A setup for identifying low-energy (1–10 MeV) ions with charges Z ≥ 1 by simultaneously measuring the energy losses and the time of flight is described. The setup is composed of a multiwire proportional chamber and a strip silicon detector, which are used to measure the ion energy, and two low-pressure avalanche wireless detectors for measuring the energy losses and the time of flight. Results obtained in measuring α particles from 226Ra source and p, Be, C, and O ions produced on the ITs-100 cyclotron at the Flerov Laboratory of Nuclear Reactions are presented.

Описывается установка, предназначенная для индентификации ионов с зарядами Z 1 в интервале малых энергий (1–10 МэВ) с помощью одновременного измерения удельных потерь и времени пролета. Установка содержит координатную многопроволочную камеру и стриповый полупроводниковый детектор для измерения энергии ионов и два лавинных беспроволочных детектора низкого давления для измерения потерь энергий и времени пролета ионов. Представлены результаты измерения -частиц от 226Ra. Даны результаты идентификации ионов (p, Be, C, O), полученных на циклотроне ИЦ-100 ЛЯР ОИЯИ.

New results from a series of experiments dedicated to the study of the C-12 exotic state (the so-called Hoyle state) are presented. In spite of the many investigations that have been carried out, the structure of this state (which lies above the threshold for breaking up into three alpha particles) is still unknown. The different models assume that the nucleus has an abnormally large size in this excited state. However, until recently, methods for measuring the radii of unbound states have not been suggested. The best way to solve this problem seems to be by measuring the angular distributions of elastic and inelastic scattering of C-12 on different target nuclei, and the determination of the radii is based on the fact that, at small scattering angles, the cross sections for direct reactions at high enough energies behave like Frauenhofer diffraction on a black ball. Accordingly, an experiment was performed aimed at measuring the elastic and inelastic angular distributions of C-12 with an energy of (121.5 +/- 0.5) MeV on a C-12 target. The elastic scattering was measured in the angular range from 18 degrees to 50 degrees in the c.m. system with uncertainty in the angle of measurement equal to Delta theta = +/- 0.6 degrees. The inelastic cross section was measured for the C-12 excited state 2(+) (4.44 MeV) and 0(+) (7.65 MeV). Estimates were made for the diffraction radii for the ground and excited states. An increase was observed in the radius of the state at 7.65 MeV compared to those of the ground and first excited states.

New results from a series of experiments dedicated to the study of the 12 C exotic state (the so-called Hoyle state) are presented. In spite of the many investigations that have been carried out, the structure of this state (which lies above the threshold for breaking up into three alpha particles) is still unknown. The different models assume that the nucleus has an abnormally large size in this excited state. However, until recently, methods for measuring the radii of unbound states have not been suggested. The best way to solve this problem seems to be by measuring the angular distributions of elastic and inelastic scattering of 12 C on different target nuclei, and the determination of the radii is based on the fact that, at small scattering angles, the cross sections for direct reactions at high enough energies behave like Frauenhofer diffraction on a black ball. Accordingly, an experiment was performed aimed at measuring the elastic and inelastic angular distributions of 12 C with an energy of (121.5 ± 0.5) MeV on a 12 C target. The elastic scattering was measured in the angular range from 18° to 50° in the c.m. system with uncertainty in the angle of measurement equal to Δθ = ± 0.6°. The inelastic cross section was measured for the 12 C excited state 2 + (4.44 MeV) and 0 + (7.65 MeV). Estimates were made for the diffraction radii for the ground and excited states. An increase was observed in the radius of the state at 7.65 MeV compared to those of the ground and first excited states.

A profilometer for diagnostics of secondary ion beams with Z ≥ 2 is described. Two methods of beam profile measurements are compared: a counting method, when pulses from each particle are registered, and a current method with channel-by-channel measurement of the integral current. The counting characteristics and the lifetimes of the profilometer for these methods of beam profile measurements are compared.

Описан профилометр для диагностики вторичных пучков ионов с Z 2. Проведено сравнение двух методов измерения профиля пучков таким профилометром: счетного, когда регистрируются импульсы от каждой частицы; токового с поканальным измерением интегрального тока. Проведены сравнение и оценка счетных характеристик и сроков службы профилометра для двух методов измерения профиля пучка.

Two methods for obtaining monochromatic beams of radioactive nuclei with energies near the Coulomb barrier on Joint Institute of Nuclear Research accelerator complex DRIBs are described. In the first method, an MSP-144 magnetic spectrometer was used as the monochromator of low-energy 6He beam obtained after passing through an energy degrader. In the second method, a specially developed probe was used for experiments with the internal beam of the DRIBs complex post-accelerator (the U-400 cyclotron).

Two methods for obtaining monochromatic beams of accelerated 6He ions with energies around the Coulomb barrier on the DRIB accelerator complex at the Joint Institute for Nuclear Research (JINR) is described. In the first method, the MSP-144 magnetic spectrometer is used as a monochromator of low-energy 6He beam after its passing through an energy absorber. The energy resolution of the 6He beam, which is 500 keV, is governed by the linear dimension of the target in the focal plane (18 mm). In the other method, a special probe is used to investigate nuclear reactions with accelerated 6He beams without loss of the beam intensity. With this probe, it is possible to perform experiments on the internal beam of the postaccelerator (U-400 cyclotron) of the DRIB complex. As a result, a 6He beam with a required energy and a beam resolution of 150 keV or better is produced at the target.

