Direct measurements of neutron reactions on radionuclides - DIMER
September / October, 2023

Welcome

Rationale

Depending on the reaction channel, direct determinations of neutron-induced reaction cross sections on stable and unstable isotopes for energies above 1 keV cross face different challenges. Neutron captures, neutron-induced fissions, charged-particle production reactions, elastic and inelastic scatterings are important and of interest for astrophysics and nuclear applications. With the existing neutron beam capabilities, available radioactive isotope productions, and ideas for future facilities, we want to discuss directions and possible solutions for current challenges in an informal and constructive atmosphere. Each day will be dedicated to a certain topic with about 2 hours formal presentations, but enough time for breakout and discussion to develop new ideas.

Meeting Topics

Depending on the reaction channel, direct determinations of neutron-induced reaction cross sections for energies above 1 keV cross face different challenges.
  • Neutron captures are important for astrophysics and many applications. In particular, radioactive isotopes are interesting, but extremely difficult to investigate. The reason is that current techniques almost always require the detection of gammas or electrons to prove the neutron capture. These particles are also emitted during the intrinsic decay of the radioactive sample material and poses therefore strong limitations on the isotopes that can be investigated. The current limit is approximately 1 year - isotopes with shorter half-lives cannot be investigated. In addition to the detection limitations, the production of suited radioactive samples requires huge efforts. 
  • Neutron-induced fission or charged-particle production  experiments face the challenge of detecting the short-range reaction products. The solution is usually thin samples, which limits the number of reactions. Hardly any measurements exist for fast neutrons on radioactive nuclei with half-lives of less than 100 years.
  • Measurements of elastic scattering cross sections are typically based on total reaction measurements. The reduction of the neutron flux in the sample is used to derive the cross sections. In principle, this technique allows the investigation of radioactive material. The most important prerequisite is the production of enough sample material. Current alf-life limits are about 1 month or longer. 
  • Inelastic scattering reactions including (n,2n)  are particularly difficult to measure. Hardly any measurements on radioactive nuclei exist. The reason is that traditional methods require the detection of gammas or neutrons in a background of elastically scattered neutrons, which can interact with the detector or other materials.