V. I. Zhemenik

Independent yields of Kr and Xe fragments in the photofission of 237Np and 243Am odd nuclei

Results are presented that were obtained by measuring the independent yields of Kr (A = 89–93) and Xe (A = 135–142) appearing as fragments in the photofission of 237Np and 243Am odd nuclei. The respective experiments were performed in a beam of bremsstrahlung photons from electrons accelerated to an energy of 25 MeV at the microtron of the Laboratory of Nuclear Reactions at the Joint Institute for Nuclear Research (JINR, Dubna). Use was made of the procedure involving the transportation of fragments emitted from the target by a gas flow along a capillary and the condensation of inert gases in a cryostat at liquid-nitrogen temperature. The identification of Kr and Xe appearing as fragments was performed by the gamma spectra of their daughter products. The mass-number distributions of the independent yields of Kr and Xe isotopes were obtained, along with those for the complementary fragments (Y and La in the fission of 237Np and Nb and Pr in the fission of 243Am).

Independent yields of Kr and Xe isotopes in the photofission of heavy nuclei

The yields of Kr (A = 87–93) and Xe (A = 138–143) primary fission fragments produced in 232Th, 238U, and 244Pu photofission upon the scission of a target nucleus and neutron emission were measured in an experiment with bremsstrahlung from electrons accelerated to 25 MeV by a microtron, and the results of these measurements are presented. The experimental procedure used involved the transportation of fragments that escaped from the target by a gas flow through a capillary and the condensation of Kr and Xe inert gases in a cryostat at liquid-nitrogen temperature. The fragments of all other elements were retained with a filter at the capillary inlet. The isotopes of Kr and Xe were identified by the γ spectra of their daughter products. The mass-number distributions of the independent yields of Kr and Xe isotopes are obtained and compared with similar data on fission induced by thermal and fast neutrons; the shifts of the fragment charges with respect to the undistorted charge distribution are determined. Prospects for using photofission fragments in studying the structure of highly neutron-rich nuclei are discussed.

Transport of Fission Fragments by a Gas Flow with Aerosols

An experimental setup for transporting fission fragments by a gas flow with aerosols is described. The results of tests of the setup on fragments of 238U photofission by bremsstrahlung from a microtron are presented. The parameters of the setup obtained experimentally (the transport efficiency reaches 70%, and the transport time reaches 0.1 s to a distance of 1 m) make it possible to successfully use it in experiments on the fission of heavy nuclei and study of properties of fission fragments

A technique for measuring the quadrupole deformation parameter of transuranium nuclei

A method for determining the quadrupole deformation parameter of transuranium nuclei is presented. This method is based on giant dipole resonance splitting in the photofission cross section. The experimental setup containing an avalanche counter of fission fragments, as well as a method for reconstructing the cross section from the measured dependence of the photofission reaction yield on the endpoint energy of the bremsstrahlung spectrum, are described. The setup was tested on the bremsstrahlung beam of the MT-25 microtron at the Flerov Laboratory for Nuclear Reactions of the Joint Institute for Nuclear Research. The test results—in particular, the measured excitation function of the uranium photofission reaction—are presented.

Efficient β-BaB2O4 frequency-doubler for ultraviolet laser spectroscopy of radionuclides

Efficient frequency-doubling systems with a specific geometry configuration are used in order to obtain ultraviolet (UV) cw coherent radiation for laser spectroscopy of exotic radionuclides in the 30 ⩽ &Zgr; ⩾ 58 region. The compensation of the walk-off angle and the use of external cavity for second harmonic generation give most noticeable doubler efficiency increase. Three frequency-conversion systems are proposed for laser spectroscopy of nuclei. Second harmonic efficiency of 18% is obtained. Perspectives of using the injection seeded nonlinear converters in laser spectroscopy are also discussed.

LASER IONIZATION SPECTROMETER BASED ON A BEAM OF CHARGED CYCLOTRON PARTICLES

An experimental setup is described for the measurement of optical atomic spectra using a beam of charged cyclotron particles. The setup consists of a gas chamber for collecting and transporting the products of nuclear reactions, an ionization spectrometer based on a pulsed Nd:YAG laser, and a system of electronic modules. The setup allows the investigation of nuclei at the limits of nucleonic stability.