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There is a place near Santander, Spain, where one can actually feel what °ÄÃÅÁùºÏ²Ê¸ßÊÖ will be like. Although we've seen dozens of drawings and 3D animations, the encounter with a true-size mockup of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ vacuum vessel comes as a shock¡ª°ÄÃÅÁùºÏ²Ê¸ßÊÖ will indeed be an awesome machine. Standing as tall as a six-storey building in a large workshop in the outskirts of the city, the massive and complex structure bears no resemblance to anything known. It could be a section of Jules Verne's Nautilus or the slice of an alien spaceship.   Although it represents only a portion of the tokamak's doughnut-shaped vacuum vessel, the mockup of two paired sectors seems to dwarf everything around it. With the exception of sector width (10 degrees versus 40 degrees) it mirrors the future reality of °ÄÃÅÁùºÏ²Ê¸ßÊÖ down to the smallest detail.   On this huge stage, a one-of-a kind dress rehearsal is underway. The °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization wrote the script; the Spanish company Equipos Nucleares SA (ENSA) provided the stage and the props. The main act is the story of the welding of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ vacuum vessel and ports—one of the longest and most complex sequences of the machine assembly phase, requiring around 200 personnel and at least four years to complete.   The °ÄÃÅÁùºÏ²Ê¸ßÊÖ vacuum vessel is made of 9 sectors, each weighing around 420 tonnes and measuring 13 metres in height and 7 metres in width. On arrival at °ÄÃÅÁùºÏ²Ê¸ßÊÖ, each sector will be suspended by one of the sector sub-assembly tools to be pre-assembled with two toroidal field coils and panels of vacuum vessel thermal shield. The resulting 1,200-tonne "sector module assembly" will be lowered by overhead crane into the Tokamak pit.   The pit will be a very crowded place by then, with the base and lower cylinder of the cryostat as well as two out of six poloidal field coils already in position (see an animation of the assembly sequences here).   An inside view of the mockup: to the right, a welding robot sits on its support as the weld cap machining tool slowly creeps along the railing, smoothing the weld surface as it moves. A second robot is visible at the bottom of the image (centre), its welding head reaching deep into the gap between the two sectors. The welding of the vacuum vessel sectors will have to be performed in a very restricted space, with tools operating from the inside the sector only. No access to the outer shell of the vacuum vessel sectors will be possible due to the thermal shield panels surrounding each sector.   These challenging in-pit welding operations are precisely what is being rehearsed on the ENSA mockup in Santander.   The mockup represents the joint between two sectors of the double-walled vacuum vessel, faithfully reproducing the 100-millimetre gap between the outer shells of two adjoining sectors and the larger inner-shell gap (160 mm) that permits a little extra leeway in the case of possible misalignment while allowing the welding tools to reach from the inside through to the outer edge of the component.   A D-shaped vessel to host a D-shaped plasma. Standing at the bottom of the structure, Brian Macklin and an ENSA engineer give us a sense of scale. Welding filler material alone is not sufficient for filling the gaps, however. Before welding operations can commence, the spaces are closed off by 60-millimetre-thick bands of steel called "splice plates" that will be positioned, one after the other, by a special tool developed by ENSA.   Fifteen inner and 16 outer plates need to be inserted into the gaps between sectors. "We will manufacture them roughly, with extra width, thickness and length, and then reverse-engineer them by precise custom machining to the exact dimensions of the gap," explains Brian Macklin, project manager in the Tokamak Assembly Division and the original responsible officer for the ENSA contract.   Using an ultra-precise laser survey (see video here), each gap will be mapped and rendered as a 3D drawing. The data will then be fed to a high-precision tool that will machine the final plates to the exact dimension and topography of the gap. With the plates in place, the distance between the sectors will be reduced to half a millimetre.   Three large welding robots will then enter the scene, introducing welding heads into the gaps at different locations around the vessel; by operating them simultaneously, the shrinkage caused by the welding process is distributed all around the D-shaped section of the sectors.   "We have now reached the final stage of tool and procedure qualification on the mockup," explains Frantz de la Burgade, °ÄÃÅÁùºÏ²Ê¸ßÊÖ group leader for sector assembly and the current responsible officer for the ENSA contract. "Half of the splice plates have been fully welded on the outer shell of the sector and the smoothing of the welds by a weld cap machining tool is ongoing. There are still a few parameters to streamline, such as assessing the importance of the weld shrinkage or detailing a few remaining interfaces with the vessel for the real work."   Amidst the din of ENSA's Special Projects' workshop, Brian Macklin, Frantz de la Burgade and Alex Martin, the °ÄÃÅÁùºÏ²Ê¸ßÊÖ group leader for vacuum vessel engineering, observe, question, discuss, and take notes and measurements. Like directors on a set, they make certain that the acts are in conformity with the scripts. The dress rehearsal is now almost over; the actual production should premiere at °ÄÃÅÁùºÏ²Ê¸ßÊÖ in the autumn of 2020.   Watch a video of what's happening "Inside the Big D."   More technical information can be found in the image gallery below.    

