22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Federico Ferraro Università degli Studi di Genova, INFN – Sezione di Genova VIII International Nuclear Physics in Astrophysics Conference, 22 June 2017 – Catania, Italy
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Nuclear astrophysics in a nutshell CONDENSATION INTERSTELLAR STAR GAS EJECTION MIXING NUCLEAR REACTIONS Isotopic Energy production abundances Nucleosynthesis September 10, 2019 TAUP 2019 2 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies The Gamow peak Consider a radiative capture reaction x + A B + The reaction rate is given by ∞ 𝑠 = N x N A 𝜚 𝑤 𝜏 𝑤 𝑤 d𝑤 0 The cross section in the Gamow peak is small! direct measurements on surface are often hampered by cosmic ray induced background The Gamow peak defines possible solutions: extrapolation, indirect and the relevant energy range underground measurements for such reactions to occur September 10, 2019 TAUP 2019 3 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Something unexpected may exist at low energies! It is possible to factorize the cross section 𝜏 𝐹 = 1 𝐹 𝑓 −2𝜌𝜃 𝑻 𝑭 and extrapolate the astrophysical factor S(E) down to astrophysical energies … September 10, 2019 TAUP 2019 4 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Something unexpected may exist at low energies! It is possible to factorize the cross section 𝜏 𝐹 = 1 𝐹 𝑓 −2𝜌𝜃 𝑻 𝑭 and extrapolate the astrophysical factor S(E) down to astrophysical energies … But… September 10, 2019 TAUP 2019 5 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Something unexpected may exist at low energies! It is possible to factorize the cross section 𝜏 𝐹 = 1 𝐹 𝑓 −2𝜌𝜃 𝑻 𝑭 and extrapolate the astrophysical factor S(E) down to astrophysical energies … But… unexpected resonances may be present in the extrapolation region! September 10, 2019 TAUP 2019 6 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Direct measurements at low energy are required Low cross section means low counting rate Background reduction is fundamental Underground measurements Material selection and cleaning An example: 22 Ne(p, ) 23 Na cross section measurement at astrophysical energies September 10, 2019 TAUP 2019 7 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies The neon-sodium (NeNa) cycle 23 Na 22 Ne 22 Ne(p, ) 23 Na and 23 Na(p, ) 24 Mg recently investigated at LUNA Advanced H-burning cycle (higher temperature w.r.t. pp chain and CNO cycle) Mainly active in TP-AGB stars (Hot Bottom Burning process) Not important for energy production Important for nucleosynthesis ( Na/O anticorrelation in GCs ) September 10, 2019 TAUP 2019 8 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies 22 Ne(p, ) 23 Na HZDR 23 Na 22 Ne LUNA It was the most uncertain reaction in the NeNa cycle Several low-energy resonances Tentative resonances at very low energy New measurements performed at HZDR , LUNA and TUNL September 10, 2019 TAUP 2019 9 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies The Gran Sasso National Laboratory (LNGS) Reduction of cosmic-ray-induced background muons: 10 6 neutrons: 10 3 Grey: surface Black: LUNA Image credit: Nature Rock overburden > 1400 m (>3000 m.w.e.) September 10, 2019 TAUP 2019 10 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies The Laboratory for Underground Nuclear Astrophysics Electrostatic accelerator 2 beamlines: gas/solid targets Beam energy: 50-400 keV Beam current: up to 1 mA Energy spread: 0.1 keV Stability: 5 eV/h September 10, 2019 TAUP 2019 11 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Gas target ~ 1 mbar ~ 10 −7 mbar • Extended gas target • 3 differential pumping stages (no entrance window) • Gas recycling and purification • Need to measure temperature and pressure profiles -> density