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Since 2001, the SPIRAL1 facility has been providing post-accelerated radioactive beams by the ISOL method. Over the last decade, SPIRAL1 has been improved to provide beams of condensable elements, by using a combination of a FEBIAD-type ion source (to produce 1+ ions) and a PHOENIX ECR charge breeder (to transform 1+ ions into N+ ions for post-acceleration). Both these elements have been improved in recent years: the FEBIAD source has been upgraded to improve its efficiency and reliability over time and the charge breeder was modified to extend the range of available charge states. In addition, a krypton beam was recently sent in a FEBIAD target ion-source system (TISS), allowing to produce medium mass radioactive 1+ ions that had not been previously produced in SPIRAL1. This papers compiles recent results illustrating the gain in performances and beam offer at SPIRAL1. [ABSTRACT FROM AUTHOR]

Active target detection systems, where the gas used as the detection medium is also a target for nuclear reactions, have been used for a wide variety of nuclear physics applications since the eighties. Improvements in Micro-Pattern Gaseous Detectors (MPGDs) and in micro-electronics achieved in the last decade permit the development of a new generation of active targets with higher granularity pad planes that allow spatial and time information to be determined with unprecedented accuracy. A novel active target and time projection chamber (ACTAR TPC), that will be used to study reactions and decays of exotic nuclei at facilities such as SPIRAL2, is presently under development and will be based on MPGD technology. Several MPGDs (Micromegas and Thick GEM) coupled to a 2×2mm2 pixelated pad plane have been tested and their performances have been determined with different gases over a wide range of pressures. Of particular interest for nuclear physics experiments are the angular and energy resolutions. The angular resolution has been determined to be better than 1° FWHM for short traces of about 4cm in length and the energy resolution deduced from the particle range was found to be better than 5% for 5.5MeV particles. These performances have been compared to Geant4 simulations. These experimental results validate the use of these detectors for several applications in nuclear physics. [ABSTRACT FROM AUTHOR]

We report on the construction of an UHV compatible 40 mm active diameter detector based on micro channel plates and assembled directly on the feed-throughs of a DN63CF flange. It is based on the charge division technique and uses a standard 2 inch Si wafer as a collector. The front end electronic is placed directly on the air side of the flange allowing excellent immunity to noise and a very good timing signal with reduced ringing. The important aberrations are corrected empirically providing an absolute positioning accuracy of 500 µm while a 150 µm resolution is measured in the center. [ABSTRACT FROM AUTHOR]

Metal ion beams are more and more requested by physicists (Nuclear Physics, Material Physics) for their experiments. At GANIL, they are produced by Electron Cyclotron Resonance (ECR) Ion Sources for the two accelerator machines: ECR4 & ECR4M (Sortais et al., 1989) [1] for the Cyclotrons and PhoenixV3 for the Linac (Thuillier et al., 2016) [2]. One of the challenges is to produce these beams with high global efficiency: today, total ionization efficiency varies between ∼ 1% and ∼ 28% regarding the method carried out. A new alternative would be the 1＋/N＋ method studied intensively for the past twenty years in the framework of Radioactive Ion Beam (RIB) production. In this article, the primary results leading to the proof of principle of that technique applied to the production of metal ion beams is presented. [ABSTRACT FROM AUTHOR]

The use of high-intensity and/or heavy-ion beams in active targets and time-projection chambers is often limited by the strong ionization produced by the beam. Besides the difficulties associated with the saturation of the detector and electronics, beam-related signals may hide the physical events of interest or reduce the detector performance. In addition, space-charge effects may deteriorate the homogeneity of the electric drift field and distort the subsequent reconstruction of particle trajectories. In anticipation of future projects involving such conditions, a dedicated beam mask has been developed and tested in the MAYA active target. Experimental results with a 136 Xe beam are presented. [ABSTRACT FROM AUTHOR]

An inelastic α -scattering experiment on the unstable N = Z , doubly-magic 56 Ni nucleus was performed in inverse kinematics at an incident energy of 50 A.MeV at GANIL. High multiplicity for α -particle emission was observed within the limited phase-space of the experimental setup. This observation cannot be explained by means of the statistical-decay model. The ideal classical gas model at kT = 0.4 MeV reproduces fairly well the experimental momentum distribution and the observed multiplicity of α particles corresponds to an excitation energy around 96 MeV. The method of distributed m α -decay ensembles is in agreement with the experimental results if we assume that the α -gas state in 56 Ni exists at around 113 - 17 + 15 MeV. These results suggest that there may exist an exotic state consisting of many α particles at the excitation energy of 113 - 17 + 15 MeV. [ABSTRACT FROM AUTHOR]

