Grand Accelerateur National d'Ions Lourds Research Articles

THE EXOGAM2 CALIBRATION USING THE NEWLY DEVELOPED NUMEXO2 DIGITAL ELECTRONIC

In this study, the calibration process of the EXOGAM2 conventional gamma detector system with the newly developed digital electronic device, namely NUMEXO2, will be presented. This experimental study was performed at the GANIL (Grand Accélérateur National d'Ions Lourds) nuclear research center in France. The energy calibration of the EXOGAM2 detector system with the newly developed NUMEXO2 digital electronic device was conducted using both low and high gamma energy levels of a 152Eu radioactive source. This calibration was carried out for two EXOGAM2 detectors, and the energy resolution of each crystal in the EXOGAM2 system was determined. 
 The energy resolution of each crystal was found to be reasonable energy resolution values of the EXOGAM2 detectors. Therefore, the use of the digital electronic device NUMEXO2 did not affect the energy resolution of the detectors, but it did enable us to acquire data at a high counting rate.

Sub-millisecond atom-to-ion transformation in the TULIP ISOL system

TULIP (Target Ion Source for Short-Lived Isotope Production) is an original Isotope Separator On Line project dedicated to the production of short-lived neutron-deficient ions. It was tested for the first time in March 2022 at GANIL (Grand Accélérateur National d’Ions Lourds )/ SPIRAL1 (Système de Production d’Ions Radioactifs Accélérés en Ligne, phase 1) with the production of Rb isotopes using a primary beam of 22Ne at an energy of 4.5 MeV/A. 76Rb and 78Rb isotope rates of ∼4 ×103 and ∼6 × 104 pps were measured for a primary beam intensity of 6 × 1012 pps and may be improved by a factor between 5 and 10.A remarkably short atom-to-ion transformation (AIT) time close to 200 μs was achieved. This result demonstrates how beneficial the design of the TULIP target ion source system is in terms of response time and allows us to confidently look forward to 74Rb+ production, which is one of the goals of the TULIP project.The results obtained on Rb production suggest testing the principle for the production of more sticky elements. Ions from metallic isotopes around 100Sn will be the next objective.

Mirror symmetry at mass A = 54: E4 effective charges near doubly magic 56Ni

Proton-emission branches of the 10+ isomer in the Tz=−1 nucleus 54Ni have been imaged with the active target and time projection chamber (ACTAR TPC) in an experiment conducted at the Grand Accélérateur National d'Ions Lourds (GANIL). The completed decay scheme allows derivation of the reduced transition strengths, B(E2;10+→8+) and B(E4;10+→6+), for the two competing γ-ray transitions. By means of a comparison with their well-known ‘mirror transitions’ in Tz=+154Fe, and aided by a variety of shell-model calculations in the fp model space, effective charges for E4 transitions near N=Z56Ni can be deduced: επ≈1.40 and εν≈0.30. Mirror-energy differences are explored with various shell-model interactions and isospin-symmetry breaking terms.

Evidence for enhanced neutron-proton correlations from the level structure of the N=Z+1 nucleus Tc444387

The low-lying excited states in the neutron-deficient N=Z+1 nucleus Tc444387 have been studied via the fusion-evaporation reaction Fe54(Ar36, 2n1p)Tc87 at the Grand Accélérateur National d'Ions Lourds (GANIL), France. The AGATA spectrometer was used in conjunction with the auxiliary NEDA, Neutron Wall, and DIAMANT detector arrays to measure coincident prompt γ rays, neutrons, and charged particles emitted in the reaction. A level scheme of Tc87 from the (9/2g.s.+) state to the (33/21+) state was established based on six mutually coincident γ-ray transitions. The constructed level structure exhibits a rotational behavior with a sharp backbending at ℏω≈0.50 MeV. A decrease in alignment frequency and increase in alignment sharpness in the odd-mass isotonic chains around N=44 is proposed as an effect of the enhanced isoscalar neutron-proton interactions in odd-mass nuclei when approaching the N=Z line.Received 16 April 2021Revised 5 July 2021Accepted 9 August 2021DOI:https://doi.org/10.1103/PhysRevC.104.L021302Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasEnergy levels & level densitiesNuclear structure & decaysNuclear Physics

