AichiSR: A Decade of Advanced Research and Innovation in Industry and Academia

1. Introduction

Aichi Synchrotron Radiation Center (AichiSR) started operations for use on March 26, 2013, with six beamlines. Over a decade, it steadily increased the number of users, reaching 12 beamlines and surpassing 10,000 hours of usage in the fiscal year (FY, from April to March) 2022. The facility is owned by the Aichi Science and Technology Foundation (ASTF), which cooperates with industry, academia, and the Aichi Prefectural Government. AichiSR is responsible for facility maintenance, management, and user services.

Aichi Prefecture is renowned for its manufacturing industries, including transportation machinery, electrical machinery, steel, and production machinery. In the FY2021, Aichi Prefecture’s shipment value of manufactured goods surpassed that of the second-ranked Osaka Prefecture by more than double. For 44 consecutive years since 1977, Aichi has played a leading role in the nation’s economy, particularly in manufacturing industries such as automobiles, aerospace, and robotics. Serving as a hub for the manufacturing sector, it has been a driving force in advancing the country’s economic development. To construct a sustainable society and further enhance the sophistication of manufacturing industries, it is essential to have research facilities that can support manufacturing at a high level. AichiSR, as a core facility within “Knowledge Hub Aichi,” represents a symbolic establishment of collaborative efforts among industry, academia, and government with a primary focus on industrial applications. Our facility realized over 20 years from conception, aims to strengthen industrial competitiveness while fostering the advancement of manufacturing.

Based on opinions expressed by both industry and academia, the design of the light source was based on a 1.2 GeV storage ring with a booster ring for top-up operation, and four superconducting bending magnets (superbends) for hard X-rays, eight normal conducting bending magnets (normal-bends) for soft X-rays, and an undulator for VUV light.

Construction of the building of AichiSR began in August 2010, and the light source equipment was delivered in September 2011. Then, in July 2012, the first light was observed, accumulating electrons of 1.2 GeV at 1.5 mA, and in September of the same year, the electron accumulation at 300 mA was achieved. Thus, the construction of the light source proceeded very smoothly. In parallel with the installation of the light source, the installation of the beamlines also progressed. The opening ceremony was held on March 22, 2013, and the six beamlines were opened to users the following week on March 26, 2013.

The construction costs. 7.2 billion Japanese Yen for the facility was covered by Aichi Prefecture (50%), donations from industries in Japan (20%), and the Japanese Government (30%). It has been 10 years since we started using our facility. On April 20, 2023, a commemorative lecture was held to celebrate the 10th anniversary of AichiSR. The special lecturer for this event was Professor Hiroshi Amano, who won the Nobel Prize in Physics in 2014 and was selected as a distinguished professor of research excellence at Nagoya University in FY2022. The event was grand, marking a decade of achievements and advancements at AichiSR.

The construction of beamlines has been steadily progressing since then, with 12 beamlines currently in operation as of FY2023. Among them, two beamlines were constructed by a private company, and one was constructed by Nagoya University. The total beamtime for users has increased steadily with the increase in the number of beamlines, reaching more than 10,000 hours in FY2022. Of the total beamtime, 60% of the time is used by companies, and the remaining 40% is used by universities and public research institutes, making our facility unique in that companies heavily use it. In addition, more than half of the beamtime at the facility is used by users within Aichi Prefecture. This trend has remained almost unchanged since the opening of AichiSR in FY2013.

Ten years have passed since AichiSR opened to users. More than 30 years have passed since the planning stage. During this period, there have been many technological innovations in the field of measurement, including detectors. There have also been remarkable innovations in analytical methods. We, the staff of the facility, will continue to incorporate these new changes to realize a sustainable facility that will be trusted by our users.