Working as an integrated team, the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization and seven Domestic Agencies are continuing to meet the project's demanding schedule to First Plasma in 2025. Pace and performance were confirmed this week at °ÄÃÅÁùºÏ²Ê¸ßÊÖ Headquarters by senior representatives from China, the European Union, India, Japan, Korea, Russia, and the United States, who had gathered for the Twenty-Third Meeting of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Council. Every six months, the governing body of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization meets to evaluate project progress on the basis of detailed performance metrics that track manufacturing, construction, and installation activities. The Twenty-Third Meeting of the Council, which took place on 14 and 15 November at °ÄÃÅÁùºÏ²Ê¸ßÊÖ Headquarters, was no different. By reviewing the latest reports and indicators on technological and organizational performance, the Council was able to confirm that the project has completed nearly 60 percent of the work scope to First Plasma.   Since January 2016, °ÄÃÅÁùºÏ²Ê¸ßÊÖ has achieved 36 scheduled Council-approved milestones, including the completion in August of the concrete crown that will receive the full weight of the machine, and the timely manufacturing and delivery of the first flux loop magnetic sensors for the °ÄÃÅÁùºÏ²Ê¸ßÊÖ vacuum vessel.   Project progress is tracked against the 2016 Baseline schedule, which was endorsed by the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Council in November 2016 as the fastest technically achievable path to First Plasma, and the Revised Construction Strategy, which has been developed by the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization to optimize equipment installation in the Tokamak Complex Building.     At the end of the second day, the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Director-General proposed a visit on site. One group of delegates can be seen here standing on the floor of the cryostat base, with the rim of the base in the background. Specifically, the Revised Construction Strategy brings all installation activities in the critical Tokamak Complex area under the coordination of the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization, including building services falling under the scope of the European Domestic Agency's TB04 contract for mechanical and electrical installation works.   Instead of planning sequential installation activities in the Tokamak Complex—first TB04 building services, and then the installation of machine components and systems by °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization contractors—the transfer of TB04 installation activities to the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization through the partial novation of the contract allows significant time to be saved by facilitating early access for °ÄÃÅÁùºÏ²Ê¸ßÊÖ contractors and allowing the most efficient integrated assembly sequences to be developed to avoid clashes, dismantling and/or rework.   "I confirm to you that critical transitions lie ahead for the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Project--as we move from design, engineering and manufacturing to assembly and installation," said the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Director-General Bernard Bigot in his opening remarks to the 23rd °ÄÃÅÁùºÏ²Ê¸ßÊÖ Council. "All the large components of the Tokamak will be arriving on site within the three next years, 2019-2021, and in parallel we will be carrying out the first steps to commission and prepare for operation. We believe that we have found the best way to adjust our overall organization to face the challenges of this transition."   The first machine component—part of the magnet feeder for poloidal field coil #4—will be installed in the Tokamak Pit late November.   Read the full press release in English or French.