Описываются два метода получения монохроматических пучков ускоренных ионов 6 с энергией вблизи кулоновского барьера реакций на ускорительном комплексе DRIBs ОИЯИ. В первом методе магнитный спектрометр МСП-144 использовался в качестве монохроматора пучка частиц 6 низкой энергии, полученного после прохождения поглотителя энергии. Линейный размер мишени вдоль фокальной плоскости (18 мм) определял разрешение пучка 6 по энергии, которое составляло 500 кэВ. Во втором методе для исследования ядерных реакций с ускоренными пучками частиц 6He без потери интенсивности использовался специально разработанный зонд, позволяющий проводить эксперименты на внутреннем пучке постускорителя (циклотрона У-400) комплекса DRIBs. Это позволило получать на мишени пучок 6He требуемой энергии с разрешением пучка не хуже 150 кэВ.

Excitation functions of the reaction products were measured for the reactions induced by He-4,He-6 projectiles on Pb-206,Pb-208 targets, leading to the same compound nucleus. This was accomplished by using the stacked-foil-activation technique. The identification of the reaction products (accumulated in the Pb targets) was done by their radioactive alp ha decays. The excitation functions for the 2n evaporation channels were obtained at energies below the sub-Coulomb barrier region. A large value of the fusion cross section was observed in the case of the reaction induced by the weakly bound He-6 projectile.

We present new measurements of the α + 12 C elastic and inelastic (to the states 4.44, 7.65, and 9.64 MeV) scattering at E lab = 110 MeV in the wide angular range from ∼10° to 175°, which enable us to examine the condensate and cluster properties of the low-lying excited states in 12 C. We present the diffraction-radius analysis of our data together with a considerable amount of the existing data. The magnitudes of the diffraction radii for the ground and the first excited (4.44 MeV) states are found to be equal, whereas they appear to be enhanced by ∼0.6 fm both for 7.65 and 9.64 MeV states. This result shows that the radius of the Hoyle’s 0 2 + , 7.65 MeV state in 12 C is by a factor of ∼1.2–1.3 larger than that of the ground state. It is demonstrated that the direct transfer mechanism of 8 Be dominates at the largest angles in all four reactions reported here. The configuration corresponding to the transfer of 8 Be in its ground state ( I π = 0 + ) with L = 0 turns out to be the most important for the 7.65 MeV state of 12 C. Evidence of existence of some features of α -condensed structure of the Hoyle’s 0 2 + state in 12 C was obtained: its enhanced radius and large contribution of α -particle configuration with L = 0.

Excitation functions of the reaction products were measured for the reactions induced by 4,6He projectiles on 206,208Pb targets, leading to the same compound nucleus. This was accomplished by using the stacked‐foil‐activation technique. The identification of the reaction products (accumulated in the Pb targets) was done by their radioactive alp ha decays. The excitation functions for the 2n evaporation channels were obtained at energies below the sub‐Coulomb barrier region. A large value of the fusion cross section was observed in the case of the reaction induced by the weakly bound 6He projectile.

Experimental excitation functions are presented for fusion-evaporation and transfer reactions in the interaction of Li-6 with Bi and Pt targets. The data on the cross sections obtained for the produced evaporation residues are in agreement with calculations within the framework of the statistical model using the ALICE-MP code. Enhancement of the cross section for deuteron transfer reactions is observed at energies below the Coulomb barrier. The results are discussed from the point of view of how the nuclear cluster structure influences the probability of interaction at near-barrier energies.

Excitation functions of the reaction products were measured for the reactions induced by 4,6He projectiles on 208,206Pb targets, leading to the same compound nucleus. This was accomplished by using the stacked-foil activation technique. The identification of the reaction products (accumulated in the Pb targets) was done by their radioactive α-decays. The excitation functions for the various products were obtained at energies including the sub-Coulomb barrier region. A large value of the fusion cross section was observed in the case of the reaction induced by the weakly bound 6He projectile.

Измерены функции возбуждения реакций слияния с последующим испарением нейтронов 197Au(6He, xn)203-xnTl, где x = 2–7, а также реакций передачи нейтронов с образованием изотопов 196Au и 198Au. Наблюдалось необычно высокое сечение образования изотопа 198Au при энергиях ниже кулоновского барьера. Рассмотрены возможные механизмы образования и распада продуктов реакций передачи нуклонов.

The excitation functions for the fusion reactions with subsequent neutron evaporation, 197Au(6He, xn)203 − xnTl (x = 2−7), and the neutron transfer reactions with production of the 196Au and 198Au isotopes have been measured. Unusually high cross section of the 198Au isotope production at energies below the Coulomb barrier has been observed. Possible mechanisms of production and decay of the transfer reaction products are considered.

. Excitation functions for evaporation residues in the reactions 197 Au( 6 He, x n) 203- x n Tl, x = 2-7, and 206 Pb( 6 He, 2n) 210 Po, as well as for neutron transfer reactions for the production of 196 Au and 198 Au in the interaction of 6 He with 197 Au were measured. The 6 He beam was obtained from the accelerator complex for radioactive beams DRIBs (JINR). The maximum energy of the beam was about 10AMeV and the intensity reached 2×10 7 pps. The stacked-foil activation technique was used directly in the beam extracted from the cyclotron or in the focal plane of the magnetic spectrometer MSP-144. The identification of the reaction products was done by their radioactive γ- or α-decay. The fusion reaction with the evaporation of two neutrons was characterized by an increase in the cross-section compared to statistical model calculations. The analysis of the data in the framework of the statistical model for the decay of excited nuclei, which took into account the sequential fusion of 6 He has shown good agreement between the experimental and the calculated values of the cross-sections in the case of sub-Coulomb-barrier fusion in the 206 Pb + 6 He reaction. An unusually large cross-section was observed below the Coulomb barrier for the production of 198 Au in the interaction of 6 He with 197 Au. Possible mechanisms of formation and decay of transfer reaction products are discussed.