This article summarizes the current specifications and the latest features of the CERN-ISOLDE resonance ionization laser ion source (RILIS). This includes a description of the optical layout and the ...newly designed reference system. The ionization schemes for the laser ionized beams at ISOLDE are tabulated, including six new elements. All RILIS schemes are also made publicly available in the RILIS elements on-line database. Finally, we announce a paradigm shift in RILIS operation – the combination of a machine protection and a monitoring and control system has enabled on-call operation of the laser ion source for selected beams in 2014 and has become the standard mode of operation in 2015.
In-source resonant ionization laser spectroscopy of the even-A polonium isotopes (192-210,216,218)Po has been performed using the 6p(3)7s (5)S(2) to 6p(3)7p (5)P(2) (λ=843.38 nm) transition in the ...polonium atom (Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope shifts in (200-210)Po with a previous data set allows us to test for the first time recent large-scale atomic calculations that are essential to extract the changes in the mean-square charge radius of the atomic nucleus. When going to lighter masses, a surprisingly large and early departure from sphericity is observed, which is only partly reproduced by beyond mean field calculations.
•The Laser Ion Source and Trap (LIST) was successfully operated on-line at ISOLDE.•LIST showed no signs of degradation after 48h of intense proton irradiation.•Transmission, selectivity, efficiency, ...time structure were extensively characterized.•Suppression factor for surface-ionized isobaric contaminants is more than 103–104.•Loss in LIST efficiency compared to RILIS operation is only a factor of 20.
At radioactive ion beam facilities like ISOLDE at CERN, a high purity of the element of interest in the ion beam is essential for most experiments on exotic nuclei. Due to its unique combination of high ionization efficiency and ultimate elemental selectivity, the Resonance Ionization Laser Ion Source, RILIS, has become the most frequently used ion source at ISOLDE and at the majority of similar facilities worldwide. However, isobaric contamination predominantly stemming from unspecific surface ionization may still introduce severe limitations. By applying the highly selective resonance ionization technique inside a radio-frequency quadrupole ion guide structure, the novel approach of the Laser Ion Source and Trap, LIST, suppresses surface ionized isobaric contaminants by an electrostatic repelling potential. Following extensive feasibility studies and off-line tests, the LIST device has been adapted and refined to match the stringent operational constraints and to survive the hostile environment of the ISOLDE front-end region enclosing the highly radioactive nuclear reaction target. The LIST operation was successfully demonstrated for the first time on-line at ISOLDE during two experiments, attesting its suitability for radioactive isotope production under routine conditions. Data of these on-line characterization measurements confirm a suppression of surface-ionized isobars by more than a factor of 1000 in accordance to off-line studies that were carried out for the preparation of the on-line experiments. During the first on-line test, the suppression was associated with an efficiency loss of not more than a factor of about 50 with respect to normal RILIS operation. These losses could be further reduced to only about 20 during the second run. Results of the off-line studies in comparison to the first on-line characterization data are discussed here.
At the radioactive ion beam facility REX-ISOLDE, neutron-rich zinc isotopes were investigated using low-energy Coulomb excitation. These experiments have resulted in B(E2,2{sub 1}{sup +}{yields}0{sub ...1}{sup +}) values in {sup 74-80}Zn, B(E2,4{sub 1}{sup +}{yields}2{sub 1}{sup +}) values in {sup 74,76}Zn and the determination of the energy of the first excited 2{sub 1}{sup +} states in {sup 78,80}Zn. The zinc isotopes were produced by high-energy proton- (A=74,76,80) and neutron- (A=78) induced fission of {sup 238}U, combined with selective laser ionization and mass separation. The isobaric beam was postaccelerated by the REX linear accelerator and Coulomb excitation was induced on a thin secondary target, which was surrounded by the MINIBALL germanium detector array. In this work, it is shown how the selective laser ionization can be used to deal with the considerable isobaric beam contamination and how a reliable normalization of the experiment can be achieved. The results for zinc isotopes and the N=50 isotones are compared to collective model predictions and state-of-the-art large-scale shell-model calculations, including a recent empirical residual interaction constructed to describe the present experimental data up to 2004 in this region of the nuclear chart.
