Status report on survey and alignment activities @ GANIL-SPIRAL2 facilities (CEA/CNRS, Caen, France)

International audienceThe over 30 years old GANIL laboratory (heavy ionsnational accelerator) is still delivering beams that interestthe nuclear physicist community. That is why AGATA(Advanced GAmma Tracking Array, a Europeancollaboration of 12 countries) settled at GANIL for a 4years campaign. This π gamma-ray detector requested aquite strong effort in term of 3D positioning metrologyand in term of environment adaptation.Furthermore, since 2013, GANIL is constructing andinstalling the SPIRAL2 facility: a superconducting linearaccelerator and experimental areas that represent 150mlong beam lines. Two injectors (ions, protons anddeutons), a RFQ, a medium energy beam line, a 30m longLINAC (26 supraconducting accelerating cavities) andhigh energy beam lines supplying two experimental hone dedicated to neutron and the other containing S3(Super Separator Spectrometer).This project requested full time survey and alignmentwork from the underground network linked to historicalGANIL coordinates system to the process installation stiin progress

Survey and alignment concept for the SPIRAL2 accelerator (status report)

International audienceThe SPIRAL2 project located at the GANIL facility (Caen, France) has been studied since the beginning of 2003, and is now under construction. This project aims at delivering rare (radioactive) isotope beams with intensities not yet available with presently running machines. An important aspect of this project is that it is foreseen to deliver up to five different beams in parallel to the users. This paper is a status report on the survey and alignment techniques selected for installation of the SPIRAL2 accelerator device

The initial geodetic survey for the SPIRAL2 process installation

International audienceThe SPIRAL2 project located at the Grand Accélérateur National d'Ions Lourds (GANIL facility - Caen, France) has been studied since the beginning of 2003, and is now under construction. This project aims at delivering rare (radioactive) isotope beams with intensities not yet available with presently running machines. An important aspect of this project is that it is foreseen to deliver up to five different beams in parallel to the users. This paper is focused mainly on the initial geodetic survey for the SPIRAL2 process installation. The positioning of the process and by extension of the buildings is subject to an important constraint due to the future connection of the radioactive beam line to the existing accelerator (see Fig.3). In order to reach the performances, a geodetic reference network (surface network) linked to the local survey network of the existing accelerator is designed [1]. The surface network will be transferred to the floor of the SPIRAL2 accelerator tunnel (9m under the ground), in order to define the underground reference network for the process setup. Final goal of the initial geodetic survey is to align process components of accelerator according to design within required tolerances

Overview on the preliminary geodetic network for SPIRAL2 process installations at GANIL

The SPIRAL2 project located at the Grand Accélérateur National d'Ions Lourds (GANIL facility - Caen, France) is now under construction. This project aims at delivering rare (radioactive) isotope beams with intensities not yet available with presently running machines. An important aspect of this project is that it is foreseen to deliver up to five different beams in parallel to the users. This paper is focused mainly on the preliminary geodetic network for the SPIRAL2 process installation. The positioning of the process and by extension of the buildings is subject to an important constraint due to future connection of the radioactive beam line to the existing accelerator complex. To reach the required accelerator performances, a geodetic surface network made up of concrete monuments around the construction is linked to the local network of the existing accelerator [1]. The surface network has been transferred to the slab of the accelerator tunnel at -2 level (-9.50 m) in order to define the underground reference network for the process setup. Final goal of the geodetic network is to allow the alignment of the process accelerator components [2] [3] [4] [5] [6] according to design within required tolerance. Various tolerances objectives will be given

Upgrade of the SPIRAL identification station for high-precision measurements of nuclear β decay

The low-energy identification station at SPIRAL (Système de Production d'Ions Radioactifs Accélérés en Ligne) has been upgraded for studying the β decays of short-lived radioactive isotopes and to perform high-precision half-life and branching-ratio measurements for superallowed Fermi and isospin T=1/2 mirror β decays. These new capabilities, combined with an existing Paul trap setup for measurements of β-ν angular-correlation coefficients, provide a powerful facility for investigating fundamental properties of the electroweak interaction through nuclear β decays. A detailed description of the design study, construction, and first results obtained from an in-beam commissioning experiment on the β+ decays 14 O and 17F is presented

