0000000000184210
AUTHOR
M. Mendel
The recoil transfer chamber—An interface to connect the physical preseparator TASCA with chemistry and counting setups
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 o…
Digital liquid-scintillation counting and effective pulse-shape discrimination with artificial neural networks
Abstract A typical problem in low-level liquid scintillation (LS) counting is the identification of α particles in the presence of a high background of β and γ particles. Especially the occurrence of β-β and β-γ pile-ups may prevent the unambiguous identification of an α signal by commonly used analog electronics. In this case, pulse-shape discrimination (PSD) and pile-up rejection (PUR) units show an insufficient performance. This problem was also observed in own earlier experiments on the chemical behaviour of transactinide elements using the liquid-liquid extraction system SISAK in combination with LS counting. α-particle signals from the decay of the transactinides could not be unambigu…
Application of fast solvent extraction processes to studies of exotic nuclides
Fast solvent extraction is a chemical separation method, which can be applied to study exotic nuclides. Since about 1970 the SISAK technique, which is an on-line method based on multi-stage solvent extraction separations, has been successfully used to investigate the nuclear properties of β-decaying nuclides with half-lives down to about one second. During the last decade it has become possible to produce transactinide elements in high enough yields to investigate their chemical properties on a one-atom-at-a-time scale. For this purpose it was necessary to improve and change the detection part of the SISAK system in order to be capable to detect spontaneously fissioning and α-decaying nucli…
Review of the SISAK system in transactinide research
Abstract The performance of the SISAK 1 liquid–liquid extraction system applied in transactinide experiments has been improved with respect to the equipment itself and the way it is operated. The improvements were checked in on-line experiments, under conditions similar to those during transactinide experiments. As a result, the yield of the separation system was increased by a factor >5. Furthermore, a cleaner organic scintillation phase was obtained due to a better phase separation. This reduced the β-background, which disturbs the α-measurements. The sensitivity of the SISAK apparatus, including the gasjet and the detection system has been improved by more than one order of magnitude.
Liquid-scintillation detection of preseparated 257Rf with the SISAK-system
Abstract The fast liquid–liquid extraction system SISAK with continuous liquid scintillation detection was coupled to the Berkeley Gas-filled Separator to enable studies of the chemical properties of α -decaying transactinide elements. The preseparated transactinide 257Rf (4.7 s), was transported via a He/KCl-jet directly into the scintillation solution. This permitted the first unambiguous detection of transactinide atoms by the means of the α -liquid scintillation detectors of the SISAK-system. During the experiment, 89 257Rf atoms were observed. The type of events observed correspond well with the expectations based on half-lives, decay branches and transport- and hold-up times. The succ…
Radiochemical study of the kinematics of multi-nucleon transfer reactions in 48Ca + 248Cm collisions 10% above the Coulomb barrier
Abstract The kinematics of multi-nucleon transfer reactions in 48Ca + 248Cm collisions at 262 MeV (center of target) was investigated by using a stacked-foil technique and radiochemical separations of trans-curium elements. Trans-curium isotopes were identified by α-particle spectroscopy. For Fm isotopes, by comparing the centroids of the measured post-neutron emission isotope distributions with the most probable primary mass number predicted by Volkov's generalized Q g g systematics, the missing mass (number of evaporated neutrons) is estimated. The latter is compared with that deduced from the measured centroid of the laboratory angular distribution peaked closely to the grazing angle and…