The nuclides 104-108Sn, 106-110Sb, 108,109Te, and 111I at the expected endpoint of the astrophysical rp process have been produced in 58Ni+natNi fusion-evaporation reactions at IGISOL and their mass ...values were precisely measured with the JYFLTRAP Penning trap mass spectrometer. For 106Sb, 108Sb, and 110Sb these are the first direct experimental mass results obtained. The related one-proton separation energies have been derived and the value for 106Sb, Sp=424(8) keV, shows that the branching into the closed SnSbTe cycle in the astrophysical rp process is weaker than expected.
The fundamental principles and assumptions underlying an FEM model are described and this model has been used to predict the final dimensions of shaped components produced by hot isostatically ...pressing (HIPping) Ti–6Al–4V powder. A CAD module (solidworks) has been used for dimensional calibration, tooling design and engineering drawings. A relatively simple small casing component has been produced and the dimensions compared with those predicted from the modelling. It has been shown that there is agreement within about 2% between the achieved geometries and the predictions for this axial-symmetric cylinder body. The physical bases for some of the local discrepancies are discussed and future developments required for improved modelling are outlined.
The radioactive element astatine exists only in trace amounts in nature. Its properties can therefore only be explored by study of the minute quantities of artificially produced isotopes or by ...performing theoretical calculations. One of the most important properties influencing the chemical behaviour is the energy required to remove one electron from the valence shell, referred to as the ionization potential. Here we use laser spectroscopy to probe the optical spectrum of astatine near the ionization threshold. The observed series of Rydberg states enabled the first determination of the ionization potential of the astatine atom, 9.31751(8) eV. New ab initio calculations are performed to support the experimental result. The measured value serves as a benchmark for quantum chemistry calculations of the properties of astatine as well as for the theoretical prediction of the ionization potential of superheavy element 117, the heaviest homologue of astatine.
A Laser Ion Source and Trap (LIST) for a thick-target, isotope-separation on-line facility has been implemented at CERN ISOLDE for the production of pure, laser-ionized, radioactive ion beams. It ...offers two modes of operation, either as an ion guide, which performs similarly to the standard ISOLDE resonance ionization laser ion source (RILIS), or as a more selective ion source, where surface-ionized ions from the hot ion-source cavity are repelled by an electrode, while laser ionization is done within a radio-frequency quadrupole ion guide. The first physics application of the LIST enables the suppression of francium contamination in ion beams of neutron-rich polonium isotopes at ISOLDE by more than 1000 with a reduction in laser-ionization efficiency of only 20. Resonance ionization spectroscopy is performed directly inside the LIST device, allowing the study of the hyperfine structure and isotope shift of ^{217}Po for the first time. Nuclear decay spectroscopy of ^{219}Po is performed for the first time, revealing its half-life, α-to-β-decay branching ratio, and α-particle energy. This experiment demonstrates the applicability of the LIST at radioactive ion-beam facilities for the production and study of pure beams of exotic isotopes.
This article solves the problem of detecting medical masks on a person's face. Medical mask is one of the most effective measures to prevent infection with COVID-19, and its automatic detection is an ...actual task. The introduction of automatic recognition of medical masks in existing information security systems will allow quickly identify the violator of the mask regime, which in turn will increase security in a pandemic. The article provides a detailed analysis of existing solutions for face detection and automatic recognition of medical masks, method based on the use of convolutional neural networks was proposed. A distinctive feature of the new method is the use of two neural networks at once, using the RetinaFace neural network architecture at the face search stage and using the Resnet neural network architecture at the face mask recognition stage. It is shown that the use of transfer learning on scales, learned to work with faces, significantly accelerates learning and increases the accuracy of recognition. However, with this approach, there are some false positives, for example, when you try to cover your face with your hands, imitating a medical mask. Based on the study, we can conclude that the algorithm is applicable in the security system to determine the presence/absence of a medical mask on a person's face, as well as the need for additional research to solve the problems of false positives of the algorithm.
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