Subscribe options

Select your newsletters:


Please enter your email address:

@

News & Media

Latest ITER Newsline

  • Video | How does the ITER cryoplant work?

    Cold is essential to ITER—10,000 tonnes of superconducting magnets, the thermal shield that surrounds the machine, the cryopumps that achieve the high vacuum in [...]

    Read more

  • Component logistics | Consistency "from the cradle to the grave"

    There's a fun and easy way to demonstrate the importance of having all ITER parts properly tagged and identified in storage—organize a workshop and ask four com [...]

    Read more

  • Image of the week | Brewing storm

    In Provence, one gets tired of blue skies... so when the opportunity arises to capture the ITER site plunged in the darkness of an approaching storm, we rush to [...]

    Read more

  • Toroidal field coils | First cold test in Europe

    The first ITER toroidal field coil winding pack has spent nearly 20 days in a specially conceived cryostat at minus 193 °C (80 K), in a cold testing operation t [...]

    Read more

  • Central solenoid | All conductor received

    Officials from the US and Japanese fusion energy programs were at General Atomics' Magnet Technologies Center in California in early May to celebrate the delive [...]

    Read more

Of Interest

See archived articles

HTS technology leads the way

Pierre Bauer, Superconductor Systems and Auxiliaries Section

The ASIPP ''trial'' 68 kA current lead for ITER. (Click to view larger version...)
The ASIPP ''trial'' 68 kA current lead for ITER.
Current leads are the components that transmit the large currents from room-temperature power supplies to very low-temperature superconducting coils. The current leads for the ITER Tokamak have come a long way: from the original 60 kA proposals from the Japan Atomic Energy Research Institute (JAERI) and European partners (KIT's "demonstrator"), to the first prototypes fabricated and tested in China at the Chinese Academy of Sciences, Institute of Plasma Physics (ASIPP), and on to the presentation of the final design at the ninth High Temperature Superconductor (HTS) working group that met at Cadarache this week.

The HTS working group, which brings together experts from institutes in Japan (NIFS), Europe (KIT, CERN), China (ASIPP) and the ITER Organization, has been supporting the development of the HTS current leads for ITER since 2008. The current lead designs presented this week were fully endorsed by the working group, an endorsement crowning not only the ITER Organization's recent efforts, but also the significant investment by ASIPP/China in the fabrication and testing of four current lead pre-prototypes over the last three years.

The ''demonstrator'', a 70kA HTS current lead, produced at the Karlsruhe Institute of Technology (Photo courtesy:EFDA) (Click to view larger version...)
The ''demonstrator'', a 70kA HTS current lead, produced at the Karlsruhe Institute of Technology (Photo courtesy:EFDA)
It did not take long after the discovery of High Temperature Superconductors (HTS) in the 1980s for engineers to realize that HTS would permit significant reduction in the heat conducted into cryogenic systems through current leads. This is a particularly pertinent discovery for ITER because of the expense of removing heat at the liquid-helium temperatures at which the ITER magnets are operated.

HTS current leads use a short segment of HTS that can sustain much higher current-densities than even good conductors such as copper, allowing the reduction of the material cross-section and the related heat conduction by about tenfold. In ITER, where 60 current leads transfer a staggering 2.7 MA (MegaAmperes) into—and out of—the cryostat, conventional current leads without HTS would conduct approximately 1W/kA into the cryogenic system. This represents approximately 20 percent of the total heat extraction capacity of the cryoplant that will be installed in ITER.

The factor 2 increase in the cost of current leads due to addition of (still relatively expensive) HTS material is more than offset by the cost savings for cryoplants and power savings during operation. Most importantly, HTS current leads—in a similar way to superconducting magnets—contribute to the positive energy balance of the ITER Tokamak. They are thus a minor, but crucial element of a tokamak ... that is, if you can call a 3-metre-long object that weighs half a ton and carries 68 kA "minor." 

For the design of the ITER HTS current leads, the ITER Organization has chosen a safe approach. Due to the unprecedented scale of these leads both in current (68 kA for the TF coil feeders) and voltage (30 kV), an effort has been made to adopt proven concepts wherever possible. Also, the design had to be completed within a tight schedule and with limited resources. For this effort, the HTS working group played a crucial role, bringing together experience from other projects that use superconductivity on a large scale, such as EAST, LHC, LHD and W7X. Major features of the design are derived directly from the successful CERN development undertaken for the more than 1000 HTS current leads that were built for the LHC.

More news will follow when the ITER current lead designs are qualified in ASIPP/China in mid-2012.


return to the latest published articles