Linear IFMIF Prototype Accelerator Research Articles

High beam current operation with beam diagnostics at LIPAc

The Linear International Fusion Materials Irradiation Facility Prototype Accelerator (LIPAc) is under commissioning in Rokkasho Fusion Institute in Japan and aims to accelerate 125 mA D+ at 9 MeV in Continuous Wave mode for validating the IFMIF accelerator design. To ensure a fine characterization and tuning of the machine many beam diagnostics are installed spanning from injector to the beam dump. The beam operations in 1.0 ms pulsed D+ at 5 MeV were successfully completed with a low power beam dump in 2019. Despite the challenges posed by the pandemic, the crucial transition to a new LINAC configuration was also finalized to enable operation in 1.0 ms — CW D+ at 5 MeV with the high-power beam dump. The 1st beam operation of the configuration was carried out in 2021. The experiences and challenges encountered during these beam campaigns are described in this paper.

Achievement of high-current continuous-wave deuteron injector for linear IFMIF prototype accelerator (LIPAc)

The Linear IFMIF (International Fusion Materials Irradiation Facility) Prototype Accelerator (LIPAc) is aiming at demonstrating the low-energy section of a 40 MeV/125 mA IFMIF deuteron accelerator up to 9 MeV with a full beam current in continuous-wave operation. For such a high-power beam, the LIPAc injector is required to produce a beam current of 140 mA and 100 keV D+ beams. The injector commissioning to reach high beam current has been progressing at high duty cycle operation, then stable operation for many hours at a beam condition of 150 mA total extracted current. This result demonstrates that the LIPAc injector can meet the required performance for nominal 125 mA long pulse deuteron beam acceleration.

IFMIF/EVEDA achievements overview

In a fusion reactor, the plasma based on a deuterium-tritium reaction generates high energy neutron flux interacting with the materials of the plasma facing components. In order to study the irradiated behavior of these materials, the International Fusion Materials Irradiation Facility (IFMIF) was conceived to generate these fusion relevant neutrons through d-Li stripping source. IFMIF is presently in its Engineering Validation and Engineering Design Activities (EVEDA) phase under the Broader Approach agreement signed between EURATOM and Japanese Government in 2007. This agreement mandates the IFMIF/EVEDA project to validate the design of the different systems of IFMIF and to produce an integrated engineering design of IFMIF, together with the data necessary for future decisions on its construction and operation. While the Engineering Validation Activity (EVA) of the Lithium Target Facility and the Test Facility was completed by constructing prototypes, the EVA of the Accelerator Facility with the Linear IFMIF Prototype Accelerator (LIPAc) is still on-going at the Rokkasho Fusion Institute, Japan. This paper overviews the achievements in the previous phase ended on 31 March 2020 and the progress in the current phase to complete the commissioning of the LIPAc.

Design and manufacturing of the combined quadrupole and corrector magnets for the LIPAc accelerator high energy beam transport line

The International Fusion Materials Irradiation Facility (IFMIF) is a project aiming to investigate candidate materials to be used in the most exposed zones of future fusion reactors. The linear IFMIF prototype accelerator (LIPAc), presently under commissioning in Rokkasho, Japan, is a prototype of the frontend section of one of the IFMIF accelerators. Eight quadrupole magnets, six pairs of corrector magnets and one dipole are responsible for generating the magnetic fields needed for a proper beam handling along the 10 m long LIPAc high energy beam transport line, which connects the end of the superconducting radio frequency Linac with the beam dump. A novel design of combined magnets with the correctors integrated in the quadrupole poles is chosen for compactness reasons. The different stages of the production of the combined magnets, from the magnetic and mechanical design to their manufacturing and testing, including exhaustive characterization of the magnetic performance are described in this work. The results from the tests revealed the quality of the magnetic field produced. The materials selection was done carefully, to withstand the high levels of ionizing radiation expected at the magnet locations. This paper focuses on the activities performed in Europe, before sending the magnets to Japan for their installation and commissioning at the Rokkasho site.

