Université de Strasbourg

Benoît Gall

Biography - Benoît Gall

Hubert Curien Pluridisciplinary Institute (IPHC), University of Strasbourg and CNRS, France

Benoît Gall, USIAS Fellow 2021Professor Benoît Gall is a graduate of the Louis Pasteur University in Strasbourg (1990), and defended his PhD at the University Paris-Saclay (Paris XI) in 1994. He is a nuclear spectroscopist and investigates the disappearance of nuclear pairing in high spin structures (super-deformed nuclei) and in the rotational bands of deformed nuclei. He passed his accreditation (habilitation) to direct research at the University of Strasbourg in 2000. In 2011, his developments in digital instrumentation, the innovative rotary target system and the development of 50Ti isotopic beam, made possible the first prompt spectroscopy of a superheavy nucleus, the 256Rf (Z=104). In 2008, he was awarded the first international Zdzisław Szymański Prize at the ENAM Conference for outstanding contribution to experimental in-beam studies of superdeformed, octupole deformed and heavy nuclei. In 2015, he and his collaborators were awarded with the second JINR (Joint Institute for Nuclear Research) prize for the production of intense ion beams from metallic compounds from ECR (Electron cyclotron resonance) ion sources using the MIVOC (Metallic Ions out of Volatile Organic Compounds) method. His work has made it possible to provide new accelerators, dedicated to superheavy element studies, with isotopic beams of 50Ti and 54Cr of unprecedented intensity that will allow, in the coming months, to tackle the synthesis of the new elements Z= 119 and 120 located in the 9th period of Mendeleev’s table.

A university teacher with a multidisciplinary approach to research, including societal issues, Benoît Gall was co-responsible for the dismantling of the university reactor in Strasbourg and is also interested in the natural reactors in Oklo (Gabon, Africa). Together with his close collaborators, he explained the Inception and evolution of these natural cores almost two billion years ago.

With the new superheavy elements factories the intense beams leave only very little chance of survival to the rare isotope targets required for the production of superheavy nucleis. With this USIAS project, Professor Gall is taking this problem into the realm of the physics of innovative materials in order to identify a target support that can withstand these extreme conditions and make it possible to synthesize elements beyond Z=120. This will also allow sufficient nuclei to be produced beyond the copernicium (Z=112) to study their chemical properties, where relativistic effects no longer allow for periodic element classification and where the first effects of the g electron shells will be observed.

Project - Developing innovative materials for extreme beams and rare targets

01/10/2021 - 31/03/2024

Our present-day understanding of atomic physics and nuclear cohesion is based on a long tradition of confrontation between experimental data and theoretical models. Although all the models agree that an island of increased stability should exist for superheavy nuclei, as an ultimate fingerprint of nuclear quantal effects, they do not agree on its location. Theoretical approach of atom cohesion demonstrates the need to account for relativistic effects in the superheavy elements (SHE) region setting limits to “traditional” Mendeleev’s classification. Will the first “g-shell” atoms appear at Z=121 as predicted by Mendeleev's table? What are their properties? Is Oganesson (Z=118), the heaviest element synthesized to date, a rare gas as suggested by the periodic table of elements or a metalloid due to increasing influence of relativistic effects? Experiments will reveal the truth. Nuclear physicists and chemists will extract strong and efficient constraints on theoretical models through the study of these extreme nuclei. 

New instruments dedicated to the study of the heaviest elements have recently become operational in Russia and Japan. They will use unprecedented beam intensities to compensate the extremely low production probability of superheavy elements (SHE). IPHC has developed world-leading expertise in beams produced using Metallic Ions out of Volatile Organic Compounds (MIVOC). This has been achieved through a multidisciplinary collaboration between chemists, physicists and ion source experts that has existed for almost ten years. This USIAS project opens a new interdisciplinary collaboration around plasma physics in ion sources with a new high temperature inductive oven, in order to enable the new installations to operate at nominal intensity with 50Ti and 54Cr isotopic beams.

With up to 60 trillion (6 1013) heavy ions per second, the beam spot power will be unsustainable for standard target backing materials. The search for new, existing, materials or the development of innovative materials is of utmost importance for the future of SHE studies. This project will explore the heavy-ion induced defects and the dose effects for new target materials and innovative target material support developed within this project. The proximity of the Institute of Physics and Chemistry of Materials of Strasbourg (IPCMS), and the existing close collaboration with Oak Ridge National Laboratory (United States), FLNR Dubna (Russia) and RIKEN Tokyo (Japan), represent a unique opportunity to develop these new materials for SHE science, nuclear applications and even for space applications. The issues addressed in the present USIAS project aim to solve what will be the most critical limitation for the new scientific facilities dedicated to SHE science within the next years. Without these innovative foils, the new SHE machines will not be able to run at nominal intensity. This development is therefore of utmost importance for the production of the next SHE elements!

Post-doc biography - Kieran Kessaci

Hubert Curien Pluridisciplinary Institute (IPHC), University of Strasbourg and CNRS, France

Kieran KessaciKieran Kessaci holds a master's degree in subatomic physics and a general engineering degree from Télécom Physique Strasbourg. He defended his PhD thesis at the University of Strasbourg in March 2022, in the field of superheavy element physics. During his thesis, he took part in numerous fundamental physics experiments on the study of the fine structure of superheavy nuclei, and in particular the isomeric high-K states that are omnipresent in this particular mass region. In Dubna, he carried out spectroscopy of Nobelia 255 and 256, nuclei at the limits of our experimental capabilities. These studies led to the discovery of five new K isomers in these nuclei.

In parallel, he joined the American-French-Japanese nSHE collaboration in 2018, which was set up in the RIKEN laboratory with the aim to synthesise new elements. He is one of three analysts who took part in the element 119 synthesis experiment. In this context, metal beams of unprecedented intensity have been developed, highlighting new problems of target mechanical strength. Studies of target supports capable of withstanding these extreme intensity and dose conditions have been undertaken. The IPHC in Strasbourg is making a significant contribution to these studies that have, among other things, given rise to the present USIAS project, with the ambition of meeting this ambitious challenge.

Kieran Kessaci has been involved in a number of real-life tests of innovative materials at RIKEN and has begun to redirect these studies towards the field of thin film materials physics.

This project can only be carried out successfully via a strong multidisciplinary collaboration between nuclear physics and materials physics. It will eventually allow us to fully exploit the latest facilities that are dedicated to the synthesis of unknown atoms, beyond the heaviest element ever observed to date: Oganesson (Z=118). This will allow us to explore the 8th period of the Mendeleev table, which should shed light on the properties of the new g electron shells and allow us to fully appreciate the relativistic effects that arise from Copernicium (Z=112).

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