profile September 10, 2019 TAUP 2019 12 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies 22 Ne gas target (99.9% enriched) temperature pressure Determines: • number of density target nuclei (1.3% uncertainty) • energy loss • beam current September 10, 2019 TAUP 2019 13 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Beam calorimeter 𝑋 𝑑𝑏𝑚 = 𝑋 0 − 𝑋 𝑠𝑣𝑜 beam 𝐽 𝑐𝑓𝑏𝑛 = 𝑞 0 + 𝑞 1 𝑋 𝑑𝑏𝑚 𝑓 𝐹 𝑞 − Δ𝐹 𝑢𝑏𝑠𝑓𝑢 𝑈 ℎ𝑝𝑢 𝑈 𝑑𝑝𝑚𝑒 Power compensation calorimeter Copper cylinder. Hot side, cold side, constant ∆𝑈 2 heat sources: beam and resistors beam OFF – beam ON measurements to calculate the beam power 𝑋 𝑑𝑏𝑚 Systematic uncertainty: 0.5 W 𝑋 𝑑𝑏𝑚 < 30 W 1.5% 𝑋 𝑑𝑏𝑚 ≥ 30 W September 10, 2019 TAUP 2019 14 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies HPGe setup (high resolution, low efficiency) • Collimated HPGe detectors • 137% detector @ 55° • 90% detector @ 90° • Lead shielding • Copper liners • Radon box (N 2 flushing) September 10, 2019 TAUP 2019 15 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies HPGe setup - results e.g. 189.5 keV resonance Black : on-resonance Turquoise : off-resonance Discovery of 3 new low-energy resonances Upper limits on 2 tentative resonances New evaluation of TNRR Better description of Na/O anti-correlation in GS New high-efficiency Tentative resonances not completely excluded setup is required for Direct capture and broad resonances not addressed further infestigation September 10, 2019 TAUP 2019 16 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies In the meantime … TUNL (North Carolina) confirmed the existence of two out of three new resonances observed at LUNA They found slightly larger strengths , probably because of: • weak branches • angular distribution effects not detected at LUNA using HPGe detectors September 10, 2019 TAUP 2019 17 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies BGO setup (low resolution, high efficiency) BGO detector 4 solid angle coverage 6 segments Low resolution ( 𝐺𝑋𝐼𝑁 ≅ 500 keV @ 𝐹 𝛿 = 9 MeV) High efficiency (65% @ 𝐹 𝛿 = 662 keV) Sensitivity to weak decay branches Target chamber 420 mm long connecting tube 40 mm long collimator 108 mm long interaction region Beam calorimeter Calorimeter body Chiller Power supply Acquisition & control system September 10, 2019 TAUP 2019 18 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies DAQ 14 N(p, ) 15 O Addback 6 segments spectrum Independent DAQ List mode acquisition Independent calibration Offline coincidence analysis Gated spectrum Single spectra September 10, 2019 TAUP 2019 19 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Background Black: laboratory background Red: BIB (E p =156 keV, Ar target) 40 K 11 B(p, ) 12 C 214 Bi 18 O(p, ) 19 F 208 Tl (n, ) events from Present in every ( ,n) reactions spectrum, used for energy calibration 22 Ne(p, ) 23 Na ROI Background laboratory (depends on acquisition time only) scaled and subtracted • beam-induced (depends on E , I , contaminants,…) inert target, scaling to ROI monitor • September 10, 2019 TAUP 2019 20 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Results New resonances at 156.2, 189.5 and 259.7 keV Because of the detector geometry, BGO results are nearly unaffected by • target thickness/resonance width (max. effect of 1-2%) • angular distribution (max effect of 4%) New measurements of resonance strengths and branching ratios have been obtained for the resonances at 156.2, 189.5 and 259.7 keV September 10, 2019 TAUP 2019 21 Federico Ferraro | federico.ferraro@ge.infn.it
22 Ne(p, ) 23 Na cross section measurement at astrophysical energies Branching ratios (e.g.: 189.5 keV resonance) September 10, 2019 TAUP 2019 22 Federico Ferraro | federico.ferraro@ge.infn.it
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