An Upgrade for the 1.4 MeV/u Gas Stripper at the GSI UNILAC

The GSI UNILAC will serve as part of an injector system for the future FAIR facility, currently under construction in Darmstadt, Germany. For this, it has to deliver short-pulsed, high-current, heavy-ion beams with highest beam quality. An upgrade for the 1.4 MeV/u gas stripper is ongoing to increase the yield of uranium ions in the desired charge state. The new setup features a pulsed gas injection synchronized with the beam pulse transit to increase the effective density of the stripper target while keeping the gas load for the differential pumping system low. Systematic measurements of charge state distributions and energy-loss were conducted with 238U-ion beams and different stripper gases, including H2 and He. By using H2 as a stripper gas, the yield into the most populated charge state was increased by over 50%, compared to the current stripper. Furthermore, the high gas density, enabled by the pulsed injection, results in increased mean charge states

Online chemical adsorption studies of Hg, Tl, and Pb on SiO2 and Au surfaces in preparation for chemical investigations on Cn, Nh, and Fl at TASCA

Online gas-solid adsorption studies with single-atom quantities of Hg, Tl, and Pb, the lighter homologs of the superheavy elements (SHE) copernicium (Cn, Z =112), nihonium (Nh, Z =113), and flerovium (Fl, Z =114), were carried out using short-lived radioisotopes. The interaction with Au and SiO 2 surfaces was studied and the overall chemical yield was determined. Suitable radioisotopes were produced in fusion-evaporation reactions, isolated in the gas-filled recoil separator TASCA, and flushed rapidly to an adjacent setup of two gas chromatography detector arrays covered with SiO 2 (first array) and Au (second array). While Tl and Pb adsorbed on the SiO 2 surface, Hg interacts only weakly and reached the Au-covered array. Our results contribute to elucidating the influence of relativistic effects on chemical properties of the heaviest elements by providing experimental data on these lighter homologs

U28+^{28+}-intensity record applying a H2_2-gas stripper cell

To meet the Facility for Antiproton and Ion Research science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. For this an advanced upgrade program for the UNILAC is ongoing. Stripping is a key technology for all heavy ion accelerators. For this an extensive research and development program was carried out to optimize for high brilliance heavy ion operation. After upgrade of the supersonic N_{2}-gas jet (2007), implementation of high current foil stripping (2011) and preliminary investigation of H_{2}-gas jet operation (2012), recently (2014) a new H_{2}-gas cell using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An obviously enhanced stripper gas density as well as a simultaneously reduced gas load for the pumping system result in an increased stripping efficiency, while the beam emittance remains the same. A new record intensity (7.8 emA) for ^{238}U^{28+} beams at 1.4  MeV/u has been achieved applying the pulsed high density H_{2} stripper target to a high intensity ^{238}U^{4+} beam from the VARIS ion source with a newly developed extraction system. The experimental results are presented in detail

Development of Pulsed Gas Strippers for Intense Beams of Heavy and Intermediate Mass Ions

The GSI UNILAC together with SIS18 will serve as injector for the future FAIR. A modified 1.4~MeV/u gas stripper setup has been developed, aiming at an increased yield into the particular desired charge state. The setup delivers short pulses of high gas density in synchronization with the beam pulse. This provides a higher gas density. Different gases as stripping targets were tested. Measurements with various isotopes and gas densities were conducted to investigate the stripping properties. High intensity beams of ²³⁸U⁴⁺ were successfully stripped using hydrogen as stripping gas. The stripping efficiency was significantly increased while the beam quality remained suitable. The new stripper setup and major results achieved during the development are presented. Problems with the fast valves arose while they were used for a longer duration. Another revision of the setup took place to exchange the valves. In parallel, the installation of the required infrastructure for regular operation of the gas stripper using hydrogen was planned

In situ synthesis of volatile carbonyl complexes with short-lived nuclides

Rapid in situ formation of metal carbonyl complexes with short-lived nuclides has been demonstrated to be feasible with recoiling ions formed in nuclear fusion and fission reactions. These carbonyl complexes are highly volatile and can be transported rapidly in a gas-stream to counting or chemistry devices. This method was already successfully applied in the chemical investigation of the superheavy element seaborgium (Z = 106) and appears promising for various fields of nuclear research. In this article, we give an overview on the current status of metal carbonyl complex studies with short-lived d-element isotopes.status: publishe