Processing of 72-K water-rich ices by keV and MeV oxygen ions: implications for the Saturnian moon Enceladus

ABSTRACT The processing of H2O:CO2:CH4 (10:1:1) and H2O:CO2:CH4:NH3 (10:1:1:1) ices at 72 K by oxygen ions was studied in an attempt to simulate the physicochemical effects induced by energetic ions on the surface of Enceladus (or similar cold surfaces in the outer Solar System). The experiments were carried out at the Grand Accélérateur National d’Ions Lourds (GANIL) in Caen/France. The samples were irradiated with 15.7-MeV O5+ at the IRRadiation SUD (IRRSUD) beamline and with 108-keV O6+ at the Accélérateurs pour les Recherches avec les Ions de Basses Energies (ARIBE) beamline. The frozen samples were monitored by Fourier Transform Infrared Spectroscopy (FTIR) spectroscopy (4000–650 cm−1, 2.5–15.4 μm, at 1 cm−1 resolution). The identified molecular species formed during irradiation were CO, OCN−, CH3OH, HCN, CN−, H2CO3, HNCO, HCO and CO3. The effective formation cross-sections for the synthesis of new species and the effective molecular destruction cross-sections of the parent species in the experiments with MeV ions were found to be of the order of 10−14–10−13 cm2. For the keV ion experiments, these values were of the order of 10−16–10−15 cm2. The fluence at which the sample reaches chemical equilibrium and the molecular abundances in this region (equilibrium branching ratios) were estimated. These experiments suggest that the chemical inventory on the surface of Enceladus can be influenced by the incidence of charged particles on to the moon’s surface.

Isospin Properties of Nuclear Pair Correlations from the Level Structure of the Self-Conjugate Nucleus Ru88

The low-lying energy spectrum of the extremely neutron-deficient self-conjugate (N=Z) nuclide _{44}^{88}Ru_{44} has been measured using the combination of the Advanced Gamma Tracking Array (AGATA) spectrometer, the NEDA and Neutron Wall neutron detector arrays, and the DIAMANT charged particle detector array. Excited states in ^{88}Ru were populated via the ^{54}Fe(^{36}Ar,2nγ)^{88}Ru^{*} fusion-evaporation reaction at the Grand Accélérateur National d'Ions Lourds (GANIL) accelerator complex. The observed γ-ray cascade is assigned to ^{88}Ru using clean prompt γ-γ-2-neutron coincidences in anticoincidence with the detection of charged particles, confirming and extending the previously assigned sequence of low-lying excited states. It is consistent with a moderately deformed rotating system exhibiting a band crossing at a rotational frequency that is significantly higher than standard theoretical predictions with isovector pairing, as well as observations in neighboring N>Z nuclides. The direct observation of such a "delayed" rotational alignment in a deformed N=Z nucleus is in agreement with theoretical predictions related to the presence of strong isoscalar neutron-proton pair correlations.

Approach to a self-calibrating experimental [formula omitted]-ray tracking algorithm

A first approach to a novel, self-calibrating γ-ray tracking algorithm based on experimental data and non-Gaussian behavior of geometrical scattering angles for the Advanced GAmma Tracking Array (AGATA) is presented. A brief performance test using a 137Cs source run measured with AGATA at the Grand Accélérateur National d’Ions Lourds (GANIL), France is performed. The achievable tracking performance of the novel method is compared to the Orsay Forward Tracking algorithm.

Infrared complex refractive index of N-containing astrophysical ices free of water processed by cosmic-ray simulated in laboratory.

Several nitrogen-containing molecules have been unambiguously identified in the Solar System and in the Interstellar Medium. It is believed that such a rich inventory of species is a result of the energetic processing of astrophysical ices during the interaction with ionizing radiation. An intrinsic parameter of matter, the complex refractive index, stores all the "chemical memory" triggered by energetic processing, and therefore might be used to probe ice observations in the infrared. In this study, four N-containing ices have been condensed in an ultra-high vacuum chamber and processed by heavy ions (O and Ni) with energies between 0.2 and 15.7 MeV at the Grand Accélérateur National d'Ions Lourds (GANIL), in Caen, France. All chemical changes were monitored in situ by Infrared Absorption Spectroscopy. The complex refractive index was calculated directly from the absorbance spectrum, by using the Lambert-Beer and Kramers-Kroning relations, and the values are available in an online database: https://www1.univap.br/gaa/nkabs-database/data.htm. As a result, other than the database, it was observed that non-polar ices are more destroyed by sputtering than polar ones. Such destruction and chemical evolution lead to variation in the IR albedo of samples addressed in this paper.

