Factory Acceptance Tests of the Ion Source and Extraction Power Supplies (ISEPS) for the SPIDER experiment completed successfully

Anticipation and excitement in the air. A wave of concentration falls upon the people in the hall. Focus and precision. With quiet optimism, the button is pushed and all attention is focused on the control panel.

The location, OCEM Energy Technology premises in San Giorgio di Piano, near Bologna, an Italian company employing around 70 staff. A gathering of people consisting of OCEM Energy Technology employees, representatives from the German sub-contractor Himmelwerk GmbH, as well as F4E and ITER Organization staff and representatives from the Italian European Fusion Laboratory RFX, huddle together in order to witness the outcome of the final Factory Acceptance Tests before on-site delivery of the full first unit of Ion Source and Extraction Power Supplies (ISEPS) for the SPIDER experiment. SPIDER (Source for Production of Ion of Deuterium Extracted from Radio frequency plasma) is one of the two independent test beds (the other one is MITICA) which make up the Neutral Beam Test Facility which is dedicated to the testing and developing of the ITER Neutral Beam Injectors, and located in Padua, Italy.

One of the main F4E contributions to ITER additional heating systems, the two Neutral Beam injectors are essential in supplying 16.5 MW of power each in order to inject high-energy beams of neutral atoms into the core of the ITER plasma and provide the high temperature necessary for fusion reactions to occur in the plasma. The neutral beam is obtained by creating a beam of negatively charged ions, then accelerating it to high speeds and finally neutralising it through an interaction with neutral gas of the same type. Any non-neutralised atoms are removed from the beam through an electrostatic field. The Neutral Beam injectors are unique in terms of high energy (1 MeV), pulse duration (up to 3,600 s) and power and therefore need to be tested before being installed in ITER. SPIDER is the test bed where the first full-scale ITER ion source will be tested and developed with an acceleration voltage of up to 100 kV.

The Ion Source and Extraction Power Supplies (ISEPS) include all the power supplies required for feeding the ion source of the Neutral Beam injector and for extracting an ion beam from the source, through the use of 4 radio frequency generators. The ISEPS unit has an overall power rating of 5 MVA and are composed of a heterogeneous set of items, ranging from power distribution equipment at 6.6 kV to solid state power converters (both high voltage, up to -12 kV and high current, up to 5 kA). Each radio frequency generator has a power capacity of 200kW and an operating frequency of 1MHz, and is fed by a direct current (dc) power supply of 12kV with a 140A output feed current. The power supplies are hosted on a platform insulated at -100kV from the ground over a surface of approximately 12 x 10 metres.

The final Factory Acceptance Tests, which were carried out over a three week period included test-runs of the major individual sub-assemblies of ISEPS, followed by power tests of the whole system connected to one of the four radio frequency generators supplied by subcontractor Himmelwerk GmbH (the remaining three radio frequency generators have already been successfully tested at the company’s production site in Germany and the future on-site test will include all four radio frequency generators). Muriel Simon, the F4E Responsible Officer for this contract, explains, “This is the first complete, complex system (in fact, composed of several sub-systems, each of them with many main components) including its control, protections and interlocks procured for ITER which has been fully manufactured and successfully tested in factory”. Indeed, it was to the sound of applause amongst the participants that it was concluded that the testing had been extremely successful: the equipment performed in accordance with requirements and met without any issue all set criteria, including full power level and long pulses.The testing involved running the power supplies at the maximum nominal power of 200kW for a period of 15 minutes, a longer duration than foreseen in the test plan for such high power level. Tullio Bonicelli, Leader of F4E’s Project Team dealing with the technical and contractual monitoring in order to provide the ISEPs Unit for ITER, says, “OCEM Energy Technology have proven to be highly skilled collaborators and have shown great adaptability in terms of the demanding specifications for ISEPS. The expertise of German SME Himmelwerk GmbH has been very useful thanks to the company’s proven expertise in radio-frequency generators. Likewise, the RFX team has provided vital support to F4E in the technical monitoring of this key contract for the overall procurement of SPIDER power supplies”.

In total, the procurement contract signed between F4E and OCEM Energy Technology encompasses four almost identical ISEPS units being delivered, two of which will be used for the Neutral Beam Test Facility. The remaining two units will cover the needs of the two ITER Neutral Beam injectors on the ITER site in Cadarache, France.

a. The ISEPS power supplies are hosted on a 12 x 10 m insulated platform. They are fed and insulated at -100kV from ground via an insulating transformer (22kV/6.6kV, 5MVA) located outdoors, (Image courtesy of OCEM).

Some of the ISEPS components, from left to right:

b. Insulating transformer (Image courtesy of OCEM)

c. Power supply feeding in the direct current (DC) the 4 radio frequency generators (1.6MW)

d. The radio frequency oscillators hosted in these cubicles generate high frequency (1MHz) energy used by the source to produce the plasma from which negative ions are then extracted (Image courtesy of OCEM.

To learn more about the F4E-OCEM Energy Technology collaboration, see our newly released clip of OCEM representative Giuseppe Taddia speaking about the benefits of working with F4E: