V. G. Vovchenko

Total cross sections for fission of heavy nuclei by intermediate-energy protons

The results of measuring total cross sections for proton-induced fission of natPb, 209Bi, 232Th, 233U, 235U, 238U, 237Np, and 239Pu nuclei at proton energies from 200 to 1000 MeV are reported. The measurements were carried out in steps of ≈100 MeV. Complementary fission fragments were detected in coincidence by two parallel-plate avalanche gas counters placed in the beam line on both sides of the thin target close to it. Energy and isotope dependences of the fission cross sections are analyzed.

Inelastic interactions of fast nucleons with nuclei and fission of nuclei

The cross section for the fission of actinide nuclei that is induced by fast neutrons is considered as a fraction of the cross section for inelastic nucleon interaction with nuclei. In turn, inelastic nucleon interaction with a nucleus is treated as scattering on intranuclear nucleons. It is shown that this interaction model describes satisfactorily the cross section for the inelastic interaction of 60- to 2200-MeV nucleons for a broad set of nuclei and that the energy dependence of the cross section for the fission of actinide nuclei that is induced by 400- to 1000–MeV protons replicates the energy dependence of the cross section for inelastic interactions with respective nuclei. From the model used, it follows that the cross sections for proton-nucleus interactions exceed cross sections for respective neutron-nucleus interactions in the energy range extending up to 550 MeV; at higher energies neutron cross sections are larger than proton cross sections.

New approximations to the energy dependences of the total cross sections for the proton-induced fission of 197Au, 203Tl, natPb, and 209Bi nuclei

The total cross sections for 197Au and 203Tl fission induced by protons of energy varied from about 200 to 1000 MeV with a step of about 100 MeV are measured. New approximations to the energy dependences of the cross sections for the proton-induced fission of 197Au, 203Tl, natPb, and 209Bi nuclei are presented and discussed. For all of these nuclei, exponential functions are used as approximations.

Isotopic effect in the energy dependence of the total fission cross section of lead and 209Bi nuclei for protons with energies up to 1 GeV

The results from measurements of the total fission cross sections of 206Pb, 207Pb, and 208Pb nuclei for protons with energies from 207 to 1000 MeV and a step of ≈100 MeV. These results complemented by our data for 209Bi and the data of the EXFOR world base allow determination of absolute and relative contributions of the isotopic effect.

Analysis of data on proton-proton scattering in the energy range 100-1300 MeV

The results of a partial-wave analysis of data on proton-proton interaction in the energy range 100–1300 MeV are presented. The real parts of phase shifts were found for states of orbital angular momentum up to L = 9, while their imaginary parts were determined for states of orbital angular momentum up to L = 5. The sixth parameter of the S matrix was introduced in order to describe states of total angular momentum J = 2 and 4. The inelasticity thresholds were chosen individually for each state and were found to be substantially different from one another. The resulting solution was characterized by χ2 = 1.155 per point in the case where the number of experimental data was 12 841 and by a large imaginary part of the phase shift in the 3P2-wave state at the edge of the energy range. Special features of the interaction in orbital states are discussed along with the energy dependence of integrated amplitudes and amplitudes of the scattering matrix at zero angle.

Experimental Study of Energy Dependence of Proton Induced Fission Cross Sections for Heavy Nuclei in the Energy Range 200–1000 MeV

The results of the total fission cross sections measurements for natPb, 209Bi, 232Th, 233U, 235U, 238U, 237Np and 239Pu nuclei at the energy proton range 200–1000 MeV are presented. Experiments were carried out at 1 GeV synchrocyclotron of Petersburg Nuclear Physics Institute (Gatchina). The measurement method is based on the registration in coincidence of both complementary fission fragments by two gas parallel plate avalanche counters, located at a short distance and opposite sides of investigated target. The insensitivity of parallel plate avalanche counters to neutron and light charged particles allowed us to place the counters together with target immediately in the proton beam providing a large solid angle acceptance for fission fragment registration and reliable identification of fission events. The proton flux on the target to be studied was determined by direct counting of protons by scintillation telescope. The measured energy dependence of the total fission cross sections is presented. Obtained...

Polarization parameters of elastic pp scattering in the angular range 22.5°–42.5° at an energy of 1 GeV and partial-wave analysis of data

The polarization properties of elastic scattering are studied experimentally for pp interaction at 1 GeV. The respective experimental results are presented for the spin-transfer parameter Kn00n and the polarization Pn000 at c.m. angles of 22.5°, 27.5°, 32.5°, and 42.5° and for the analyzing power A000n at c.m. angles of 22.5° and 27.5°. The experiment employed an unpolarized proton beam from the accelerator of the Petersburg Nuclear Physics Institute, a polarized proton target, and a high-resolution magnetic spectrometer. The data from this experiment are analyzed and compared with the predictions of partial-wave analyses.