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Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*
Journal of Physics; Conference Series, 2687(5), p.052008_1 - 052008_6, 2024/01
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Maekawa, Fujio; Meigo, Shinichiro
Proceedings of 14th International Particle Accelerator Conference (IPAC 23) (Internet), p.1591 - 1593, 2023/05
The Japan Atomic Energy Agency (JAEA) is designing a 30 MW continuous wave (cw) superconducting proton linear accelerator (linac) for the Accelerator Driven System (ADS) proposal. The JAEA-ADS linacs ion source must provide a proton beam over 20 mA with an energy of 35 keV and a normalized rms emittance of less than 0.1 
mm mrad. As the extraction system determines the beam properties and quality, systematic optimizations on the geometry and input values of the extraction system design were conducted using the AXCEL-INP 2-D simulation program to satisfy the goal requirements. This work describes the extraction system design and reports the beam dynamics results of the first study for the proton source of the JAEA-ADS linac.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Nakano, Keita; Maekawa, Fujio; Meigo, Shinichiro; Jameson, R. A.*
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.499 - 502, 2023/01
The Japan Atomic Energy Agency (JAEA) is designing a 30-MW proton linear accelerator (linac) for the accelerator-driven subcritical system (ADS). The Radio Frequency Quadrupole (RFQ) is an essential component for the performance of high-intensity linac, especially in ADS, where stringent reliability is demanded. The present RFQ will capture a 20 mA proton beam and accelerate from the energy of 35 keV to 2.5 MeV, where the space-charge effects are severe. The present RFQ's design employs the equipartitioning (EP) beam scheme to control the emittance growth and compactness. As a result, the beam halo formation was minimized and allowed to optimize the superconducting linac downstream part. A remarkable feature of this RFQ is the low Kilpatrick factor of 1.2 adopted to achieve high stability by reducing the probability of surface sparking on the vane. This work presents and discusses the results of this RFQ design.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Nakano, Keita; Maekawa, Fujio; Meigo, Shinichiro
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.179 - 183, 2023/01
The Japan Atomic Energy Agency accelerator-driven subcritical system (JAEA-ADS) pursues the reduction of nuclear waste by transmuting minor actinides. JAEA-ADS project drives a 30-MW proton beam to a lead-bismuth eutectic (LBE) spallation target to produce neutrons for a subcritical core reactor. To this end, the JAEA-ADS beam transport (BT) must provide a suitable beam profile and stable beam power to the beam window of the spallation target to avoid high-thermal stress in the components, such as the beam window. The beam transport was optimized by tracking a large number of macroparticles to mitigate the beam loss, performance with high stability in the presence of errors, and fulfill the length requirement on the transport. This work presents beam transport design and beam dynamics research for the JAEA-ADS project.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Nakano, Keita; Maekawa, Fujio; Meigo, Shinichiro
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.286 - 290, 2023/01
Japan Atomic Energy Agency (JAEA) is designing a 30-MW proton linear accelerator (linac) as one of the fundamental components for its accelerator-driven subcritical system (ADS) project. ADS accelerators demand extremely high reliability and availability to avoid thermal stress in the subcritical reactor structures. Thus, reliability and availability assessments of the accelerator are mandatory to detect weakness in the lattice designed and evaluate redundancy configurations to fulfill the demanded operation. This study applied the Reliability Block Diagrams (RBD) method to calculate the Medium Time Between Failures (MTBF) for different linac configurations: all the linac's elements in a series configuration and a combination of hot-standby for the low-energy section of the linac and k-out-n redundancy for the high-energy part. The estimation considered the detailed arrangement of the cavities and magnets that compose the linac lattice. In this report, we describe the reliability model of the JAEA-ADS linac, report the MTBF results, and point out the potential route toward operating with the required availability.