2. Facility overviews

2.1. Light sources

Details of the light source of AichiSR are shown in Table 1. The light source consists of three accelerators with a 50 MeV LINAC, a 50 MeV–1.2 GeV booster ring, and a 1.2 GeV electron storage ring as shown in Figure 2 [1, 2]. The storage energy of 1.2 GeV was chosen based on the desire to construct a compact ring. The circumference of the storage ring is 72 m. In addition to the eight normal-bends with a magnetic field of 1.4 T for supplying soft X-rays, four superbends with a magnetic field of 5 T installed in this storage ring supply hard X-rays exceeding 20 keV to eight or more beamlines. The superbends are cooled by one cryopump without using any liquid He nor N₂. Apple-II type Undulator with a period of 60 mm is also installed to supply higher brilliance soft X-rays. Brilliance curves of these light sources are shown in Figure 1.

Figure 1: Brilliance curves of the X-ray from superbend (red line), normal-bend (blue line), and Undulator with linear mode.

Figure 2: Layout of light source and beamlines at AichiSR.

Table 1: Details of accelerators and light sources at AichiSR.

Linear accelerator [S-band]	Beam energy: 50 MeV
Booster synchrotron	Electron energy: 50 MeV → 1.2 GeV Circumference: 48 m Natural emittance: 200nm⋅rad
Storage ring	Storage electron energy: 1.2 GeV Circumference: 72 m Natural emittance: 53nm⋅rad Storage current: 300 mA
Normal conducting bending magnet (normal-bend)	Peak magnetic field: 1.4 T Critical energy: 1.3 keV
Superconducting bending magnet (superbend)	Peak magnetic field: 5 T Critical energy: 4.8 keV
Undulator (Apple-II type)	Remanent field: 1.3 T Period length: 60 mm Number of periods: 33 Maximum K value Linear: 3.4 Vertical: 2.0 Helical: 1.7

The total machine time of the light source was 1,979 hours and the supply time of light to beamlines was about 1,235 hours in FY2022. The whole system is maintained in April and early May.

2.2. Beamlines

Table 2 shows the beamline list at AichiSR. Six beamlines ­constructed at the first stage of AichiSR in FY2013 were: (1) hard ­X-ray XAFS and fluorescence X-ray analysis (BL5S1), (2) soft X-ray XAFS and Photoelectron spectroscopy (BL6N1), (3) soft X-ray XAFS, VUV and photoelectron spectroscopy (BL7U), (4) powder X-ray diffraction (BL5S2), (5) thin film and surface X-ray diffraction (BL8S1), and (6) small angle X-ray scattering (BL8S3). Soft X-ray XAFS beamline (BL1N2) and Single Crystal Diffraction beamline (BL2S1) were ­constructed by AichiSR and Nagoya University in FY2015, respectively. In FY2017, X-ray Topography and Computed Tomography (CT) beamline (BL8S2) and new hard X-ray XAFS beamline were constructed by Aichi Prefecture and AichiSR, respectively. In the same fiscal year, a beamline was constructed by DENSO Corporation (DENSO). DENSO also constructed another beamline as the twelfth beamline of AichiSR in FY2021. These 12 beamlines are also shown in Figure 2.

Table 2: Specifications of beamlines at AichiSR as of FY2024.

Beamline	Name/Experiment	Energy range	Owner	Fiscal year
BL1N2	Soft X-ray XAFS/XPS II	0.15–2 keV	AichiSR	2015
BL2S1	Single crystal X-ray diffraction	4–17 keV	Nagoya Univ.	2015
BL2S3	Industry owned beamline (DENSO BL I)	5–22 keV	DENSO	2017
BL5S1	Hard X-ray XAFS I	5–22 keV	AichiSR	2013
BL5S2	Powder X-ray diffraction	5–22 keV	AichiSR	2013
BL6N1	Soft X-ray XAFS/XPS I	1.75–6.0 keV	AichiSR	2013
BL7U	VUV spectroscopy/Soft X-ray XAFS	30–850 eV	AichiSR	2013
BL8S1	Surface X-ray Diffraction	9.1, 14.3, 22.7 keV	AichiSR	2013
BL8S2	X-ray Topo./CT (White/Mono.)	7–24 KeV/White	AichiSR	2017
BL8S3	SAXS/WAXS	8.2, 13.5 keV	AichiSR	2013
BL11S2	Hard X-ray XAFS II	5–26 keV	AichiSR	2017
BL11S3	Industry owned beamline (DENSO BL II)	5–26 keV	DENSO	2021

Beamlines with “S” and “N” are connected to superconducting and normal conducting bending magnets, respectively. BL7U is equipped with an Apple-II type undulator.

