The 2nd IBS Conference on Exotic Nuclei (ICEN2026)

22 Jul 2026, 01:30 → 24 Jul 2026, 19:00 Asia/Seoul

Science Culture Center

The Center for Exotic Nuclear Studies (CENS) and Institute for Rare Isotope Science (IRIS) at the Institute for Basic Science were founded in order to answer fundamental questions in nuclear physics and astrophysics, through investigations of radioactive atomic nuclei not found in nature.

The IBS conference on “exotic nuclei” focuses on forefront challenges in nuclear physics and astrophysics, namely the fundamentals of nuclear structure and reactions and key topics in nuclear astrophysics such as the origin of chemical elements heavier than iron, Furthermore, there will be in-depth discussions on the current status of the RAON facility and its future perspective during the conference.

Invited Speakers

Deuk Soon Ahn (FRIB)
Jung Keun Ahn (Korea Univ.)
Andrei Andreyev (Univ. of York)
Faical Azaiez (INFN-LNL)
Kyungyuk Chae (Sungkyunkwan Univ.)
Myung-Ki Cheoun (Soongsil Univ.)
Yeonsei Chung (IRIS)
Robert Grzywacz (Univ. of Tennessee, Knoxville)
Cheolmin Ham (IRIS)
Byungsik Hong (Korea Univ.)
Kate Jones (Univ. of Tennessee, Knoxville)
Rituparna Kanungo (TRIUMF)
Michelle Kuchera (Davidson Univ.)
Dean Lee (FRIB)
Jenny Lee (Univ. of Hong Kong)
Grant Mathews (Univ. of Notre Dame)
Jie Meng (Peking Univ.)
Taeksu Shin (IRIS)
Tomohiro Uesaka (RIBF, RIKEN)
Hidetoshi Yamaguchi (Univ. of Tokyo)
Zaihong Yang (Peking Univ.)
Hee-Joong Yim (IRIS)

ICEN2026_Poster.jpg

Wednesday 22 July

09:00 → 09:30 Registration

09:30 → 10:40 Session 1

Convener: Prof. Byungsik Hong (Korea Univ.)

09:30 Welcome Address

Speaker: Prof. Suk Bok Chang (Institute for Basic Science)

09:40 Opening Remark

Speaker: Kevin Insik Hahn (CENS, IBS)

09:50 Knockout reaction studies of few-nucleon correlations in nuclei

Few-nucleon correlations take on completely different forms depending on the isospin and/or density of the nuclear medium. Knockout reactions at several hundred MeV are found to be an excellent experimental tool to investigate the evolution of the few-nucleon correlations in nuclei located near the stability line toward the neutron dripline.
In the talk, I will pickup several topics from experimental studies at the SAMURAI spectrometer of RIBF and at the GR-LAS spectrometers at RCNP.

Speaker: Tomohiro Uesaka (RIBF, RIKEN)

IBSConference-Uesaka.pdf

10:15 What can we learn from electron-capture delayed fission?

The beta-delayed fission of very heavy and extremely neutron-rich nuclides is believed to play an important role in the so-called 'fission termination' of the astrophysical $r$-process, together with spontaneous and neutron-induced fission. However, its properties are very difficult for investigations, because of the experimental problems to reach relevant regions of nuclei. Due to this, only about 25 cases of the Electron Capture Delayed Fission (ECDF), being a sub-type of beta-delayed fission, are known so far, in the neutron-deficient nuclides [1].

The talk will introduce the general concepts of beta-delayed fission, and will present an overview of results from recent ECDF experiments at several facilities. A special emphasis will be given to the two representative experiments. First, an ISODLDE study of ECDF of $^{180}$Tl (Z=81), in which a new island of asymmetric fission was discovered [2]. The second experiment will concern the ECDF of the very neutron-deficient isotope $^{234}$Bk (Z=95), performed at the gas-filled recoil separator SHANS2 at the Institute for Modern Physics, IMP-Lanzhou, China. The isotope $^{234}$Bk was produced in the fusion-evaporation reaction $^{40}$Ar+$^{197}$Au $\rightarrow$ $^{237}$Bk$^{*}$ $\rightarrow$ $^{234}$Bk+3n. The highest ECDF probabilities, PECDF($^{234}$Bk)=0.57(11) and PECDF($^{230}$Am)=0.34(9), among all beta- or EC-delayed fission cases known so far are reported, showing the tendency of approaching the expected saturation towards PECDF=1 [4]. The comparison of the PECDF systematics with two theoretical fission models shows significant discrepancies in respect of corresponding fission barrier values. The important role of beta-decay strength function and the comparison of ECDF systematics in the lead and heavy actinides will be presented. The need for a theoretical framework that can provide realistic beta-delayed fission probabilities for astrophysical predictions will be strongly underlined.