Yee-Rendon, B.; Meigo, Shinichiro; Kondo, Yasuhiro; Tamura, Jun; Nakano, Keita; Maekawa, Fujio; Iwamoto, Hiroki; Sugawara, Takanori; Nishihara, Kenji
Journal of Instrumentation (Internet), 17(10), p.P10005_1 - P10005_21, 2022/10
Times Cited Count：0 Percentile：0(Instruments & Instrumentation)To reduce the hazard of minor actinides in nuclear waste, JAEA proposed an accelerator-driven subcritical system (JAEA-ADS). The JAEA-ADS drives a subcritical reactor 800-MWth by 30-MW proton linac delivering the beam to the spallation neutron target inside the reactor. The beam transport to the target (BTT) is required for high-beam power stability and low peak density to ensure the integrity of the beam window. Additionally, the design should have compatible with the reactor design for the maintenance and replacement of the fuel and the beam window. A robust-compact BTT design was developed through massive multiparticle simulations. The beam optics was optimized to guarantee beam window feasibility requirements by providing a low peak density of less than 0.3 
A/mm
. Beam stability was evaluated and improved by simultaneously applying the linac's input beam and element errors. The input beam errors to the reactor were based on the beam degradation obtained by implementing fast fault compensation in the linac. Those results show that the BTT fulfills the requirements for JAEA-ADS.
Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.
Journal of Nuclear Science and Technology, 59(9), p.1174 - 1205, 2022/09
Times Cited Count：5 Percentile：84.97(Nuclear Science & Technology)In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Domae, Takeshi*
Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.180 - 183, 2022/09
The Japan Atomic Energy Agency (JAEA) has proposed an accelerator-driven subcritical system (ADS) to efficiently reduce high-level radioactive waste generated at nuclear power plants. One of the challenging R&D aspects of ADS is the reliability of the accelerator. In preparation for the full-scale design of the CW proton linac for the JAEA-ADS, we are now prototyping a low-beta (around 0.2) single spoke cavity. Since there is no experience in Japan in manufacturing a superconducting spoke cavity, prototyping and performance testing of the cavity is essential to ensure the feasibility of the JAEA-ADS linac. In the Japanese fiscal year 2021, we have started welding cavity parts together. By preliminarily examining the electron beam welding conditions, each press-formed niobium part was joined with a smooth welding bead. At present, we have fabricated the cavity's body part.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Nakano, Keita; Maekawa, Fujio; Meigo, Shinichiro
Physical Review Accelerators and Beams (Internet), 25(8), p.080101_1 - 080101_17, 2022/08
Times Cited Count：2 Percentile：52.69(Physics, Nuclear)High reliability and availability are primary goals for the operation of particle accelerators, especially for accelerator-driven subcritical systems (ADS). ADSs employ high-power beams for the transmutation of minor actinide; as a result, the amount and the radiotoxicity of the nuclear waste are considerably reduced. To this end, the Japan Atomic Energy Agency is designing a 30-MW continuous wave (cw) super-conducting proton linear accelerator (linac) that supplies neutrons to an 800-MW subcritical reactor by a spallation process. The major challenge for an ADS linac is the strict control of the beam trip duration and its frequency to avoid thermal stress in the subcritical reactor structures. The maximum allowed beam trips for failures longer than a few seconds are estimated to be far below the rate achieved in current accelerators. Thus, we implemented a combination of hot standby and local compensation that enables a fast beam recovery. This work comprehensively investigated the tolerance of our linac lattice for the local compensations for failures in superconducting cavities and magnets. This scheme includes simultaneous compensation of multiple cavities in independent and same cryomodules that significantly enhance the reliability of the linac. The returned schemes present acceptable beam performance to guarantee the integrity of the linac and the beam transport to the target; moreover, they satisfy the beam stability in the beam window. In addition, the readjusted elements are subjected to moderate stress to ensure a sustainable operation. This manuscript reports the beam dynamics results toward fulfilling the high reliability demanded by an ADS linac.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio
Proceedings of 64th ICFA Advanced Beam Dynamics Workshop on High Intensity and High Brightness Hadron Beams (ICFA-HB2021) (Internet), p.30 - 34, 2022/04
The Japan Atomic Energy Agency (JAEA) is working in the research and development of an Accelerator Driven Subcritical System (ADS) for the transmutation of nuclear waste. To this end, JAEA is designing a 30-MW CW proton linear accelerator (linac) with a beam current of 20 mA. The JAEA-ADS linac starts with a Normal Conducting (NC) up to an energy of 2.5 MeV. Then, five Superconducting (SC) sections accelerate the beam up to 1.5 GeV. The biggest challenge for this ADS linac is the stringent reliability required to avoid thermal stress in the subcritical reactor, which is higher than the achieved in present accelerators. For this purpose, the linac pursues a strong-stable design that ensures the operation with low beam loss and fault-tolerance capabilities to continue operating in case of failure. This work presents the beam dynamics results toward achieving high reliability for the JAEA-ADS linac.