LIPAc RF power system: design and main practical implementation issues

The Linear IFMIF (International Fusion Materials Irradiation Facility) Prototype Accelerator (LIPAc) is a 9 MeV, 125 mA, continuous wave (CW) deuteron accelerator aimed to validate the technology for the IFMIF accelerators. The construction of LIPAc, which is currently the most powerful deuteron accelerator in the world, has been carried out under the Broader Approach (BA) Agreement between EU and Japan, and it is located at Rokkasho (Japan). CIEMAT is one of the five European Institutions that has participated in the design, manufacturing and commissioning/operation of the main accelerator components, among them, the Radio Frequency Power System (RFPS). The RFPS contains all the equipment necessary to generate the required RF power to feed the LIPAc cavities. These cavities demand eighteen RF power chains at 175 MHz being distributed as follows: eight 200 kW tetrode-based chains for the Radiofrequency Quadrupole (RFQ), two 16 kW solid-state chains for the re-buncher cavities, and eight 105 kW tetrode-based chains for the Superconducting RF Linac Half-Wave Resonators. The design of the RFPS main components is presented in this paper, including the tetrode-based chains, the Solid-State Power Amplifier (SSPA) for the re-buncher cavities, the High Voltage Power Supplies (HVPSs) for the final amplifiers anodes and the RF water cooling system. Additionally, the main difficulties encountered during the first months of the RFPS commissioning and operation will be described, together with the applied improvements.

Design, manufacturing and tests of the LIPAc high energy beam transport line

The International Fusion Materials Irradiation Facility (IFMIF) is a projected accelerator-based, D-Li neutron source for fusion reactor materials qualification. LIPAc (Linear IFMIF Prototype Accelerator) is an accelerator aiming to generate a 125 mA, 9 MeV continuous wave deuteron beam, which is currently being commissioned in Rokkasho (Japan) with the objective of validating the IFMIF accelerator design.In LIPAc, a 10 m long High Energy Beam Transport line (HEBT) will connect the exit of the superconducting linac to the beam dump (BD). The HEBT line must accommodate the diagnostics for beam characterization and open the beam at the end to allow its stopping at the BD. The line contains several magnets to control the beam shape and its trajectory, maintaining beam losses below 1 W m−1 along the beamline to limit activation of surrounding elements and allow hands-on maintenance.In this work, the LIPAc HEBT line project is described since its origins. A summary of the beam dynamics calculations and other studies (vacuum, radioprotection, assembly, alignment) that led to the conceptual design of the line is done. After that, the detailed design of the line is presented, justifying the main design decisions taken and finally, the manufacturing and procurement process and the acceptance tests performed are summarized.

Validation of the Linear IFMIF Prototype Accelerator (LIPAc) in Rokkasho

For the development of the International Fusion Materials Irradiation Facility (IFMIF) aiming at material tests for fusion power plants, the construction of the Linear IFMIF Prototype Accelerator (LIPAc) has been conducted at Rokkasho, Japan under the Broader Approach Agreement. The commissioning of LIPAc has been progressing significantly. The world most powerful RFQ successfully accelerated proton beam of 58 mA, and an important project milestone of the acceleration of deuteron beam to 5 MeV with the beam current of 125 mA in pulse mode was successfully achieved. The result proves the validity of the present RFQ design. The adjustment and tuning of the RF power system and the injector for enabling an operation at maximum performances played an important role in achieving this result. For the next step, the preparation of the high duty cycle operation of RFQ is underway. The installation of the HEBT (High Energy Beam Transport line) and the beam dump accepting 1 MW, CW beam, has been completed and a new beam transport line is under manufacturing. Also the assembly of the Superconducting RF (SRF) linac to accelerate the beam up to 9 MeV started in a clean room in Rokkasho.

Commissioning of high current H+/D+ ion beams for the prototype accelerator of the International Fusion Materials Irradiation Facility.

The Linear IFMIF (International Fusion Materials Irradiation Facility) Prototype Accelerator (LIPAc) is aiming at demonstrating the low energy section of a 40 MeV/125 mA IFMIF deuteron accelerator up to 9 MeV with a full beam current in cw operation. For such a high-power beam, the LIPAc injector is required to produce a 100 keV D+ beam with 140 mA and match it for injection into the Radio Frequency Quadrupole (RFQ) accelerator. The injector is designed by CEA-Saclay based on the high intensity light ion source (SILHI). In 2019, the commissioning of the RFQ to demonstrate the D+ beam acceleration at a low duty cycle (0.1%) was conducted. A nominal beam current of 125 mA D+ beam was accelerated up to 5 MeV through the RFQ successfully. The LIPAc injector fully satisfied the requirements for RFQ beam commissioning at the pulse mode.

