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The isotopic distribution of nuclei produced in the 50Ti + 249Cf reaction has been studied at the gas-filled recoil separator TASCA at GSI Darmstadt, which separates ions according to differences in magnetic rigidity. The bombardment was performed at an energy around the Bass barrier and with the TASCA magnetic fields set for collecting fusion-evaporation reaction products. Fifty-three isotopes located “north-east” of 208Pb were identified as recoiling products formed in non-fusion channels of the reaction. These recoils were implanted with energies in two distinct ranges; besides one with higher energy, a significant low-energy contribution was identified. The latter observation was not expected to occur according to kinematics of the known types of reactions, namely quasi-elastic, multi-nucleon transfer, deep-inelastic collisions or quasifission. The present observations are discussed within the framework of two-body kinematics passing through the formation of a composite system.

The paper overviews the challenges associated with the development of a system thermal-hydraulic code applied for lead coolant by the example of a Russian system thermal-hydraulic code HYDRA-IBRAE/LM. It presents the PIRT describing relevant thermal-hydraulic phenomena that are to be simulated to model operational transients and accidents of Russian lead-cooled reactor BREST-OD-300. The paper also mentions the points in favor of using three-fluid model as a basic one. The results of evaluation and selection of lead coolant closure relations, that could be used in system thermal-hydraulic code, are presented. The paper demonstrates that heat transfer in the lead coolant may be calculated using closure relations obtained for the other liquid metal coolants introducing correction factors depending on the value of contact thermal resistance caused, for example, by oxide films present at the surface. The paper presents recommended properties of the lead coolant and summarizes experimental research findings of the Russian project PRORYV that can be used to validate system thermal-hydraulic codes. The paper discusses validation results for HYDRA-IBRAE/LM code based on experiments carried out using a BREST-OD-300 steam generator model and those with lead coolant cooldown due to argon injection.

A new method of intermetallic target preparation is described. Based on the molecular plating technique followed by “coupled reduction”, this method allows producing stable and homogeneous metallic targets for high intensity irradiations. In the first step, the target material is electroplated on a noble metal surface, ensuring homogeneous distribution of the desired element on the target backing. In the second step, the foil with the plated material is heated in a hydrogen flow. Due to the formation of an intermetallic compound with the noble metal support, reduction of the target material with hydrogen at high temperatures becomes thermodynamically possible. Nitrates of all six investigated elements (U, Th, Am, Gd, Nd, and Eu) were electroplated with excellent yields on Pd backing foils by the molecular plating technique and completely reduced in hydrogen atmosphere. A homogeneous distribution of the target material over the whole thickness of the Pd foil was observed suggesting a pronounced diffusion of the reduced metals into the backing material already during the reduction process. A first test irradiation experiment with a thin 3.5 μm U/Pd intermetallic target is described.

Performing experiments with transactinide elements demands highly sensitive detection methods due to the extremely low production rates (one-atom-at-a-time conditions). Preseparation with a physical recoil separator is a powerful method to significantly reduce the background in experiments with sufficiently long-lived isotopes (t1/2≥0.5 s). In the last years, the new gas-filled TransActinide Separator and Chemistry Apparatus (TASCA) was installed and successfully commissioned at GSI. Here, we report on the design and performance of a Recoil Transfer Chamber (RTC) for TASCA—an interface to connect various chemistry and counting setups with the separator. Nuclear reaction products recoiling out of the target are separated according to their magnetic rigidity within TASCA, and the wanted products are guided to the focal plane of TASCA. In the focal plane, they pass a thin Mylar window that separates the ∼1 mbar atmosphere in TASCA from the RTC kept at ∼1 bar. The ions are stopped in the RTC and transported by a continuous gas flow from the RTC to the ancillary setup. In this paper, we report on measurements of the transportation yields under various conditions and on the first chemistry experiments at TASCA—an electrochemistry experiment with osmium and an ion exchange experiment with the transactinide element rutherfordium.

The new, highly efficient gas-filled TransActinide Separator and Chemistry Apparatus (TASCA) was designed and built at GSI with the aim to study chemical and physical properties of superheavy elements with atomic numbers 104 and higher produced in heavy-ion reactions with actinide targets. To reach the highest possible transmission, while exploiting an existing dipole magnet and two quadrupoles of a previously used gas-filled separator, an optimization of the ion-optical structure of TASCA was performed with the program TRANSPORT. Two modes of TASCA operation, the “High Transmission Mode” and the “Small Image-size Mode” were selected. Magnetic field measurements were carried out with the dipole and were compared with KOMPOT model calculations. Magnetic field model calculations of the dipole and the quadrupoles, including a duct and a large exit valve, were performed to optimize the pole pieces of the dipole and the ducts. This increased the efficiency up to 50%. Both modes of operation were successfully tested in first commissioning experiments.