High efficiency ISOL system to produce neutron deficient short-lived alkali RIBs on GANIL/SPIRAL 1 facility

The SPIRAL1 (Système de Production d’Ions Radioactifs Accélérés en Ligne) facility at GANIL (Grand Accélérateur National d’Ions Lourds) is developing new techniques to access nuclei in the neutron-deficient isotope region far from the stability-valley, with Z ranging from 30 to 60. The availability of different primary beams, ranging from carbon to uranium with energies up to 95 MeV/A, gives an opportunity to produce a large variety of radioactive ion beams. The production of neutron-deficient short-lived alkalis by fusion-evaporation reactions is the focus of this work. A simple and compact target ion source system (TISS) is designed to produce isotopes of 74Rb (τ1/2 = 64.8 ms) and 114Cs (τ1/2 = 570 ms). The efficiencies of the different processes involved in the production are evaluated. Radioactive recoils are produced through the interaction of heavy-ion beams, respectively 20Ne beam and 58Ni beam at an intensity of 1013 and 1012 pps, with a thin 58Ni target. High atom-to-ion transformation (ATI) efficiency should be obtained above 70% and 90% for 74Rb and 114Cs nuclei respectively. The expected intensities of the RIBs are estimated to be around 104 pps at the exit of the TISS.

Preliminary results of lifetime measurements in neutron-rich 53Ti

To study the nuclear structure of neutron-rich titanium isotopes, a lifetime measurement was performed at the Grand Accélérateur National d'Ions Lourds (GANIL) facility in Caen, France. The nucleiwere produced in a multinucleon-transfer reaction by using a 6.76 MeV/u 238U beam. The Advanced Gamma Tracking Array (AGATA) was employed for the γ-ray detection and target-like recoils were identified event-by-event by the large-acceptance variable mode spectrometer (VAMOS++). Preliminary level lifetimes of the (5/2−) to 13/2− states of the yrast band in the neutron-rich nucleus 53Ti were measured for the first time employing the recoil distance Doppler-shift (RDDS) method and the compact plunger for deep inelastic reactions. The differential decay curve method (DDCM) was used to obtain the lifetimes from the RDDS data.

M1 and E2 transition rates from core-excited states in semi-magic 94Ru

Lifetimes of high-spin states have been measured in the semi-magic $(N=50)$ nucleus 94Ru. Excited states in 94Ru were populated in the 58Ni(40Ca, 4p)94Ru* fusion-evaporation reaction at the Grand Accelerateur National d’Ions Lourds (GANIL) accelerator complex. DSAM lifetime analysis was performed on the Doppler broadened line shapes in energy spectra obtained from $\gamma$ -rays emitted while the residual nuclei were slowing down in a thick 6mg/cm^2 metallic 58Ni target. In total eight excited-state lifetimes in the angular momentum range $I = (13-20)\hbar$ have been measured, five of which were determined for the first time. The corresponding B(M1) and B(E2) reduced transition strengths are discussed within the framework of large-scale shell model calculations to study the contribution of different particle-hole configurations, in particular for analyzing contributions from core-excited configurations.

Double differential neutron spectra generated by the interaction of a 12 MeV/nucleon [formula omitted]S beam on a thick [formula omitted]Cu target

Double differential neutron spectra (energy, angle) originating from a thick natCu target bombarded by a 12 MeV/nucleon 36S16+ beam were measured by the activation method and the Time-of-flight technique at the Grand Accélérateur National d’Ions Lourds (GANIL). A neutron spectrum unfolding algorithm combining the SAND-II iterative method and Monte-Carlo techniques was developed for the analysis of the activation results that cover a wide range of neutron energies. It was implemented into a graphical user interface program, called GanUnfold. The experimental neutron spectra are compared to Monte-Carlo simulations performed using the PHITS and FLUKA codes.