[1] A.N. Andreyev, M. Huyse, Piet Van Duppen, Reviews of Modern Physics 85 (4), 1541 (2013)
[2] A.N. Andreyev et al., Phys. Rev. Lett., 105, 252502 (2010)
[3] Z. Zhang et al., submitted, May 2026

Speaker: Andrei Andreyev

10:40 → 11:10 Coffee Break

11:10 → 12:00 Session 2

Convener: Prof. Grant Mathews (Univ. of Notre Dame)

11:10 Relativistic density functional PC-PK1: Nuclear mases and dynamics

The relativistic density functional PC-PK1 and its application for nuclear structure and dynamics will be reviewed. The DRHBc mass table, the physics around N=Z nuclei, the relativistic density functional theory as well as its time-dependent version in space lattice and application for novel nuclear shape, shape fluctuations in chiral rotation, the entanglement and cross-section in multinucleon transfer reaction, and quantum fluctuations and dissipative mechanism in nuclear fission will be introduced. Main contents can be found in the references followed.
1. Atom. Data Nucl. Data Tabl. 144, 101488 (2022)
2. Atom. Data Nucl. Data Tabl. 158, 101661 (2024)
3. Phys. Rev. Lett. 136, 252502 (2026) - Published 23 June, 2026
4. Phys. Rev. Lett. 136, 232503 (2026) - Published 10 June, 2026
5. Phys. Rev. Lett. 133, 022501 (2024) - Published 11 July, 2024
6. Phys. Rev. Lett. 132, 232501 (2024) - Published 4 June, 2024
7. Phys. Rev. Lett. 128, 172501 (2022) - Published 29 April, 2022

Speakers: Jie Meng (Peking Univ.), Jie Meng (Peking University)

11:35 Evidence for multimodal superfluidity in neutrons and neutron-rich nuclei

Speaker: Dean Lee (FRIB)

DLee_ICEN_2026.pdf

12:00 → 13:30 Lunch

13:30 → 15:10 Session 3

Convener: Prof. Robert Grzywacz (Univ. of Tennessee, Knoxville)

13:30 Nuclear Structures of 100Sn and Neighbouring Nuclei

The heaviest self-conjugate system bound by the strong force, $^{100}$Sn (Z = N = 50), represents the last of the “classical” doubly magic nuclei awaiting experimental confirmation and the final member along the N = Z line. It has long been a central objective in the quest to understand how nuclear forces behave under extreme conditions. $^{100}$Sn also serves as a unique testing ground for proton-neutron symmetry at the edge of stability. With further proton captures suppressed by the closed shells, $^{100}$Sn is considered as the endpoint of the astrophysical rapid-proton ($rp$) process.
In this talk, we report on the first in-beam $\gamma$-ray and mass spectroscopy of $^{100}$Sn performed at the RIKEN Radioactive Isotope Beam Factory. The level scheme of $^{100}$Sn provides the first direct spectroscopic information on the nature of Z = N = 50 shell. Results compared with the state-of-the-art theoretical calculations will be discussed. In addition, the structures and masses of the neighbouring nuclei will also be presented.

Speaker: Jenny Lee (Univ. of Hong Kong)

13:55 Multineutron Correlations and Clustering: Progress and Perspectives

Speaker: Zaihong Yang (Peking Univ.)

14:20 Rare Isotope Beam Production Studies

Speaker: Deuk Soon Ahn (FRIB)

14:45 Recent highlights on exploration of rare isotopes at TRIUMF

Rare isotopes in nature are offering a wealth of new information that markedly deviate from the traditional structural properties predicted by models based on observations from stable nuclei. These isotopes play key roles in the element synthesis in the universe and bring access to unravel the state of matter in the cosmic neutron-rich environments such as neutron stars.

The Isotope Separator and Accelerator (ISAC) facility at TRIUMF is an ISOL type radioactive beam facility with maximum beam power of 50 kW on target that open access to study the short-lived exotic nuclei. The low-energy ISOL beams allows high precision measurement of ground state properties. To measure nuclear reactions the isotopes are re-accelerated using the superconducting linear accelerator to energies E/A ~ 3-12 MeV.

Some examples of mass measurements of neutron-rich nuclei using the TITAN MR-TOF will be presented to discuss their implications on nuclear structure evolution and on the r-process nucleosynthesis. The re-accelerated ISOL beams bring suitable conditions for measuring reactions of importance in nuclear astrophysics. Measurement of reaction cross section for the weak r-process using EMMA and TIGRESS will be shown. The presentation will show the scope of the IRIS facility with a unique thin windowless solid H2/D2 target for studying reactions of astrophysical importance and for investigating novel features of nuclear structure of exotic nuclei.

Speaker: Rituparna Kanungo (TRIUMF)

15:10 → 15:35 Coffee Break

15:35 → 17:15 Session 4

Convener: Prof. Hidetoshi Yamaguchi (CNS, Univ. of Tokyo)

15:35 Precision Mass Measurements of 130Te, 130Sn, and Their Impact on Models for R-Process Nucleosynthesis

The astrophysical rapid neutron capture nucleosynthesis process ($r$-process) remains an active area of research due to the fact that it occurs in extreme conditions and involves reactions with exotic nuclei that are difficult to study experimentally. For the first time using the Phase-Imaging Ion Cyclotron Resonance (PI-ICR) technique, we measured the mass excesses of $^{130}$Te, $^{130}$Sn, and $^{130}$Sn$^{m}$ with the Canadian Penning Trap (CPT). Our results show good agreement with previous Penning trap values obtained using the Time-of-Flight Ion Cyclotron Resonance (TOF-ICR) and the Fourier Transform Ion Cyclotron Resonance (FT-ICR) techniques, while being twice as precise for $^{130}$Sn.

