Fusion-evaporation reactions with the doubly magic projectile 48Ca were used to access neutron-deficient nuclei around neptunium at the velocity filter SHIP, and investigated using the COMPASS decay ...spectroscopy station. With the use of digital electronics, several isotopes produced via neutron, proton, and α evaporation channels were identified by establishing correlated α-decay chains with short-lived sub-μs members. Data are given on decay chains stemming from 225,226Np, 225U, and 222,223Pa. New information on the isotopes 225,226Np and 222Pa was obtained. Production cross sections of nuclei in the region using a variety of projectiles are discussed. The measured production cross-sections indicate that the usual advantages of using 48Ca as a beam projectile to produce nuclei Z>100 are absent in the production of these slightly lighter nuclei.
Very high quantum efficiency PMTs with bialkali photo-cathode Mirzoyan, R.; Laatiaoui, M.; Teshima, M.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2006, Letnik:
567, Številka:
1
Journal Article
Recenzirano
Since the mid-1960s and until today the classical PMTs with semitransparent bialkali photo-cathode provide peak Quantum Efficiency (QE) of ∼25%. About 2 years ago we started a program with the PMT ...manufacturers Hamamatsu, Photonis and Electron Tubes for boosting up the QE of bialkali PMTs. In the mean time we have obtained several batches of experimental PMTs from the above-mentioned manufacturers and measured few samples with QE values as high as 32–36% in the peak. Also, we want to report on the modest (5–7) % increase of the QE of the PMTs with flat input window after sandblasting. Earlier we have reported that by coating the hemi-spherical input window of bialkali PMTs with a milky layer we could enhance their QE by ∼10–20% for wavelengths ∼320
nm. Assuming that the industry can reliably produce PMTs with 32–35% QE in the peak, by applying the milky layer coating technique to the PMTs with hemi-spherical input window one shall be able to achieve peak QE values of ∼35–40%. Being by an order of magnitude cheaper and providing a matching level of QE such PMTs will become strong competitors for hybrid photo-diodes (HPD) with GaAsP photo-cathode.
A compact silicon detector array with high spatial granularity and fast, fully digital data recording has been developed and commissioned for the investigation of heavy and superheavy nuclear ...species. The detector array can be combined in close geometry with large volume germanium detectors. It offers comprehensive particle and photon coincidence and correlation spectroscopy by highly efficient evaporation residue, α, γ, conversion electron and X-ray detection supported by the high granularity of the implantation chip. Access to fast decay events in the sub-microsecond region is made possible by the fast timing properties of the digital signal processing. A novel Si-chip support design allows direct cooling of the Si-chips and short signal transport. The compact and modular mechanical design equipped with a standard flange facilitates its transport and connection to different separators at different ion beam facilities. After initial tests, first α-γ coincidence spectroscopy experiments have been performed at the LISE separator of GANIL in Caen, France, in FULIS (velocity filter) mode and at the velocity filter SHIP of GSI in Darmstadt, Germany.
Alpha- and EC-decay measurements of $^{257}$Rf Hessberger, F.P.; Antalic, S.; Mistry, A. K. ...
The European physical journal. A, Hadrons and nuclei,
07/2016, Letnik:
52, Številka:
7
Journal Article
Recenzirano
Alpha- and Electron capture (EC) decay properties of 257Rf were investigated by measuringα-γ coincidences and correlations between conversion electrons (CE) emitted during the process of ECdecay of ...257Rf and α decays of the daughter isotope 257Lr. So far, previously unobserved α (8296 keV)-γ(557 keV) coincidences were measured and interpreted as decays of 257mRf (11/2−725) into the 7/2−743 level in 253No. A search of delayed coincidences between α particles and signals at E ≤ 1000 keV, which are interpreted as being due to CE emission, revealed a clear correlation between CE and α particles fromthe decay of 257Lr, which is regarded as a direct proof of the EC decay of 257gRf and 257mRf.
Strong efforts are undertaken at GSI in Darmstadt preparing for laser spectroscopy of the synthetic element nobelium. Several excimer- and dye lasers will be used in the forthcoming search for the
1
...P
1
-level in
254
No. Based on the highly-efficient Radiation Detected Resonance Ionization Spectroscopy (RADRIS) technique, the identification of this excited state predicted around 3.8 eV becomes possible within a relatively short period of beam-time. This will form the basis for future studies of the atomic structure of the heaviest elements.
Flerovium (Fl, element 114) is the heaviest element chemically studied so far. To date, its interaction with gold was investigated in two gas-solid chromatography experiments, which reported two ...different types of interaction, however, each based on the level of a few registered atoms only. Whereas noble-gas-like properties were suggested from the first experiment, the second one pointed at a volatile-metal-like character. Here, we present further experimental data on adsorption studies of Fl on silicon oxide and gold surfaces, accounting for the inhomogeneous nature of the surface, as it was used in the experiment and analyzed as part of the reported studies. We confirm that Fl is highly volatile and the least reactive member of group 14. Our experimental observations suggest that Fl exhibits lower reactivity towards Au than the volatile metal Hg, but higher reactivity than the noble gas Rn.
Nihonium (Nh, element 113) and flerovium (Fl, element 114) are the first superheavy elements in which the
shell is occupied. High volatility and inertness were predicted for Fl due to the strong ...relativistic stabilization of the closed
sub-shell, which originates from a large spin-orbit splitting between the
and
orbitals. One unpaired electron in the outermost
sub-shell in Nh is expected to give rise to a higher chemical reactivity. Theoretical predictions of Nh reactivity are discussed, along with results of the first experimental attempts to study Nh chemistry in the gas phase. The experimental observations verify a higher chemical reactivity of Nh atoms compared to its neighbor Fl and call for the development of advanced setups. First tests of a newly developed detection device miniCOMPACT with highly reactive Fr isotopes assure that effective chemical studies of Nh are within reach.
Until recently, ground-state nuclear moments of the heaviest nuclei could only be inferred from nuclear spectroscopy, where model assumptions are required. Here, laser spectroscopy in combination ...with modern atomic structure calculations is now able to probe these moments directly, in a comprehensive and nuclear- model-independent way. In this work, we reported on unique access to the differential mean-square charge radii of 252,253,254No, and therefore to changes in nuclear size and shape. State-of-the-art nuclear density functional calculations describe well the changes in nuclear charge radii in the region of the heavy actinides, indicating an appreciable central depression in the deformed proton density distribution in 252,254No isotopes.
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