Numerical simulation of an experimental setup for measuring capture and fission reactions at n_TOF (CERN)

Full description

Plutonium (Pu) is produced in current power reactors that use uranium (U) for fuel. Pu-239 is produced by neutron capture on U-238 and then double β decay (U-238(n,γ)U-239 –> Np-239 –> Pu-239). Pu-240 and Pu-241 are produced by successive captures on Pu-239. At the end of a cycle, when the fuel is spent, the fissile isotopes of plutonium (Pu-239, Pu-241) contribute significantly to energy production. In the case of a reactor using plutonium as fuel, the contribution of Pu-241 is important from the beginning of the cycle. Pu-241 is not well known because of the difficulties inherent to its study, on the one hand because of its short half-life (~14 years) and on the other hand because of its decay into Am-241 whose very high capture cross-section disturbs the measurement. The Nuclear Energy Agency therefore recommends to improve the accuracy of the capture and fission cross sections of Pu-241.
The capture cross section of Pu-241 is about 4 times smaller than the fission cross section in the energy range of interest. In order to realize an accurate measurement of the capture it is thus necessary to develop a device for the detection of gammas and the identification of those coming from the fission. In the proposed experiment at the CERN n_TOF neutron source, gammas from the (n,γ) and (n,f) reactions are detected by a 4pi calorimeter (TAC) while fission events are identified by a fission chamber (CaF) containing Pu-241 samples placed in the center of the TAC. This measurement will improve the accuracy of the capture cross section while providing additional information on the fission reaction (prompt gammas and cross section).
In order to design the elements of the detectors (CaF and samples in particular) and to demonstrate the feasibility of the measurement, it is necessary to carry out numerical simulations. During the internship, the candidate will contribute to the preparation of the experiment within the host team. The candidate will carry out numerical simulations of the experimental set-up (TAC + Fission Chamber + samples) using the Geant4 code and will propose preliminary specifications for the design of the Fission Chamber and the Pu-241 samples.
The internship is intended to be followed by a PhD thesis on the same subject, pending approval of the subject, candidate, funding, etc…

Location

Saclay

Internship conditions

• Internship duration: 6 months
• Level of study: Bac+5
• Training: Ingenieur/Master
• Continuation in PhD thesis: Yes
• Application deadline: 1 février 2023

Useful methods and technics:
Geant4 simulation code; Programmation with ROOT and C/C++ languages; Experimental techniques

Computer languages and software:
Geant4, ROOT, C/C++

Supervisor

DUPONT Emmeric
Phone: +33 1 69 08 75 53
Email :

Head of the laboratory DPhN / LEARN

LETOURNEAU Alain
Phone: +33 1 69 08 76 01