Speaker
Description
The Superconducting Linear Accelerator (SPIRAL2-LINAC) facility of GANIL is designed to deliver heavy-ion beams with highest intensities ever achieved [1,2]. The Super Separator Spectrometer (S$^3$), a high-resolution recoil separator coupled to the LINAC, will use these high-intensity beams to produce neutron-deficient nuclei close to the proton dripline and super heavy nuclei via fusion–evaporation reactions . It is designed to separate the reaction products from the intense primary beams [3]. The Low Energy Branch of S$^3$ (S$^3$-LEB) [4,5], currently under commissioning at LPC Caen, will be installed at the focal plane of S$^3$ and aims to study ground state and isomeric state properties of the produced neutron-deficient species using the in-gas laser ionization and spectroscopy technique. This technique allows the determination of isotope shifts and hyperfine constants of exotic isotopes and thus nuclear properties such as spin, moments and difference in mean-square charge radii.
The reaction products will be stopped and neutralized in a buffer gas cell filled with argon gas. After extraction through a “de-Laval nozzle” of Mach number M ~ 8, the atoms of interest are ionized a two or three step laser scheme. The use of the de-Laval nozzle creates a homogeneous hypersonic gas jet of low temperature and pressure. Probing and ionizing the atoms by lasers in the gas jet will reduce the Doppler and pressure broadening by at least an order of magnitude compared to the gas cell [6]. An improved spectral resolution (≤300 MHz) can thus be achieved in laser spectroscopy studies with S$^3$-LEB while maintaining high efficiency and selectivity. The S$^3$-LEB set-up will allow for further mass and decay spectroscopy experiments.
In this contribution, the status of the S$^3$-LEB experiment will be presented, results from the most recent in-gas-cell and in-gas-jet laser spectroscopy measurements performed off-line will be discussed and the upgrate program to allow for the study of short-lived isotopes addressed. The goal of the off-line measurements is to identify suitable atomic transition schemes for erbium, the first study case at S$^3$. Determination of the isotope shift and hyperfine structure parameters in the hypersonic gas jet, a comparison with literature values and characterization of the pressure broadening effects in gas cell will be reported. With the upgrade program (FRIENDS3 [7]), the extraction time of the current S$^3$-LEB gas cell that is on the order of a few hundred milliseconds, will be reduced substantially, allowing to study isotopes with half lives well below 100 ms. An important condition to reach this goal is the presence of a fast neutralization process. The neutralization efficiency is contingent upon the number of electrons created by the incident beam during the stopping process in the buffer gas. The latter heavily relies on the beam intensity. The FRIENDS$^3$ project [7] aims to design a fast gas cell with an independent neutralization technique in order to enable nuclear-structure studies by laser spectroscopy on short-lived isotopes. A status of the simulation, design and experimental work performed in this project will also be given.
- Grand Accélérateur National d'Ions Lourds, URL: https://www.ganil-spiral2.eu/en/
- F. Déchery et al., Eur. Phys. J. A 51, 66 (2015).
- F. Déchery, et al., Nucl. Instrum. Meth. B 376, 125 (2016).
- J. Romans, et al., Atoms 10, 21 (2022).
- A. Ajayakumar et al., Nucl. Instrum. Meth. B 539, 102-107 (2023).
- R. Ferrer. et.al., NIMS B, 317570 (2013).
- V. Manea, et al., ‘Fast radioactive ion extraction and neutralization device for s$^3$’, project ANR-21-CE31-0001 (2021).
