Underground laboratory JUNA shedding light on stellar nucleosynthesis 增强出版

Underground laboratory JUNA shedding light on stellar nucleosynthesis 1 2 3 corresp first-author * kajino@buaa.edu.cn * kajino@buaa.edu.cn kajino@buaa.edu.cn https://orcid.org/0000-0002-0233-9900 School of Physics, and International Research Center for Big-Bang Cosmology and Element Genesis, Beihang University, Beijing 100083, China School of Physics, and International Research Center for Big-Bang Cosmology and Element Genesis, Beihang University, Beijing 100083, China Division of Science, National Astronomical Observatory of Japan, Tokyo 181-8588, Japan Division of Science, National Astronomical Observatory of Japan, Tokyo 181-8588, Japan Graduate School of Science, The University of Tokyo, Tokyo 113-033, Japan Graduate School of Science, The University of Tokyo, Tokyo 113-033, Japan Extremely low background experiments to measure key nuclear reaction cross sections of astrophysical interest are conducted at the world’s deepest underground laboratory, the Jingping Underground laboratory for Nuclear Astrophysics (JUNA). High precision measurements provide reliable information to understand nucleosynthetic processes in celestial objects and resolve mysteries on the origin of atomic nuclei discovered in the first generations of Pop. III stars in the universe and meteoritic SiC grains in the solar system. Nuclear astrophysics is a growing interdisciplinary research field of nuclear physics and astrophysics. It investigates the origin and evolution of hundreds of atomic nuclei in the universe to understand the evolution of stars and galaxies. In addition to the events of the century, SN1987A and GW170817, many complementary data have been accumulated from the high-resolution spectroscopic observations of old faint stars and precise meteoritic analysis of isotopic anomalies and correlations among them. The origin of atomic nuclei is classified into three astrophysical sites and epochs in cosmic evolution [ 1 1 ]: Big-Bang nucleosynthesis in the first 3–10 min of the early universe for the production of light mass nuclei, thermonuclear and explosive nucleosyntheses in stars for the production of intermediate-to-heavy mass nuclei after galaxies formed, and Galactic cosmic-ray interactions with interstellar medium for the production of rare abundant nuclei. In nuclear astrophysics [ 2 2 ], identifying key nuclear reactions and precisely determining their rates [ 3 3 ] have been a long-standing challenge for several nucleosynthetic processes, as shown in Figure 1 Figure 1 . Several nucleosynthetic paths, such as the rapid-neutron capture process (r-process), involve many radioactive unstable nuclei, which are challenging to study experimentally because of their short lifetimes and low beam intensities. This difficulty remains even for the measurements of the cross sections of stable nuclei because most cosmic or stellar nucleosynthesis occurs at temperatures of T = 10 8 -10 9 K under extreme conditions. Although these temperatures are relatively lower than those of other astronomical phenomena, their energy scale is as low as E = 10 - 100 keV. This energy scale is too low to directly measure the reaction cross sections of charged particles in laboratories because extremely small Coulomb penetrability significantly reduces the cross section[ 4 4 ]. In addition, the cosmic-ray background prevents the precise measurement of small reaction cross-sections. Hence, eliminating the cosmic-ray background is critical for the detection of neutral particles like photons and neutrons to measure the reliable reaction rates of radiative-capture <math id="M1"><mrow><mo stretchy="false">(</mo><mi>α</mi><mn>,</mn><mi>γ</mi><mo