Energy dependence of proton induced fission cross sections for heavy nuclei in the energy range 200–1000 MeV

Total cross sections for proton induced fission of ${}^{\mathrm{nat}}\mathrm{Pb}$, ${}^{209}\mathrm{Bi}$, ${}^{232}\mathrm{Th}$, ${}^{233}\mathrm{U}$, ${}^{235}\mathrm{U}$, ${}^{238}\mathrm{U}$, ${}^{237}\mathrm{Np}$, and ${}^{239}\mathrm{Pu}$ nuclei were measured in the range 200–1000 MeV with an energy step of 100 MeV. The experiment was carried out at 1 GeV in a PNPI synchrocyclotron. Complementary fragments of the binary fission from a thin target were detected in coincidence by two parallel plate avalanche counters (PPAC) located close to the target. An assembly of the two PPACs and with the target in between them was placed directly into the beam, which provided a large solid angle acceptance. The beam monitoring system employed a scintillation counter telescope that was used for direct proton counting as well as for registration of the elastic $\mathit{pp}$-scattering events from the auxiliary (${\mathrm{CH}}_2){}_n$ target. The measured energy dependence of the total fission cross sections is presented. The results are compared with other available experimental data as well as with calculations in the frame of the cascade-evaporation model.

Figure 1

System of beam transport. D, copper degrader; BM, bending magnet; C1, C2, C3, A collimators; ML1, ML2, quadrupole doublets.

Figure 2

Schematic drawing of the method of fission fragment registration. 1, target; 2, backing; 3, target support; 4, PPAC; HV, high voltage; FP, fast amplifier; D, discriminator; AND, coincidence unit; CDC, charge-to-digital converter.

Figure 3

Registration efficiency of the PPAC for fission fragments of ${}^{252}\mathrm{Cf}$ versus the anode-cathode potential.

Figure 4

(a) Amplitude scatter plot of fission events for the uranium target. (b) Distribution over the sum of the amplitudes.

Figure 5

Experimental setup. 1, chamber filled by heptane; 2, entrance window; 3, PPACs; 4, target; S1, S2, S3, S4, S5, and S6 scintillation counters.

Figure 6

Electronic scheme.

Figure 7

Energy dependence of fission cross sections for ${}^{239}\mathrm{Pu}$. Solid circles, our data; open circles, data of previous experiments; dashed line, parametrization from Ref. [2]; solid line, the results of calculations in the framework of the cascade-evaporation model.

Figure 8

Energy dependence of fission cross sections for ${}^{237}\mathrm{Np}$. Solid circles, our data; open circles, data from Refs. [2, 3]; dashed line, a parametrization from Ref. [2]; solid line, theoretical calculation.

Figure 9

Energy dependence of the fission cross sections for ${}^{238}\mathrm{U}$. Solid circles, our data; open circles, data from Refs. [2, 3]; dashed line, a parametrization from Ref. [2]; solid line, theoretical calculation.

Figure 10

Energy dependence of fission cross sections for ${}^{235}\mathrm{U}$. Solid circles, our data; open circles, data from Refs. [2, 3]; dashed line, a parametrization from Ref. [2]; solid line, theoretical calculation.

Figure 11

Energy dependence of fission cross sections for ${}^{233}\mathrm{U}$. Solid circles, our data; open circles, data from Refs. [2, 3]; dashed line, a parametrization from Ref. [2]; solid line, theoretical calculation.

Figure 12

Energy dependence of fission cross sections for ${}^{232}\mathrm{Th}$. Solid circles, our data; open circles, data from Refs. [2, 3]; dashed line, a parametrization from Ref. [2]; solid line, theoretical calculation.

Figure 13

Energy dependence of fission cross sections for ${}^{209}\mathrm{Bi}$. Solid circles, our data; open circles, data from Refs. [2, 3]; dashed line, a parametrization from Ref. [2]; solid line, theoretical calculation.

Figure 14

Energy dependence of fission cross sections for ${}^{\mathrm{nat}}\mathrm{Pb}$. Solid circles, our data; open circles, data from Refs. [2, 3]; dashed line, a parametrization from Ref. [2]; solid line, theoretical calculation.

Figure 15

Dependence of total fission cross sections on the parameter $Z^2/A$ of the target nucleus.