These new mass excesses were added to a SkyNet network calculation to determine their impact on r-process abundances and to find the best astrophysical conditions to reproduce the Solar System $r$-process abundance pattern. Finally, by treating lighter and heavier elements separately, we assess the relative frequency of events producing elements in a cold versus a hot $r$-process scenario.

Speaker: Grant Mathews (Univ. of Notre Dame))

16:00 Microscopic Nuclear Mass Models and the r-Process

In this presentation, we will briefly introduce modern microscopic nuclear mass models and discuss their role in r-process nucleosynthesis.

Speaker: Youngman Kim (CENS, IBS)

ICEN-2026-YKim.pptx

16:25 Knockout Reactions In and Around Neutron-Deficient Tin Isotopes

The light tin isotopes are interesting owing to the vicinity of the doubly-magic $^{100}$Sn, which is the heaviest alpha-conjugate nucleus and has a cluster structure at its low-density surface [1]. The single-particle states outside of this unique core are important for predicting and understanding the structure of nuclei in the region. The ordering of the lowest single-particle states, which are separated by only approximately 200 keV, has yet to be experimentally verified and remains unresolved [2,3].

Our group measured the one-neutron knockout from $^{108}$Sn to establish that the first-excited state of 107Sn has J$^{\pi}$=7/2$^{+}$, strongly suggesting that the ground state has J$^{\pi}$=5/2$^{+}$ [4]. With the increased beam rates at FRIB, the ARIS separator, and Gretina, we were able to measure momentum distributions of the ground and first-excited states of $^{105}$Sn to verify that they have J$^{\pi}$=5/2$^{+}$ and J$^{\pi}$=7/2$^{+}$, respectively [5]. The measured cross sections for these states were compared with shell-model predictions [5]. The lifetimes of the first excited states in $^{103}$Sn, $^{101}$Cd, and $^{103}$Cd were used to extract B(M1) strengths, which were compared with state-of-the-art VS-IMSRG calculations, showing a systematic underprediction [6].

[1] I. Cox et al., Nature 654, 53 (2026).
[2] D. Seweryniak et al., PRL 99, 022504 (2007).
[3] I. Darby et al., PRL 105, 162502 (2010).
[4] G. Cerizza et al., PRC 93, 021601R (2016).
[5] A. Peter, University of Tennessee PhD Dissertation (2026).
[6] T. J. Gray et al., PRC accepted (2026).

Speaker: Kate Jones (UTK)

ICEN Daejeon Tins Kate 2026.pdf

ICEN Daejeon Tins Kate 2026.pptx

16:50 Nuclear Astrophysics at CENS: Direct Reaction Studies and Future Opportunities at RAON

This presentation summarizes recent research activities of the Nuclear Astrophysics Group at CENS, with particular emphasis on direct reaction studies relevant to explosive nucleosynthesis and the origin of the elements. Topics include selected direct and indirect studies of astrophysically important reactions, associated detector developments, and international collaborative experiments at major rare-isotope facilities. Future opportunities for nuclear astrophysics research at RAON, including direct reaction measurements with rare-isotope beams, will also be discussed.

Speaker: Sunghoon Ahn (CENS, IBS)

ICEN2026_TonyAhn_final.pdf

ICEN2026_TonyAhn_final.pptx

17:15 → 18:00 Discussion

18:00 → 19:30 Welcome Dinner

Thursday 23 July

09:00 → 10:15 Session 5

Convener: Dr Jinho Lee (IRIS)

09:00 Welcome Address

Speaker: Myun Kwon (IRIS, IBS)

09:05 Recent Progress at RAON and the IBS TOPTIER Project

Since 2023, the RAON accelerator facility has been operating its low-energy accelerator and experimental systems, steadily producing its scientific achievements in rare isotope science. These early successes have demonstrated the capability of the facility and established a strong foundation for future scientific programs.

To further strengthen international collaboration, the IBS TOPTIER (Top-Tier Platform in the Extremely Rare Isotope Science Project) was launched in 2024. Through this initiative, RAON has established close partnerships with leading rare isotope research facilities, including the RIKEN Radioactive Isotope Beam Factory (RIBF) in Japan. The TOPTIER project promotes collaborative research, researcher exchange, joint workshops and schools, and the development of long-term strategic partnerships in rare isotope science.

This presentation introduces the current status of RAON, highlights recent scientific and technical achievements, and outlines the progress of the IBS TOPTIER project in fostering international collaboration to advance the next generation of rare isotope science.

Speaker: Taeksu Shin (IRIS, IBS)

09:25 Operation Status of the RAON Accelerator Facility

The RAON (Rare isotope Accelerator complex for ON-line experiments) is a rare isotope accelerator facility in Korea focused on fundamental science research by generating and accelerating RIBs (Rare Isotope Beams). Recently, a low-energy linear accelerator, comprising an injector system and a superconducting linear accelerator, was successfully commissioned. Additionally, RIBs produced by the ISOL (Isotope Separator On-Line) system were successfully reaccelerated using this low-energy linear accelerator. This presentation will provide an update on the operation status of the RAON accelerator facility, including the beam commissioning results of the low-energy linac.

