Electron screening in palladium Cvetinović, A.; Đeorđić, D.; Guardo, G.L. ...
Physics letters. B,
03/2023, Letnik:
838
Journal Article
Recenzirano
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The electron screening effect was studied in the 1H(7Li,α)4He, 1H(19F,αγ)16O and 2H(19F,p)20F nuclear reactions on two different hydrogen-containing palladium foils. In one of the targets we did not ...detect a large enhancement of the cross section due to electron screening, and in the second one we measured a high electron screening potential for all three reactions, up to an order of magnitude above the theoretical models. Contrary to the predictions given by the available theories, the data suggest that the reason behind this difference is linked to a dependence of the electron screening potential on the host's crystal lattice structure and the location of the target nuclei in the metallic lattice.
Proton–deuteron fusion reaction has been studied using a proton beam with an energy of 260 keV and a deuterium-implanted graphite target. The reaction product, 3He, usually de-excites by γ-ray ...emission. However, instead of a γ ray, 3He can emit an electron with a discrete energy of 5.6 MeV, due to electron screening in graphite. Such electrons were identified with the ΔE–E technique. The emission of fast electrons shows that electron screening causes the electrons to approach the nuclei during the reaction very closely. Different behavior of nuclear reactions at low and high energies was also demonstrated.
The dependence of electron screening potential on the position of the target nucleus in host-material lattice was investigated by measuring the rate of the 2H(19F,p)20F reaction in zirconium, ...titanium and palladium targets containing deuterium. Very different values of the screening potential were measured, thus showing the link with the valence electron densities around deuterium nuclei.
When dealing with high count rate γ-ray spectrometry, the pile-up phenomenon is an important obstacle to high detection efficiency and good energy resolution. In traditional pulse processing piled-up ...events are rejected to preserve good energy resolution at the expense of detection efficiency. This is especially problematic in in-beam γ-ray spectrometry, where searching for coincidences between two different detection signals further accentuates the loss of efficiency. Consequently we want to detect as many events as possible and obtain the best possible energy resolution. We propose a method that reduces the number of piled-up events, using a parallel moving window deconvolution (MWD) block implementation where the shaping time parameter differs for every MWD block. With appropriate analysis logic we get more experimental information through reduced dead time, at the cost of controlled and selectively worsened energy resolution, on an event-by-event basis, thus achieving better overall detection efficiency. We tested our method on real experimental data for different count rates. At 500 kcps count rate the detection efficiency of our method is higher, by a factor of about 37, than the efficiency of a standard digital method commonly used in commercial systems with pile-up rejection.
Abstract
Interests on few-body hypernuclei have been increased by recent results of experiments employing relativistic heavy ion beams. Some of the experiments have revealed that the lifetime of the ...lightest hypernucleus, hypertriton, is significantly shorter than 263 ps which is expected by considering the hypertriton to be a weakly-bound system. The STAR collaboration has also measured the hypertriton binding energy, and the deduced value is contradicting to its formerly known small binding energy. These measurements have indicated that the fundamental physics quantities of the hypertriton such as its lifetime and binding energy have not been understood, therefore, they have to be measured very precisely. Furthermore, an unprecedented Λnn bound state observed by the HypHI collaboration has to be studied in order to draw a conclusion whether or not such a bound state exists. These three-body hypernuclear states are studied by the heavy-ion beam data in the WASA-FRS experiment and by analysing J-PARC E07 nuclear emulsion data with machine learning.
The pile-up rejection in nuclear spectroscopy has been confronted recently by several pile-up correction schemes that compensate for distortions of the signal and subsequent energy spectra artifacts ...as the counting rate increases. We study here a real-time capability of the event-by-event correction method, which at the core translates to solving many sets of linear equations. Tight time limits and constrained front-end electronics resources make well-known direct solvers inappropriate. We propose a novel approach based on the Gauss-Seidel iterative method, which turns out to be a stable and cost-efficient solution to improve spectroscopic resolution in the front-end electronics. We show the method convergence properties for a class of matrices that emerge in calorimetric processing of scintillation detector signals and demonstrate the ability of the method to support the relevant resolutions. The sole iteration-based error component can be brought below the sliding window induced errors in a reasonable number of iteration steps, thus allowing real-time operation. An area-efficient hardware implementation is proposed that fully utilizes the method's inherent parallelism.
