How it works

Preparation of fission-product sources

Recoil spectrometry has a double goal:

• to study the fission process, which provides information about intra-nuclear forces;
• to produce and isolate new atomic nuclei (exotic nuclei), making it possible to develop models further.

At PN1, the target sample is bombarded with a high flux of thermal neutrons to break up atomic nuclei and produce new ones. Fission reactions involving neutron capture then generally produce nuclei with excess neutrons.

Sorting particles with PN1

The role of a recoil spectrometer is to sort and recognize the nuclei fragments ejected from the sample very soon after fission, because the lifetime of fission products is often short.

PN1-Lohengrin is the largest mass spectrometer in the world. The particles with the same speed (v) all arrive on the same parabola, each parabola point corresponding to a given charge/mass (q/m) ratio. As the detector is fixed, the nuclear fragments of the desired q/m ratio are collected by varying the deflection of the electric and magnetic fields until the corresponding parabola intersects the detector.

Working at PN1-Lohengrin

This film was shot in the RED magnet housing on 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 the 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 an experiment is removed and the equipment required for the following experiment is installed.

The only point of the film is to show you how nuclear physicists must be slim and well-trained climbers, competent not only in in physics but also in screwing and unscrewing objects!