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1. First (p,n) reaction measurement in inverse kinematics with SECAR

   https://doi.org/10.1051/epjconf/202327502016  

   Tsintari, Pelagia; Berg, Georg; Blackmon, Jeff; Chipps, Kelly; Couder, Manoel; Deibel, Catherine; Dimitrakopoulos, Nikolaos; Garg, Ruchi; Greife, Uwe; Hermansen, Kirby; et al (January 2023, EPJ Web of Conferences)

   Lamia, L.; Pizzone, R.G.; Rapisarda, G.G.; Sergi, M.L. (Ed.)

   Nucleosynthesis in the ν p-process occurs in regions of slightly proton-rich nuclei in the neutrino-driven wind of core-collapse supernovae. The process proceeds via a sequence of (p, γ ) and (n,p) reactions, and depending on the conditions, may produce elements between Ni and Sn. Recent studies show that a few key (n,p) reactions regulate the efficiency of the neutrino-p process ( ν p-process). We performed a study of one of such (n,p) reactions via the measurement of the reverse (p,n) in inverse kinematics with SECAR at NSCL/FRIB.Such proton-induced reaction measurements are particularly challenging, as the recoils and the unreacted projectiles have nearly identical masses. An appropriate separation level can be achieved with SECAR, and along with the incoincidence detection of neutrons these measurements become attainable. The preparation of the SECAR system for accommodating its first (p,n) reaction measurement, including the development of alternative ion beam optics, and the setup of the in-coincidence neutron detection, along with discussion on preliminary results from the p( 58 Fe,n) 58 Co reaction measurement are presented and discussed. 

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2. Machine learning enabled measurements of astrophysical ( $p,n$ ) reactions with the SECAR recoil separator

   https://doi.org/10.1103/PhysRevResearch.7.013074  

   Tsintari, P; Dimitrakopoulos, N; Garg, R; Hermansen, K; Marshall, C; Montes, F; Perdikakis, G; Schatz, H; Setoodehnia, K; Arora, H; et al (January 2025, Physical Review Research)

   The synthesis of heavy elements in supernovae is affected by low-energy $(n,p)$and $(p,n)$reactions on unstable nuclei, yet experimental data on such reaction rates are scarce. The SECAR (SEparator for CApture Reactions) recoil separator at FRIB (Facility for Rare Isotope Beams) was originally designed to measure astrophysical reactions that change the mass of a nucleus significantly. We used a novel approach that integrates machine learning with ion-optical simulations to find an ion-optical solution for the separator that enables the measurement of $(p,n)$reactions, despite the reaction leaving the mass of the nucleus nearly unchanged. A new measurement of the ${}^{58}\mathrm{Fe}(p,n){}^{58}\mathrm{Co}$reaction in inverse kinematics with a $3.66\pm 0.12$MeV/nucleon ${}^{58}\mathrm{Fe}$beam (corresponding to $3.69\pm 0.12$MeV proton energy in normal kinematics) yielded a cross-section of $20.3\pm 6.3$ mb and served as a proof of principle experiment for the new technique demonstrating its effectiveness in achieving the required performance criteria. This novel approach paves the way for studying astrophysically important $(p,n)$reactions on unstable nuclei produced at FRIB. Published by the American Physical Society2025 

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3. SECAR: A recoil separator for nuclear astrophysics

   https://doi.org/10.1051/epjconf/202226011044  

   Tsintari, Pelagia; Garg, Ruchi; Berg, Georg; Blackmon, Jeff; Chipps, Kelly; Couder, Manoel; Deibel, Catherine; Dimitrakopoulos, Nikolaos; Greife, Uwe; Hood, Ashley; et al (January 2022, EPJ Web of Conferences)

   Liu, W.; Wang, Y.; Guo, B.; Tang, X.; Zeng, S. (Ed.)

   Proton-and alpha-capture reactions on unstable proton-rich nuclei power astrophysical explosions like novae and X-ray bursts. Direct measurements of these reactions are crucial for understanding the mechanisms behind these explosions and the nucleosynthesis at such sites. The recoil mass separator, SECAR (SEparator for CApture Reactions) at the National Superconducting Cyclotron Laboratory (NSCL) and the Facility for Rare Isotope Beams (FRIB), has been designed with the required sensitivity to study (p, γ ) and ( α , γ ) reactions, directly at astrophysical energies in inverse kinematics, with radioactive beams of masses up to about A = 65. The complete SECAR system, including two Wien Filters for high mass resolution, has been installed at Michigan State University and is currently being commissioned. The present article introduces the SECAR concept, its scientific goals, and provides an update of the current status of the project. 

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4. Demonstration of neutron identification in neutrino interactions in the MicroBooNE liquid argon time projection chamber

   https://doi.org/10.1140/epjc/s10052-024-13423-z  

   Abratenko, P; Alterkait, O; Aldana, D Andrade; Arellano, L; Asaadi, J; Ashkenazi, A; Balasubramanian, S; Baller, B; Barnard, A; Barr, G; et al (October 2024, The European Physical Journal C)

   Abstract A significant challenge in measurements of neutrino oscillations is reconstructing the incoming neutrino energies. While modern fully-active tracking calorimeters such as liquid argon time projection chambers in principle allow the measurement of all final state particles above some detection threshold, undetected neutrons remain a considerable source of missing energy with little to no data constraining their production rates and kinematics. We present the first demonstration of tagging neutrino-induced neutrons in liquid argon time projection chambers using secondary protons emitted from neutron-argon interactions in the MicroBooNE detector. We describe the method developed to identify neutrino-induced neutrons and demonstrate its performance using neutrons produced in muon-neutrino charged current interactions. The method is validated using a small subset of MicroBooNE’s total dataset. The selection yields a sample with$$60\%$$ $60\%$of selected tracks corresponding to neutron-induced secondary protons. At this purity, the integrated efficiency is 8.4% for neutrons that produce a detectable proton. 

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5. Investigation of the ⁷ Li(p,n) neutron fields at high energies

   https://doi.org/10.1051/epjconf/202226011005  

   Brückner, Benjamin; Erbacher, Philipp; Göbel, Kathrin; Heftrich, Tanja; Khasawneh, Kafa; Kurtulgil, Deniz; Langer, Christoph; Nolte, Ralf; Reich, Markus; Reifarth, René; et al (January 2022, EPJ Web of Conferences)

   Liu, W.; Wang, Y.; Guo, B.; Tang, X.; Zeng, S. (Ed.)

   The neutron activation method is well-suited to investigate neutron-capture cross sections relevant for the main s-process component. Neutrons can be produced via the 7 Li(p,n) reaction with proton energies of 1912 keV at e.g. Van de Graaff accelerators, which results in a quasi-Maxwellian spectrum of neutrons corresponding to a temperature of k B T = 25 keV. However, the weak s-process takes place in massive stars at temperatures between 25 and 90 keV. Simulations using the PINO code [2] suggest that a Maxwellian spectrum for higher energies, e.g. k B T = 90 keV, can be approximated by a linear combination of different neutron spectra. To validate the PINO code at proton energies E p ≠ 1912 keV, neutron time-of-flight measurements were carried out at the PTB Ion Accelerator Facility (PIAF) at the Physikalisch-Technische Bundesanstalt in Braunschweig, Germany. 

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