Speaker: Yeonsei Chung (IRIS, IBS)

Operation Status of Accelerator Facility.pptx

09:50 Status of Experimental Systems of RAON

RAON (Rare isotope Accelerator complex for ON-line experiments) [1-3] is a heavy-ion accelerator facility in South Korea designed to provide both stable and rare isotope (RI) beams. The ISOL (Isotope Separation On-Line) system produces rare isotopes using a 70 MeV proton beam from the cyclotron incident on a production target. The extracted RI beams, with energies of several tens of keV, are delivered to the CLaSsy [4] and MRTOF-MS [5] for low-energy precision experiments. CLaSsy recently completed its first on‑line spectroscopy measurements using $^{22–24}$Na RI beams, establishing a practical foundation for performing high‑precision laser spectroscopy of unstable nuclei [6]. RAON also includes the superconducting linear accelerator (SCL3), which accepts beams from either the ECR ion source (ECR-IS) or the ISOL system and accelerates them up to several tens of MeV per nucleon. The accelerated beams are delivered to the KoBRA [7] and NDPS [8]. At KoBRA, experiments on nuclear reactions, nuclear structure, and radiation effects on semiconductor devices for space applications have been carried out. At NDPS, studies on neutron production are currently in progress. In this presentation, the details and current status of the CLaSsy, KoBRA, and NDPS, and will be presented.

[1] K. Tshoo et al., Experimental systems overview of the Rare Isotope Science Project in Korea, Nucl. Instrum. Methods Phys. Res. B 317 (2013) 242-247.
[2] D. Jeon et al., Design of the RAON accelerator systems, J. Korean Phys. Soc. 65 (2014) 1019-1019.
[3] M. Kwon et al., RAON, Korean Heavy Ion Accelerator Facility, J. Particle Accelerator Soc. Jpn. 17 (2020) 293-301.
[4] S.J. Park et al., Development of the collinear laser spectroscopy (CLaSsy) at RAON, J. Korean Phys. Soc. 87 (2025) 649-654.
[5] J.Y. Moon et al., Construction of a new multi-reflection time-of-flight mass spectrograph at RAON, J. Korean Phys. Soc. 87 (2025) 640-648.
[6] C. Lim et al., Commissioning of the collinear laser spectroscopy (CLaSsy) at RAON, JINST 21 (2026) P05026.
[7] K. Tshoo et al., Recent progress in the construction of KoBRA for low-energy nuclear physics experiments, Nucl. Instrum. Methods Phys. Res. B 541 (2023) 56-60.
[8] C. Ham et al., Status of nuclear data production system at RAON, J. Korean Phys. Soc. 87 (2025) 662-669.

Speaker: Cheolmin Ham (IRIS, IBS)

10:15 → 10:40 Coffee Break

10:40 → 12:00 Session 6

Convener: Dr Young-Ouk Lee (KAERI)

10:40 Current Status of the RAON ISOL System

The RAON ISOL system has been developed to produce and deliver rare isotope beams.
Recent activities have focused on stable system operation and rare isotope beam development.
Several isotope beams, including Na, Mg, Al, Cs, and Ba, have been produced and tested using different ionization methods.
This presentation provides an overview of the current status of the RAON ISOL system.

Speaker: Hee-Joong Yim (IRIS, IBS)

11:05 Collinear Laser Spectroscopy of 21,23Na at the RAON CLaSsy Beamline

Collinear laser spectroscopy provides a sensitive probe of hyperfine interactions, electromagnetic moments, and isotope shifts in short-lived nuclei. In particular, radioactive sodium isotopes provide a useful testing ground for nuclear-structure studies as well as precision tests of atomic calculations.
In this presentation, I will present recent collinear laser spectroscopy measurements of $^{21}$Na and $^{23}$Na performed at the CLaSsy beamline of the RAON ISOL facility in Korea, with a focus on the hyper-fine structure measurement of the neutron-deficient isotope $^{21}$Na. Sodium beams were produced from a SiC target bombarded by a 70-MeV proton beam, mass separated, accelerated to 20 keV, cooled and bunched in an RFQ cooler-buncher, and delivered to the CLaSsy beamline. After charge exchange, neutral sodium atoms were probed on the atomic D1 transition using a 589-nm laser, and fluorescence photons were detected in time coincidence with the ion bunches.
The talk will discuss the experimental method, including the use of collinear and anti-collinear geometries to control beam-energy-related systematics. The stable isotope $^{23}$Na was measured as a reference to validate the spectroscopic analysis and evaluate systematic effects. I will then present the hyperfine-structure analysis of $^{21}$Na, focusing on the extraction of the magnetic-dipole hyperfine constants A(3s2S1/2) and A(3p2P1/2). The results are compared with previous measurements and with relativistic coupled-cluster calculations, providing a benchmark for higher-order electron-correlation effects. The outlook for future isotope-shift and charge-radius measurements of $^{21}$Na at RAON will also be discussed.

Speaker: Junho Won (CENS, IBS)

20260722_ICEN_JHW_upload.pdf

11:17 Development and characterization of SCIGA for direct reaction experiments at RAON

Direct reaction experiments in inverse kinematics are one of the best suited tools to probe a broad range of nuclear properties, providing great insight into the nuclear structure of exotic nuclei. Thus a large amount of effort was devoted at the Center for Exotic Nuclear Studies (CENS) to develop nuclear detection instruments especially intended for experiments with direct reactions in inverse kinematics at RAON. With the aforementioned constraints in mind, SCIGA (Silicon-CsI-GAGG Array) was designed as a large solid angle array of Silicon-CsI telescopes for charged-particle detection and an array of GAGG scintillators for efficient coincidence measurements of $\gamma$-rays.

