Engineering topics
Publications and source records attributed to Døssing, Thomas.
Here, we present a simple semiclassical treatment of photon cascades, suitable for use in nuclear fission simulation codes. The approximation is here developed for E1 and E2 transitions and its quality is illustrated for a variety of two-photon cascades. Implementation of the treatment into Monte Carlo simulations would make it possible to address photon correlation observables quantitatively.
We discuss how the measurement of photon angular correlations can reveal information about the orientation of the fission fragment angular momenta. Photons from identified stretched E2 collective transitions in even-even fission product nuclei are particularly suitable because they do not affect the orientation of the nuclear spin. Their angular distribution relative to the direction of a fission fragment may reveal the orientation of the fragment spins relative to the fission axis. A novel means of probing the correlated fission fragment spins is the distribution of the opening angle between E2 photons from even-even partner fragments which reveals the mutual correlation of the fragment spins, if the photon helicities can be determined, demonstrating the potential power of helicity measurements in fission.
Fission-fragment mass and total-kinetic-energy (TKE) distributions following fission of even-even nuclides in the region \(74 \le Z \le 126\) and \(92 \le N \le 230\) , comprising 896 nuclides have been calculated using the Brownian shape-motion method. The emphasis is the region of superheavy nuclei. To show compatibility with earlier results the calculations are extended to include earlier studied regions. An island of asymmetric fission is obtained in the superheavy region, \(106\le Z\le 114\) and \(162\le N\le 176\) , where the heavy fragment is found to be close to \(^{208}\) Pb and the light fragment adjusts accordingly. Most experimentally observed \(\alpha \) -decay chains of superheavy nuclei with \(Z > 113 \) terminate by spontaneous fission in our predicted region of asymmetric fission. In these cases, the pronounced large asymmetry is accompanied by a low TKE value compatible with measurements.