°ÄÃÅÁùºÏ²Ê¸ßÊÖ

Whether captured from the top of a crane or from a drone hovering at an altitude of a few dozen metres, the °ÄÃÅÁùºÏ²Ê¸ßÊÖ site is always spectacular.

A visit to the deep "well" where the °ÄÃÅÁùºÏ²Ê¸ßÊÖ Tokamak assembly will begin next year begins with a journey underground ... through a maze of giant pillars, omnipresent scaffolding and spiral staircases. This is a place where one can get easily lost. Access, safeguarded pathways, and metal staircases move as work progresses and once-familiar itineraries often turn into dead ends.   But there's a reward to this erring. Having found (and climbed) the proper staircase, the view opens at last to what we have come to see: a concrete arena, bristling with steel rebar. The scene that sets the stage for one of the most awesome experiments in human history.   Soon, though, the view will change. The installation of a temporary steel cap—whose purpose is to protect teams below while allowing work to continue on the bioshield, above—will hide the lowest level of the Tokamak Pit from our view.

In °ÄÃÅÁùºÏ²Ê¸ßÊÖ, huge volumes of liquid helium will be circulated throughout a complex, five-kilometre network of pipes, pumps and valves to keep the 10,000-tonne magnet system at superconducting temperature. Helium will also be required to provide cooling power to the thermal shields—which reduce the large temperature gradient between the superconducting magnets and the Tokamak environment—and the cryopumps, which use extreme cold to achieve high vacuum in the plasma chamber. As a consequence, the °ÄÃÅÁùºÏ²Ê¸ßÊÖ cryoplant will be the largest in the world. Nearly 25 tonnes of liquid helium at minus 269 °C will circulate in the °ÄÃÅÁùºÏ²Ê¸ßÊÖ installation during operation.   Helium however is not the only ultra-cold fluid that the cryoplant will produce. Liquid nitrogen, at a temperature of minus 196 °C, will be used as a "pre-cooler" in the liquid helium plants.   Nitrogen, which accounts for approximately 78 percent of the air we breathe, will be extracted directly from the atmosphere in an on-site gaseous nitrogen generator with a production capacity of 50 tonnes per day, and then processed in two large liquid nitrogen plants.   The complexity of the cooling processes, along with the flux rate required for the cooling of magnets, cryopumps and thermal shield, has dictated the size and design of the cryoplant.   Construction is underway now on the buildings and technical areas of the cryoplant.   The images below show recent progress on site. Access for the first installation activities is expected in June.

The triple convoy that reached °ÄÃÅÁùºÏ²Ê¸ßÊÖ on Thursday 13 April was the heaviest ever organized since the beginning of "highly exceptional" deliveries in January 2015. Two 278-tonne electrical transformers and one 150-tonne helium tank were delivered in a three-trailer convoy that travelled at night.   The two mammoth transformers are part of a set of three destined for °ÄÃÅÁùºÏ²Ê¸ßÊÖ's pulsed power electrical network, responsible for delivering DC current for plasma operations (power injection into the magnets, plasma heating ...). One of the transformers was delivered last June and has been installed in its permanent position on the platform; transformer "bays" have been created to receive the two others.   With a total load in excess of 700 tonnes, the triple convoy was the heaviest since the transport of exceptional loads began in January 2015. The helium tank is part of Europe's contribution to the °ÄÃÅÁùºÏ²Ê¸ßÊÖ cryoplant. The tank will be installed vertically in the exterior storage area of the cryoplant zone, along with five other similar containers (see a schematic of the area here). The six-tank set, each holding 400 cubic metres of gas, will act as a buffer to keep the gas/liquid balance in the cryogenic system, and store the helium inventory when the Tokamak is in shutdown or in case of a magnet quench.