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Scientific Council public talks

Spherical Neutron Polarimetry: A pioneering ILL technique and its unique contribution to multiferroics research

Thursday 26 October 2023

Navid QURESHI
Institut Laue Langevin

Spherical Neutron Polarimetry: A pioneering ILL technique and its unique contribution to multiferroics research

When paradigms shift, an immediate adoption is often prevented by resistance from incumbents. This is certainly what happened in 1988, when Francis Tasset presented an apparatus able to unveil the full vectorial information of the neutron spin change in the scattering process from a magnetic material [1]. Even though the theoretical groundwork had been laid out independently by Blume and Maleev in 1963 [2,3] and the longitudinal component of the initial neutron beam polarisation was successfully analysed in a groundbreaking experiment six years later [4], it was not believed or accepted by the experts in the field until 1998 that the transverse components of the scattered polarisation could also be measured with Tasset’s zero-field polarimeter, which we today know as Cryopad. In this talk I will illustrate the basics of this elegant and pioneering technique as well as how the rotation (and also creation and annihilation) of the neutron beam polarisation is related to generalised cross sections which cannot be accessed by conventional methods. The technique’s unprecedented precision in determining complex magnetic structures and magnetic domain populations has been and still is hugely beneficial to the study of magnetoelectric and multiferroic materials, which play an important role in the realisation of future spintronic devices. I will show several examples, both historic and recent, underlining the enormous potential of spherical neutron polarimetry as a cutting-edge technique for tackling present and upcoming scientific challenges.


Watch the recorded talk on Youtube


Seeing the chemistry in biology using neutron crystallography

Wednesday 31 March 2021,  15.30

Matthew Blakeley
Institut Laue Langevin

Seeing the chemistry in biology using neutron crystallography

Hydrogen atoms and protons play critical roles in biological structure and function. Neutron crystallography allows us to directly visualise their locations in damage-free crystal structures of biological macromolecules and their complexes at room-temperature, revealing key details of protonation, hydrogen-bonding and hydration.  Here I will describe (i) the current status of the field using examples of recent studies performed and (ii) on-going instrument developments that will further extend the limits for neutron macromolecular crystallography.


Watch the recorded talk on Youtube


How to test Dark Energy at ILL?

Friday 6 November 2020,  9.00

Tobias JENKE
Institut Laue Langevin

How to test Dark Energy at ILL?

Neutrons are excellent probes to test gravity at short distances – electrically neutral and only hardly polarizable. Furthermore, very slow, so-called ultracold neutrons form quantum states bound by the gravity potential of the Earth.

This allows combining gravity experiments with powerful resonance spectroscopy techniques, as well as tests of the interplay between gravity and quantum mechanics. In the last decade, the qBounce collaboration has been performing several measurement campaigns at the ultracold and very cold neutron facility PF2 at the Institut Laue-Langevin.

A new spectroscopy technique, Gravity Resonance Spectroscopy, was developed and snapshots of falling wavepackets of these gravitationally bound quantum states were recorded. The results were applied to test gravity at micron distances as well as various Dark Energy and Dark Matter scenarios in the lab, like Axions, Chameleons and Symmetrons.

In my talk, I will summarize the physics that can be addressed, and review the experiments and its results.


Watch this short animation about the axion quest at the ILL on Youtube:


Magnetic PDF-analysis: a real-space probe of static and dynamic short-range spin-spin correlations

Friday 8 November 2019,  9.00
101st Scientific Council

Dr Henry FISCHER
Institut Laue Langevin

Magnetic PDF-analysis: a real-space probe of static and dynamic short-range spin-spin correlations

View presentation here (pdf - 6.35 Mi)