Scientific Colloquium Webinars 2022

Monday, 25/04 (16h, CET): hosted by GdR RESANET
Probing nuclear superfluidity and superconductivity with neutron stars,
Nicolas CHAMEL (IAA, ULB Bruxelles)

Formed in the furnace of gravitational core-collapse supernova explosions, neutron stars contain matter crushed at densities exceeding that found inside the heaviest atomic nuclei. Despite typical temperatures of order ten million degrees, the extremely dense matter in neutron stars is expected to be cold enough for the appearance of superfluids and superconductors – frictionless quantum liquids respectively electrically neutral and charged – made of neutrons and protons, and more speculatively of other particles such as hyperons or even deconfined quarks. If these phase transitions really occur, neutron stars would not only be the largest superfluid and superconducting systems known in the Universe, but also the hottest ones with critical temperatures reaching ten billion degrees. After describing the main properties of terrestrial superfluids and superconductors, our current understanding of analogous phenomena in neutron stars will be reviewed together with their astrophysical manifestations.
pdf of the talk.

Monday, 24/01 (16h, CET): hosted by GdR RESANET
Angular momentum generation in nuclear fission,
Jon N. WILSON (IJCLab Orsay)

When a heavy atomic nucleus fissions, the resulting fragments are observed to emerge spinning [1]; this phenomenon has been an outstanding mystery in nuclear physics for a long time. The internal generation of around 6-7 units of angular momentum in each fragment is particularly puzzling for systems which start with zero, or almost zero, spin.
Over the last 5 decades much experimental and theoretical effort has been devoted to understanding the fission mechanism and questions such as angular momentum generation, energy partition between fragments and neutron emission. In this presentation I will review this body of research and look particularly in detail at current efforts, including very recent experimental results [2,3] and related theoretical works [4,5,6] which attempt to better understand this fascinating phenomenon. This research is not only important for the fundamental understanding and theoretical description of fission, but also has consequences for the γ-ray heating problem in nuclear reactors, for the study of the structure of neutron-rich isotopes, and for the synthesis and stability of super-heavy elements.
[1] J. B. Wilhelmy, Phys. Rev. C 5 2041 (1972)
[2] J.N. Wilson et al., Nature 590 566 (2021)
[3] M. Travar et al. Phys. Lett. B 817 136293 (2021)
[4] J. Randrup and R. Vogt, Phys. Rev. Lett. 127 062502 (2021)
[5] P. Marevic et al., Phys. Rev. C104, L021601 (2021)
[6] I. Stetcu et al., Phys. Rev. Lett. 127 222502 (2021)
The pdf of the talk can be find here.

Organizers: F. Arleo (SUBATECH Nantes), P. Ascher (CENBG Bordeaux), O. Dorvaux (IPHC Strasbourg), J. Dudouet (IP2I Lyon), A. Fantina (GANIL Caen), G. Henning (IPHC Strasbourg), A. Korichi (IJCLab Orsay), O. Lopez (LPC Caen), J. Margueron (IP2I Lyon), G. Quemener (LPC Caen), O. Sorlin (GANIL Caen), B. Sulignano (IRFU Saclay), J.-C. Thomas (GANIL Caen), L. Thulliez (IRFU Saclay), A. Uras (IP2I Lyon), M. Vandebrouck (IRFU Saclay), P. Van Hove (IPHC Strasbourg), G. Verde (L2IT Toulouse).