The US Domestic Agency and vendor General Atomics completed a major milestone on 6 April by winding the first module for the ITER central solenoid. The feat was accomplished at the General Atomics Magnet Development Facility in Poway, California.   Each central solenoid module is fabricated from approximately 6,000 metres of niobium-tin (Nb3Sn) conductor, supplied by Japan in seven spools. The central solenoid, a giant electromagnet considered the "heartbeat of ITER," will consist of six stacked modules surrounded by a support structure.  When assembled, the entire 13 Tesla central solenoid and associated structures will be 13 metres tall and weigh 1,000 metric tons.   Conductor from six spools is wound to form six separate hexapancakes (6 layers) containing 14 turns. The seventh spool is wound to form a quadpancake (4 layers) containing 14 turns.   After winding, the completed hexapancakes and quadpancake will be stacked and joined prior to heat treatment, insulation, vacuum pressure impregnation, and final testing.

Spring has appeared on the ITER site, with green and yellow sprouting in the surrounding hills and along the platform's embankments — for Newsline, the perfect time to take a spring break. We'll be back on 25 April to commemorate one of fusion history's watershed moments — Soviet physicist Igor Kurchatov's speech at the Atomic Energy Research Establishment in Harwell (UK) on 26 April 1956.In the meantime work continues to progress on site, as the gallery below can attest. Workers are installing rebar at the second basement level (B1) on the east side of the Tokamak Complex; cladding work is nearly finished on the Assembly Hall; and concrete pouring for the cryoplant's underground structure almost complete.

In the basement of the ITER Tritium Plant, four storage tanks and two security tanks procured by Europe will handle the water involved in the recycling process of tritium. Installation on the tanks into the lower basement level (B2) began in late March and will continue until all six plant components are in place.   In the short video shot on 7 April, we watch as one of the 100 m³ security tanks is removed from temporary storage, transported to the platform, and lifted by crane into place.   The six water detritiation tanks (four 20 m³ tanks and two 100 m³ tanks) are the first plant components to be installed in the ITER Tokamak Complex.    Watch the short video here.

On Thursday 20 April in Washington DC, the Science, Space & Technology Subcommittee on Energy of the US House of Representatives conducted a hearing on fusion energy science. Bernard Bigot, Director-General of the ITER Organization, Stewart Prager, Director of the Princeton Plasma Physics Laboratory, and Scott Hsu, a Physics Division scientist at the Los Alamos National Laboratory, were the three "witnesses" called to testify on the present state, perspectives and challenges of fusion research. While the atmosphere was studious and supportive, the questions were without concession. "There is no single idea that is a magic bullet that would deliver commercial fusion in 10 years," answered Stewart Prager to a question from Ranking Member Alan Grayson (D-FL). "But we can greatly accelerate the pace. There's no question fusion can be developed in a time scale to have a huge impact on how we procure energy in the middle of this century." Answering a question from Vice-Chairman Steve Knight (R-CA) ITER Director-General Bigot stressed that keeping the schedule was now paramount and confirmed that ITER "will be able to deliver on time." We'll have a more detailed report on the hearing in the coming days. Read the Committee's press release here.

--By Raphael Rosen Scientists at the US Department of Energy's Princeton Plasma Physics Laboratory (PPPL) have helped design and test a component that could improve the performance of doughnut-shaped fusion facilities known as tokamaks. Called a "liquid lithium limiter," the device has circulated the protective liquid metal within the walls of China's Experimental Advanced Superconducting Tokamak (EAST) and kept the plasma from cooling down and halting fusion reactions. The journal Nuclear Fusion published results of the experiment in March 2016. This system reduces the production of impurities that typically are created when the plasma reaches other components of the vessel. Moreover, plasmas tolerate higher amounts of lithium impurities, compared with the impurities from other materials, because the low atomic number of lithium produces very low amounts of plasma radiation that typically cools the plasma core. Serving as the main point of contact with plasma enables the lithium to absorb the hot deuterium ions that drift from the centre of the plasma, and keeps them from striking the interior walls of the tokamak and cooling down. Limiting the amount of cool deuterium at the edge of the plasma reduces the difference in temperature between the hot plasma centre and the cooler edge, and reduces turbulence. As a side note, however, contact with the ions was found to slightly damage the thin stainless steel foil surface of the limiter device, prompting work on an improved design. Read the full report on the PPPL website. Photo of the white-hot limiter glowing in contact with the plasma during an EAST discharge.