Due to the stochastic nature of the pulse creation in a scintillation detector the output pulses are not all of the same shape but rather 'noised' with statistical fluctuations on the pulse tails, ...which may induce false triggers. The current state of the art in solving this kind of problems is either introducing a deadtime after each pulse which makes the detector inefficient at higher count rates or raising the trigger threshold above the fluctuactions level, which on the other side, lowers the dynamic range of the detector from the low energy side. In order to meet the ever growing demand for high precision efficient experiments the solutions to these limitations are highly desirable. We propose a new method, the adaptive triggering for scintillation signals.
We present first preliminary results of a novel method for measuring independent isotopic fission yields (IIFYs) of spontaneous fission (SF) via direct mass measurements, at the FRS Ion Catcher ...(FRS-IC) at GSI. Fission products were generated from a 252Cf source installed in a cryogenic stopping cell, and were identified and counted with the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS-IC, utilizing well-established measurement and data analysis methods. The MR-TOF-MS resolves isobars unambiguously, even with limited statistics, and its non-scanning nature ensures minimal relative systematic uncertainties amongst fission products. The analysis for extracting IIFYs includes isotope-dependent efficiency corrections for all components of the FRS-IC. In particular, we applied a self-consistent technique that takes into account the element-dependent survival efficiencies in the CSC, due to chemical reactions with the buffer gas. Our IIFY results, which cover several tens of fission products in the less-accessible high-mass peak (Z = 56 to 63) down to fission yields at the level of 10−5, are generally similar to those of the nuclear database ENDF/B-VII.0. Nevertheless, they reveal some structures that are not observed in the database smooth trends. These are the first results of a planned campaign to investigate IIFY distributions of spontaneous fission at the FRS-IC. Upcoming experiments will extend our results to wider Z and N ranges, lower fission yields, and other spontaneously-fissioning actinides.
An experiment was performed at GSI with the objective of measuring theβ-intensity distribution in the decay of Hg, Au and Pt isotopes around N=126 using the total absorption gamma-ray spectroscopy ...technique. The aim is to benchmark theoretical models used to make predictions of half-life and neutron emission probabilities of exotic nuclei involved in the rapid neutron capture process, leading to the synthesis of very heavy elements. This paper presents some experimental details and the current status of the analysis.
The current understanding of light hypernuclei, which are sub-atomic nuclei with strangeness, is being challenged and studied in detail by several European research groups and collaborations. In ...recent years, studies of hypernuclei using high-energy heavy ion beams have reported unexpected results on the three-body hypernuclear state
3
Λ
H, named the hypertriton. For some time, reports of a shorter lifetime and larger binding energy than what was previously accepted have created a puzzling situation for its theoretical description; this is known as the "hypertriton puzzle". With the inclusion of the most recent experimental measurements, the current status of the hypertriton puzzle is evolving. Additionally, the possible neutral bound state of a Λ hyperon with two neutrons, nnΛ, has raised questions about our understanding of the formation of light hypernuclei either in bound or resonance states. These results have initiated several ongoing experimental programs all over the world to study these three-body hypernuclear states precisely. We are studying these light hypernuclear states by employing heavy ion beams at 2
A
GeV on a fixed carbon target with the WASA detector system and the Fragment Separator (FRS) at GSI. The WASA-FRS experimental campaign was performed during the first quarter of 2022, and this paper presents a short overview of the campaign and how it seeks to tackle the hypertriton and nnΛ puzzles. Data analysis is ongoing, and several preliminary results will be reported.
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