The Transactinide Separator and Chemistry Apparatus (TASCA) is a recoil separator with maximized transmission designed for performing advanced chemical studies as well as nuclear reaction and structure investigations of the transactinide elements ( Z >103) on a one-atom-at-a-time basis. TASCA will provide a very clean transactinide fraction with negligible contamination of lighter elements from nuclear side reactions in the target. For TASCA a new target chamber was designed and built at GSI including the rotating target wheel assembly ARTESIA for beam intensities up to 2 μA (particle). For the production of longer-lived isotopes of neutron-rich heavier actinide and transactinide elements, hot fusion reactions with actinide targets are required. Here, possible target materials range from thorium up to curium or even heavier elements. For the deposition of lanthanide and actinide elements on thin aluminum and titanium backings by means of Molecular Plating (MP), a new deposition cell has been constructed that allows precise temperature control of the organic solvent and stirring of the solution. The electrode geometry ensures homogeneity of the electric field inside the cell. With the new set-up, holmium and gadolinium layers (500 μg/cm 2 ) on 2–5 μm thin titanium backings have been produced with deposition yields of the order of 90%. Systematic investigations are under way to further optimize the deposition conditions for other lanthanide and actinide elements including uranium and plutonium on different backing materials.

The problem of magnetic field reconstruction inside a sub-region in R3 from magnetic measurements on the closed boundary of this sub-region is considered. Efficiency of the proposed method, the algorithm and associated software for precision magnet systems are discussed. The results of the software verification and numerical experiments are presented. A comparison between the reconstructed field and the measured field in the M1 magnet of the separator COMBAS is given. Requirements to the position accuracy of sensors consistent with the required accuracy of magnetic field reconstruction are defined. Recommendations on magnetic scheme design for field mapping are given. These investigations have been performed at the Flerov Laboratory of Nuclear Reactions, JINR.

The high-resolution wide aperture separator COMBAS was installed and commissioned in the Flerov Laboratory of Nuclear Reactions, JINR (Dubna) [Nucl. Instr. and Meth. A 306 (1991) 123; 426 (1999) 605; 479 (2002) 467]. It is designed for in-flight radioactive beam production of short-lived isotopes and experiments with them. The separator operates in the (20–50)A MeV ion energy region. It consists of the two stages, dispersive and achromatising. The second half of the separator is a mirror symmetrical counterpart of the first one, the intermediate focal plane being the plane of the symmetry. Multipole magnets with special profiled poles are used to correct higher order aberrations at the intermediate and final foci. The 3D magnetic measurements of the analysing magnets of the separator were done. The KOMPOT program for the 3D magnetic field calculations [Doinikov et al., 1986, Preprint/CNNI atominform: B-0741, 13p; Belyaev et al., Int. Conf. “Optimisation of Finite Element Approximations”, St.Pt., Russia, 25–29 June 1995, p.101; IEEE Transact. On Magnetics, 28 (1) (1992) 908; Frenkel, Selected works, USSR Academy of Sciences publ., Moscow–Leningrad, v.1 (Electrodynamics), 1956; Proc. IEEE, 114 (7) (1967) 995; Livingston, Blewett, Particle accelerators, No. 7, McGraw-Hill, 1962, p. 253] was used for the analysis of these magnetic measurements data, as well as for the reconstruction of the magnet fields inside the total volume closed by the 3D surface, where the magnetic measurements had been performed. As a result of the magnetic field reconstruction we obtained field maps, which would be used in simulations of particle trajectories.

A systematic study of the forward-angle production of nuclei with 2⩽Z⩽11 induced in nucleus–nucleus collisions of 18O with 9Be and 181Ta in the Fermi energy domain (35 A MeV) has been performed. The reaction products were measured by using the double achromatic fragment-separator COMBAS in the spectrometry mode. The inclusive velocity, the isotopic and element distributions were measured. The dominant role of low-energy reaction mechanisms is observed.

The high-resolving wide aperture separator COMBAS has been designed and commissioned at the FLNR, JINR. Three-component magnetic measurements of all the magnets were performed. The measured data allow reconstruction of the 3D-distributions of the fields in all the magnets. 3D-maps are needed for particle trajectory simulations throughout the entire separator. The magnetic fields of analysing magnets, M 1 , M 2 , M 7 , and M 8 , contain quadrupole components of alternating sign that provide necessary beam focusing. All the magnets M 1 –M 8 , contain sextupole and octupole field components, which minimizes the second and third order aberrations. All this allowed one to increase their apertures, to form effectively a beam of the required sizes and to decrease the channel length.

The COMBAS large solid angle and high momentum acceptance and high-resolving kinematic separator has been created at the Flerov Laboratory of Nuclear Reactions, JINR, to efficiently collect extremely short-lived nuclei near the zero angle which are produced in intermediate energy fragmentation reactions with wide momentum and wide angular distributions. For the first time the M 1 M 2 M 3 M 4 F d M 5 M 6 M 7 M 8 F a magneto-optical configuration of the COMBAS separator has been realized on the strong focussing principle. The separation and trajectory analysis of particles by the separator are carried out by three parameters: the magnetic rigidity (B· ρ ), the energy loss difference in the degrader (Δ E /Δ x ) and the time-of-flight (Δ T ) of the analyzed particles. The COMBAS separator can be used efficiently both in the mode of a high- resolving spectrometer to study reaction mechanisms and in the mode of an in-flight separator in experiments on the synthesis and study of properties of short-lived exotic nuclei near the drip-lines.