBPF), which identifies weak links in the data flow within the Linux kernel. Another is Darshan, used by the HPC community to study the input and output behaviours of applications. Not only does information have to be stored and preserved, but it also needs to be curated. There will certainly be some mistakes, which need to be spotted and corrected to avoid skews. For example, if the time synchronization is not working on a sensor, all the archived data from that sensor will have the wrong timestamps. Even with a robust time synchronization network in place, the archiving tools will add markers to some of the files to enable a comparison between the time in the server file and the sensor file—just to be sure. To assist in analysis, the Data, Connectivity & Software Section is developing a number of applications to allow scientists to visualize and plot data. The MINT tool (pictured, for Make Informative and Nice Trends) is a data visualization tool that will help scientists and engineers analyze physics parameters. High-volume retrieval for meaningful analysis The second part of the challenge is making the data accessible for analysis. In some cases, trends will be computed and stored in aggregate form. But for deeper dives, scientists will need to see all the data. Access times need to be quick—a second or two in the worst case, rather than hours. "Not only do you need to access all the data, but you also need to consider concurrency," says Abadie. "When you have one person accessing the data, it's not the same as having thousands of people. For First Plasma we estimate as many as 1,000 concurrent users." To make the load more manageable, the team came up with a design that partitions the file system based on predicted usage patterns. Just as they profile and tune the tools that store the data, they also profile and tune the software and hardware that reads it back. To assist in analysis, Abadie and colleagues are acquiring and developing a number of applications to allow scientists to visualize and plot data. "We developed a data visualization tool with diagnostics colleagues and gave it the name MINT, for Make Informative and Nice Trends," says Abadie. "This tool will help scientists and engineers analyze physics parameters."  Furthermore, the team will release software libraries to help researchers build their own analysis tools. Using a common software technique called "encapsulation," the outer structure of the library will stay the same, hiding the specifics of the underlying software as it evolves over the decades to come. Developers using encapsulated libraries do not have to be concerned with the changes underneath. "The sheer volume of data is what makes our work most challenging," says Abadie. "We try to provide the tools that make it easier for scientists and engineers to make sense of it all."

In the southern part of the construction platform, a one-hectare yard hosts some of the strangest-looking components of the entire ITER installation. Rows of tower-like cylindrical structures stand 8 metres tall; other oddly shaped devices line up like soldiers in a frozen parade. This vast area is the realm of reactive power compensation and harmonic filtering—characterized by a dense arrangement of thyristor-controlled valves, reactors, capacitors, resistors and sensors that aim to smooth the flow of AC current and eliminate harmonics, both inside the ITER installation and in the immediate vicinity. Procured by China, the equipment is now almost completely installed. After factory acceptance tests at the manufacturer's facility, a new set of on-site tests was launched in early March. "Basically, we are following the same strict procedure as the factory acceptance tests. Everyone needs to make sure that we still have a no-default situation despite the long journey from China and subsequent handling on site," explains Massimiliano Camuri, the electrical engineer in charge of verifying the integrity of the components. What is at stake is both functionality and safety. Most of the installed equipment is high voltage, which means a high risk of electrical arcs in case of defective insulation. All in all, the inspection test plans defined by the Chinese manufacturer Rongxin Power Electronic Co. Ltd comprise close to 2,000 individual tests, half of them qualifying as "high voltage/high risk." In order to be tested, the equipment must be energized first. This is done by connecting the component to a control box the size of a small suitcase, whose twin transformers elevate the standard voltage (230 V) to 112 kV. "The operational voltage will be in the range of 66 kV, but we have to take some phenomena, like switching overvoltage, into consideration. Testing at 112 kV gives us a comfortable safety margin," says Massimiliano. The first equipment to be tested is the 8-metre-tall thyristor-controlled reactors, whose function is to compensate the reactive power. As Massimiliano, protected by fire-resistant work wear, headpiece and face shield slowly turns the knob that elevates the voltage, the hum of electrical current, like the buzzing of a thousand bees, fills the air. The test lasts one minute and aims to check the integrity of the massive ceramic insulators that are integrated in the tall towers. The test is conducted in compliance with all electrical safety rules—the most important being the rule of equal-potentiality, which means that all metallic parts must be connected to ground. The dials on control box are of course essential to monitoring the stability of the current. But electrical engineers also rely on their trained ears. "There are noises that are 'normal' and some that aren't," says Massimiliano. "You've got to listen carefully to tell the difference." All the while, at a safe distance, two engineers from Rongxin Power Electronic Co. Ltd observe the operation. A representative of SAET, the Italian company responsible for the installation, is also present to provide support. The minute is now over and the hum has stopped.  Another thyristor-controlled reactor has passed the test. More are waiting ... enough to keep Massimiliano and his team busy until mid-June.

While the advent of Covid-19 has not stopped the relentless advancement of the ITER Project, it has certainly prompted ingenuity in how ITER conducts its work. The latest example took place on 7-8 April, as industrial representatives from around the world "gathered" virtually to learn about coming business opportunities. The meeting was both a test and first full-scale use of the upgraded ITER studio and supporting features: a mix of live talks, pre-recorded videos, lively Q&A sessions, and one-on-one meetings. Two years ago the ITER Business Forum (IBF) took place in Antibes, a traditional face-to-face conference with more than 1,100 participants, setting an attendance record for these biennial meetings. The expectation was that the 2021 ITER Business Forum would take place in Marseille. The pandemic blocked those plans, but it did not slow down the march of ITER procurements that require industrial expertise across dozens of high-tech and scientific disciplines. The next in-person IBF has been postponed to 5-7 April 2022, but something was needed in the interim. For the ITER Organization and Domestic Agencies to have no large-scale interaction with prospective supplier companies was unacceptable. The challenge was how to build a quality event, enabling meaningful interaction, while minimizing physical interaction. And the result? A hybrid arrangement featuring a maze of cameras, cables, lighting, green screen, and multiple software platforms suited to the laptops and bandwidths of hundreds of individual users, all coordinated through a multi-channel "tricaster" in the ITER studio. The result was a unique success. With more than 1,280 registered participants (a new record), the Remote ITER Business Meeting kicked off on time with a live introduction from the ITER Director-General and a pre-recorded video in which he presented an overview of project progress. The ensuing two days featured more than 250 one-on-one meetings with ITER experts, and more than 500 attendees at individual presentations. Industrial partners and potential partners were led through careful explanations of the ITER procurement process: tips on how to build consortia, smart subcontracting, balancing risks and pricing, and the constant emphasis on meeting ITER's demanding technical specifications as well as adherence to quality, safety, and timeliness. Thematic presentations covered large upcoming projects such as the Hot Cell Complex and Tritium Plant, specific tenders related to diagnostics and in-vessel coil power converters, and broader needs related to maintenance services and machine assembly. Fusion for Energy, the European Domestic Agency, also presented a broad range of its upcoming tenders.

The French company CNIM (Toulon) has produced a tenth pre-compression ring for the ITER Project on behalf of Fusion for Energy, the European Domestic Agency. The completed component is made of pultruded laminate, wound into a ring shape on specialized winding tooling, with alternate layers of 0.12 mm-thick epoxy tape applied. The completed ring is cured and then machined to the required final dimensions. In the ITER machine, two sets of three pre-compression rings will be installed at the top and bottom of the toroidal field coil structures. Mounted around the "tips" of the structures, the high tensile strength of the rings "pushes back" against the against the forces exerted on the toroidal field coils during operation, relieving stress and fatigue. Four other pre-compression rings will serve as spares. The completion of this procurement package has been celebrated by the European Domestic Agency and contractors alike. Read the full report here. 

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