stretchy="false">)</mo></mrow></math> , (p, γ ) and neutron emission ( α , n) reactions, which are key to the nucleosynthetic processes in Fig. 1 Fig. 1 . The JUNA Collaboration is directed by CIAE, jointly supported by NSFC, CNNC, and CAS, and has established a unique underground facility equipped with a high-intensity accelerator for the direct measurements of extremely small cross sections at low astrophysical energies. JUNA is 2400 m underground at the China JinPing Laboratory complex (CJPL-II) established in 2014 and is the deepest underground laboratory in the world ( Fig. 2 Fig. 2 ). The laboratory is beneath rocks with a thickness of several kilometers; the rocks shield cosmic rays and their corresponding background. Since the first beam was delivered in Dec. 2020, experiments on several key reactions have been carried out with a high-intensity accelerator in an ultra-low background environment. From the onset, JUNA was dedicated to experiments at 19 F(p, αγ ) 16 O at very low energies of E cm = 72.4–344 keV, covering the Gamow window [ 5 5 , 6 6 ]. Fluorine is one of the most mysterious monoisotopic elements whose predicted abundance has a large uncertainty for the reaction rate. To have multiple origins, that is, asymptotic giant branch stars (AGB stars) in a relatively recent epoch with solar metallicity [ 7 7 ], and the core-collapse type II supernova (cc-SN II) in the early galaxy at low metallicity [ 8 8 ]. The JUNA experiment reduces theoretical uncertainties significantly, and the breakout condition of the carbon–nitrogen–oxygen cycle (CNO cycle) in AGB stars is more precisely constrained. The SN ν nucleosynthesis of 19 F is also revisited by considering flavor oscillation effects to infer nucleosynthetic constraints on an unknown mass hierarchy [ 9 9 ]. As part of the inception objectives of the JUNA collaboration, 25 Mg(p, γ ) 26 Al, which plays an important role in the production of 26 Al ( τ 1/2 =7.17×10 5 y) in massive srars [ 10 10 ], was successfully studied. γ rays with an energy of 1.809 MeV emitted from 26 Al were observed by the Gamma-ray Satellite INTEGRAL that provides the distribution and total accumulated mass of 26 Al in the Milky Way. The estimated frequency of cc-SN II and Ib/c was 1.9 ± 1.1 events per century [ 11 11 ], providing a firm basis for the theoretical study of the Galactic chemical evolution of r-process elements [ 12 12 ]. The JUNA Collaboration team determined the reaction rate of 25 Mg(p, γ ) 26 Al with high accuracy by measuring resonance parameters at 92 keV and contributed to establishing a scheme of estimating the rate of SN events. The production mechanism of 40 Ca observed in the oldest ultra-metal-poor star [ 13 13 ] remains an unresolved mystery in recent astronomical observations. In the standard stellar evolution model, most 19 F produced by the hot CNO cycle are recycled back to 16 O by the 19 F(p, α ) 16 O reaction; therefore, the flow cannot reach the production of 40 Ca. However, this scenario is subject to the error bars of its competing reaction rate for 19 F(p, γ ) 20 Ne that breaks the hot CNO cycle as the temperature increases. The JUNA Collaboration team directly measured this reaction down to E cm = 186 keV and found that the resonance at 225 keV contributes to the enhancement in the thermonuclear reaction rate of 19 F(p, γ ) 20 Ne [ 14 14 ]. The hydrostatic burning in Pop. III stars calculated using new rate results of 40 Ca abundance are consistent with those observed in the oldest known ultra-metal-poor stars [ 14 14 ]. The JUNA Collaboration team studied the 13 C( α , n) 16 O reaction and successfully measured its cross section in the range of E cm = 240 keV-1.9 MeV, removing uncertainty from previous