EVEDA PHASE (ENGINEERING VALIDATION AND ENGINEERING DESIGN ACTIVITIES)
The IFMIF/EVEDA project is framed by the Broader Approach Agreement signed between Euratom and the Japanese government.
Coordination is shared between Europe (F4E) and Japan (QST, formerly JAEA), the main European partners being France, Italy, Spain and Germany. Two types of activity are underway:
? Design of the complete IFMIF infrastructure, an intense source of neutrons with an energy spectrum similar to that of fusion reactors, used to assess materials behavior under very high neutron flux in order to qualify certain materials for design, construction and safe operation of the DEMO fusion demonstrator.
? Qualification of critical IFMIF systems, namely the accelerator front-end tested up to 9 MeV, the 1/3-scale lithium target, and the instrumented modules of the irradiation cells. The project represents a tremendous challenge, since IFMIF is considered by the international fusion community as essential for finalizing design and achieving startup of the fusion-based electrical power plant (DEMO).
For historical and strategic reasons, CEA is an important contributor to the design and validation of the IFMIF accelerator. Other project participants include INFN-Legnaro, SCK-CEN, CIEMAT and QST (formerly JAEA). The accelerator, featuring two 40-MeV linacs, is to deliver a 10-MW deuteron beam, an unprecedented performance. To demonstrate feasibility, a prototype consisting of a single 9-MeV and 125-mA linac, delivering a deuteron beam of more than 1 MW is being installed at the Rokkasho site in Japan.
SACM is in charge of engineering for the entire IFMIF/EVEDA project. It is responsible for the deuteron injector, the SRF-linac, the cryogenic plant and the RF system amplifiers, while the diagnostics work packages for the beam and the command & control system come under the responsibility of SEDI and SIS. Supported by other IRFU departments, SACM also provides considerable expertise in occupational safety and beam dynamics, while participating in the installation and commissioning of the prototype accelerator in Japan, and contributing to IFMIF design studies.
After five years of design work, the detailed engineering package for the IFMIF facility, defining the construction, operation and dismantling phases, was delivered in 2013, including scheduling and cost analyses. SACM and IRFU were responsible for several accelerator system work packages (injector, SRF- linac, high-energy beam transport line, diagnostics, cryogenic system, and services). They coordinated several cross-functional work packages such as beam dynamics, vacuum systems, alignment, cooling and the control system, and also participated in the IFMIF infrastructure cost assessment.
In May 2008, the International Steering Committee of the Broader Approach program agreed to use the solution based on superconducting cavities as the reference for the LIPAC prototype accelerator developed for the IFMIF/EVEDA project. Never before has a low-energy (<40 MeV) superconducting accelerator been designed or built to generate a light-ion current featuring such a high intensity (125 mA of D+). Developing this type of system is essential for IFMIF and similar projects, such as DONES, which will be equipped with several cryomodules housing superconducting cavities.
Design studies, component construction and qualification are being conducted under CEA-Saclay responsibility, assisted by CIEMAT-Madrid. SACM, with support from SIS, is in charge of providing almost all the cryomodule components, in particular the eight HWR superconducting cavities, the RF power couplers and the frequency tuning systems, as well as certain conventional equipment such as vacuum, alignment and control systems.
CEA will also conduct qualification tests on the critical components under its responsibility. Since there has never been a superconducting HWR cavity energized at the RF power targeted in this project, CEA developed a dedicated test bench (SATHORI) allowing HWR cavities with the associated coupler and frequency tuning system to be tested at a high RF power level. Between 2013 and 2015, the coupler prototypes were qualified, the design and inspection plan for the superconducting cavity identified as high pressure vessels were approved by the Japanese certification agency (KHK), the manufacture of most of the cryomodule components (cavities, tuning system, couplers, vacuum chamber, thermal screen, support frame) was launched and installation of the SATHORI test bench began.
These components will be assembled into a cryomodule in first half of 2018, under the responsibility of F4E, assisted by CEA, in an infrastructure including a clean room being built at the Rokkasho site. Installation and connection to the accelerator prototype are scheduled for 2018.
To cool down the cryomodule of the IFMIF/EVEDA accelerator prototype at 4.5 K, SACM is to deliver and install a cryogenic plant at the Rokkasho site. After several calls for tender that found no bidders, the cryogenic plant was broken down into two packages: the cryogenic production plant (cryogenic power generation and command & control) and cryogenic distribution (specific equipment and installation on site). In addition to the flexibility required for the particular type of operation implemented on the two loops that cool the solenoid coils and the cavities respectively, the challenges involved in building the cryogenic plant include: low pressure in the cavities where relative pressure of the fluid is controlled to 250 mbar and maximum pressure is below 500 mbar relative; irradiated valve box requiring special materials; HPGSL (Japan) or ASME regulatory framework with specific requirements and a 10-bar relative pressure limit; installation in Japan; commissioning and acceptance tests performed without the cryomodule; connection to the cryomodule by means of a simple flanged connection fit with precision to achieve the alignment required between cryomodule and accelerator.
The cryogenic plant includes a refrigerating liquefier that provides just over 100 W and 50 L/h simultaneously, pre-cooled by liquid nitrogen, but with no helium recovery system. As the plant is designed for non-stop operation, the compressor is equipped with a frequency-variable drive that adapts to the various operating states. Cooling is achieved using the liquid helium extracted from a 2000-liter Dewar unit. Air Liquide was chosen for construction of the cryogenic production plant, on which qualification tests began at the end of 2015. The contract for cryogenic distribution was awarded to Alat. All components will be delivered in 2016, with overall testing and startup scheduled for the first quarter of 2017.
INSTALLATION AND COMMISSIONING
The LIPAC prototype accelerator will be installed and commissioned at Rokkasho under the terms of a specific agreement. This phase began in 2013, after delivery of the injector. These activities are carried out by experts from the different organizations contributing to the project. CEA being the main EU contributor, SACM’s contribution represents approximately 14 man-years which are shared between installation and commissioning of each sub-system (injector, SRF-linac, cryogenic plant) as well as optimization of the whole accelerator operation. Part of the staff is assigned for long-term missions at the Rokkasho site.
Installation and commissioning are carried out in phases: Phase A: 100 keV (Injector); Phase B: 5 MeV (RFQ and MEBT); Phase C: 9 MeV (SRF-linac and HEBT). Phases B and C are carried out in pulsed mode to limit accelerator activation. Then, in Phase D, the duty cycle is raised gradually up to 100%.
In 2013 the injector was built and tested at Saclay, then completely dismantled and transferred to the Rokkasho site. Reassembly actually began in March 2014, after preliminary checks and conditioning, and the first plasma was produced in October 2014. On November 4, 2014, after high-voltage conditioning of the extraction system, the first 40-mA hydrogen ion beam (H+ and other molecular ions) was extracted at 70 kV. After two days of adjustments, the total extracted ion current reached 100 mA, for an energy of 100 keV. On-site commissioning continued in December 2014, following performance tests conducted on the various diagnostics systems provided by SACM. The first deuteron beam was generated in July 2015. Injector commissioning was completed at the end of 2015, achieving a record-breaking D+ beam of 112 mA at the exit of the LEBT line with emittance of 0.25 π mm-mrad. The services of SACM and the associated IRFU departments will once again be in great demand as of 2017 to prepare cryomodule assembly, install the SRF-linac, connect it to the cryoplant and then start up the entire facility. Once this phase has been achieved, with the complete accelerator operating at its nominal performance level, scheduled for December 2019 at the latest, IRFU will have demonstrated its technical advance in the field of ultra-high-intensity proton and deuteron accelerators.