In this blog post, we’ll examine the process by which nihonium—discovered through Japanese research on heavy-ion accelerators—came into being, the principles behind heavy-ion accelerators, their potential applications in medicine, new materials, and basic science, and the current status of South Korea’s RAON project.
On June 9, 2016, Japanese media reported that “nihonium” (element symbol Nh)—derived from the Japanese word “Nihon,” meaning “Japan”—had been proposed as the name for element 113, discovered by Japanese researchers. At that time, the official name had not yet been finalized; the International Union of Pure and Applied Chemistry (IUPAC) announced the name in June 2016 and conducted a five-month public review process. Subsequently, on November 28, 2016, “nihonium” and the element symbol “Nh” were officially approved. When the discovery of an element is officially recognized, the research team responsible for the discovery is granted the right to propose a name for the element; in the case of Element 113, the discovery by researchers at the RIKEN Institute in Japan was recognized by IUPAC. Nihonium is particularly significant as it is the first element discovered in Asia to be granted a permanent name. This tremendous achievement was by no means a coincidence. Behind it were RIKEN’s Heavy Ion Accelerator Research Facility, the RILAC heavy-ion linear accelerator operated within it, and the GARIS gas-filled recoil separator, which isolates the produced atomic nuclei. Accelerators are key research instruments that have driven the advancement of particle physics and nuclear physics; some analyses suggest that accelerator science contributed to approximately one-quarter of all research recognized by the Nobel Prize in Physics from 1939 to 2018.
First, it is necessary to discuss the world of elements studied by heavy-ion accelerators. Atoms consist of an atomic nucleus and electrons, and the atomic nucleus is composed of protons and neutrons. The type of element is determined by the number of protons in the atomic nucleus—that is, the atomic number. Currently, there are 118 elements officially recognized by IUPAC, and of these, 94 can be classified as elements found naturally on Earth, including those present in trace amounts. In particular, since neptunium (element 93) and plutonium (element 94) can exist naturally—albeit in extremely trace amounts—it is no longer consistent with current scientific classification to view the number of naturally occurring elements as simply 92, as was done in the past. Elements from number 95, americium, through number 118, oganesson, do not exist stably in nature but are synthesized in laboratories. Because the atomic nuclei of these superheavy elements are extremely unstable, they do not persist for long after being created but decay into other atomic nuclei. Therefore, to confirm their existence, they must be artificially synthesized, and the decay process—which occurs in an extremely short period—must be precisely observed.
To produce such unstable elements, it is necessary to cause nuclear reactions by colliding atomic nuclei with one another, rather than colliding entire atoms. Simply causing particles to collide with one another does not result in the desired nuclear reaction. The collision energy must be precisely controlled to ensure the target atomic nucleus is produced, and when the probability of production is extremely low, an enormous number of collisions must be repeated. This is where the heavy-ion accelerator comes into play. Let’s use a gun as a simple analogy for a heavy-ion accelerator. In this analogy, the gun is the accelerator, and the bullet corresponds to a “heavy ion”—which literally means “heavy ion.” Just as a real gun uses the explosion of gunpowder to propel a bullet at high speed, a heavy-ion accelerator uses electric and magnetic fields to accelerate charged ions and guide them along the desired path. When an electron is stripped from an atom to ionize it, the resulting charged particle is injected into the accelerator, where a strong electric field increases its speed. Subsequently, a magnetic field is used to control the beam’s direction while accelerating it to the target energy. In RIKEN’s experiment to discover nihonium, zinc ions were accelerated to about 10% of the speed of light before being collided with a bismuth target. In contrast, RIKEN’s RIBF complex includes devices capable of accelerating heavy ions to much higher energies; the Superconducting Ring Cyclotron (SRC) can accelerate heavy ions such as uranium to 350 MeV per nucleon and operate at speeds reaching approximately 70% of the speed of light. When these accelerated atomic nuclei collide with target nuclei, nuclear fusion reactions occur, and new elements or isotopes can be produced through subsequent particle emission and radioactive decay.
At first glance, this might seem like a very simple process. Which is harder: throwing a pebble at a large rock to shatter it, or throwing a grain of sand at a pebble to shatter it? We can easily surmise that shattering a pebble is much more difficult. Therefore, we can begin to grasp just how difficult it is to fire a heavy ion at an atomic nucleus—which is much smaller than a pebble—to induce the desired nuclear reaction. In fact, the synthesis of nihonium was an extremely challenging experiment. The RIKEN research team had been attempting to synthesize element 113 since 2003 and confirmed the existence of a nihonium atom for the first time on July 23, 2004. They subsequently confirmed synthesis events for the same element on April 2, 2005, and August 12, 2012; the third event conclusively confirmed the discovery by verifying a continuous alpha decay path leading to a previously known atomic nucleus. It took approximately 100 trillion collisions to produce a single nihonium atom, and in the actual experiment, collision tests were conducted nonstop for 80 days just to confirm a single synthesis event.
Because nihonium—produced under such difficult conditions—is extremely unstable, the possibility of its direct practical application in everyday life is currently very low. In fact, nihonium has no stable isotopes, and the nihonium with mass number 278 used in the discovery exists for only a very short time—about 2 milliseconds—before decaying. However, not all atomic nuclei produced by heavy-ion accelerators exist for only a short time like nihonium. Some new nuclides or substances can exist for relatively longer periods, and their properties can be studied or new characteristics explored by irradiating or introducing them into other materials. For example, suppose we briefly create a highly unstable substance called CO₄ by adding two oxygen atoms to CO₂, which consists of one carbon and two oxygen atoms. Of course, this does not mean the substance actually exists stably, but it helps us understand that if a new substance exists—even for just a few years, months, or days—and exhibits unique properties, there is potential to study and utilize those properties. In this way, research related to heavy-ion accelerators involves using new nuclides and ion beams to alter or analyze the properties of matter, enabling the exploration of various applications across multiple fields, including new materials and materials engineering.