Katano, Ryota; Nishihara, Kenji; Kondo, Yasuhiro; Meigo, Shinichiro
JAEA-Research 2021-016, 16 Pages, 2022/03
JAEA-Research-2021-016.pdf:1.65MB
It has to be confirmed that the accelerator-driven system (ADS), which is dedicated to transmuting minor actinides, is subcritical in any state by measurements. In the previous research, we have proposed a procedure in which the core safely and efficiently approaches the target subcriticality before the operation. In this procedure, the reference value of the subcriticality at the initial state is measured by the area ratio method capable of the absolute value measurement. The area ratio method uses a pulsed neutron source. However, specific and practical parameters of the accelerator for the area ratio method have not been determined. In this study, we determined the accelerator parameters with the consideration of the uncertainties derived by the dead-time of the detector and the statistical error of the count ratio. In addition, we estimate the coating amount of the sample nuclide in the assumption of the use of the fission chambers.
Yee-Rendon, B.; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Tamura, Jun
Physical Review Accelerators and Beams (Internet), 24(12), p.120101_1 - 120101_17, 2021/12
Times Cited Count：3 Percentile：46.8(Physics, Nuclear)The Japan Atomic Energy Agency (JAEA) is working on the research and development of a 30-MW continuous wave (CW) proton linear accelerator (linac) for the JAEA accelerator-driven subcritical system (ADS) proposal. The linac will accelerate a 20 mA proton beam to 1.5 GeV, using mainly superconducting cavities. The main challenge for an ADS accelerator is the high reliability required to prevent thermal stress in the subcritical reactor; thus, we pursue a robust lattice to achieve stable operation. To this end, the beam optics design reduces the emittance growth and the beam halo through the superconducting part of the linac. First, we simulated an ideal machine without any errors to establish the operation conditions of the beam. Second, we applied element errors and input beam errors to estimate the tolerance of the linac design. Finally, we implemented a correction scheme to increase the lattice tolerance by reducing the beam centroid offset on the transverse plane. Massive multiparticle simulations and a cumulative statistic of 1
10
macroparticles have shown that the JAEA-ADS linac can operate with less than 1 W/m beam losses in error scenarios.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio
Proceedings of 20th International Conference on RF Superconductivity (SRF 2021) (Internet), p.372 - 375, 2021/11
To overcome the nuclear waste problem, the Japan Atomic Energy Agency (JAEA) has been developing an accelerator-driven subcritical system (ADS) since the late 1980s. In the JAEA-ADS proposal, an 800 MWth subcritical reactor is driven by a 30 MW CW-proton linear accelerator (linac). One of the biggest challenges for the ADS accelerator is the high reliability and availability required for their operations. To this end, the present JAEA-ADS linac was redesigned by adopting the current developments in Superconducting Radio-Frequency (SRF) technology. Additionally, we developed a robust lattice to control the beam loss and implemented a fault-tolerance scheme for the fast recovery of SRF cavity failures. This work presents the latest results of the R&D of the JAEA-ADS superconducting linac.
Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Nakano, Keita; Takei, Hayanori; Maekawa, Fujio; Meigo, Shinichiro
Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.61 - 65, 2021/10
Japan Atomic Energy Agency (JAEA) is designing a 30 MW CW superconducting proton linac as a major component for the accelerator-driven subcritical system (ADS) project. The main challenge of the linac operation is the high reliability required to suppress thermal stress in the subcritical reactor. To this end, we implemented fault compensation schemes to enable a fast beam recovery; consequently, reducing the beam trip duration. This work presents strategies to increase the fault-tolerance capacity of the JAEA-ADS linac.