Design, mechanical analysis and manufacturing of the IFMIF LIPAc beam dump shielding

The International Fusion Materials Irradiation Facility (IFMIF) aims to provide an accelerator-based, D-Li neutron source to produce high energy neutrons at enough intensity and irradiation volume for DEMO materials qualification. As part of the Broader Approach (BA) agreement between Japan and EURATOM, the goal of the IFMIF/EVEDA project is to work on the engineering design of IFMIF and to validate the main technological challenges which, among a wide diversity of hardware includes the LIPAc (Linear IFMIF Prototype Accelerator), a 125 mA continuous wave deuteron accelerator up to 9 MeV mainly designed and manufactured in Europe.The beam is stopped in a copper cone involving a high production of neutron and gamma radiation and activation of its surface. A shield has been designed to attenuate both the radiation produced during accelerator operation and the residual radiation. This shield is made of an inner layer of polyethylene to moderate neutrons and an outer layer of iron to attenuate gammas produced by deuteron interactions with Cu but also those generated by neutrons in the polyethylene.The present work summarizes the upgraded design of the shielding, as well as its upgraded mechanical analysis following the ASME Boiler and Pressure Vessel Code Division VIII Section 2. It also shows the manufacturing processes and requirements imposed on the shielding along with the acceptance tests performed and the lessons learned.

Deuteron beam commissioning of the linear IFMIF prototype accelerator ion source and low energy beam transport

During the EVEDA (engineering validation and engineering design activities) phase of the International Fusion Materials Irradiation Facility (IFMIF) project, a 125 mA/9 MeV linear prototype accelerator (LIPAc) has to be built, tested and operated in Rokkasho-mura (Japan). Involved in this project for several years, CEA-Saclay designed the injector of this accelerator which is composed of an electron cyclotron resonance ion source, delivering a 140 mA deuteron beam at 100 keV, and a low energy beam transport (LEBT) line to match the beam for the injection into the radio-frequency quadrupole. In this paper, the components of the LIPAc injector are described.The commissioning of the ion source and LEBT with beam started in November 2014. The different phases of the commissioning are explained and some noticeable experimental results obtained with a beam at 100 keV are presented.

FPGA-based interlock system for the chopper of the Linear IFMIF prototype accelerator injector

The Linear IFMIF (International Fusion Materials Irradiation Facility) Prototype Accelerator (LIPAc) injector consists of a 140 mA proton/deuteron source, its associated low energy beam transport line (LEBT) as well as ancillaries such as water cooling skid, vacuum groups, High Voltage Power Supplies (HVPS), etc. A specific element, the beam “Chopper”, was included in the LEBT to generate short (˜ 100μs) and sharp-edged beam pulses (˜10μs) and allow the use of interceptive diagnostics in the high energy part of the LIPAc during commissioning phases of the Radio Frequency Quadrupole RFQ (5 MeV) and the Superconducting Radio Frequency SRF Linac (9 MeV). The chopper was designed to operate in pulsed mode with very sharp rise and fall times, meaning the chopper will be used to “cut” the long rise time of the source as well as the fall time of the beam pulse.The chopper thermal screen has not been designed to withstand very high beam power (i.e., beam length and duty cycle need to be monitored); in addition, the chopper HVPS needs to be monitored in real time to detect a possible trip and extract the beam before downstream devices are damaged. For these applications, standard PLC based interlocks are too slow; therefore, faster solutions are envisaged.The proposed solution for the required interlock system is based on COTS technology with XILINX FPGAs using RIO (Reconfigurable Input/Output) technology from National Instruments (CompactRIO platform). The paper discusses the implementation of the interlock system, the response times of the proposed architecture and the fitness of the technology. Additionally, the system can be integrated into the IFMIF control system using EPICS as a standalone solution.

Lead shutter for the IFMIF LIPAc accelerator

The International Fusion Materials Irradiation Facility (IFMIF) aims to provide an accelerator-based, D-Li neutron source to produce high energy neutrons at sufficient intensity and irradiation volume for DEMO (Demonstration Fusion Power Plant) materials qualification. As part of the Broader Approach agreement between Japan and EURATOM, the goal of the IFMIF/EVEDA project is to work on the engineering design of IFMIF and to validate the main technological challenges which, among a wide diversity of hardware includes the LIPAc (Linear IFMIF Prototype Accelerator), a 125 mA continuous wave deuteron accelerator up to 9 MeV mainly designed and manufactured in Europe.The LIPAc beam is stopped in a copper cone involving a high production of neutron and gamma radiation and activation of its surface. A lead shutter has been designed to shield against the gamma radiation coming from the copper cone through the beam tube when the beam is off, in order to allow access inside the accelerator vault. The lead shutter is located in a multipurpose chamber that also contains a scraper and two vacuum ports. The function of the scraper is to protect the last part of the beam tube in case of abnormal beams.The requirements imposed on the lead shutter chamber include the motion of the lead shutter to locate it in open (beam on) and closed position (beam off), resistance to the radiation environment, vacuum and leak tightness, alignment capabilities of the scraper and leak tightness of its cooling circuit. In this article the radioprotection calculations demonstrating the shutter performance are presented and the mechanical system of the lead shutter and the layout of the different elements contained in the chamber are described, along with their functions.