experimental data [ 15 15 ]. Since this reaction and 22 Ne( α , n) 25 Mg are a major neutron source for the s-process in AGB stars, the precise determination has long been wanted to predict reliable nuclear abundances from iron to 209 Bi theoretically. The JUNA experiment covers the Gamow window for the intermediate-neutron capture process (i-process) recently identified as a new process in metal-deficient AGB stars and collapsars, which are major r-process sites of massive stars collapsing to a black holes [ 16 16 ]. Comprehensive theoretical studies of the s-, i-, and r-processes in multiple astrophysical sites are being conduncted with JUNA’s new precise data. Recently, the JUNA Collaboration team reported an experimental result [ 17 17 ] on 18 O <math id="M2"><mrow><msup><mrow><mo stretchy="false">(</mo><mi>α</mi><mn>,</mn><mi> </mi><mi>γ</mi><mo stretchy="false">)</mo></mrow><mrow><mn>22</mn></mrow></msup></mrow></math> Ne. For the first time, the team successfully determined the energy E lab = 474.0 ± 1.1 keV, spin-parity J π = 1 - , and γ -width ω γ = 0.25 ± 0.03 μ eV of the most effective resonance dominating the total reaction rate at the Gamow window. 22 Ne is produced via <math id="M3"><mrow><msup><mrow/><mrow><mn>14</mn></mrow></msup><mtext>N</mtext><msup><mrow><mrow><mo>(</mo><mrow><mi>α</mi><mo>,</mo><mtext> </mtext><mi>γ</mi></mrow><mo>)</mo></mrow></mrow><mrow><mn>18</mn></mrow></msup><mtext>F</mtext><msup><mrow><mo stretchy="false">(</mo><msup><mi>e</mi><mo>−</mo></msup><mi>ν</mi><mo stretchy="false">)</mo></mrow><mrow><mn>18</mn></mrow></msup><mtext>O</mtext><msup><mrow><mrow><mo>(</mo><mrow><mi>α</mi><mo>,</mo><mtext> </mtext><mi>γ</mi></mrow><mo>)</mo></mrow></mrow><mrow><mn>22</mn></mrow></msup><mtext>Ne</mtext></mrow></math> , which is key to identifying the conversion efficiency of the CNO cycle, whose main product is 14 N, to the advanced burning stage where the s-process occurs using neutrons produced via the reaction 22 Ne( α , n) 25 Mg in both AGB and supergiant stars. The improved JUNA data also contributes to probing the unknown origin of the isotopic abundance ratio of 21 Ne/ 22 Ne observed in meteoritic stardust SiC grains. The so-called mainstream components of SiC grains arise from AGB stardust. Therefore, both 18 O <math id="M4"><mrow><msup><mrow><mo stretchy="false">(</mo><mi>α</mi><mn>,</mn><mi> </mi><mi>γ</mi><mo stretchy="false">)</mo></mrow><mrow><mn>22</mn></mrow></msup></mrow></math> Ne and its competing reaction 18 O( α , n) 21 Ne affect the resultant isotopic ratio. The improved JUNA data remove the uncertaity in this isotopic ratio. The observed 21 Ne/ 22 Ne ratios in meteoritic stardust SiC grains are used to constrain the physical conditions of nuclear burning processes that depend on the initial mass of the parent AGB star and other astronomical parameters in modeling stellar evolution. Phase I of the JUNA collaboration has almost completed the high precision measurements of several key reactions at the lowest cosmic-ray background. Phase II of the JUNA collaboration has began and will study the following reactions: 12 C( α , γ ) 16 to improve knowledge on stellar evolution and the explosion mechanism of massive stars and resolve the mystery of the massive black-hole mass-gap [ 18 18 ]; 12 C( 12 C, α ) 20 Ne and 12 C( 12 C, p) 23 Na to identify the unknown heat source of X-ray Superburst and clarify the double-degenerate explosion mechanism of SN Ia [ 19 19 ]; 3 He( α, γ ) 7 Be and 3 H( α, γ ) 7 Li to understand the overproduction of Big-Bang lithium and precisely constrain neutrino-mixing parameters from missing solar neutrino flux [ 20 20 ]; 11 B( α , n) 14 N, 15 N( α, γ ) 19 F, and 17 O(n, α ) 14 C and its reverse reaction