On the computer screen, a set of three metal bellows "breathe" in a steady rhythm. Nuclear engineer Natalia Casal and materials engineer Toshimichi Omori are on a Skype call with the Swiss Plasma Center in Lausanne to witness a specially designed endurance test for this equipment, which is critical to the rotation of steering mirrors that will direct high-frequency microwave beams into the °ÄÃÅÁùºÏ²Ê¸ßÊÖ plasma. Thousands of times during the operational lifetime of °ÄÃÅÁùºÏ²Ê¸ßÊÖ, the steering mirrors of the electron cyclotron heating system will pivot to direct powerful microwave beams to the appropriate location in the plasma.   The steering mirrors are part of the electron cyclotron upper launchers, the delivery mechanisms that will "launch" 24 microwave beams generated by the electron cyclotron heating system into the vacuum vessel during full operation. The main functions are to provide central heating and current drive to the plasma, and to direct heat to localized areas within the plasma to prevent instabilities from cooling it down.   In addition, operators will rely on the electron cyclotron system to deliver the "spark" that initiates each plasma. Inside of the upper launchers, two steering mirrors direct the beams into the plasma where they target a set of fixed mirrors on the central column with millimetre precision. From there the beams spread out and pan across the "plasma null," the optimum region for initiating the plasma.   Natalia Casal during a Skype video conference reviewing the launch of the bellows test stand at the Swiss Plasma Center. About 30 cm wide and 15 cm high, the steering mirrors consist of two parts: a stainless steel body and a reflective top layer made of a copper-chrome-zirconium alloy. The biggest challenge, however, is the mechanism that powers the mirrors' precise rotational capabilities.    Conventional steering mechanisms use traditional ball bearings controlled by push-pull rods to allow mirror rotation, but in the harsh environment near the °ÄÃÅÁùºÏ²Ê¸ßÊÖ plasma these would tend to jam. In addition, this mechanical solution would require lubricant to prevent friction, which could potentially contaminate the vacuum environment. "Similar to the ultra-high vacuum instruments that were developed for use on board the International Space Station, we had to come up with an innovative solution," says Casal.   To avoid this problem, engineers at the Swiss Plasma Center designed a frictionless system that cannot jam. Thin metallic fins replace the ball bearings and permit the necessary rotation of the steering mirrors. The fins are powered by a set of gas pistons, similar to those in a car engine, with a set of four small bellows replacing the piston chambers. About 7 cm in length and 3.2 cm in diameter, the bellows are compressed or released by helium that is pumped in and out of their casing.   The bellows are considered the weakest point of the entire steering mechanism, as they need to survive thousands of mirror movement cycles with high reliability. In collaboration between the European Domestic Agency (Fusion for Energy), the Swiss Plasma Center, the Japanese Domestic Agency and the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization, engineers in Lausanne are currently conducting a first set of tests with bellows manufactured by the Japanese company Kuze.   This endurance test, which runs for several months, involves a test rig to compress and extend the bellows over millions of cycles in order to demonstrate their compliance with the stringent °ÄÃÅÁùºÏ²Ê¸ßÊÖ requirements.   The completion of testing is expected in early 2019 and will be followed by the final design review of the upper launcher later in the same year.   In the meantime, the bellows in Lausanne continue their huffing and puffing ...   Thank you to Natalia Casal and Electron Cyclotron Section head Mark Henderson for their contributions to this article.

At Consorzio RFX, where °ÄÃÅÁùºÏ²Ê¸ßÊÖ's most powerful external heating system will be tested in advance, activities are progressing well on two distinct test beds. °ÄÃÅÁùºÏ²Ê¸ßÊÖ will rely on two heating neutral beam injectors to deliver more than 50 percent of the external heating required by °ÄÃÅÁùºÏ²Ê¸ßÊÖ. Although neutral beam injection is routinely used for plasma heating in fusion devices, the size of °ÄÃÅÁùºÏ²Ê¸ßÊÖ imposes enhanced requirements: particle beams have to be much thicker, for example, and individual particles have to be much faster in order to travel far into the core of the plasma.   The challenging physics and technology issues will be investigated at the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Neutral Beam Test Facility in Padua, Italy, a facility hosted by the Italian research organization Consorzio RFX. The Domestic Agencies for Europe, Japan and India are all contributing components according to Procurement Arrangements signed with the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization; Italy is building the facility as a voluntary contribution to the neutral beam development program.   The components are the same as those that will be used on the heating neutral beams at °ÄÃÅÁùºÏ²Ê¸ßÊÖ, which will allow the neutral beam teams to acquire valuable information about neutral beam manufacturability and operation.   Update on SPIDER   The SPIDER test bed is designed to test and develop the °ÄÃÅÁùºÏ²Ê¸ßÊÖ full-scale radio-frequency negative ion source.   