Among these, one of the most notable application areas for heavy-ion accelerators is the life sciences and medical fields. X-rays and gamma rays currently used in cancer treatment transfer energy as they pass through the human body, and normal tissues along the path of the radiation may also be affected to some extent during treatment. In contrast, proton and heavy-ion beams possess a characteristic known as the Bragg peak, whereby energy is concentrated at a specific depth as the beam passes through matter; this makes it easier to focus the radiation dose on tumors located deep within the body by adjusting the beam’s energy and irradiation conditions. In particular, carbon ions can leverage their high linear energy transfer (LET) characteristics and relative biological effectiveness (RBE), leading to ongoing research and clinical applications for treating various cancers, including some radiation-resistant tumors. Therefore, while it would be overly simplistic to characterize heavy-ion therapy as a treatment that has absolutely no effect on normal cells, it is regarded as an important radiation therapy technology because it allows for the concentration of radiation on tumors while minimizing unnecessary exposure to normal tissue. Carbon-ion therapy facilities, which were primarily operated in Germany and Japan in 2016, have since expanded to China, Italy, Austria, and other countries. In South Korea, Yonsei Cancer Hospital became the first in the country to begin offering carbon-ion therapy in 2023. As of August 2026, all three treatment rooms at Yonsei Cancer Hospital—one fixed treatment room and two rotating treatment rooms—are fully operational.
Research has also been conducted to irradiate microorganisms and plants with these heavy-ion beams to induce DNA mutations, thereby developing mutant strains or varieties with useful traits. This type of ion-beam breeding can be utilized by inducing genetic mutations with radiation and then selecting individuals with desired traits; heavy-ion accelerators can serve as research equipment that provides the various ion beams necessary for such studies. Therefore, the application of heavy-ion accelerators extends beyond the discovery of new elements to fields such as life sciences and agricultural research.
As such, heavy-ion accelerators—which serve as a key to unlocking the world of new materials and atomic nuclei—have a wide range of applications, including basic sciences such as physics and nuclear science, as well as materials and new materials research, radioactive isotope research, basic research for new drug development, cancer treatment, nuclear transmutation and nuclear waste processing research, and crop breeding. Furthermore, it can be used as a research tool to examine the internal structure of matter and the properties of atomic nuclei by precisely analyzing the particles and radiation emitted when matter decays or is synthesized. It can also be utilized to study the origins of the universe and atomic nuclei by creating extreme conditions—which are difficult to reproduce naturally on Earth—using high-energy particles and atomic nuclei. As such, an accelerator is not merely a machine for creating new elements, but rather a platform for basic scientific research that explores the structure of matter and the origins of the universe, while also developing new technologies. Considering that accelerator-based research has continuously contributed to scientific discoveries and technological advancements across various fields, its importance remains significant even today.
Given its overwhelming potential for application and the growing demand for rare isotope research and production, the importance of heavy-ion accelerators is increasing even further. In line with this global trend, South Korea has been constructing RAON, a large heavy-ion accelerator, to conduct research on rare isotopes. The figures of 583.8 billion won and a 2021 completion date originally presented in the source text refer to the initial facility construction phase and past project plans; they are not appropriate to use as figures describing the current scale and progress of the RAON project. The total project cost for the RAON construction project was adjusted to approximately 1.4 trillion won following revisions to the project plan, and Phase 1 of the project was completed in 2022. Since then, beam commissioning and user experiments have been conducted primarily using the low-energy superconducting linear accelerator (SCL3) and the ISOL facility, and in 2024, the first user experiment utilizing the RAON beam was carried out. In 2025, a beam access program for South Korean researchers was conducted, and in 2026, heavy-ion beam commissioning and research using experimental devices such as KoBRA are continuing. On the other hand, development of the high-energy section, SCL2, is still underway; once completed, it aims to accelerate heavy ions to a maximum of 200 MeV/u. Therefore, while RAON has already entered the research utilization phase, it is difficult to say that the entire system, as originally planned, has been fully completed.
RAON is a key basic science research facility in South Korea that focuses specifically on producing rare isotopes and accelerating them to study the properties of atomic nuclei. A distinctive feature is that it is designed to utilize both the ISOL method, which employs a 70 MeV proton cyclotron, and the in-flight fission (IF) method, which uses a heavy-ion superconducting linear accelerator. Experiments to generate and extract beams of various rare isotopes—including sodium, aluminum, cesium, and barium—have already been conducted, and integrated operations to accelerate rare isotope beams, such as sodium-25, and deliver them to experimental devices have also been carried out. This demonstrates that South Korea is moving beyond simply possessing a heavy-ion accelerator to a stage where it is actually producing and accelerating rare isotopes for use in research.
It may be a cliché, but looking forward to the day when a new element discovered by South Korea and the names of South Korean researchers are added to the periodic table remains a meaningful dream. However, scientific progress is not achieved simply by discovering a single new element in the short term. As seen in the case of nihonium, discovering a single element requires years of research, countless collision experiments, precise detection technology, and an international verification process. RAON, too, is significant not merely as a project to build a massive accelerator, but as a long-term research infrastructure designed to explore the properties of rare isotopes and atomic nuclei, thereby broadening the foundation for both basic science and related applied research. If South Korea continues to steadily develop its research capabilities within the global trend of heavy-ion accelerator research, we can look forward to the day when South Korean researchers pioneer the world of new elements and new atomic nuclei, thereby elevating the status of basic science to a new level.