to elucidate the physical conditions of α -rich freezeout and the r-process nucleosynthesis in magneto-hydrodynamic jets from cc-SN II, collapsars, and binary neutron star mergers [ 21 21 , 12 12 ]. JUNA is expected to produce relevant nuclear data to enrich our knowledge of stellar and cosmic nucleosyntheses to solve many mysteries in astronomy and astrophysics. References C.A. Bertulani , T. Kajino , Frontiers in nuclear astrophysics . Prog. Part. Nucl. Phys. 89 , 56 - 100 ( 2016 ). doi: 10.1016/j.ppnp.2016.04.001 http://doi.org/10.1016/j.ppnp.2016.04.001 Frontiers in nuclear astrophysics E.M. Burbidge , G.R. Burbidge , W.A. Fowler et al. , Synthesis of the elements in stars . Reviews of Modern Physics 29 , 547 - 650 ( 1957 ). doi: 10.1103/RevModPhys.29.547 http://doi.org/10.1103/RevModPhys.29.547 Synthesis of the elements in stars A.A. Aziz , N.S. Ahmad , S. Ahn et al. , Progress in nuclear astrophysics of east and southeast Asia . Association of Asia Pacific Physical Societies Bulletin 31 , 18 ( 2021 ). doi: 10.1007/s43673-021-00018-z http://doi.org/10.1007/s43673-021-00018-z Progress in nuclear astrophysics of east and southeast Asia C.E. Rolfs , W.S. Rodney , Cauldrons in the cosmos: nuclear astrophysics . Theoretical Astrophysics , Chicago : University of Chicago Press , 1988 . Cauldrons in the cosmos: nuclear astrophysics L.Y. Zhang , J. Su , J.J. He et al. , Direct measurement of the astrophysical 19 F(p, αγ ) 16 O reaction in the deepest operational underground laboratory . Phys. Rev. Lett. 127 , 152702 ( 2021 ). doi: 10.1103/PhysRevLett.127.152702 http://doi.org/10.1103/PhysRevLett.127.152702 Direct measurement of the astrophysical 19F(p, αγ)16O reaction in the deepest operational underground laboratory L.Y. Zhang , J. Su , J.J. He et al. , Direct measurement of the astrophysical 19 F(p, αγ ) 16 O reaction in a deep-underground laboratory . Phys. Rev. C 106 , 055803 ( 2022 ). doi: 10.1103/PhysRevC.106.055803 http://doi.org/10.1103/PhysRevC.106.055803 Direct measurement of the astrophysical 19F(p, αγ)16O reaction in a deep-underground laboratory S. Cristallo , O. Straniero , R. Gallino , Evolution, nucleosynthesis, and yields of low-mass asymptotic giant branch stars at different metallicities . Astrophys. J. 696 , 797 - 820 ( 2009 ). doi: 10.1088/0004-637X/696/1/797 http://doi.org/10.1088/0004-637X/696/1/797 Evolution, nucleosynthesis, and yields of low-mass asymptotic giant branch stars at different metallicities S.E. Woosley , W.C. Haxton , Supernova neutrinos, neutral currents and the origin of fluorine . Nature 334 , 45 - 47 ( 1988 ). doi: 10.1038/334045a0 http://doi.org/10.1038/334045a0 Supernova neutrinos, neutral currents and the origin of fluorine H. Ko , D. Jang , M.K. Cheoun et al. , Comprehensive analysis of the neutrino process in core-collapsing supernovae . Astrophys. J. 937 , 116 ( 2022 ). doi: 10.3847/1538-4357/ac88cd http://doi.org/10.3847/1538-4357/ac88cd Comprehensive analysis of the neutrino process in core-collapsing supernovae J. Su , H. Zhang , Z.H. Li et al. , First result from the Jinping Underground Nuclear Astrophysics experiment JUNA: precise measurement of the 92 keV 25 Mg(p, γ ) 26 Al resonance . Science Bulletin 67 , 125 - 132 ( 2022 ). doi: 10.1016/j.scib.2021.10.018 http://doi.org/10.1016/j.scib.2021.10.018 First result from the Jinping Underground Nuclear Astrophysics experiment JUNA: precise measurement of the 92 keV 25Mg(p, γ)26Al resonance R. Diehl , H. Halloin , K. Kretschmer et al. , Radioactive 26 Al from massive stars in the Galaxy . Nature 439 , 45 - 47 ( 2006 ). doi: 10.1038/nature04364 http://doi.org/10.1038/nature04364 Radioactive 26Al from massive stars in the Galaxy Y. Yamazaki , Z.Y. He , T. Kajino et al. , Possibility