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1. The 41 Ar(n,y) 42 Ar reaction

   https://doi.org/10.1051/epjconf/202328401037  

   Sahoo, R. N. ; Paul, M. ; Köster, U. ; Scott, R. ; Tessler, M. ; Zylstra, A. ; Avila, M. L. ; Dickerson, C. ; Jayatissa, H. ; Kohen, M.S. ; et al ( January 2023 , EPJ Web of Conferences)

   Mattoon, C.M. ; Vogt, R. ; Escher, J. ; Thompson, I. (Ed.)

   The cross-section of the thermal neutron capture⁴¹Ar(n,γ)⁴²Ar(t_1/2=32.9 y) reaction was measured by irradiating a⁴⁰Ar sample at the high-flux reactor of Institut Laue-Langevin (ILL) Grenoble, France. The signature of the two-neutron capture has been observed by measuring the growth curve and identifying the 1524.6 keV γ-lines of the shorter-lived⁴²K(12.4 h) β⁻daughter of⁴²Ar. Our preliminary value of the⁴¹Ar(n,γ)⁴²Ar thermal cross section is 240(80) mb at 25.3 meV. For the first time, direct counting of⁴²Ar was performed using the ultra-high sensitivity technique of noble gas accelerator mass spectrometry (NOGAMS) at Argonne National Laboratory, USA.

    

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2. Threshold effects in the 10B(p,α)7Be, 12C(p,γ)13N and 14N(p,γ)15O reactions

   https://doi.org/10.3389/fphy.2022.1009489  

   Wiescher, M. ; deBoer, R.J. ; Görres, J. ( October 2022 , Frontiers in Physics)

   The typical energy range for charge particle interactions in stellar plasmas corresponds to a few 10s or 100s of keV. At these low energies, the cross sections are so vanishingly small that they cannot be measured directly with accelerator based experimental techniques. Thus, indirect studies of the compound structure near the threshold are used in the framework of reaction models to complement the direct data in order to extrapolate the cross section into the low energy regime. However, at the extremely small cross sections of interest, there maybe other quantum effects that modify the such extracted cross section. These may result from additional nuclear interactions associated with the threshold itself or could be due to other processes, such as electron screening. Measurements in plasma environments like at the OMEGA or National Ignition Facility facilities offer an entirely new set of experimental conditions for studying these types of reactions, often directly at the energies of interest. In this paper, we examine three reaction, 10 B( p , α ) 7 Be, 12 C( p , γ ) 13 N and 14 N( p , γ ) 15 O, which have all been measured at very low energies using accelerator based methods. All three reactions produce relatively long-lived radioactive nuclei, which can be collected and analyzed at plasma facilities using a variety of collection and identification techniques. 

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3. 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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4. Characterization of SABRE crystal NaI-33 with direct underground counting

   https://doi.org/10.1140/epjc/s10052-021-09098-5  

   Antonello, M. ; Arnquist, I. J. ; Barberio, E. ; Baroncelli, T. ; Benziger, J. ; Bignell, L. J. ; Bolognino, I. ; Calaprice, F. ; Copello, S. ; Dafinei, I. ; et al ( April 2021 , The European Physical Journal C)

   Ultra-pure NaI(Tl) crystals are the key element for a model-independent verification of the long standing DAMA result and a powerful means to search for the annual modulation signature of dark matter interactions. The SABRE collaboration has been developing cutting-edge techniques for the reduction of intrinsic backgrounds over several years. In this paper we report the first characterization of a 3.4 kg crystal, named NaI-33, performed in an underground passive shielding setup at LNGS. NaI-33 has a record low$$^{39}$$${}^{39}$K contamination of 4.3 ± 0.2 ppb as determined by mass spectrometry. We measured a light yield of 11.1 ± 0.2 photoelectrons/keV and an energy resolution of 13.2% (FWHM/E) at 59.5 keV. We evaluated the activities of$$^{226}$$${}^{226}$Ra and$$^{228}$$${}^{228}$Th inside the crystal to be$$5.9\pm 0.6~\upmu $$$5.9\pm 0.6\mu$Bq/kg and$$1.6\pm 0.3~\upmu $$$1.6\pm 0.3\mu$Bq/kg, respectively, which would indicate a contamination from$$^{238}$$${}^{238}$U and$$^{232}$$${}^{232}$Th at part-per-trillion level. We measured an activity of 0.51 ± 0.02 mBq/kg due to$$^{210}$$${}^{210}$Pb out of equilibrium and a$$\alpha $$$\alpha$quenching factor of 0.63 ± 0.01 at 5304 keV. We illustrate the analyses techniques developed to reject electronic noise in the lower part of the energy spectrum. A cut-based strategy and a multivariate approach indicated a rate, attributed to the intrinsic radioactivity of the crystal, of$$\sim $$$\sim$1 count/day/kg/keV in the [5–20] keV region.

    

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5. Direct measurement of the 19 F( p , αγ ) 16 O reaction in JUNA

   https://doi.org/10.1051/epjconf/202226008004  

   Zhang, L.Y. ; Su, J. ; He, J.J. ; Wiescher, M. ; deBoer, R.J. ; Kahl, D. ; Chen, Y.J. ; Li, X.Y. ; Wang, J.G. ; Zhang, L. ; et al ( January 2022 , EPJ Web of Conferences)

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

   The 19 F( p , αγ ) 16 O reaction is of crucial importance for Galactic 19 F abundances and CNO cycle loss in first generation Population III stars. Due to its extremely small cross sections, the 19 F( p , αγ ) 16 O reaction has not been measured in the low energy part of the Gamow window(70-200 keV). As a day-one campaign, the experiment was performed under the extremely low cosmicray-induced background environment of the China JinPing Underground Laboratory(CJPL), one of the deepest underground laboratories in the world. The γ -ray yields were measured over E c . m . =72.4–344 keV, covering the full Gamow window for the first time. The direct experimental data will help people to expound the fluorine over-abundances, energy generation, as well as heavy-element nuclosynthesis scenario in asymptotic giant branch (AGB) stars, with the astrophysical model on the firm ground. 

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