Concrete pouring operations resumed early on Wednesday 22 January in the southern corner of the Tokamak Pit.Two large concrete pumps, one equipped with a 58-metre extensible arm (the largest available in France), were mobilized to fill a 500 square-metre area with specially formulated concrete produced in the nearby batching plant.Operations began at 4:00 a.m. and continued for 10 hours. This was the second segment (out of 15) poured for the Tokamak Complex basemat, and one of three that will support the future ITER Diagnostics Building.Special measures were set into place to counter the early morning cold, such as producing warm concrete in the batching plant (by heating the water and gravel) and using plastic sheeting as the work progressed to avoid too rapid cooling. Some 800 cubic metres of warm (14-17 °C) concrete were poured in the course of the 10-hour long operation. Hot air blowers were also activated once the pour was complete to regulate the drying process.The complete Tokamak Complex basemat (1.5-metre-thick) is scheduled to be in place in July. Work will resume next week on the rebar installation in the central area of the Tokamak Pit.

With a peak AC current at 415 kA and a peak DC current at 385 kA, the ITER power supply test facility at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) set a new record on 2 December 2013, demonstrating its capability to host the demanding short circuit test for ITER power converters. The facility, under construction since 2008, consists of three test platforms that can support the AC short circuit test up to 350 kA, the DC multifunction test up to 400 kA and 2 kV and a steady state test up to 60kA/1.35 kV. The three platforms can perform all the tests required for qualifying the ITER poloidal field power converters, including rated current tests, short circuit current tests, temperature rise tests and control/protection/operation verification. In addition, they are able to provide a wide range of regulated current and voltage for the different purposes of the tests.    The test facility has already started accompanying the development of the ITER poloidal field converter prototype components. (Pictured: the DC disconnector test platform.) Moreover, the facility can host the installation of an entire poloidal field converter unit and operate it in different modes to simulate real ITER operation.  The test facility has already started accompanying the development of the ITER poloidal field converter prototype components. Several types of tests have been run, including the short-circuit (175 kA) and temperature rise (28 kA/4 hr) tests of the DC reactor; the short circuit withstand (350 kA/100 ms) and thermal stability (140 kA/2 s) tests of the enclosed AC busbar; and the short circuit withstand (350 kA/100 ms) and temperature rise (55 kA) tests of the DC disconnector. The short circuit withstand (350 kA) and the current balance tests of the converter bridge and external bypass will be performed soon.

An important aspect of ITER's scientific program revolves around the development of collaborative and training activities with academic and research organizations in the Members. A significant expansion of these activities occurred on Christmas Eve when ITER Director-General Osamu Motojima signed a Memorandum of Understanding with Tohoku University on Scientific, Academic and Educational Cooperation, the first such agreement established with a Japanese university.   Tohoku University, founded in 1907 and based in Sendai in northern Honshu, is one of Japan's leading universities, with approximately 6,000 staff and 18,000 students.   At the signing ceremony for the Memorandum of Understanding, held in Tokyo on the afternoon of 24 December, DG Motojima was joined by Prof Susumu Satomi, President of Tohoku University and Mr Kanji Fujiki, Deputy Minister of MEXT (Ministry of Education, Culture, Sports, Science and Technology) in expressing the need to expand ties between the ITER Project and academic institutions, with their deep expertise in many areas of science and technology of importance to the success of ITER. The agreement will promote opportunities for collaboration between the university's researchers and ITER scientists and engineers, and will also open the possibility of Tohoku students carrying out research projects at the ITER Organization as part of their training.   At the celebration which followed the signing ceremony and a series of presentations on the ITER Project's construction, technology and science activities, several members of ITER staff had the opportunity to meet senior academics from Tohoku and discuss possibilities for future collaboration.

