Correlations of neutron multiplicity and $\gamma$-ray multiplicity with fragment mass and total kinetic energy in spontaneous fission of ${}^{252}\mathrm{Cf}$

The dependence of correlations of neutron multiplicity $\nu$ and $\gamma$-ray multiplicity $M_{\gamma }$ in spontaneous fission of ${}^{252}\mathrm{Cf}$ on fragment mass $A^{*}$ and total kinetic energy (TKE) have been investigated by employing the ratio of $M_{\gamma }/\nu$ and the form of $M_{\gamma }\left(\nu \right)$. We show for the first time that $M_{\gamma }$ and $\nu$ have a complex correlation for heavy fragment masses, while there is a positive dependence of $M_{\gamma }$ for light fragment masses and for near-symmetric mass splits. The ratio $M_{\gamma }/\nu$ exhibits strong shell effects for neutron magic number $N=50$ and near doubly magic number shell closure at $Z=50$ and $N=82$. The $\gamma$-ray multiplicity $M_{\gamma }$ has a maximum for $\text{TKE}=165–170$ MeV. Above 170 MeV $M_{\gamma }$(TKE) is approximately linear, while it deviates significantly from a linear dependence at lower TKE. The correlation between the average neutron and $\gamma$-ray multiplicities can be partly reproduced by model calculations.

Figure 1

Schematic diagram of the experimental setup.

Figure 2

The efficiency of the LS301 neutron detector for different energy thresholds.

Figure 3

Comparison of simulated spectra for HPGe detector and tests with ${}^{137}\mathrm{Cs}$ source.

Figure 4

The dependence of the ratio of average $\gamma$-ray yield $M_{\gamma }\left(A^{*}\right)$ to the average neutron multiplicity $\nu \left(A^{*}\right)$ on the individual fragment mass.

Figure 5

The correlation of the neutron multiplicity $\nu$ and the $\gamma$-ray multiplicity $M_{\gamma }$ for light fragments $85<A^{*}<123$.

Figure 6

The correlation of the neutron multiplicity $\nu$ and the $\gamma$-ray multiplicity $M_{\gamma }$ for light fragments $124<A^{*}<131$.

Figure 7

The correlation of the neutron multiplicity $\nu$ and the $\gamma$-ray multiplicity $M_{\gamma }$ for light fragments $132<A^{*}<167$.

Figure 8

The $\gamma$-ray multiplicity $M_{\gamma }$ as a function of the total fragment kinetic energy TKE.