2.3. Operation

Daily operation time is 8.5 hours from Tuesday to Friday, while the facility is dedicated to machine study on Monday. The top-up operation has been conducted from the beginning of the open for users. User beamtime for four hours is allocated to one shift and two shifts a day are scheduled as ①10:00 – 14:00 and ②14:30 – 18:30. The time between the first and second shifts is the user’s switching time; this time can also be used if the first and second shifts are used consecutively.

Applications are accepted every other month to provide quick access to AichiSR. The decisions on usage follow a first-come-first-served basis. The review process for the applications focuses on safety and technical possibility rather than evaluation. When there is a vacancy of the beamtime, it is announced and allocation is made within one week at the shortest. Beamlines are available about 135 days a year for users. Measurement acting service by AichiSR beamline staff members is performed according to prescribed processes and conditions. It worked out effectively during the serious COVID-19 situation when user visits were prohibited by some companies.

AichiSR has several industrial application coordinators who are well-versed in their specialized fields. As a point of contact for users, we provide consistent user support in cooperation with beamline staff, from consultation to follow-up after measurement. The beamline equipment and the measurement system are set before beamtime, according to prior discussions with the beamline staff and/or the coordinators. This not only allows the user to start measuring immediately but also enables effective measurements in a short time. In addition, for those who are not familiar with the analysis and analysis equipment installed in each beamline, the beamline staff will provide on-site support, so users can use it with ease.

2.4. Operations history

Figure 3 shows the yearly change of beamlines and gross beamtime of the twelve beamlines with the fractions of user category, and beamtime used for measurement acting service. The gross beamtime has increased steadily with the increase in the number of beamlines, reaching more than 10,000 hours in FY2022. The influence of COVID-19 is clear in FYs2020 and 2021 that is the saturation of used beamtime and step increase of the beamtime used for measurement acting service. Of the beamtime, more than half of the beamtime is used by companies, and the remaining is used by universities and public research institutes, making our facility unique in that companies heavily use it. In addition, more than half of the beamtime at the facility is used by users within Aichi Prefecture. This trend has remained almost unchanged since the opening of AichiSR in March 2013.

Figure 3: Yearly change of gross beamtime (left scale) and beamtime used with the beamtime of measurement acting service (right scale and red line).

2.5. User affiliation and research field

In FY2022, 65% of our users were from industry including industry-academia collaboration, 28% were pure academia and the remainder was from public research as shown in Figure 4. This matches the purpose of this facility to support research and development activities of industries and academia.

Figure 4: Beamtime fraction of user’s affiliation in FY2022.

Figure 5 shows the fraction of user’s research field in industrial use only. The research field was diverse, but 50% of users were related to R&D for automobiles and has been top for the last 10 years. Chemistry and Research Service or Electronic devices come next changing year by year. To expand the area of users, a special program is available for new users without a fee.

Figure 5: Beamtime fraction of user’s research field in FY2022.

3. Topical research results

There have been several successful examples of usage. Towata et al. [3] characterized high-capacity hydrogen storage materials through synchrotron X-ray diffraction (XRD) measurements at beamline BL5S2 at AichiSR. They focused on Mg2NiH4, a hydride of Mg2Ni. Mg2NiH4 undergoes a structural phase transition between low-temperature (LT) and high-temperature (HT) phases, with LT further known to have two phases (LT1, LT2). However, the influence of the proportion of these low-temperature phases (LT1, LT2) on the phase transition temperature and crystal structure is unknown. XRD profiles were measured while heating samples with different proportions of crystal phases, and the proportion of crystal phases at each temperature was determined through Rietveld analysis. As a result, it was found that samples with a higher proportion of LT2 at room temperature undergo phase transition at lower temperatures. The lower transition temperature is attributed to the similarity in structure between the LT2 phase and the HT phase.