Remote disconnection system for the beam dump of the LIPAc accelerator

The International Fusion Materials Irradiation Facility (IFMIF), will be a test facility in which candidate materials for the use in fusion reactors can be fully qualified. The LIPAc (Linear IFMIF Prototype Accelerator) is a prototype of one of the two IFMIF accelerators that is currently being built in Rokkasho (Japan). There is a beam dump made of copper at the end of the accelerator to stop the deuterons. The connection of the beam dump with the rest of the accelerator is the object of this article.The requirements imposed on the connection include radiation levels in that section, vacuum and leak tightness, alignment capabilities of the system, dimensions compatible with the beam stay clear and disconnection of the system from outside the shielding.The characteristics, functions and layout of the different elements of the mechanical system are explained in this article.

Design, integration and manufacturing of the MEBT and DPlate support frames for IFMIF LIPAc

The International Fusion Materials Irradiation Facility (IFMIF) [1] aims to provide an accelerator-based, D-Li neutron source to produce high energy neutrons at sufficient intensity and irradiation volume for DEMO materials qualification. As part of the Broader Approach (BA) agreement between Japan and EURATOM, the goal of the IFMIF/EVEDA project is to work on the engineering design of IFMIF and to validate the main technological challenges which, among a wide diversity of hardware includes the LIPAc (Linear IFMIF Prototype Accelerator) [2], a 125mA continuous wave deuteron accelerator up to 9MeV mainly designed and manufactured in Europe.The Medium Energy Beam Transport line (MEBT) [3,4] is in charge of the beam transport at 5 MeV/125mA and matching beam parameters between two acceleration structures, the RadioFrequency Quadrupole (RFQ) and the Superconducting RF linear accelerator (SRF Linac), while the Diagnostic Plate (DPlate) [5] is a movable module with a set of diagnostics and instrumentations in charge of characterizing the beam in the different accelerator commissioning stages (RFQ commissioning, SRF Linac commissioning) and to provide accelerator operational parameters. Both beamline designs are state of art, being a real engineering (and mechanical) challenge, due to the compactness and alignment requirements from beam dynamics, and the seismic requirements from the accelerator site. An optimized design is critical in order to reduce beam losses and production of radiation at high power beam.The present paper summarizes the mechanical design and analysis of the MEBT and Diagnostic Plate support frames, as well as their manufacturing solutions and mechanical integration with the components installed both in the MEBT and Diagnostic Plate. The mechanical design and integration show the engineering development, adopted to fulfill the strict structural, seismic and alignment requirements.

Operation and commissioning of IFMIF (International Fusion Materials Irradiation Facility) LIPAc injector.

The objective of linear IFMIF prototype accelerator is to demonstrate 125 mA/CW deuterium ion beam acceleration up to 9 MeV. The injector has been developed in CEA Saclay and already demonstrated 140 mA/100 keV deuterium beam [R. Gobin et al., Rev. Sci. Instrum. 85, 02A918 (2014)]. The injector was disassembled and delivered to the International Fusion Energy Research Center in Rokkasho, Japan. After reassembling the injector, commissioning has started in 2014. Up to now, 100 keV/120 mA/CW hydrogen and 100 keV/90 mA/CW deuterium ion beams have been produced stably from a 10 mm diameter extraction aperture with a low beam emittance of 0.21 π mm mrad (rms, normalized). Neutron production by D-D reaction up to 2.4 × 10(9) n/s has been observed in the deuterium operation.

Installation and first operation of the International Fusion Materials Irradiation Facility injector at the Rokkasho site.

The International Fusion Materials Irradiation Facility (IFMIF) linear IFMIF prototype accelerator injector dedicated to high intensity deuteron beam production has been designed, built, and tested at CEA/Saclay between 2008 and 2012. After the completion of the acceptance tests at Saclay, the injector has been fully sent to Japan. The re-assembly of the injector has been performed between March and May 2014. Then after the check-out phase, the production of the first proton beam occurred in November 2014. Hydrogen and deuteron beam commissioning is now in progress after having proceeded with the final tests on the entire injector equipment including high power diagnostics. This article reports the different phases of the injector installation pointing out the safety and security needs, as well as the first beam production results in Japan and chopper tests. Detailed operation and commissioning results (with H(+) and D(+) 100 keV beams) are reported in a second article.