The MUGAST-AGATA-VAMOS campaign: Set-up and performances

none50The MUGAST-AGATA-VAMOS set-up at GANIL combines the MUGAST highly-segmented silicon array with the state-of-the-art AGATA array and the large acceptance VAMOS spectrometer. The mechanical and electronics integration copes with the constraints of maximum efficiency for each device, in particular γ-ray transparency for the silicon array. This complete set-up offers a unique opportunity to perform exclusive measurements of direct reactions with the radioactive beams from the SPIRAL1 facility. The performance of the set-up is described through its commissioning and two examples of transfer reactions measured during the campaign. High accuracy spectroscopy of the nuclei of interest, including cross-sections and angular distributions, is achieved through the triple-coincidence measurement. In addition, the correction from Doppler effect of the γ-ray energies is improved by the detection of the light particles and the use of two-body kinematics and a full rejection of the background contributions is obtained through the identification of heavy residues. Moreover, the system can handle high intensity beams (up to 108 pps). The particle identification based on the measurement of the time-of-flight between MUGAST and VAMOS and the reconstruction of the trajectories is investigated.noneAssie M.; Clement E.; Lemasson A.; Ramos D.; Raggio A.; Zanon I.; Galtarossa F.; Lenain C.; Casal J.; Flavigny F.; Matta A.; Mengoni D.; Beaumel D.; Blumenfeld Y.; Borcea R.; Brugnara D.; Catford W.; de Oliveira F.; Delaunay F.; De Sereville N.; Didierjean F.; Diget C.A.; Dudouet J.; Fernandez-Dominguez B.; Fougeres C.; Fremont G.; Girard-Alcindor V.; Giret A.; Goasduff A.; Gottardo A.; Goupil J.; Hammache F.; John P.R.; Korichi A.; Lalanne L.; Leblond S.; Lefevre A.; Legruel F.; Menager L.; Million B.; Nicolle C.; Noury F.; Rauly E.; Rezynkina K.; Rindel E.; Rojo J.S.; Siciliano M.; Stanoiu M.; Stefan I.; Vatrinet L.Assie, M.; Clement, E.; Lemasson, A.; Ramos, D.; Raggio, A.; Zanon, I.; Galtarossa, F.; Lenain, C.; Casal, J.; Flavigny, F.; Matta, A.; Mengoni, D.; Beaumel, D.; Blumenfeld, Y.; Borcea, R.; Brugnara, D.; Catford, W.; de Oliveira, F.; Delaunay, F.; De Sereville, N.; Didierjean, F.; Diget, C. A.; Dudouet, J.; Fernandez-Dominguez, B.; Fougeres, C.; Fremont, G.; Girard-Alcindor, V.; Giret, A.; Goasduff, A.; Gottardo, A.; Goupil, J.; Hammache, F.; John, P. R.; Korichi, A.; Lalanne, L.; Leblond, S.; Lefevre, A.; Legruel, F.; Menager, L.; Million, B.; Nicolle, C.; Noury, F.; Rauly, E.; Rezynkina, K.; Rindel, E.; Rojo, J. S.; Siciliano, M.; Stanoiu, M.; Stefan, I.; Vatrinet, L

Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni-78 Region : A Hint from Lifetime Measurements

Lifetime measurements of excited states of the light N = 52 isotones Kr-88, Se-86, and Ge-84 have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B(E2; 2(+)-> 0(+)) and B(E2; 4(+)-> 2(+)) were obtained for the first time for the hard-to-reach 84Ge. While the B(E2; 2(+)-> 0(+) ) values of Kr-88, Se-86 saturate the maximum quadrupole collectivity offered by the natural valence (3s, 2d, 1g(7/2), 1h(11/2)) space of an inert Ni-78 core, the value obtained for Ge-84 largely exceeds it, suggesting that shape coexistence phenomena, previously reported at N less than or similar to 49, extend beyond N = 50. The onset of collectivity at Z = 32 is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector rho field in shell-structure evolution

Lifetime measurements in Ti-52,Ti-54 to study shell evolution toward N=32

Lifetimes of the excited states in the neutron-rich Ti-52,Ti-54 nuclei, produced in a multinucleon-transfer reaction, were measured by employing the Cologne plunger device and the recoil-distance Doppler-shift method. The experiment was performed at the Grand Accelerateur National d'Ions Lourds facility by using the Advanced Gamma Tracking Array for the gamma-ray detection, coupled to the large-acceptance variable mode spectrometer for an event-by-event particle identification. A comparison between the transition probabilities obtained from the measured lifetimes of the 2(1)(+) to 8(1)(+) yrast states in Ti-52,Ti-54 and that from the shell-model calculations based on the well-established GXPF1A, GXPF1B, and KB3G fp shell interactions support the N = 32 subshell closure. The B(E2) values for Ti-52 determined in this work are in disagreement with the known data, but are consistent with the predictions of the shell-model calculations and reduce the previously observed pronounced staggering across the even-even titanium isotopes