The following example is a project aimed at fabricating MEMS (Micro Electro Mechanical Systems) components using LIGA (Lithographie, Galvanoformung, Abformung), which enables micromachining with a high aspect ratio by employing X-rays emitted from a synchrotron. As is well known, an X-ray-sensitive polymer photoresist is exposed to a parallel beam of X-rays through a mask partially covered with X-ray-absorbing material. Chemical removal of the exposed resist results in a 3D structure, which can be filled by electrodepositing metal. Figure 6 shows the Kochi grid with small sample posts measuring 0.1 × 0.2 mm and a thickness of 0.03 mm [4]. The Kochi grid was made for a coordinated micro/nano-analysis that utilizes a focused-ion beam apparatus, transmission electron microscope, and nanoscale secondary ion mass spectrometry for the analysis of the Hayabusa2 returned samples. The Kochi grid is composed of copper metal and processed using the synchrotron-based LIGA system at BL8S2 of AichiSR.

Figure 6: Photograph (a) and SEM images (b) 〜 (d) of Kochi grid fabricated by LIGA using synchrotron-based LIGA system at BL8S2 of AichiSR [4]. SEM image (c) shows small sample posts indicated by the yellow square in (b). The sample post size is 0.1 × 0.2 mm and a thickness of 0.03 mm. SEM image (d) is an enlarged view of the sample post shown in (c). The end face of the sample posts was inclined 30 degrees. In addition, a 10 μm wide groove was created to mark the specimen mounting.

Figure 7: The distribution of Fe oxidation states on the surface of the meteorite reconstructed from CT-XAFS using BL11S2 [5].

In addition to these activities, we will introduce CT-XAFS, which has recently become possible to implement. X-ray CT enables non-­destructive observation of the internal structure of materials. By scanning X-ray energy near the absorption edge, X-ray CT enables the ­representation of chemical bonding states in three dimensions in the materials. The CT-XAFS has recently been in high demand among ­users at AichiSR as well. Figure 7 illustrates an example of measuring the distribution of chemical bonding states in a meteorite using CT-XAFS [5]. The measurements were conducted at BL11S2, focusing on the absorption edge of Fe contained in the meteorite. The differences in Fe oxidation states are depicted in colors. This result indicates that the surface of the meteorite contains regions of trivalent iron (red) and divalent iron (yellow).

4. Future perspectives

Ten years have passed since the opening of Aichi Synchrotron Radiation Center (AichiSR) in March 2013. During this period, the social environment surrounding AichiSR has changed, and the social challenges to be addressed have also evolved. In response to these changes, the demand for SR utilization has also shifted. While the measurement techniques of synchrotron light have advanced, the time for renewal of aging light source equipment, beamline equipment, and measurement devices is approaching. Therefore, to outline the direction of technical development and facility maintenance and management for the next decade of AichiSR, a Future Planning Committee comprising users, beamline stakeholders, and external experts was established, and discussions were held over nearly a year. The committee sought to grasp the scientific and technological fields necessary for addressing current and future societal issues as a common understanding among its members. It conducted assessments of the current status and scalability of the light source and beamlines, as well as surveys on the operation and update status of facilities in other synchrotron radiation facilities.

For the future of AichiSR, recommendations were made regarding the enhancement of widely used hard X-ray beamlines and the advancement of imaging technologies that allow direct observation of internal structural changes. Accordingly, proposals were put forward for the ­advancement of measurement techniques and the development of imaging technologies such as CT-XAFS and phase-contrast CT, which combine imaging with the strengths of synchrotron light to enable the observation of light elements. We, the staff of the facility, will continue to incorporate these new changes to realize a sustainable facility that will be trusted by our users.

Disclosure statement

No potential conflict of interest was reported by the authors.