This contribution will present SCIGA detailed specifications and current status. Ongoing development efforts and upcoming SCIGA experiments will also be discussed.

Speaker: Xesus Pereira-Lopez (CENS, IBS)

11:29 Commissioning of the PlungeR INstrument at CEns (PRINCE) at the RAON facility

The PlungeR INstrument at CEns (PRINCE) is a plunger device developed at CENS for lifetime measurements in picosecond range using the recoil-distance Doppler-shift (RDDS) technique. The system is based on a high-precision piezoelectric linear stage and incorporates interchangeable target and stopper assemblies, capacitance-based distance calibration, and active feedback control to maintain the target-to-stopper separation during in-beam measurements. Its compact geometry enables operation within the ASGARD $\gamma$-ray detector array and provides flexibility for future integration with ancillary particle-detection systems. The device was commissioned at the RAON facility by measuring the lifetime of the 4$^+$ state in $^{80}$Sr, populated through the $^{64}$Zn($^{20}$Ne, $\alpha$)$^{80}$Sr fusion-evaporation reaction.
This talk will present the commissioning results and discuss prospects for future developments and lifetime measurements at RAON.

Speaker: Arunita Mukherjee (CENS, IBS)

11:41 Elastic scattering experiments 40Ar+p and Na+p using the CENS silicon detector array at RAON

We report proton elastic scattering experiments in inverse kinematics at the KoBRA beam line of the RAON facility, using ELARK (ELastic scattering detector Array for Reaction studies in inverse Kinematics), developed at CENS (Center for Exotic Nuclear Studies). The first experiment (KO-24-20) measured proton elastic scattering with a stable $^{40}$Ar beam at 4.4, 5.9, and 8.3 MeV/u. Since the phenomenological global optical potentials could not reproduce the data, new optical potential parameters were extracted through Chi-square minimization. The second experiment (KO-25-20) will measure proton elastic scattering with $^{21,25}$Na beams using additional silicon detectors covering the forward region. This experiment was designed based on differential cross sections calculated from double-folding optical potentials with deformed nuclear density profiles, and the silicon detectors will be placed at the expected dip positions. The result will allow us to verify the reliability of this calculation method in describing nuclear scattering cross sections.

Speaker: Jungwoo Lee (CENS, IBS)

ICEN2026_JungwooLee.pdf

12:00 → 13:30 Lunch

13:30 → 14:45 Session 7

Convener: Prof. Rituparna Kanungo (TRIUMF)

13:30 Decay Spectroscopy Projects at the RAON ISOL Facility

The RAON ISOL facility is currently in operation and is continuously expanding its portfolio of radioactive isotope (RI) beams through the development of new target materials and ion source techniques. The rich variety of RI beams will be available at the ISOL facility in near future and will open new opportunities across a broad range of physics programs, including nuclear structure, weak interaction studies, nuclear data evaluation, and nuclear astrophysics.
The Center for Exotic Nuclear Studies (CENS) brings together researchers with broad expertise in decay spectroscopy to pursue these programs. To support this effort, a suite of detection systems is being developed and commissioned at CENS. These include a decay station coupled with various detectors such as coaxial HPGe and ASGARD HPGe Clover detector arrays, X-ray detector, the SCEPTER conversion-electron detector, tape transport systems and etc. In addition, a total absorption spectrometer (TAS) and a polarized RI decay setup based on a dilution refrigerator are currently under development, further extending the physics reach of the program.
Two dedicated beamlines, STRAIT and HIPPIE, are under development to host these detector systems. STRAIT is designed for high-statistics measurements, while HIPPIE is optimized for high-precision experiments, together providing complementary capabilities for the full decay spectroscopy program at RAON.

Speaker: Yung Hee KIM (CENS)

13:55 Science opportunities with decays of exotic nuclei

Speaker: Robert Grzywacz (Univ. Tennessee, Knoxville)

raon-neutrons_03.pdf

14:20 Production and Application of the low-energy RI beams at CRIB

CRIB [1,2] is a low-energy radioactive-isotope (RI) beam separator operated by CNS, University of Tokyo, located at RIBF of RIKEN Nishina Center. Various experimental projects based on interests for nuclear structure, reaction, and nuclear astrophysics have been carried out at CRIB, forming international collaborations. CRIB can produce intense RI beams at low energies (< 10 MeV/nucleon) by in-flight method, using a cryogenic gas target system for the beam production.

One of the major interests of CRIB collaboration is on the astrophysical reactions in high-temperature stellar environments, such as X-ray bursters, where many reactions involving RI play important roles. In the breakout path from the hot hydrogen burning to the rp-process, several alpha-induced reactions define the energy production rate and nucleosynthesis paths, however, those reactions are often difficult to measure experimentally. Recent experimental efforts at CRIB to pin down those reaction rates are introduced [3,4].

CRIB has a similar design with the KoBRA spectrometer in RAON, and the knowledge and experience at CRIB could be inherited to future experiments at KoBRA, based on the firm collaboration that was already established between Korean and Japanese researchers. Possibilities of new experimental projects in this direction are also suggested and discussed.