TULIP (T arget Ion So u rce for Short- L ived I sotope P roduction) 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 μ s 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. • Response time breakthrough in an innovative fast ISOL system. • Improved ISOL efficiency limits with respect to radioactive decay. • A new ISOL method for the production of neutron-deficient short-lived isotopes. [ABSTRACT FROM AUTHOR]

The design, realization and operation of a prototype or “demonstrator” version of an active target and time projection chamber (ACTAR TPC) for experiments in nuclear physics is presented in detail. The heart of the detection system features a micromegas gas amplifier coupled to a high-density pixelated pad plane with square pad sizes of 2 × 2 mm 2 . The detector has been thoroughly tested with several different gas mixtures over a wide range of pressures and using a variety of sources of ionizing radiation including laser light, an α -particle source and heavy-ion beams of 24 Mg and 58 Ni accelerated to energies of 4.0 MeV/u. Results from these tests and characterization of the detector response over a wide range of operating conditions will be described. These developments have served as the basis for the design of a larger detection system that is presently under construction. [ABSTRACT FROM AUTHOR]

The fission of a variety of actinides was induced by fusion and transfer reactions between a 238 U beam and 12 C nuclei, in the active target MAYA. The performance of MAYA was studied, as well as its capability to reconstruct the fission-fragment trajectories. Furthermore, a full characterization of the different transfer reactions was achieved, and the populated excitation-energy distributions were investigated as a function of the kinetic energy in the entrance channel. The ratio between transfer- and fusion-induced fission cross-sections was also determined, in order to investigate the competition between both reaction types and its evolution with the incident energy. The experimental results will be discussed with a view to forthcoming radioactive-ion beam facilities, and next-generation active-target setups. [ABSTRACT FROM AUTHOR]

The Isoscalar Giant Monopole Resonance (ISGMR) and the Isoscalar Giant Dipole Resonance (ISGDR) compression modes have been studied in the doubly-magic unstable nucleus 56 Ni. They were measured by inelastic α -particle scattering in inverse kinematics at 50 MeV/u with the MAYA active target at the GANIL facility. The centroid of the ISGMR has been obtained at E x = 19.1 ± 0.5 MeV . Evidence for the low-lying part of the ISGDR has been found at E x = 17.4 ± 0.7 MeV . The strength distribution for the dipole mode shows similarity with the prediction from the Hartree–Fock (HF) based random-phase approximation (RPA) [1] . These measurements confirm inelastic α -particle scattering as a suitable probe for exciting the ISGMR and the ISGDR modes in radioactive isotopes in inverse kinematics. [ABSTRACT FROM AUTHOR]

In a proof-of-principle measurement, the Maya active target detector was employed for a C( p, p) resonant elastic scattering experiment in inverse kinematics. The excitation energy region from 0 to 3MeV above the proton breakup threshold in N was investigated in a single measurement. By using the capability of the detector to localize the reaction vertex and record the tracks of the recoiling protons, data covering a large solid angle could be utilized, at the same time keeping an energy resolution comparable with that of direct-kinematics measurements. The excitation spectrum in N was fitted using the R-matrix formalism. The level parameters extracted are in good agreement with previous studies. The active target proved its potential for the study of resonant elastic scattering in inverse kinematics with radioactive beams, when detection efficiency is of primary importance. [ABSTRACT FROM AUTHOR]

Abstract: Measurements and ion optic calculations showed that the large momentum acceptance of the VAMOS spectrometer at GANIL could be further increased from to by suitably enlarging the dimensions of the detectors used at the focal plane. Such a new detection system built for the focal plane of VAMOS is described. It consists of larger area detectors (1000mm×150mm) namely, a Multi-Wire Parallel Plate Avalanche Counter (MWPPAC), two drift chambers, a segmented ionization chamber and an array of Si detectors. Compared to the earlier existing system (VAMOS), we show that the new system (VAMOS++) has a dispersion-independent momentum acceptance. Additionally, a start detector (MWPPAC) has been introduced near the target to further improve the mass resolution to . The performance of the VAMOS++ spectrometer is demonstrated using measurements of residues formed in the collisions of 129Xe at 967MeV on 197Au. [Copyright &y& Elsevier]