Determination of ${}^{59}\mathrm{Ni}(n,xp)$ reaction cross sections using surrogate reactions

The ${}^{59}\mathrm{Ni}(n,xp)$ reaction cross sections have been measured following the surrogate reaction ratio method in the equivalent neutron energy range of 11.9–15.8 MeV by populating the compound nucleus ${}^{60}\mathrm{Ni}^{*}$ through transfer reaction ${}^{56}\mathrm{Fe}({}^6\mathrm{Li},d)$ at $E_{\text{lab}}=35.9$ MeV. The ${}^{59}\mathrm{Co}({}^6\mathrm{Li},\alpha ){}^{61}\mathrm{Ni}^{*}$ transfer reaction at $E_{\text{lab}}=40.5$ MeV has been used as the reference reaction which is the surrogate of ${}^{60}\mathrm{Ni}(n,xp)$ reaction populating the compound nucleus ${}^{61}\mathrm{Ni}^{*}$. The proton decay probabilities have been determined by measuring evaporated protons at backward angles in coincidence with projectile like fragments (PLFs, either $d$ or $\alpha$) detected around grazing angles. The cross sections for the reference reaction ${}^{60}\mathrm{Ni}(n,xp)$ are taken from jendl-4.0 library, which closely reproduce the available experimental data. The cross sections for the desired ${}^{59}\mathrm{Ni}(n,xp)$ reaction so obtained compare well with the nuclear-reactions-model code talys-1.8 using microscopic level densities. The present experimental data are consistent with the evaluated data library of rosfond-2015 but not with tendl-2015 and endf/b-viii, indicating the need of new evaluations for this reaction of importance to fusion technology.

Figure 1

Schematic of ${}^{59}\mathrm{Ni}$ formation pathways in a typical fusion reactor.

Figure 2

A schematic diagram of experimental setup inside a 1.5-m-diameter scattering chamber. Here, T1 and T2 are particle telescopes for detecting the projectile like fragments (PLFs) placed at a distance of about 17 cm from the target center. The strip telescopes S1 and S2 have been used to identify the evaporated particles like proton and $\alpha$ and placed at about the same distance as T1 and T2.

Figure 3

A typical plot of particle identification (PI) versus total energy ($E_{\mathrm{tot}}$) of the PLFs produced in ${}^6\mathrm{Li}+{}^{56}\mathrm{Fe}$ reaction at $E_{\mathrm{lab}}=35.89$ MeV, measured in T1.

Figure 4

A typical two-dimensional $\mathrm{\Delta }E$ versus $E_{\text{tot}}$ spectrum obtained from one of the 32 $\mathrm{\Delta }E\text{−}E$ strip combinations placed at backward angles, for ${}^6\mathrm{Li}+{}^{56}\mathrm{Fe}$ reaction at $E_{\text{lab}}=35.89$ MeV.

Figure 5

A typical PLF -proton TAC versus deuteron (PLF) energy plot in the ${}^6\mathrm{Li}+{}^{56}\mathrm{Fe}$ reactions at $E_{\text{lab}}=35.9$ MeV.

Figure 6

Measured proton energy spectra in coincidence with deuteron PLFs for the ${}^6\mathrm{Li}+{}^{56}\mathrm{Fe}$ reaction at 35.89 MeV corresponding to a compound nucleus excitation energy of $\approx 25$ MeV. The statistical model prediction by pace4 normalized to the data is shown as a continuous line.

Figure 7

A comparison of proton emission cross sections, estimated using talys-1.8, for pre-equilibrium, direct, compound nucleus, and total production in case of two different reactions, i.e., (a) $\alpha$ transfer and (b) deuteron transfer reactions, respectively. The “direct” production in the second case is very small and cannot be seen above the x axis.

Figure 8

Ratio of proton counts in coincidence to singles as a function of excitation energy of the composite nucleus ${}^{60}\mathrm{Ni}^{*}$ obtained using the gate of the PLF telescopes (a) T1 and (b) T2.

Figure 9

Angular distributions of protons produced in ${}^6\mathrm{Li}+{}^{56}\mathrm{Fe}$ system as measured by strip telescopes in coincidence with PLFs detected by (a) T1 and (b) T2.

Figure 10

Excitation energy spectra of the target-like fragments produced in ${}^6\mathrm{Li}+{}^{56}\mathrm{Fe}$ and ${}^6\mathrm{Li}+{}^{59}\mathrm{Co}$ reactions corresponding to PLF deuteron and $\alpha$ respectively with [(a), (b)] and without [(c), (d)] coincidence with evaporated protons.

Figure 11

${}^{60}\mathrm{Ni}(n,xp)$ data from jendl compared to available experimental data taken from EXFOR.

Figure 12

Experimental cross sections for ${}^{59}\mathrm{Ni}(n,xp)$ reactions have been compared with talys-1.8 predictions using different level density models with (a) default parameters and (b) $rv$ adjusted parameters.

Figure 13

talys-1.8 results for cross sections of $(n,p),(n,2p),(n,np)$ components of ${}^{57,59,60,61}\mathrm{Ni}(n,xp)$ for $rv$ adjusted level density model option 5.

Figure 14

The ${}^{59}\mathrm{Ni}(n,xp)$ cross sections as a function of equivalent neutron energy along with the ones from various nuclear data libraries and talys-1.8 nuclear model calculations for the cases of enriched and natural targets as discussed in the text.