TheLa139(n,γ) cross section: Key for the onset of the

R. Terlizzi¹,

U. Abbondanno²,

G. Aerts³

et al.

Abstract

The nuclear resonance parameters and the capture cross section of the neutron magic isotope 139 La have been measured relative to 197 Au in the energy range of 0.6 eV to 9 keV at the neutron time-of-flight (n TOF) facility at CERN. We describe the experimental apparatus and the data analysis procedures, which concerned mainly the efficiency correction by means of the pulse height weighting function technique and the determination of different background components. We extracted the resonance parameters and the main nuclear quantities such as the resonance integral RI = 10.8 ± 1.0 b, the average γ widths for s and p waves γ l=0 = 50.7 ± 5.4 meV and γ l=1 = 33.6 ± 6.9 meV, the nuclear level densities D l=0 = 252 ± 22 eV and D l=1 < 250 eV, and the neutron strength functions S 0 = (0.82 ± 0.05) × 10 −4 and S 1 = (0.55 ± 0.04) × 10 −4 . These results represent a significant improvement over previous data. The deduced Maxwellian-averaged capture cross sections are important for the interpretation of the most recent spectroscopic observations in low-metallicity stars.

96Zr(n,γ) measurement at the n_TOF facility at CERN

“…Different background components were identified from capture of sample-scattered neutrons in the detectors or in surrounding materials, from capture events in the aluminum can of the Zr sample, from 055802-3 the ambient background in the experimental area, and mainly from in-beam γ rays produced in the spallation target. The evaluation of these backgrounds has been discussed in detail elsewhere [28].…”

The93Zr(n,γ) reaction up to 8 keV neutron energy

“…Other background components originate from capture of sample scattered neutrons in the detectors or in surrounding materials, from capture events in the aluminum and titanium cans of the sample, from in-beam γ rays produced by capture events in the water moderator around the spallation target, and from the ambient background in the experimental area. These backgrounds, which have been discussed in detail elsewhere [22], dominate the overall background for neutron energies above 1 keV. The present resonance analysis was restricted to the region below 8 keV not only for background reasons, but also because the resonances of Ti, one of the 93 Zr sample containers used for security prescriptions, overlap the Zr resonances, not allowing their resolution.…”

Present status and future programs of the n_TOF experiment

“…Cortés-Giraldo 13) , M. Diakaki 14) , I. Dillmann 15) , C. Domingo-Pardo 16) , I. Duran 17) , N. Dzysiuk 18) , C. Eleftheriadis 19) , M. Fernández-Ordóñez 7) , A. Ferrari 1) , K. Fraval 9) , S. Ganesan 20) , G. Giubrone 21) , M.B. Gómez-Hornillos 11) , I.F.…”

“…Gonçalves 12) , E. González-Romero 7) , F. Gramegna 18) , E. Griesmayer 2) , C. Guerrero 1) , F. Gunsing 9) , M. Heil 16) , D.G. Jenkins 22) , E. Jericha 2) , Y. Kadi 1) , F. Käppeler 23) , D. Karadimos 24) , M. Kokkoris 14) , M. Krtička 8) , J. Kroll 8) , C. Lederer 25) , H. Leeb 2) , L.S. Leong 4) , R. Losito 1) , M. Lozano 13) , A. Manousos 19) , J. Marganiec 3) , T. Martinez 7) , C. Massimi 26) , P.F.…”

“…Quesada 13) , T. Rauscher 29) , R. Reifarth 16) , A. Riego 11) , F. Roman 1,5) , C. Rubbia 1,30) , R. Sarmento 12) , G. Tagliente 6) , J.L. Tain 21) , D. Tarrìo 17) , L. Tassan-Got 4) , A. Tsinganis 1) , S. Valenta 8) , G. Vannini 26) , V. Variale 6) , P. Vaz 12) , A. Ventura 27) , M.J. Vermeulen 22) , R. Versaci 1) , R. Vlastou 14) , A. Wallner 25) , T. Ware 10) , T.J. The neutron time-of-flight facility n_TOF at CERN, Switzerland, operational since 2001, delivers neutrons using the Proton Synchrotron (PS) 20 GeV/c proton beam impinging on a lead spallation target.…”