Yee-Rendon, B.; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Tamura, Jun
Proceedings of 12th International Particle Accelerator Conference (IPAC 21) (Internet), p.790 - 792, 2021/08
The Medium Energy Beam Transport (MEBT) will transport a CW proton beam with a current of 20 mA and energy of 2.5 MeV from the exit of the normal conducting Radiofrequency Quadrupole (RFQ) to the superconducting Half-Wave resonator (HWR) section. The MEBT must provide a good matching between the RFQ and HWR, effective control of the emittance growth and the halo formation, enough space for all the beam diagnostics devices, among others. This work reports the first lattice design and the beam dynamics studies for the MEBT of the JAEA-ADS.
Yee-Rendon, B.; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Tamura, Jun; Cicek, E.*
Proceedings of 12th International Particle Accelerator Conference (IPAC 21) (Internet), p.793 - 795, 2021/08
The Five-cell Elliptical Superconducting Radio-Frequency Cavities (SRFC) provide the final acceleration in the JAEA-ADS linac (from 600 MeV to 1.5 GeV); thus, their performance is essential for the success of the JAEA-ADS project. After their optimization of the cavity geometry to achieve a high-acceleration gradient with lower electromagnetic peaks, the next step in the R&D strategy is the accurate estimation of beam-cavity effects which can affect the performance of the cavities. To this end, multipacting studies were developed to investigate its effect in the cavity operation regimen and find countermeasures. The results of this study will help in the development of the SRFC models and in the consolidation of the JAEA-ADS project.
Tamura, Jun; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Yee-Rendon, B.; Domae, Takeshi*; Kako, Eiji*; Sakai, Hiroshi*; Umemori, Kensei*
Proceedings of 20th International Conference on RF Superconductivity (SRF 2021) (Internet), p.612 - 615, 2021/06
Tamura, Jun; Kondo, Yasuhiro; Yee-Rendon, B.; Meigo, Shinichiro; Maekawa, Fujio; Hasegawa, Kazuo; Kako, Eiji*; Umemori, Kensei*; Sakai, Hiroshi*; Konomi, Taro*
JPS Conference Proceedings (Internet), 33, p.011049_1 - 011049_6, 2021/03
Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Hasegawa, Kazuo; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo
JPS Conference Proceedings (Internet), 33, p.011043_1 - 011043_5, 2021/03
The Japan Atomic Energy Agency (JAEA) has been working in the research and development of an Accelerator Driven Subcritical System (ADS) for the transmutation of nuclear waste. The ADS proposed by JAEA consists of a CW proton linac of 30 MW coupling with a subcritical core reactor. The accelerator will be operated with a beam current of 20 mA. Normal conducting Radio-Frequency Cavities (NRFC) and Superconducting Radio-Frequency Cavities (SRFC) will be used to achieve final energy of 1.5 GeV, and the SRFC will be employed for the main part of the acceleration: from 2 MeV to 1.5 GeV. In the first stage of the accelerator development, the focus was the design and optimization of the SRFC models and the beam optics. For the SRFC sections, the acceleration will be done by using Half Wave Resonators (HWR), Single Spokes (SS), and Elliptical cavities (Ellip) operating with a frequency of 162, 324, and 648 MHz, respectively. The beam optics were optimized satisfying the equipartitioning condition to control the emittance growth, which helped to reduce the beam halos and the beam loss.
Yee-Rendon, B.; Tamura, Jun; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Oguri, Hidetomo
Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.33 - 37, 2020/09
Japan Atomic Energy Agency (JAEA)- Accelerator Driven System (ADS) linac consists of a CW proton accelerator with a beam current of 20 mA driven with the energy of 1.5 GeV. Most of the beam acceleration is achieved by using superconducting cavities to obtain high acceleration efficiency at CW mode. The main superconducting linac is composed of five families of cavities (Half Wave resonators, Spokes resonators, and Elliptical cavities) with theirs respectively magnets. Due to the large beam power in the linac of 30 MW and the high reliability required for the ADS project, a robust beam optic designed is necessary to have a stable beam operation and control the beam loss power. The JAEA-ADS linac is composed of several sections and components; thus, the misalignment of these elements together with field errors enhance the beam loss rate and compromises the safety of the linac. To this end, an error linac campaign was launched to estimate the error tolerance of the components and implement a correction scheme to reduce the beam loss power around the linac.
