Muon-induced fission in ²³⁵U and ²³⁸U

Abstract

Muon-induced prompt and delayed fission yields in 235U and 238U have been measured. A coincidence with the muonic uranium Kα X-rays was used to identify the muon stop in the target. The experimental absolute fission yields per muon stop were 0.142 ± 0.023 for 235U and 0.068 ± 0.013 for 238U. The disappearance rate of muons from the 1s state of muonic uranium has also been measured in the fission mode. Muon-induced fission lifetimes were 71.6 ± 0.6 ns for 235U and 77.2 ± 0.4 ns for 238U. No evidence for a short-lifetime fission – isomer component was found. Comparison of lifetime results with previously measured values in the electron, gamma, and neutron decay modes indicated that the systematic discrepancies could be explained by muon capture on fission fragments produced from prompt fission.

The study of prompt and delayed muon induced fission

“…The amount of prompt events is given by the difference between this integral and the sum of events with t < r 0. [19] a, [20] [191" [8] a The result is depending on the data evaluation procedure applied a The error is essentially due to the error given in Table 5a. The results obtained by this procedure are confirmed by the conventional way of fitting, but the errors are smaller.…”

Detecting special nuclear material using muon-induced neutron emission

“…In light nuclei, negative muons can also decay as a free particle, 𝜇 − → 𝑒 − + 𝜈 𝑒 + 𝜈 𝜇 ̅̅̅, but when they are stopped LA-UR-14-21076 in a material with high atomic number (Z), they can be captured by a bound proton and produce a neutron and a neutrino, 𝜇 − ⨂ 𝐴 → 𝑛 + (𝐴 − 1) * + 𝜈 𝜇 ̅̅̅. The lifetime of a muonic atom depends on its atomic number and was measured to be 71.6 ± 0.6 ns for 235 U and 77.2 ± 0.4 ns for 238 U [25].…”

Cosmic Ray Muon Radiography Applications in Safeguards and Arms Control

“…Negative muons that are stopped in fissile material and captured in atomic orbitals can undergo interactions with the nucleus that lead to subsequent neutron emission [11]. The lifetimes of these muonic atoms are characteristic to each isotope, and have been measured to be 71.6±0.6 ns for 235 U and 77.2±0.4 ns for 238 U [36]. With a combination of muon tracking detectors and fast neutron detectors, muons which encounter fissile material can be identified by detecting the emitted neutrons.…”