DESIR high resolution separator at GANIL, France

A high-resolution separator for the SPIRAL2/DESIR project at GANIL has been designed. The extracted isotopes from SPIRAL2 will be transported to and cooled in a RFQ cooler yielding beams with very low transverse emittance and energy spread. These beams will then be accelerated to 60 keV and sent to a high-resolution mass separator where a specific isotope will be selected. The good beam properties extracted from the RFQ cooler will allow one to obtain a mass resolution of č26000 with the high-resolution mass separator

First approach to half-life measurements around N=126

The present piece of work reviews recent progress on β-decay half-life measurements around the neutron shell N=126. The production of heavy neutron-rich nuclei is discussed, including the present status of the experimental data available for this region of the chart of nuclides. The impact of the theoretical calculations used to model the properties of nuclei involved in the r-process nucleosynthesis is discussed

The Regulated NiCu Cycles with the new 57^{57}Cu(p,γ\gamma)58^{58}Zn reaction rate and the Influence on Type-I X-Ray Bursts: GS 1826−-24 Clocked Burster

During the X-ray bursts of GS 1826$-$24, "clocked burster", the nuclear reaction flow that surges through the rapid-proton capture process path has to pass through the NiCu cycles before reaching the ZnGa cycles that moderate the further extent of hydrogen burning in the region above germanium and selenium isotopes. The $^{57}$Cu(p,$\gamma$)$^{58}$Zn reaction located in the NiCu cycles plays an important role in influencing the burst light curves as found by Cyburt et al. (2016). We deduce the $^{57}$Cu(p,$\gamma$)$^{58}$Zn reaction rate based on the experimentally determined important nuclear structure information, isobaric-multiplet-mass equation, and large-scale shell model calculations. Based on the isobaric-multiplet-mass equation, we propose a possible order of $1^+_1$ and $2^+_3$ dominant resonance states and constrain the resonance energy of the $1^+_2$ state. The latter reduces the contribution of the $1^+_2$ dominant resonance state. The new reaction rate is up to a factor of four lower than the Forstner et al. (2001) rate recommended by JINA REACLIB v2.2 at the temperature regime sensitive to clocked bursts of GS 1826$-$24. Using the simulation from the one-dimensional implicit hydrodynamic code, KEPLER, to model the thermonuclear X-ray bursts of GS 1826$-$24 clocked burster, we find that the new $^{57}$Cu(p,$\gamma$)$^{58}$Zn coupled with the latest $^{56}$Ni(p,$\gamma$)$^{57}$Cu and $^{55}$Ni(p,$\gamma$)$^{56}$Cu reaction rates redistributes the reaction flow in the NiCu cycles and strongly influences the burst ash composition, whereas the $^{59}$Cu(p,$\alpha$)$^{56}$Ni and $^{59}$Cu(p,$\gamma$)$^{60}$Zn reactions suppress the influence of the $^{57}$Cu(p,$\gamma$)$^{58}$Zn reaction and diminish the impact of nuclear reaction flow that by-passes the important $^{56}$Ni waiting point induced by the $^{55}$Ni(p,$\gamma$)$^{56}$Cu reaction on burst light curve

Regulated NiCu Cycles with the New

In Type-I X-ray bursts (XRBs), the rapid-proton capture (rp-) process passes through the NiCu and ZnGa cycles before reaching the region above Ge and Se isotopes that hydrogen burning actively powers the XRBs. The sensitivity study performed by Cyburt et al. [1] shows that the 57Cu(p,γ)58Zn reaction in the NiCu cycles is the fifth most important rp-reaction influencing the burst light curves. Langer et al. [2] precisely measured some low-lying energy levels of 58Zn to deduce the 57Cu(p,γ)58Zn reaction rate. Nevertheless, the order of the $1_1^ +$ and $2_3^ +$ resonance states that dominate at 0:2 ≲ T(GK) ≲ 0:8 is not confirmed. The $1_2^ +$ resonance state, which dominates at the XRB sensitive temperature regime 0:8 ≲ T(GK) ≲ 2 was not detected. Using isobaric-multipletmass equation (IMME), we estimate the order of the $1_1^ +$ and $2_3^ +$ resonance states and estimate the lower limit of the $1_2^ +$ resonance energy. We then determine the 57Cu(p,γ)58Zn reaction rate using the full pf -model space shell model calculations. The new rate is up to a factor of four lower than the Forstner et al. [3] rate recommended by JINA REACLIBv2.2. Using the present 57Cu(p,γ)58Zn, the latest 56Ni(p,γ)57Cu and 55Ni(p,γ)56Cu reaction rates, and 1D implicit hydrodynamic Keple

