The second part of the vessel for MITICA, the experiment of the ITER Neutral Beam Test Facility (NBTF) hosted by Consorzio RFX in Padua (Italy), has been delivered. Manufactured by De Pretto Industrie, through a contract awarded by F4E, this stainless steel “shell” will operate under vacuum and will house the beam line components of the most powerful Neutral Beam Injector to accelerate deuterium atoms at 1 MeV.
As the 60 t equipment entered the premises of the facility, staff on-site welcomed it with a round of applause. Another European component has been completed and delivered to this international experiment which counts with contributions also from Japan and ITER Organization. The vessel was transported from Vicenza to Padua and unloaded next to the first part of the MITICA vessel completed almost a year earlier.
The second part of the vessel is rectangular and measures 10 m long by 4 m wide and 3.5 m high. It has gone through a similar manufacturing process to the first part of the vessel counting with approximately 110 tolerance requirements. All surfaces have been chemically cleaned to comply with the needs of the ultra-high vacuum conditions for testing and operation. Manufacturing of the beam line vessel included a wide variety of activities such as the preparation of more than 200 manufacturing drawings, purchasing big amounts of stainless steel, cutting, machining and welding 700 m of welds. Most of the welds were executed using TIG (Tungsten Inert Gas) process and special attention was put on welds in contact with vacuum. Precise measuring with several methods including laser tracker have been used to control the final dimensions of the pieces and the component. Many important technical aspects had to be taken into account to connect hydraulic lines, cooling pipes, gas and vacuum system. In addition, specific features had to be taken into account to match with other in-vessel pieces of equipment such as the beam line components and the cryogenic pumps that will be installed inside the vessel.
What about the equipment that will be housed in the vessel, what is its main purpose? The mission of the beam line components is to remove the electrically-charged number of the negative ions, and to guide them to the final target in the form a neutralised beam. Approximately 60% of the negative ions as they emerge from the accelerator will be neutralised when they go through the neutraliser. The remaining non-neutralised ions will be deflected and dumped on the electrostatic residual dump panels. Once the beam is free from charged ions it will enter into the calorimeter, likened to a gate. In MITICA, the calorimeter will be closed in order to diagnose the beam and its power.
Gonzalo Micó, F4E’s Project Manager working in the team of Neutral Beam & Electron Cyclotron, Power Supplies and Sources, has been following the fabrication of this component. “The delivery marks the successful completion of this phase of the contract which is fruit of our good collaboration with De Pretto Industrie, Consorzio RFX and ITER Organization. But, we still have some way to go. The vessel will need to be vacuumed and leak-tested on-site in order to demonstrate that it is air-tight, as already checked at the factory. Later, both parts of the MITICA vessel will be welded together on-site,” he explains.
View the time lapse of the MITICA beam line vessel installation at the NBTF site here.