Isotope production in proton-, deuteron-, and carbon-induced reactions on Nb 93 at 113 MeV/nucleon

Isotope-production cross sections for p-, d-, and C-induced spallation reactions on Nb93 at 113 MeV/nucleon were measured using the inverse-kinematics method employing secondary targets of CH2, CD2, and C. The measured cross sections for Mo90, Nb90, Y86,88 produced by p-induced reactions were found to be consistent with those measured by the conventional activation method. We performed benchmark tests of the reaction models INCL-4.6, JQMD, and JQMD-2.0 implemented in the Particle and Heavy Ion Transport code System (PHITS) and of the nuclear data libraries JENDL-4.0/HE, TENDL-2017, and ENDF/B-VIII.0. The model calculations also showed generally good agreement with the measured isotope-production cross sections for p-, d-, and C-induced reactions. It also turns out that, among the three nuclear data libraries, JENDL-4.0/HE provides the best agreement with the measured data for the p-induced reactions. We compared the present Nb93 data with the Zr93 data, that were measured previously by the same inverse kinematics method (Kawase et al., Prog. Theor. Exp. Phys. 2017, 093D03 (2017)2050-391110.1093/ptep/ptx110), with particular attention to the effect of neutron-shell closure on isotope production in p- and d-induced spallation reactions. The isotopic distributions of the measured production cross sections in the Zr93 data showed noticeable jumps at neutron number N=50 in the isotopic chains of ΔZ=0 and -1, whereas no such jump appeared in isotopic chain of ΔZ=0 in the Nb93 data. From INCL-4.6 + GEM calculations, we found that the jump formed in the evaporation process is smeared out by the intranuclear cascade component in Nb91 produced by the Nb93(p,p2n) and (d,d2n) reactions on Nb93. Moreover, for Nb93, the distribution of the element-production cross sections as a function of the change in proton number ΔZ is shifted to smaller ΔZ than for Zr93, because the excited Nb prefragments generated by the cascade process are more likely to emit protons than the excited Zr prefragments, due to the smaller proton-separation energies of the Nb isotopes

Coulomb breakup reactions of 93,94 Zr in inverse kinematics

Coulomb breakup reactions of 93,94 Zr have been studied in inverse kinematics at incident beam energies of about 200 MeV/nucleon in order to evaluate neutron capture reaction methods. The 93 Zr(n,γ) 94 Zr reaction is particularly important as a candidate nuclear transmutation reaction for the long-lived fission product 93 Zr in nuclear power plants. One- and two-neutron removal cross sections on Pb and C targets were measured to deduce the inclusive Coulomb breakup cross sections, 375 ± 29 (stat.) ± 30 (syst.) and 403 ± 26 (stat.) ± 31 (syst.) mb for 93 Zr and 94 Zr, respectively. The results are compared with estimates using the standard Lorentzian model and microscopic calculations. The results reveal a possible contribution of the pygmy dipole resonance or giant quadrupole resonance in the Coulomb breakup reactions of 94 Zr

Spallation reaction study for fission products in nuclear waste: Cross section measurements for 137

Spallation reactions for the long-lived fission products 137Cs, 90Sr and 107Pd have been studied for the purpose of nuclear waste transmutation. The cross sections on the proton- and deuteron-induced spallation were obtained in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory. Both the target and energy dependences of cross sections have been investigated systematically. and the cross-section differences between the proton and deuteron are found to be larger for lighter fragments. The experimental data are compared with the SPACS semi-empirical parameterization and the PHITS calculations including both the intra-nuclear cascade and evaporation processes

Geochemical Determination of the pp-Neutrino Flux with 205Tl-LOREX: A Progress Report

Intensive research from the 1970's to 1990's towards geochemical detection of solar neutrinos using 205 Tl, 98 Mo and 81 Br has left 205 Tl the only viable candidate. LOREX (LORandite EXperiment ) is based on determining the solar (pp) neutrino flux for the period of 4.3 Ma from the reaction 205 Tl+v e → 205 Pb+e - , the lowest threshold (52 keV) for neutrino capture. The ratio of 205 Pb/ 205 Tl in lorandite (TlAsS 2 ) depends also on contributions from fast muon cosmic radiation. The latter is a function of paleo - depth, including the eroded layer over 4.3 Ma, determined using cosmogenic nuclides ( 26 Al, 36 Cl, 3 He and 21 Ne) in the ore body Crven Dol (Tl - As - Sb - S) in Allchar (Macedonia). The results give a l ower limit of paleo - depth of 490mwe and an upper limit of 2300mwe. From this the ratios 205 Pb ve / 205 Pb tot are estimated as 2:8 and 6:4, respectively. Identification of the 205 Pb nuclei in the lead sample extracted from the lorandite mineral requires 10 - 10 to 10 - 11 overall detection sensitivity for 205 Pb/Pb and comparable suppression of the 205 Tl isobar. This is proposed by full stripping of 205 Pb at high energy (345MeV/u) at the RIKEN - RIBF ion - beam facility. 205 Tl isobar separation is already largely achiev ed by chemical Pb - Tl separation by the overall sample preparation. Samples with a higher concentration ( 205 Tl/natPb=1%) are necessary for a guide - beam and initial accelerator tuning. A sample with a considerably lower level of about 10 - 8 is needed for cont rol of the beam analysis system with 205 Tl ions, in the presence ultimately of a lighter guide beam, to limit the in - beam production of 205 Pb by the (p,n) reaction on 205 Tl in the energy - loss and ion - stripping steps in the accelerator and the subsequent Bi gRIPS/Mass - Ring experimental apparatus. The relative cross sections between full stripping of 205 Pb and (p,n) on 205 Tl is estimated as 10 5 . Test experiments to verify the various aspects of the proposed approach at the RIBF are under preparation

Geochemical Determination of the Solar pp-Neutrino Flux with LOREX: A Progress Report

LOREX (LORandite EXperiment) is a geochemical experiment addressing the solar (pp) neutrino flux for the period of 4.3 Ma from the reaction 205Tl + ve → 205Pb + e- with an unprecedentedly low threshold (52 keV) for solar pp-neutrino capture. A decisive step for this purpose is getting the precise, background-corrected ratio of 205Pb/205Tl in lorandite (TlAsS2). This report presents the status of major challenges being addressed, in particular the determination of the paleo-depth of lorandite, including the eroded layer over 4.3 Ma, as well as the choice of appropriate techniques for extraction, separation and quantitative determination of the ultra-low 205Pb concentration in the extracted lorandite samples