Commissioning of the DESIR High-Resolution Separator at CENBG

International audienceDESIR is the low-energy part of the SPIRAL2 ISOL facility under construction at GANIL. The high-resolution mass separator (HRS) included in DESIR is a 180 degree symmetric online separator with two 90 degree magnetic dipole sections arranged with electrostatic quadrupoles, sextupoles and a multipole on the mid plane. The HRS is now completely mounted at CENBG and under commissioning for the next 2 to 3 years before its transfer at the entrance of the DESIR facility. The objective is to test, characterise and correct all HRS elements contributing to the higher order aberration by performing experimental measurements and comparing them with the results from different simulation tools. The recently mounted pepperpot-type emittance-meter will allow us to observe the emittance figures and dynamically tune the multipole to improve the optical parameters of the HRS. We will present the first results concerning the hexapolar correction with the multipole, the associated emittance measurements and the resolution currently achieved

Measurement of 242^{242}Pu(n,f) in the [1;2MeV] energy range

International audienceThe design of new generation fast nuclear reactors requires highly accurate cross-section measurements in the MeV energy region. The 242 Pu fission cross section is of particular interest for Pu incineration and nuclear waste production. There are discrepancies around 1 MeV incident neutron energy between libraries and among experimental data. Some data suggest the presence of a strong structure between 1 and 1.2 MeV whereas it is barely visible on some other data and its shape is very different among evaluations. The large majority of the 242 Pu(n,f) measurements have been carried out with respect to the 235 U(n,f) secondary-standard cross section. This introduces a strong correlation between independent measurements and this cross section exhibits structures, in particular a steep increase of +10% at 1 MeV. Therefore, we aim to re-measure the 242 Pu(n,f) cross section relative to the primary-standard 1 H(n,n)p cross section, by using a proton recoil detector. This standard has a very high accuracy (0.4%), is not used for of other 242 Pu measurements, and is structureless. An experiment has been carried out in October 2022 at the MONNET facility in JRC Geel, with incident neutron energies from 0.9 MeV to 2.0 MeV. The experimental setup will be presented, and the analysis procedure will be detailed

Measurement of 242^{242}Pu(n,f) in the [1;2MeV] energy range

International audienceThe design of new generation fast nuclear reactors requires highly accurate cross-section measurements in the MeV energy region. The 242 Pu fission cross section is of particular interest for Pu incineration and nuclear waste production. There are discrepancies around 1 MeV incident neutron energy between libraries and among experimental data. Some data suggest the presence of a strong structure between 1 and 1.2 MeV whereas it is barely visible on some other data and its shape is very different among evaluations. The large majority of the 242 Pu(n,f) measurements have been carried out with respect to the 235 U(n,f) secondary-standard cross section. This introduces a strong correlation between independent measurements and this cross section exhibits structures, in particular a steep increase of +10% at 1 MeV. Therefore, we aim to re-measure the 242 Pu(n,f) cross section relative to the primary-standard 1 H(n,n)p cross section, by using a proton recoil detector. This standard has a very high accuracy (0.4%), is not used for of other 242 Pu measurements, and is structureless. An experiment has been carried out in October 2022 at the MONNET facility in JRC Geel, with incident neutron energies from 0.9 MeV to 2.0 MeV. The experimental setup will be presented, and the analysis procedure will be detailed

New nuclear structure data after fission: The g.s. of 136^{136}Sb

Nuclei in the neutron-rich region beyond 132Sn have been produced recently by various experiments using fission. Using isomer and β-decay studies nuclear structure data has been collected on the orbital evolution and collectivity in the region with both the increase of proton and neutron numbers. Examples on particular questions related to the g.s. of the A=136 odd-odd 136Sb nucleus and its heavier neighbours are given in the scope of expectations by shell-model theory