Characterization and performances of DOSION, a dosimetry equipment dedicated to radiobiology experiments taking place at GANIL

Currently, radiobiology experiments using heavy ions at GANIL (Grand Accélérateur National d′Ions Lourds) are conducted under the supervision of the CIMAP (Center for research on Ions, MAterials and Photonics). In this context, a new beam monitoring equipment named DOSION has been developed. It allows to perform measurements of accurate fluence and dose maps in near real time for each biological sample irradiated. In this paper, we present the detection system, its design, performances, calibration protocol and measurements performed during radiobiology experiments. This setup is currently available for any radiobiology experiments if one wishes to correlate one's own sample analysis to state-of-the-art dosimetric references.

Evolution of nuclear shapes in odd-mass yttrium and niobium isotopes from lifetime measurements following fission reactions

Lifetimes of excited states in Y99,Y101,Nb101,Nb103, and Nb105 were measured in an experiment using the recoil distance Doppler shift method at GANIL (Grand Accélérateur National d'Ions Lourds). The neutron-rich nuclei were produced in fission reactions between a U238 beam and a Be9 target. Prompt γ rays were measured with the EXOGAM array and correlated with fission fragments that were identified in mass and atomic number with the VAMOS++ spectrometer. The measured lifetimes, together with branching ratios, provide B(M1) and B(E2) values for the strongly coupled rotational bands built on the [422]5/2+ ground state in the Y and Nb nuclei with neutron number N≥60. The comparison of the experimental results with triaxial particle-rotor calculations provides information about the evolution of the nuclear shape in this mass region.9 MoreReceived 19 November 2016DOI:https://doi.org/10.1103/PhysRevC.95.034302©2017 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCollective levelsCollective modelsElectromagnetic transitionsLifetimes & widthsNuclear structure & decaysProperties90 ≤ A ≤ 149TechniquesRadiation detectorsSpectrometers & spectroscopic techniquesNuclear Physics

Measurement of lifetimes in Fe62,64,Co61,63 , and Mn59

Lifetimes of the 41+ states in 62,64Fe and the 11/21− states in 61,63Co and 59Mn were measured at the Grand Accelerateur National d'Ions Lourds (GANIL) facility by using the Advanced Gamma Tracking Array (AGATA) and the large-acceptance variable mode spectrometer (VAMOS++). The states were populated through multinucleon transfer reactions with a U238 beam impinging on a Ni64 target, and lifetimes in the picosecond range were measured by using the recoil distance Doppler shift method. The data show an increase of collectivity in the iron isotopes approaching N=40. The reduction of the subshell gap between the ν2p1/2 and ν1g9/2 orbitals leads to an increased population of the quasi-SU(3) pair (ν1g9/2,ν2d5/2), which causes an increase in quadrupole collectivity. This is not observed for the cobalt isotopes with N<40 for which the neutron subshell gap is larger due to the repulsive monopole component of the tensor nucleon-nucleon interaction. The extracted experimental B(E2) values are compared with large-scale shell-model calculations and with beyond-mean-field calculations with the Gogny D1S interaction. A good agreement between calculations and experimental values is found, and the results demonstrate in particular the spectroscopic quality of the Lenzi, Nowacki, Poves, and Sieja (LNPS) shell-model interaction.

Optimization of a hot-cavity type resonant ionization laser ion source

Resonant Ionization Laser Ion Source (RILIS) is nowadays an important technique in many Radioactive Ion Beam (RIB) facilities for its reliability and ability to ionize efficiently and element selectively. Grand Accélérateur National d'Ions Lourds (GANIL) Ion Source using Electron Laser Excitation (GISELE) is an off-line test bench for RILIS developed to study a fully operational resonant laser ion source at GANIL facility. The ion source body has been designed as a modular system to investigate different experimental approaches by varying the design parameters, to develop the future on-line laser ion source. The aim of this project is to determine the best technical solution which combines high selectivity and ionization efficiency with small ion beam emittance and stable long term operation. Latest results concerning emittance and time profile development as a function of the temperature for different ion source versions will be presented.

