Investigating neutron-unbound excited states in 53Ca

In a recent experiment at FRIB conducted from January 30 to February 2, 2026, the MoNA Collaboration created excited neutron-unbound states of ⁵³Ca and detected their decay products, ⁵²Ca and a neutron, in coincidence. The experiment e21066 “Neutron-Unbound Excited States in ⁵³Ca” (Spokesperson: Thomas Baumann) utilized the Sweeper-MoNA setup together with the CAESAR gamma detector array with the goal to measure the decay energy of these unbound excited states.

Drawing of the experimental setup in the S2 vault at FRIB

For the first time a new segmented target was used. While the segmented target follows the proven concept of an earlier version (T. Redpath et al. https://doi.org/10.1016/j.nima.2020.164284), the updated target and vacuum chamber design allows the installation inside the CAESAR 4p array. The segmented target consists of a stack of four Si-PIN detectors and three interleaved carbon reaction targets.

The excited states of⁵³Ca were populated by a proton removal from an incoming⁵⁴Sc beam. The segmented target detected in which of the three reaction targets this proton removal occurred, improving the accuracy of the decay-energy measurement.

MSU undergraduate student Alexander George is assembling the segmented target, which consists of four silicon detectors and three interleaved carbon targets.

MoNA Collaboration at the 2025 American Physical Society Division of Nuclear Physics

The MoNA Collaboration had a strong presence at the 2025 American Physical Society Division of Nuclear Physics (APS/DNP) which was held on October 17-20, 2025 at the Hilton Chicago hotel in Chicago, Illinois.

A total of 23 combined oral and poster presentations on MoNA-related science or by a member of the MoNA Collaboration were delivered throughout the meeting, covering a wide range of topics that included new detector technologies, multi-neutron systems, novel materials and manufacturing processes for nuclear physics detectors, nuclear reaction, applications of advanced statistics and machine learning methods in nuclear physics, nuclear structure studies, instrumentation and measurements, low energy particle detectors and particle tracking, as well as in education and outreach. The presentations were delivered by faculty, postdocs, and students (graduate, undergraduate and high school). The contribution of the Collaboration also extended beyond presentations as several members chaired various sessions throughout the conference.

Session	Presentation title
D05	Extracting the nuclear charge distribution from electron scattering
	The 2025 Physicists Inspiring the Next Generation: Exploring the Nuclear Matter
	Low-energy nuclear physics program with the Tandem Van De Graaff Accelerator at Western Michigan University
	Physics Immersion, Simulation of the angular distribution with the MoNA-LISA neutron detector
E05	Global analysis of Rutherford scattering data from the PING 2023-2025 cohort
	PYXIS Detector Support Structure
	Probing neutron-rich nuclei along the dripline with PYXIS
	PYXIS neutron detector prototype: from raw events to physics
E06	Next-Generation Neutron Detector: Study of Position Resolution via Machine Learning
G05	Mapping the Invisible: Modeling Nuclear Densities for Rare Isotope Analysis
	Software to predict and analyze neutron scattering patterns in the MoNA and PYXIS Array
	Simulating Quantum Entanglement Through Photon and Neutron Detection
G10	Aerogel layer embedded gaseous electron multiplier
H01	The comparison in counts from PYXIS detector prototypes and MoNA detector bars
	Measuring 12C(n,x) Cross Sections with Diamond Detectors
	Configuring an NGn Prototype Detector using Cosmic Muons for CNN Training and Testing
	Simulation Validation of Neutron Interaction with SiPMs
K12	Optical matrix optimization for the study of unbound nuclei
	Investigating Nuclear Matter Radii Extraction with the MoNA-LISA-Sweeper Setup at FRIB
	Probing neutron-rich prefragment distributions for 9Be(32Mg,X) at 86 MeV/u
L10	Next Generation Neutron Detector Development
N06	Characterizing silicon photomultipliers for a next generation neutron detector
T12	Nuclear radii and nuclear structure with the MoNA Collaboration

LANSCE Neutron Beam Experiment (2025)

Researchers from the MoNA Collaboration, including students and post docs, traveled to New Mexico to test Next Generation Neutron Detector (NGn) prototypes at the Los Alamos Neutron Science Center (LANSCE).

Figure 1: LANSCE celebrated its 50th anniversary in 2022.

Figure 2: Location of the 90 m Station with respect to the neutron production target (Target 4).

The setup was located on a flight path of 90 m from the neutron spallation target that is bombarded with an intense 800 MeV proton beam and produces neutrons with energies up to hundreds of MeV. The neutron beam was tightly collimated to a diameter of 3 mm at the 90-m station, and one prototype detector with 63 SiPM sensors was mounted on a translation stage that was remote controlled to move in the horizontal direction. Different vertical beam positions were achieved by manually adjusting the height of the setup. In addition, two more prototype detectors were mounted in a fixed position downstream of the first detector.

The translation stage was designed and assembled by undergraduate students at Davidson College. Prototype detectors from Virginia State University, Davidson College, and Michigan State University were used in this test.

The collected data will be used to optimize the final detector design. The next generation neutron detector is a collaborative project of Augustana College, Davidson College, Hope College, IndianaWesleyan University, James Madison University, Michigan State University, Wabash College, and Virginia State University and funded by the National Science Foundation [https://www.nsf.gov/awardsearch/showAward?AWD_ID=2320400].

Figure 3: The detector is mounted inside a light-tight wooden box on a translation stage in front of the collimator.

Figure 4: Postdoc Juan Lois Fuentes is adjusting the mount for the stationary detectors.

Figure 5: A 9 by 7 SiPM array detects the scintillation light.

Figure 6: Anthony Kuchera and students R J Devlin and Andrew LaRochelle pose for a selfie in Los Alamos.

Figure 7: In addition to the moveable detector, additional prototypes were mounted stationary at a larger distance from the collimator.