In SPIDER, negative ions are generated in the plasma, which is powered by the injection of electromagnetic waves. Once generated, the plasma expands into the source volume and takes the only possible way out: the 1,280 openings of the so-called plasma grid. A potential difference between this grid and the next extraction grid (which has the same aperture pattern) provides the extraction of the negative charges from the neutral plasma; their acceleration at full energy (0.1 MeV in SPIDER) is provided by another potential difference, applied with respect to a third electrode: the acceleration grid.   SPIDER entered into operation in June 2018, and the team is now pursuing the optimization of negative particle extraction and the entry into operation of all systems.   The first phase of experimentation is focused on the plasma. So far, hydrogen plasmas have been sustained for hundreds of seconds; the response of the system to variations of injected power, magnetic field intensity and source filling pressure has been in accord with expectations based on similar test beds.   Together with the generation of hydrogen and deuterium plasmas, the NBTF team is beginning to study the process of separating out the negative particles, which occurs thanks to a difference in electrical potential applied at the level of the plasma and extraction grids. Specialized diagnostics will be used to confirm the success of this first phase before a third grid—the acceleration grid—enters into action to accelerate the negative ion beam.   Update on MITICA A second test bed—the full scale neutral beam injector prototype MITICA—is under construction in parallel to SPIDER. The process behind the generation of the plasma in MITICA will be exactly the same as in SPIDER, but in MITICA the acceleration grid system will involve seven electrodes, up to a final energy of 1 MeV. Moreover, MITICA will demonstrate the conversion of the fast ions into neutrals and will validate the concept of the electrostatic residual ion dump, required to filter out the remaining charged particles from the neutral beam.      While the MITICA beam source—fruit of many years of research—is under construction now in Europe, power supply equipment from Europe and Japan is being delivered and installed at the Neutral Beam Test Facility.   The power supply for the residual ion dump has been delivered to the MITICA test bed at Consorzio RFX in Padua, Italy. On the left, the conversion system for the test bed's acceleration grid power supplies is also visible. Recently, the conversion system for the acceleration grid power supply completed site acceptance testing with excellent results. This equipment, manufactured by the Italian firm Nidec ASI, will convert AC power from the grid to the DC power required for the acceleration of the ion beam. Power supply equipment for the residual ion dump, whose role it is to "catch" any of the ions left after the negative ions have been neutralized for injection into the plasma, has also been delivered by OCEM ET (Italy).   With the delivery of the ion source and extraction power supply at the end of the year, Europe will have completed its contributions to MITICA's power supplies.   Read more on the Fusion for Energy website here.

The Vacuum Section hosted approximately 40 people last week from the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Organization and the Domestic Agencies for a two-day training session on vacuum.      From the fundamentals of vacuum technologies to the discipline needed to install vacuum components, experts demonstrated all the ways vacuum is absolutely key to °ÄÃÅÁùºÏ²Ê¸ßÊÖ success. Lectures were supported by practical demonstrations including vacuum leak testing and the production of plasma discharges in vacuum.    The vacuum lecture series ... or how to learn all about the importance of vacuum in an intensive and hands-on environment. 

Another Highly Exceptional Load (HEL) passes through the six-kilometre-long channel (the Canal de Caronte) that leads from the Mediterranean into the inland sea ?tang de Berre through the town of Martigues. The load consists of four transformers¡ªone poloidal field coil rectifier procured by China and three central solenoid converters (89 tonnes each) procured by Korea. All four are "step down transformers" that lower the 66 kV tension to a few kilovolts before the AC current is transformed into DC to be fed to the magnets. The HEL convoy will begin its land journey on Wednesday and is expected at °ÄÃÅÁùºÏ²Ê¸ßÊÖ in the wee hours of Friday. Three more poloidal field coil rectifiers, stored in DAHER facility in Berre, will hit the road on Wednesday 28 November to be delivered at °ÄÃÅÁùºÏ²Ê¸ßÊÖ the following Friday.

The Chinese Academy of Sciences has reported that the Experimental Advanced Superconducting Tokamak (EAST) at the Institute of Plasma Physics in Hefei has achieved an electron temperature of over 100 million degrees in its core plasma during a four-month experiment carried out earlier this year in collaboration with domestic and international colleagues. Power injection exceeded 10 MW, and plasma stored energy reached 300 kJ after scientists optimized the coupling of different heating techniques (lower hybrid wave heating, electron cyclotron wave heating, ion cyclotron resonance heating and neutral beam ion heating). The experiment utilized advanced plasma control and theory/simulation prediction. Research at EAST on physics and technology issues under steady-state operational conditions is directly relevant to °ÄÃÅÁùºÏ²Ê¸ßÊÖ. Recent experiments on plasma equilibrium and instability, confinement and transport, plasma-wall interaction, and energetic particle physics have demonstrated long-time scale, steady-state H-mode operation with good control of impurity, core/edge MHD stability, and heat exhaust using an °ÄÃÅÁùºÏ²Ê¸ßÊÖ-like tungsten divertor.  Read a detailed report here.