PN1 (also called LOHENGRIN) is the world-leading fission fragment separator.

A target of a fissile isotope placed near the core of the ILL reactor in a thermal neutron flux of 5.3 x 10¹⁴ n cm^-2 s^-1 emits a variety of fission products. These radioactive isotopes originating from the target are separated (sorted) by LOHENGRIN which is nothing else than an unusually large mass spectrometer i.e. a combination of a magnetic and an electric sector field whose deflections are perpendicular to each other. This makes it possible to study mass, kinetic energy and charge distribution for products from thermal neutron induced nuclear fission at very high resolution.

Its main applications are:
- the study of the decay of exotic neutron-rich nuclei (e.g. better understanding of supernova explosions)
- fission process investigation (e.g. better understanding of different fissile systems from binary and ternary fission reactions)
- Practical applications (e.g. study of diffusion of actinides in different surrounding materials)

In the last part of their flight through LOHENGRIN, fission products are focalized on an arrangement of detectors by the RED magnet (Reverse Energy Dispersion dipole magnet). 

The video below was shot in the RED magnet housing by 28 May 2007, i.e. between experiment 3-01-498 (Beta-gamma spectroscopy of very neutron-rich Ge, As and Se isotopes) and experiment 3-01-501 (Determination of mass and nuclear charge of heavy fission fragments from fission of Pu isotopes). It shows how the complicated set of measuring devices and detectors required for the first experiment is removed and then the equiment required for the second experiment is installed. This has no other goal than showing you that nuclear physicists must be slim, well trained to climb and, in addition to physics, must be good at screwing and unscrewing !