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CERN-INTC-2014-047/INTC-P-415Tackling the s-process stellar neutron density via the 147Pm(n,g) reactionSpokespersons: C. Guerrero (U. Sevilla) and C. Domingo-Pardo (IFIC)Close Collaborators: U. Koester (ILL), D. Schumann (PSI) and S. Heinitz (PSI)47th Meeting of the INTC(25th June 2014)

Carlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)1Nucleosynthesis through the s-process2Nuclear reactions: energy generation nucleosynthesiscondensationejection, explosioninterstellargas & dust Mixing(abundance distribution)Chemical elements beyond Iron are synthesized via neutron capture reactions in stars:~ by the s-process (red giants)~ by the r-process (explosive)

Fusion reactionsNeutron capture reactionsCarlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)FeCoNiRbGaGeZnCuSeBrAsZrYSrKr(n,g)(b-)(b+)79Se, t1/2=65 ky80Br, t1/2=17 min, 92 % (b-), 8 % (b+)85Kr, t1/2=11 ys-onlyneutron numberproton number63Ni, t1/2=100 yNucleosynthesis through the s-processUnderstanding abundances around branching points:Half lifes(n,g) cross sectionsNeutron density and temperatureCarlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)Motivation: branching points (@nTOF)4

Lederer et al., PRL 110 (2013) 022501 Abbondanno et al., PRL 93 (2004) 161103Carlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)Branching point at A=147-1485Figure 1. The s-process flow in the mass region A=144-150. Branching points are indicated by dotted blue boxes, and the one of interest in this work (147Pm) is marked in red. The s-only isotopes 148Sm and 150Sm are indicated by double squares.En5keV8keV10keV15keV20keV25keV30keV40keV50keV60keV80keV100keV151Sm0.931.00.900.890.890.880.880.880.880.880.890.90147Pm1.01.01.01.01.00.990.980.960.950.930.900.88Stellar Enhancement Factors (SEF) according to Kadonis

*Studies at thermal ongoing @ILLCarlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)Previous measured and calculated values6

Only one measurement to date: Reifarth et al. [APJ 582 (2003) 12511262] at FZK in which they irradiated 28 ng of 147Pm with a MACS @ 25 keV.Measurement at ~25 keV, but the 95% of the neutron exposure in the main s-process occurs at much lower stellar temperatures, of about 90 MK (kT = 8 keV). Sizable extrapolations with HF needed.KadonisEAR-2 + sufficient material first ever ToF measurement in the En range of interestCarlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)Sample production in three stepsBranching points are radioactive!Production via (n,g) or (n, g)b- in the ILL research reactor Neutron flux: 1.5x1015 n/cm2/s (highest Fn,th worldwide)Irradiation time: 60 days (1.3 cycles) [March June 2012]

Step 1: Purchase of the stable isotopes and production of pellets @PSI [J. Neuhausen]Step 2: Irradiation at the ILL High Flux reactor [U. Koester]147Pm: 146Nd(n,g)147Nd (b-, 10d)147Pm (enrichment 0.35%) 0.29 mg of 147Pm (2.6 y) [1.2e18 atoms]Step 3: Chemical separation and target preparation @PSI [S. Heinitz and D. Schumann]

Carlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)Innovation and exploitation of C6D6 for (n,g)82003. IMPROVING THE HARDWARE: R. Plag et al. (The n_TOF Collaboration), An optimized C6D6 detector for studies of resonance-dominated (n,) cross-sections, Nucl. Instrum. Meth. A 496 (2003) 425-436

2004. IMPROVING THE SOFTWARE: U. Abbondanno et al. (The n_TOF Collaboration), New experimental validation of the pulse height weighting technique for capture cross-section measurements, Nucl. Instrum. Meth. A 521 (2004) 454467

2004-2012. EXPLOITING THE TECHNIQUE: U. Abbondanno et al. (The n_TOF Collaboration), Neutron capture cross section measurement of 151Sm at the CERN neutron Time of Flight facility, Phys. Rev. Lett. 93, 161103 (2004) and 24 PRC and PRL papers using C6D6 at n_TOF between 2004 and 2014

2013. ONE FINAL STEP HARDWARE-WISE: P. Mastinu et al. (The n_TOF Collaboration), New C6D6 detectors: reduced neutron sensitivity and improved safety, n TOF-PUB-2013-002 (2013)

State-of-the-art C6D6 + n_TOF-EAR2: (n,g) on sub-milligram radioactive samples!

C6D6@n_TOF-EAR1: 151Sm (206 mg) 63Ni (111 mg) 241Am (32 mg) 240Pu (3 mg)Carlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)Detectors and 147Pm sample @n_TOF-EAR29

neutrons147Pm sampleCarlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)

URR25 bins/decadeRRR1000 bins/decadeDstat=7%The measurement and beam time request- Beam line: n_TOF EAR-2 [x27 more flux than (n,g) in EAR1]- Detectors: 4xL6D6 and the PHWT- Normalization: Saturated Resonance Method with 197Au- Background: not available at this moment, to be seen during commissioning

Based on TENDL-2012

Effect of the (reduced) En resolution @EAR-2Carlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)Summary of beam requestSampleObjectiveProtons147PmCapture Cross section of 147Pm1x1018EmptyOverall beam-on background0.2x1018Dummy Sample backing related background0.6x1018197Au Normalization 0.2x1018147Pm (beam-off)Sample activity background-Total2x10182014: EAR2 (new) + enough material from ILL (new/unique) now its possible!Appropriate sample mass: if more EAR-1 or elsewhereif less too demanding to be proposed without very well characterized EAR-2

Following the EAR-2 commissioning, best candidate for a measurement

(challenging, radioactive, sub-milligram (0.3 mg), never measured, inter-laboratory (ILL, PSI, CERN) collaboration)Carlos GUERRERO et al., Tackling the s-process stellar neutron density via the 147Pm(n,g) reaction47th CERN INTC Meeting (June 25th 2014)