With the progression of ITER conductor production all over the world, the first lengths of completed conductors are being delivered to coil manufacturers. Although the lengths may extend up to nearly one kilometre, in most cases it will be necessary to connect several lengths together in order to wind the final coils.   To connect adjacent conductor lengths electrically and to connect the coil terminals to the feeder busbars, manufacturers will have to fabricate joints . While standard brazing is generally used in industry to connect regular copper conductor lengths, it has proven far more challenging to join superconducting conductor lengths. Many years of development in laboratories and industry have proved necessary to arrive at acceptable solutions.   Coaxial joint design. Laced superconducting shells, overlapping both cable ends, are enclosed inside two copper crescents. A stainless steel jacket is installed around. One of the challenges presented by superconductors is keeping the joint resistance low enough to prevent excessive Joule heating and provide a current transfer, from one conductor to the next, with an as-even-as-possible current distribution among cable strands and within limited space. Another challenge is the cable-in-conduit design (stainless steel jacket around the conductor and an internal flow of supercritical helium) that is common to all ITER conductors. The jacket has to be removed to connect adjacent superconducting cables, while all the while respecting the continuity of the helium flow and tightness of the conduit.   In order to perform final qualification of the joints for ITER conductors, it has been decided to manufacture samples and to measure performance—in particular, joint resistance—in conditions as relevant as possible to tokamak operation. The tests will be performed at the SULTAN facility in Switzerland.   N. Martovetsky, from US ITER, presents the design of the central solenoid joint sample to the review panel chaired by P. Bruzzone (foreground, left) on 18 December 2013. The design of the joints connecting the ITER correction coils with the feeder busbars relies on the use of the overlap twin-box joint concept (see Fig. 1), initially developed in the laboratories of the French CEA and then used in the Toroidal Field Model Coil (TFMC) built by Europe during the ITER Engineering Design Activities phase. In this design, each conductor end is enclosed inside a bimetallic stainless steel-copper box and adjacent box copper faces are soldered with each other. Low resistance can be achieved, in the order of a few nanoohms, but at the expense of a large consumption of space since locally two conductors are overlapping.     Due to the specific space requirements of the central solenoid, the US Domestic Agency has developed two new types of joints, both fitting within the regular space of a single conductor: a splice joint (Fig. 4), connecting conductor lengths inside a module; and a coaxial joint (Fig. 2), connecting coil terminals to busbar extensions running along the coil outer diameter. The busbar extensions are themselves connected to the feeder busbars by classical twin-box joints.   Splice joint connecting conductor lengths inside central solenoid modules. After the jacket is removed at both cable ends, the cables are interleaved at the level of each sub-cable and jacket shells are installed around and welded to the conductor jacket. Two final design reviews were conducted in late 2013 to review the designs of a correction coil joint sample (to be manufactured by correction coil manufacturer ASIPP, China), and the design of a central solenoid joint sample (to be manufactured by central solenoid modules manufacturer General Atomics, US). Both samples are planned to be manufactured and tested in 2014.   For both the correction coil and central solenoid joint designs, the review panel provided a positive recommendation on the presented designs and on the proposed testing programs, paving the way to the start of their manufacture early 2014.

The Centre de Recherches en Physique des Plasmas (CRPP) in Switzerland has studied fundamental plasma physics since 1961, with a particular focus on magnetic fusion since 1979. Part of the Ecole Polytechnique Fédérale de Lausanne (EPFL), the CRPP operates the TCV tokamak and the SULTAN facility for testing and evaluating high current superconductors. We recently spoke with Pierluigi Bruzzone, head of CRPP's Superconductivity section, about work currently underway at SULTAN for the ITER magnets. Newsline: Since April 2012, the ITER Organization and EPFL have been linked by a service contract that guarantees the availability of the SULTAN facility for the performance testing of ITER conductors. Can you describe SULTAN's capabilities?   