---

References
[1] Y. Yanagisawa, S. Kubono et al., Nucl. Instr. Meth. A 539, 74 (2005).
[2] H. Yamaguchi, Y. Wakabayashi et al., Nucl. Instr. Meth. A 589, 150 (2008).
[3] S. Hayakawa, M.L. Cognata et al., Astrophys. J. Lett, 915, L13 (2021).
[4] J. Hu, H. Yamaguchi et al., Phys. Rev. Lett. 127, 172701 (2021).

Speaker: Hidetoshi Yamaguchi (CNS, Univ. of Tokyo)

260723_ICEN2026_HYamaguchi_mod.pdf

14:45 → 17:00 RAON Tour

17:00 → 18:00 Discussion

18:00 → 19:30 Banquet

Friday 24 July

09:00 → 10:15 Session 8

Convener: Prof. Dean Lee (FRIB)

09:00 Charge-symmetry-breaking response in mirror displacement energies and charge radii

Mirror charge radii provide a promising route to neutron-skin information, but their interpretation requires control of nuclear isospin-symmetry breaking beyond the Coulomb interaction. We present a differential Skyrme energy-density-functional analysis that treats mirror displacement energies (MDEs) and mirror charge-radius differences within the same class-III charge-symmetry breaking (CSB) framework. Coulomb-subtracted MDE residuals are mapped onto an effective CSB functional containing volume and surface-gradient terms, and the resulting response is propagated to radii without additional radius-sector parameters. For the measured anchor set $^{34}$Ar-$^{34}$S, $^{36}$Ca-$^{36}$S, $^{38}$Ca-$^{38}$Ar, and $^{54}$Ni-$^{54}$Fe, the MDE response ratios form a compact surface-like class rather than the volume and surface couplings separately. In SLy4, a joint volume-plus-surface fit gives RMS residuals of 0.0529 MeV in MDEs and 0.00312 fm in mirror charge radii; SkM$^{*}$ confirms the same response class and effective-coupling degeneracy, but shows a larger mass–radius residual, which we use as an EDF systematic. The MDE-calibrated CSB response shifts proton-rich mirror skins at the 10-2 fm level.
Applying the same response class to unmeasured proton-rich partners, we predict R$_{ch}$($^{40}$Ti) = 3.5736(56) fm, R$_{ch}$($^{42}$Ti) = 3.5809(54) fm, R$_{ch}$($^{46}$Cr) = 3.6917(55) fm, and R$_{ch}$($^{50}$Fe) = 3.7180(82) fm. The quoted parentheses include the experimental uncertainty of the known mirror partner and a numerical radius floor, while the SLy4–SkM${*}$ differences provide an additional EDF systematic of up to 0.020 fm. These results identify a surface-sensitive CSB response that must be quantified before mirror charge radii are used as clean neutron-skin or symmetry-energy probes.
These results identify a surface-sensitive CSB response that must be quantified before mirror charge radii are used as clean neutron-skin or symmetry-energy probes.

Speaker: Myung-Ki Cheoun (Soongsil Univ.)

mirror_csb_20260724_ICENS_short.pdf

09:25 Accelerating X-ray Burst Sensitivity Studies with Deep Learning

Type I X-ray bursts (XRBs) are explosive astrophysical phenomena powered by hundreds of thermonuclear reactions in the rapid proton capture process ($rp$-process). Sensitivity studies with XRB simulation codes have been used to identify nuclear reactions that have the most impact on observables and should be prioritized for future studies. Due to the high computational cost and time-consuming nature of hydrodynamic simulations, previous sensitivity studies only considered the impact of variations of one reaction rate at a time. Consequently, the impacts of reaction correlations by simultaneous variation of multiple rates have not been well investigated.
We propose a novel deep learning approach to emulate XRB simulations and significantly accelerate predictions of XRB observables. By training a deep neural network on datasets of XRB properties generated with the multi-zone hydrodynamic code MESA, we can explore the impact of simultaneous variations of multiple reaction rates. This enables us to identify unexplored combinations of reactions that have substantial influence on XRB properties. Details of the method and preliminary results will be presented.

Speaker: Kyung Yuk Chae (Sungkyunkwan Univ.)

Chae.pdf

09:50 The potential of cross-detector foundation models for nuclear physics: a case study using TPCs

Foundation models such as the GPT models, BERT, and DALL-E have shown impressive performance in text and image domains. Such models are built through large-scale training on self-supervised tasks. Similarly, foundation models built for physics-native data structures show potential for applications in nuclear physics experiments. This talk presents work toward developing a multi-purpose deep learning model for time projection chamber (TPC) detector systems that can be fine-tuned for various tasks, including event identification, particle or track identification, and regression. Time-projection chambers are widely used across various subfields of nuclear physics experiments to provide three-dimensional “images” of particle reactions or decays. By treating TPC data as 4-dimensional point clouds, we explore multiple self-supervised pre-training tasks, including a point-cloud shuffling task, to build the backbone of our foundation model. To evaluate these backbone models, we share representation learning results, which include cross-detector transferability, where a model pre-trained on data from one detector retains useful “knowledge” when transferred to another detector. Last, we demonstrate the usefulness of these models when tuned to downstream physics tasks which are evaluated using experimental data withheld in the pretraining phase. Our models are developed using data from two TPCs: the Active-Target Time Projection Chamber (AT-TPC) and the Gaseous Detector with Germanium Tagging (GADGET II) at the Facility for Rare Isotope Beams at Michigan State University and demonstrate broader applicability to nuclear physics TPCs. This work also demonstrates the broader impacts of foundation models to nuclear physics facilities beyond TPCs.