to identify the contributions from collapsars, supernovae, and neutron star mergers from the evolution of the r-process mass abundance distribution . Astrophys. J. 933 , 112 ( 2022 ). doi: 10.3847/1538-4357/ac721c http://doi.org/10.3847/1538-4357/ac721c Possibility to identify the contributions from collapsars, supernovae, and neutron star mergers from the evolution of the r-process mass abundance distribution S.C. Keller , M.S. Bessell , A. Frebel et al. , A single low-energy, iron-poor supernova as the source of metals in the star SMSS J031300.36-670839.3 . Nature 506 , 463 - 466 ( 2014 ). doi: 10.1038/nature12990 http://doi.org/10.1038/nature12990 A single low-energy, iron-poor supernova as the source of metals in the star SMSS J031300.36-670839.3 L.Y. Zhang , J.J. He , R.J. deBoer et al. , Measurement of 19 F(p, γ ) 20 Ne reaction suggests CNO breakout in first stars . Nature 610 , 656 - 660 ( 2022 ). doi: 10.1038/s41586-022-05230-x http://doi.org/10.1038/s41586-022-05230-x Measurement of 19F(p, γ)20Ne reaction suggests CNO breakout in first stars B. Gao , T.Y. Jiao , Y.T. Li et al. , Deep underground laboratory measurement of 13 C( α , n) 16 O in the Gamow windows of the s and i processes . Phys. Rev. Lett. 129 , 132701 ( 2022 ). doi: 10.1103/PhysRevLett.129.132701 http://doi.org/10.1103/PhysRevLett.129.132701 Deep underground laboratory measurement of 13C(α, n)16O in the Gamow windows of the s and i processes Z. He , M. Kusakabe , T. Kajino et al. , Collapsar, a new site of r-, i-, and s-processes for heavy element synthesis . ( 2023 ) submitted. Collapsar, a new site of r-, i-, and s-processes for heavy element synthesis L.H. Wang , J. Su , Y.P. Shen et al. , Measurement of the 18 O( α,γ ) 22 Ne reaction rate at JUNA and its impact on probing the origin of SiC grains . Phys. Rev. Lett. 130 , 092701 ( 2023 ). doi: 10.1103/PhysRevLett.130.092701 http://doi.org/10.1103/PhysRevLett.130.092701 Measurement of the 18O(α,γ)22Ne reaction rate at JUNA and its impact on probing the origin of SiC grains R. Farmer , M. Renzo , S.E. de Mink et al. , Mind the gap: The location of the lower edge of the pair-instability supernova black hole mass gap . Astrophys. J. 887 , 53 ( 2019 ). doi: 10.3847/1538-4357/ab518b http://doi.org/10.3847/1538-4357/ab518b Mind the gap: The location of the lower edge of the pair-instability supernova black hole mass gap K. Mori , M.A. Famiano , T. Kajino et al. , Impacts of the new carbon fusion cross-sections on type Ia supernovae . Monthly Notices of the Royal Astronomical Society 482 , L70 - L74 ( 2019 ). doi: 10.1093/mnrasl/sly188 http://doi.org/10.1093/mnrasl/sly188 Impacts of the new carbon fusion cross-sections on type Ia supernovae T. Kajino , X. Yao , Z. He et al. , Alpha-clustering structure of the light nuclei and its impact on astrophysics and cosmology . World Scientific , 2023 , in press . Alpha-clustering structure of the light nuclei and its impact on astrophysics and cosmology T. Kajino , W. Aoki , A.B. Balantekin et al. , Current status of r-process nucleosynthesis . Prog. Part. Nucl. Phys. 107 , 109 - 166 ( 2019 ). doi: 10.1016/j.ppnp.2019.02.008 http://doi.org/10.1016/j.ppnp.2019.02.008 Current status of r-process nucleosynthesis 10.1007/s41365-023-01196-1 2023-03-04 2023-03-06 2023-03-06 2023-03-27 2023-04-20 © China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, ChineseNuclear Society and Springer Nature Singapore Pte Ltd. 2023 This is a post-peer-review, pre-copyedit version of an article published in Nuclear Science and Techniques. The final authenticated version is available online at: http://dx.doi.org/10.1007/s41365-023-01196-1 http://dx.doi.org/10.1007/s41365-023-01196-1 . 2023 Nuclear Science and Techniques 3 34