# FRIENDS3 - Fast radioactive ion extraction and neutralization device for S3

Wenling Dong, V Manea, S Franchoo, D Lunney, E Minaya - Ramirez, S Roset

► To cite this version:

Wenling Dong, V Manea, S Franchoo, D Lunney, E Minaya - Ramirez, et al.. FRIENDS3 - Fast radioactive ion extraction and neutralization device for S3. LISA Summer Schools, Aug 2022, Cabourg/Bagnoles de l'Orne, France. hal-05235136

HAL Id: hal-05235136

https://hal.science/hal-05235136v1

Submitted on 2 Sep 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# FRIENDS³- Fast radioactive ion extraction and neutralization device for S³

W. Dong¹, V. Manea¹,², S. Franchoo¹, D. Lunney¹, E. Minaya-Ramirez¹, S. Roset¹

¹Laboratoire de Physique des 2 Infinis Irene Joliot Curie, 91405 Orsay, France

²GANIL, CEA/DRF-CNRS/IN2P3, 14076 Caen, France

GANIL
laboratoire commun CEA/DSM
Spiral2 CNRS/IN2P3

<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /></figure>

Université
Paris Cité

université
PARIS-SACLAY

UC Lab
Irène Joliot-Curie
Laboratoire de Physique
des 2 Infinis

## Abstract

The new SPIRAL2 facility with its Super Separator Spectrometer (S³) at GANIL is set to produce record intensities of neutron-deficient isotopes close to the proton dripline [1]. The FRIENDS³ project aims to design a fast gas cell with efficient neutralization techniques in order to enable nuclear-structure studies by laser spectroscopy on short-lived isotopes. The gas cell represents an essential component of the S³ - Low Energy Branch (S³-LEB) installation, being the interface between the high-energy S³ beam line and the low-energy ion-transport system. The first simulation and design studies of the FRIENDS³ prototype are presented.

## First generation gas cell at the S³ - Low Energy Branch

<figure><img src="image_4.png" /><figcaption>The fusion-evaporation recoils from S³ enter the gas cell through a thin window that separates the argon-filled volume from the spectrometer vacuum and lose energy by collisions with the buffer gas [2,3].</figcaption></figure>

The radioactive ions are subsequently:

* stopped, thermalized and neutralized in the gas cell.

* extracted through a de Laval nozzle in a supersonic gas jet.

* ionized by the combined turnable pulsed lasers.

* studied by in-jet laser spectroscopy.

Limitations of the current gas cell:

* extraction time limited to ~500 ms for 1 mm exit hole diameter [4,5,6].

* the current neutralization mechanism relies on e⁻-ion recombination in the plasma created by the stopped ion beam.

## New gas-cell prototype design & optimization

COMSOL [7] is chosen for the geometry design and the first stage of optimization without diffusion.

<figure><img src="image_5.png" /></figure>

## Design of the FRIENDS³ test bench

The mechanical design of the FRIENDS³ test bench and the required vacuum system have been specified. The first step is to study electron emission mechanisms in the neutralization tube with simplified off-line gas cells not employing an electric field.

<figure><img src="image_6.png" /></figure>

KU LEUVEN

## References

1. F. Déchery, et al., Nucl. Instrum. Meth. B 376, 125 (2016).

2. R. Ferrer et al., Nat. Comm. 8, 14520 (2017).

3. J. Romans, et al., Atoms 10, 21 (2022).

4. E. Mogelevskiy, 'Diffusion inside the gas cell for laminar flow', Tech. rep., KU Leuven (2013).

5. E. Mogelevskiy, 'Losses in the horn cell', Tech. rep., KU Leuven (2013).

6. Y. Kudryavtsev, et al., Nucl. Instrum. Meth. B 376, 345 (2016).

7. COMSOL Multiphysics v. 5.6., www.comsol.com.

8. D. A. Dahl, Int. Jour. Mass Spectrom. 200, 3 (2000).

9. R. Ferrer et al., Nucl. Instr. Meth. B 317, 570-581 (2013).

## Prototype characterization

Further optimization considering diffusion losses was then carried out based on calculations of both COMSOL (for gas flow) and SIMION [8] (for ion transport in the gas). The optimized values were chosen in a compromise between extraction efficiency, extraction time and time available for neutralization.

<figure><img src="image_7.png" /></figure>

The geometry with $L_{cage} = 78$ mm, $D_{cage} = 78$ mm, $S_{cage} = 8$ mm, $R_{tube} = 9$ mm and $D_{hole} = 1$ mm is proposed.

<figure><img src="image_8.png" /></figure>

## Electron emission study

First test of the direct creation of electrons from tungsten filaments with a basic no-field test bench has been conducted.

<figure><img src="image_9.png" /></figure>

A ⁹⁰Sr beta source with activity of 37 MBq will be purchased and used for electron production tests.

## Conclusions & perspectives

The gas-cell performance was simulated under different conditions. Comparable results obtained with COMSOL and SIMION without diffusion effects give confidence in the implemented simulation approach. Detailed simulations of the neutralization process will be performed by the COMSOL Plasma module.

A gas-cell prototype for neutralization tests is under design study. Electron generation by different mechanisms will be implemented, such as emission from a filament and ionization of the gas by beta source.

<figure><img src="image_10.png" /></figure>

(ANR-21-CE31-0001)