Developing Ti: Sa Laser Systems for REGLIS3

SPIRAL2 (Système de Production d’Ions Radioactifs Accélérés en Ligne) is a research facility under construction at GANIL (Grand Accélérateur National d’Ions Lourds) for the production of radioactive ion beams by isotope separation on-line methods and low-energy in-flight techniques. REGLIS3 (Rare Element in Gas Laser Ion source and Spectroscopy) at S3 will be the new device which is also under construction at GANIL for producing RIBs (Radioactive Ion Beams) and for studying the ground state properties of the nuclei at low energy beam. The Ti: Sa laser cavities existing now at the GISELE (GANIL Ion Source using Electron Laser Excitation) setup are going to be developed in order to adapt them for the requirements of REGLIS3. A full description of REGLIS3 is presented, RILIS technique which was developed at the last century is also discussed, developing the Ti: Sa laser cavities is presented also that is essential for the usage of automatic scan of wavelength instead of the manual one.

Progress of resonant ionization laser ion source development at GANIL

SPIRAL2 (Système de Production d'Ions Radioactifs Accélérés en Ligne) is a research facility under construction at GANIL (Grand Accélérateur National d'Ions Lourds) for the production of radioactive ion beams by isotope separation on-line methods and low-energy in-flight techniques. A resonant ionization laser ion source will be one of the main techniques to produce the radioactive ion beams. GISELE (GANIL Ion Source using Electron Laser Excitation) is a test bench developed to study a fully operational laser ion source available for Day 1 operations at SPIRAL2 Phase 2. The aim of this project is to find the best technical solution which combines high selectivity and ionization efficiency with small ion beam emittance and stable long term operation. Latest results about the new ion source geometry will be presented.

Missing mass spectroscopy on oxygen isotopes beyond the proton-drip line: mirror symmetry of nuclear shell evolution

Missing mass spectroscopy of the proton-rich 12O and 13O nuclei was performed via the neutron transfer (p, t and (p, d reactions, respectively, using a 14O beam of 51 MeV/u at GANIL (Grand Accelerateur National d’Ions Lourds). In addition to the ground states, an excited state of 12O at 1.8(4) MeV and two excited states of 13O at 2.8(3) and 4.2(3) MeV were observed. Spin-parity and/or spectroscopic factors were obtained from the comparison of the differential cross-sections to distorted-wave calculations. The excited state of 12O with a suggested spin-parity of 0+ or 2+ has a significantly low excitation energy, indicating that the proton shell closure at Z = 8 vanishes in 12O. The spin-parity of 1/2+ was suggested for the 2.8MeV state, which implies that the proton shell gap is weak in 13O, whereas the large spectroscopic factor extracted from the 14O(p , d reaction indicates that the ground 3/2− state remains dominated by normal p-shell configurations. These features of 12O and 13O have marked similarities with their neutron-rich mirror partners 12Be and 13B, respectively, demonstrating mirror symmetry in the fading of the shell closure at magic numbers 8 near the drip lines.

β-decay measurements forN&gt;40Mn nuclei and inference of collectivity for neutron-rich Fe isotopes

A decay spectroscopic study of the neutron-rich isotopes has been performed using fragmentation of a 86Kr primary beam. Fragments from this reaction have been selected by the LISE2000 spectrometer at the Grand Acc el erateur National d Ions Lourds (GANIL). Half-lives of 29 isotopes, including the first ones identified for 61Ti (15 4 ms), 64V (19 8 ms), and 71Fe (28 5 ms), have been determined and compared with model predictions. 67,68Mn -delayed rays were observed for the first time. The branching for the -delayed neutron emission was measured to be greater than 10(5)% in the 67Mn decay. The 67Fe isomeric level is firmly determined at higher energy than assigned in previous works. The excitation energies of the first (2+) and (4+) states of 68Fe are suggested to lie at 522(1) and 1389(1) keV, respectively, thus bringing confirmation of assignments based on in-beam -ray spectroscopy. Beyond-mean-field calculations with the Gogny D1S force have been performed for even-mass nuclei through the Fe isotopic chain. Not only 68Fe but most of the neutron-rich Fe isotopes with neutron numbers below N = 50 are interpreted as soft rotors. The calculated mean occupancy of the neutron g9/2 and d5/2 orbitals in correlated ground statesmore » is steadily growing with increasing neutron number throughout the isotopic chain. Interpretation of 67Fe data is based upon the present calculations for the 66Fe and 68Fe even cores.« less