This work is supported in part by NSF grants OAC-2311263, OAC-1836650, PHY-2012865 and the Davidson College RISE program.

Speaker: Michelle Kuchera (Davidson College)

MPK_ICEN_2026.pdf

10:15 → 10:40 Coffee Break

10:40 → 12:10 Session 9

Convener: Dr Taeksu Shin (IRIS, IBS)

10:40 Shape evolution of the Mo isotopes far from the valley of stability

The triaxial degree of freedom in nuclei has an important role in the shape evolution. The neutron-deficient and neutron-rich Mo isotopes provide a good example. The large collectivity of a neutron-deficient nuclide $^{84}$Mo leads to the isospin-symmetric island of inversion, and the large triaxiality is expected from the state-of-the-art shell model calculation [1]. For the nuclides lying on the neutron-rich side, their low-lying second 2$^{+}$ state is closely related to the triaxiality [2]. The study aimed to perform a detailed spectroscopy for the neutron-rich Mo isotopes $^{112,114}$Mo to understand their triaxial excitations.
The experiment was performed at the RIKEN Nishina Center. We employed the HPGe detector array EURICA to measure the $\beta$-delayed $\gamma$ rays of $^{112,114}$Mo [3]. The $\gamma$-vibrational band has been extended for $^{112}$Mo, and the yrast 2$^+$ and 4$^+$ states were observed for $^{114}$Mo. In the case of $^{114}$Mo, a reduced pairing strength motivated by Ref. [4] implies that an oblate deformation would develop. The new experimental results and the comparison with the five-dimensional collective Hamiltonian calculation will be presented. Moreover, an overview of the shape evolution of the Mo isotopes far from the valley of stability will be given.

References
[1] J. Ha, F. Recchia, S. M. Lenzi, H. Iwasaki, D. D. Dao et al., Nat. Comm. 16, 10631 (2025).
[2] J. Ha, T. Sumikama, F. Browne, N. Hinohara, A. M. Bruce et al., Phys. Rev. C 101, 044311 (2020).
[3] T. Sumikama, J. Ha, F. Browne, N. Hinohara, A. M. Bruce et al., submitted.
[4] M. Yamagami, Y. R. Shimizu and T. Nakatsukasa, Phys. Rev. C 80, 064301 (2009).

Speaker: Jeongsu Ha (CENS, IBS)

IBS_Conf_JeongsuHa.pptx

11:05 Nuclear structure of 94Pd at transition-point between the isoscalar and isovector characteristics

Nuclei near the doubly magic nucleus $^{100}$Sn (N = Z = 50) have been extensively studied to investigate nuclear structure, including shell evolution, seniority effects, and proton–neutron interactions. In this work, $^{94}$Pd with N = Z + 2 was investigated with a focus on isovector (T = 1) and isoscalar (T = 0) neutron-proton pairing using the fast-timing measurement. Half-lives of yrast excited states in $^{94}$Pd were measured using isomeric decay spectroscopy.
The experiment was performed at RIBF (Radioactive Isotope Beam Factory), RIKEN, where $^{94}$Pd ions were produced via in-flight fragmentation of a $^{124}$Xe beam impinging on a $^{9}$Be target. These ions were implanted into the GARi active stopper array, and isomeric delayed $\gamma$-rays were detected with the IDATEN fast-timing array consisting of 48 LaBr$_3$(Ce) detectors. The half-lives were determined using the generalized centroid difference method, yielding the T$_{1/2}$ values of $\leq$ 15 ps, 13(11) ps, $\leq$ 13ps, 693(72) ps, and $\leq$ 19 ps for the (2$_1^+$), (4$_1^+$), (6$_1^+$), (8$_1^+$), and (10$_1^+$) states, respectively. The half-lives of the (2$_1^+$), (4$_1^+$) and (10$_1^+$) states are reported here for the first time, and the uncertainties of the half-lives of the (6$_1^+$) and (8$_1^+$) states have been improved compared to previous measurements.
Reduced transition probabilities B(E2) were deduced from the measured half-lives and discussed in the context of shell-model calculations employing the JUN45 effective interaction, including T = 0, T = 1 and full interaction. The results suggest that $^{94}$Pd, with N = Z + 2, lies in a transitional regime between the N = Z isoscalar-pairing domain $^{92}$Pd and the N = 50 isovector-dominated region ($^{96}$Pd).

Speaker: Youngseub Jang (Korea Univ.)

ICEN YoungseubJang_submit_ver.pdf

11:17 Development of a cryogenic gas target and future experiments

Cryogenic gas targets are widely used in low-energy nuclear experiments for studies of nuclear astrophysics and nuclear structure. Compared with solid targets such as CH$_{2}$ and CD$_{2}$, cryogenic gas targets offer high purity and high density. These advantages reduce unwanted background contributions and enhance reaction yields, thereby improving the sensitivity of nuclear physics experiments. In this presentation, a cryogenic gas target system called CryoSTAR (Cryogenic Stable TARget), developed at CENS, IBS, will be introduced. In addition, future experiments using CryoSTAR planned at RAON, IRIS, will be presented.