Hardware availability calculations and results of the IFMIF accelerator facility

Hardware availability calculations have been done individually for each system of the deuteron accelerators of the International Fusion Materials Irradiation Facility (IFMIF). The principal goal of these analyses is to estimate the availability of the systems, compare it with the challenging IFMIF requirements and find new paths to improve availability performances.Major unavailability contributors are highlighted and possible design changes are proposed in order to achieve the hardware availability requirements established for each system. In this paper, such possible improvements are implemented in fault tree models and the availability results are evaluated.The parallel activity on the design and construction of the linear IFMIF prototype accelerator (LIPAc) provides detailed design information for the RAMI (reliability, availability, maintainability and inspectability) analyses and allows finding out the improvements that the final accelerator could have. Because of the R&D behavior of the LIPAc, RAMI improvements could be the major differences between the prototype and the IFMIF accelerator design.

International Fusion Materials Irradiation Facility injector acceptance tests at CEA/Saclay: 140 mA/100 keV deuteron beam characterization

In the framework of the ITER broader approach, the International Fusion Materials Irradiation Facility (IFMIF) deuteron accelerator (2 × 125 mA at 40 MeV) is an irradiation tool dedicated to high neutron flux production for future nuclear plant material studies. During the validation phase, the Linear IFMIF Prototype Accelerator (LIPAc) machine will be tested on the Rokkasho site in Japan. This demonstrator aims to produce 125 mA/9 MeV deuteron beam. Involved in the LIPAc project for several years, specialists from CEA/Saclay designed the injector based on a SILHI type ECR source operating at 2.45 GHz and a 2 solenoid low energy beam line to produce such high intensity beam. The whole injector, equipped with its dedicated diagnostics, has been then installed and tested on the Saclay site. Before shipment from Europe to Japan, acceptance tests have been performed in November 2012 with 100 keV deuteron beam and intensity as high as 140 mA in continuous and pulsed mode. In this paper, the emittance measurements done for different duty cycles and different beam intensities will be presented as well as beam species fraction analysis. Then the reinstallation in Japan and commissioning plan on site will be reported.

Progress in IFMIF Engineering Validation and Engineering Design Activities

The International Fusion Materials Irradiation Facility (IFMIF) Engineering Design and Engineering Validation Activities (EVEDA) are being developed in a joint project in the framework of the Broader Approach (BA) Agreement between EU and Japan. This project has now entered into a crucial phase as the engineering design of IFMIF is now being formulated in a series of 3 subsequent phases for delivering an Interim IFMIF Engineering Design Report (IIEDR) by mid of 2013. Content of these phases is explained, including the plant configuration detailing the 5 IFMIF facilities and their systems. Together with the Engineering Design Activities, prototyping sub-projects are pursued in the Engineering Validation Activities which consist of the design, manufacturing and testing of the following prototypical systems: Linear IFMIF Prototype Accelerator (LIPAc), EVEDA Lithium Test Loop (ELTL), and High Flux Test Module (HFTM) with the prototypical helium cooling loop (HELOKA). Highlights are described from recent experiments in the Engineering Validation Activities.

RAMI analyses of the IFMIF accelerator facility and first availability allocation between systems

An analysis in terms of Reliability, Availability, Maintainability and Inspectability (RAMI) has been done for each system (Injector, MEBT, SRF Linac, RF system⿦) of the deuteron accelerators of the International Fusion Materials Irradiation Facility (IFMIF). The goal of these analyses is to estimate the availability of the accelerator facility based on the current design in order to compare it with the high IFMIF availability requirements. A first availability allocation between accelerator systems was performed to quantify the improvement demanded in terms of RAMI to achieve such requirements. These studies highlight the critical parts and parameters that most likely can have an impact on downtime.Individual fault tree analysis was done for each system of the accelerator with the software RiskSpectrum® PSA Professional. With such model, a deep analysis was done and therefore major unavailability contributors for each system were presented. Statistical analyses were developed to evaluate time dependency, parameters and events importance, sensitivities and uncertainties. Results gave indications for possible improvements, whenever feasible, for each accelerator system.These studies have been performed in collaboration between system designers and RAMI experts enabling the creation of RAMI models that reflect the current accelerator design. The parallel activity on the design and construction of the Linear IFMIF Prototype Accelerator (LIPAc) provides detailed design information and allows the finding of the improvements that the final accelerator could have. Because of the R&D character of the LIPAc, design improvements based on the results of the RAMI analysis could be the major differences between LIPAc and the IFMIF accelerator design.