Pierluigi Bruzzone: The SULTAN test facility was built 30 years ago, in 1984, as a result of collaboration between Italy, Switzerland and the Netherlands. The machine was upgraded substantially in 1990 and fully taken over by Switzerland when the collaboration dissolved. It is not a young test machine, but it was designed by my predecessor, Georg Vecsey, in such a good way that it is still rendering very valuable service to the physics community today.SULTAN is the only facility in the world capable of producing high magnetic field (up to 11 T background field), high current (up to 100 kA) and high mass flow rate of supercritical helium for cooling. The 92 x 142 mm space available for samples can accommodate the large superconductors for present and future fusion devices. ITER has been our most frequent user since 2007.A new test facility, EDIPO, has been erected next to SULTAN and is being commissioned. In 2014, it will complement SULTAN with a higher background field, 12.5 T, and a larger high field length, up to 900 mm.What role has SULTAN played historically for ITER conductors?We accompanied all the phases of ITER conductor development, including the R&D phase, supplier qualification, production qualification, and now final production. At each phase, the ITER conductor Procurement Arrangements foresee testing. We were also involved with the prototypes for the ITER model coils back in the 1990s.Presently, the qualification phase for all conductor types for ITER is over. During this phase there was a mutual learning process. There were some question marks at first—were we conducting the right tests, was our methodology correct? We were able to resolve the doubts one after another and satisfy our client. We had an important success with the ITER central solenoid conductor.Of the 20 people that form the SULTAN team, approximately half work full time on ITER testing; we also have some contracts related to DEMO fusion power plant projects, high-temperature superconductor (HTS) R&D and testing, and smaller studies. Fusion is the core of our activity. The entire cycle of ITER conductor testing, from the day a sample is received to the day testing is completed, takes about four months. ITER has been the facility's most frequent user since 2007. How do you organize the testing for ITER conductors?We receive two kinds of ITER conductor samples. Niobium-titanium (NbTi) samples are delivered to us already assembled. Niobium-tin (Nb3Sn) samples, the more delicate technology, are delivered as raw conductor units. For the Nb3Sn conductor it takes us approximately 12 weeks to assemble a conductor sample—the main steps for a sample assembly are: preparation of the terminations, heat treatment (four weeks), and instrumentation. Each step has a rigorous sequence of quality assurance checks, with a number of protocols eventually summarized in the assembly report. The tests themselves last from one to five weeks depending on the test program, which is dictated by the phase of production. For each test we deliver to ITER a summary test report and the full set of raw data.In our facility, it takes three days to install and cool down the sample and another three to warm up and remove it again. The 20 t magnets of the test facility have remained cold for over ten years. As sample preparation takes longer than the tests, we assemble several samples in parallel to keep SULTAN busy full time.The conductor samples are tested under operating conditions that replicate ITER operation in terms of magnetic field, operating current, operating temperature and mass flow rate.  Beside the DC test and AC loss test, which aim to verify the acceptance criteria, we apply "cyclic loading", mimicking the ITER lifetime (e.g., up to 10,000 load cycles for the ITER central solenoid conductors) to make sure that no significant performance degradation occurs.The entire cycle, from the day a sample is received to the day testing is completed, takes about four months. In one year, we have up to twenty test campaigns for different conductors supplied by ITER parties. Pierluigi Bruzzone, head of CRPP's Superconductivity section. "We accompanied all the phases of ITER conductor development, including the R&D phase, supplier qualification, production qualification, and now final production. ... The ITER design requirements and the target performance are both fulfilled by the conductors that we have tested." You chaired the December 2013 final design review of central solenoid joint samples. Can you tell us more about conductor joint technology?The ITER conductor lengths will be connected one to another in the final coil assemblies by joints. The aim of the final design review at the end of last year was to agree on the joint sample assembly procedure of a company that will do the central solenoid winding. All the ITER conductor joints will be made by industrial suppliers according to ITER Organization design. According to Procurement Arrangement specifications, each supplier has to qualify its joint assembly procedure by a joint sample tested in SULTAN.We have already tested the European joint sample in two different campaigns. Next we'll test the US central solenoid joint assembly, and then samples from China and Russia—probably eight samples in all.Compared to testing the conductors, which will take three years, the joints will only require a couple months of testing if we put the campaigns back-to-back. The difficulty lies more in the work involved with checking drawings and verifying that interfaces are correct for our facility. The assembly work for joint sample must be done in industry.With all of your experience, can you say that you have confidence in the performance of the ITER conductors?Yes, definitely. The ITER design requirements and the target performance are both fulfilled by the conductors that we have tested. I don't expect that conductor performance will be an issue for ITER.Fusion magnets are very special objects. We have built up a lot of experience and know-how in working for ITER and I can only hope that there won't be too long a gap before the DEMO-phase machines are under construction. Otherwise, we risk losing the human expertise and the industrial know-how that we are accumulating now.