# Status of the Fast Radioactive Ion Extraction and Neutralization Device for S3 (FRIENDS3)

Elodie Morin, Wenling Dong, Serge Franchoo, Thierry Hourat, David Lunney, Vladimir Manea, Enrique Minaya Ramirez, Samuel Roset

► To cite this version:

Elodie Morin, Wenling Dong, Serge Franchoo, Thierry Hourat, David Lunney, et al. Status of the Fast Radioactive Ion Extraction and Neutralization Device for S3 (FRIENDS3). PLATAN 2024, Jun 2024, Jyväskylä, Finland. hal-05235480

HAL Id: hal-05235480

https://hal.science/hal-05235480v1

Submitted on 2 Sep 2025

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# Status of the Fast Radioactive Ion Extraction and Neutralization Device for S³ (FRIENDS³)

E. Morin, W. Dong, S. Franchoo, T. Hourat, D. Lunney, V. Manea, E. Minaya Ramirez, and S. Roset

Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France

## Abstract

The SPIRAL2 facility in GANIL, Caen has recently been commissioned. Combined with the Super Separator Spectrometer (S³), which is currently being constructed, it will be able to produce high intensity beams of neutron-deficient isotopes close to the proton dripline [1]. Ions produced by SPIRAL2/S³ will be studied with the experimental setup S³ Low Energy Branch (S³-LEB) [2, 3, 4] which has recently been installed at the focal plane of S³. The ions will be first thermalized in a gas stopping cell and then guided out by the gas flow, neutralized and extracted in a supersonic gas jet. The extracted species will then be studied using laser spectroscopy, mass spectrometry and decay spectroscopy. The current S³-LEB gas cell extraction time is on the order of a few hundred milliseconds. Thus, the most short-lived isotopes will be lost before being extracted. In order to improve the S³-LEB gas cell, a test bench was designed at IJCLab in Orsay within the scope of the FRIENDS³ project [5]. This test bench will be dedicated to the development of a fast extraction gas cell as well as an improvement of the neutralization techniques in order to enable nuclear structure studies on the most short-lived isotopes. The present contribution will focus on the simulations, design and construction of the new setup as well as the first tests performed with this setup and also with a simplified version operated during the design process.

## S³-LEB

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Laser spectroscopy is performed with the S³-LEB setup, at the focal plane of S³. The radioactive ion beam is **thermalized** and **neutralized** in a gas cell and extracted through a De Laval nozzle in a **supersonic gas jet** where it is laser **re-ionised**.

* **Neutralization mechanism** relies on the electron-ion recombination in the plasma created by the stopped ion beam

* **Extraction time** ≈ 500-600 ms

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

## Test bench design

A test bench was designed to develop the new gas cell and neutralization techniques.

Ions extracted from the gas cell travel through radiofrequency quadrupoles (RFQ) and an einzel lens until a microchannel plate (MCP) detector.

<figure><img src="image_4.png" /></figure>

## Purpose : Improve S³-LEB gas-cell performances

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

## Electrical field gas cell

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

The geometry of the gas cell is a reduced adaptation of the JETRIS [6] gas cell. The ensemble was designed to be compatible with S³-LEB and also flexible.

The electric fields were optimized considering diffusion losses and as a compromise between extraction efficiency, extraction time and time available for neutralization.

## Transport after extraction

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

Potentials were optimized in all RFQs and through the injection and extraction plates.

3 modes (1000 ions per run) :

* Transfer : 83 % at 1 MHz, 41 % at 500 kHz

* Mass separation

* Buncher

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

## Experimental tests

Offline test bench, how do we create our ions, how do we neutralize them ?

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

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Ions production : with resistively heated filaments aided or not by a glow discharge.

* No field acceleration ! -> Critical

* A few pA of ions detected on FC2

Our best candidate for now is the discharge source, up to 30 pA detected after the RFQ.

<figure><img src="image_13.png" /></figure>

<figure><img src="image_14.png" /></figure>

* No major effect observed with beta source

* An effect was observed with e- emitted by a W filament !

* To be tested : discharge electron production

<figure><img src="image_15.png" /></figure>

<figure><img src="image_16.png" /></figure>

[1] P. Déchery et al., NIM B 376 (2016)

[2] J. Romans et al., Atoms 10 (2022)

[3] J. Romans et al., NIM B 536 (2023)

[4] A. Ajayakumar et al., NIMB 539 (2023)

[5] V. Manea et al., project ANR-21-CE31-0001 (2021)

[6] S. Raeder et al., NIM B 463 (2020)

<figure><img src="image_17.png" /></figure>

<figure><img src="image_18.png" /></figure>