Speaker: Sunji Kim (CENS, IBS)

ICEN_2026_SKim.pptx

11:29 Development and Evaluation of a Quadrant Silicon Pad Sensor for the TexAT Active Target Detector

For low-energy rare-isotope beam experiments, a 5 x 5 cm$^2$ quadrant silicon pad sensor was developed for the TexAT active target system. To prevent premature breakdown in large-area segmented sensors, three guard-ring configurations (G6, G9, G14) were investigated via TCAD simulations and experimental measurements. Simulations proved that the G9 design, using a graded-spacing strategy, mitigates electric-field concentration more effectively than the 14-ring design. The fabricated G9 sensor demonstrated a low leakage current of several tens of nA and an energy resolution of approximately 31 keV (FWHM) for 3.18 MeV $\alpha$-particles from $^{148}$Gd. In-beam tests at RAON verified its operational reliability, providing key design criteria for TexAT detectors.

Speaker: Hyeyoung Lee (CENS, IBS)

ICEN2026_QuadrantSiliconSensor_HYLee.pdf

11:41 Universal width predictions for near-threshold neutron resonances

We establish a universal baseline for the widths of near-threshold single-neutron resonances in L>0 partial waves. The baseline arises from discrete scale invariance at zero energy in the finite square-well potential and depends only on geometry, angular momentum, and resonance energy. Comparison with data shows that it provides a robust benchmark, while deviations caused by Woods-Saxon diffuseness reveal structure-dependent effects.

Speaker: Myungkuk Kim (CENS/IBS)

MKIM_ICEN2026.pdf

11:53 Charge-Dependent Nucleon–Nucleon Interactions in Covariant Chiral Effective Field Theory

The charge-dependent nucleon-nucleon ($NN$) interaction plays a crucial role in understanding the nuclear structure and reaction problems. In this work, we explore the charge-dependent $NN$ interaction in covariant chiral effective field theory. By incorporating the isospin-breaking contributions, we derive the charge-dependent covariant chiral $NN$ potential up to next-to-next-to leading order (NNLO). The calculated $np$ and $pp$ phase shifts are in satisfactory agreement with the PWA93 partial wave analysis. Our results contribute to a deeper understanding of isospin-breaking effects in nuclear forces and provide a solid foundation for future studies of nuclear structure and reactions within the covariant framework.

Speaker: Xiao Yang (CENS, IBS)

ICEN2026_Xiao.pdf

12:10 → 13:30 Lunch

13:30 → 14:20 Session 10

Convener: Prof. Deuk Soon Ahn (FRIB)

13:30 Deep subthreshold pion production in heavy-ion collisions (SUPER)

Subthreshold pion production in heavy-ion collisions provides unique insight into high-density nuclear matter and multi-nucleon dynamics. While neutral pion creation in proton-proton collisions requires over 280 MeV, nuclear collisions achieve this at much lower energies—down to 25 MeV/nucleon—thanks to Fermi motion and collective effects, which remain incompletely understood. The SUPER experiment directly addresses these questions through $^{12}$C+$^{12}$C collisions at 25–60 MeV/nucleon. Prototype beam tests at RARiS, using a 3×3 CsI(Tl) crystal matrix, confirmed reliable high-energy photon detection and demonstrated the SUPER DAQ system's high stability and precision. The upcoming phase will deploy a 768-channel detector for the first full-scale experiment (E610) at RCNP. This talk will provide an update on the SUPER.

Speaker: Jung Keun Ahn (Korea Univ.)

ICENS2026_JungKeunAhn.pdf

13:55 The radioactive beam facility SPES reaching the major milestones

Speaker: Faical Azaiez (INFN-LNL)

14:20 → 14:45 Coffee Break

14:45 → 16:00 Session 11

Convener: Prof. Kevin Insik Hahn (CENS, IBS)

14:45 Collective flow and symmetry potential in Xe+Sn at 100 MeV/u

The density as well as momentum dependences of the symmetry potential in nuclear matter can be studied using the collective flow parameters in intermediate energy nuclear collisions, where mean-field dynamics and nucleon–nucleon collisions compete. The directed and elliptic flow parameters for light charged particles in Xe + Sn collisions at 100 MeV/u, measured by the INDRA detector, have been analyzed. The experimental data are compared with the ImQMD transport model calculations, employing two Skyrme interactions with and without applying the GEMINI++ afterburner. This comparison allows us to systematically study the momentum-dependence of the symmetry potential and secondary decay effects. This presentation also includes some prospects for the current efforts to further develop our understanding of the nuclear symmetry energy.

Speaker: Byungsik Hong (Korea Univ.)

Hong.pdf

15:10 CENS research activities on excited-state lifetime measurements

The Nuclear Structure group at CENS is promoting research projects aimed at measuring the lifetime of excited states by means of the electronic fast-timing method using LaBr3(Ce) detectors, recoil distance technique by Plunger, and low-energy Coulomb excitation. In this presentation, some results of the commissioning experiments performed at RIBF and RAON will be introduced.

Speaker: Hiroshi Watanabe (CENS, IBS)

ISEN2026_Watanabe.pptx

15:35 Closing Remark & Discussion

Speaker: Navin Alahari (GANIL)