The ^{30}P(p,γ)^{31}S reaction plays an important role in understanding the nucleosynthesis of A≥30 nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure ...^{31}Cl β-delayed proton decay through the key J^{π}=3/2^{+}, 260-keV resonance. The intensity I_{βp}^{260}=8.3_{-0.9}^{+1.2}×10^{-6} represents the weakest β-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of Γ_{p}/Γ=2.5_{-0.3}^{+0.4}×10^{-4}. By combining this measurement with shell-model calculations for Γ_{γ} and past work on other resonances, the total ^{30}P(p,γ)^{31}S rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of ^{30}Si:^{28}Si excesses in presolar nova grains and the calibration of nuclear thermometers.
Objectives
The assessment of the neurotoxic effect of arsenic (As) and its inorganic compounds is still the subject of interest due to a growing As application in a large array of technologies and ...the need to constantly verify the principles of prevention and technological parameters. The aim of this study was to determine the status of the nervous system (NS) in workers exposed to As at concentrations exceeding hygiene standards (Threshold Limit Values (TLV) − 10 μg/m
3
, Biological Exposure Index (BEI) − 35 μg/l) and to analyze the relationship between the NS functional state, species of As in urine and As levels in the workplace air.
Material and Methods
The study group comprised 21 men (mean age: 47.43±7.59) employed in a copper smelting factory (mean duration of employment: 22.29±11.09). The control group comprised 16 men, matched by age and work shifts. Arsenic levels in the workplace air (As-A) ranged from 0.7 to 92.3 μg/m
3
; (M = 25.18±28.83). The concentration of total arsenic in urine (As
tot
-U) ranged from 17.35 to 434.68 μg/l (M = 86.82±86.6).
Results
Syndrome of peripheral nervous system (PNS) was manifested by extremity fatigue (28.6%), extremity pain (33.3%) and paresthesia in the lower extremities (33.3%), as well as by neuropathy-type mini-symptoms (23.8%). Electroneurographic (ENeG) tests of peroneal nerves showed significantly decreased response amplitude with normal values of motor conduction velocity (MCV). Stimulation of sural nerves revealed a significantly slowed sensory conduction velocity (SCV) and decreased sensory potential amplitude. Neurophysiological parameters and the results of biological and environmental monitoring showed a relationship between As
tot
, As
III
(trivalent arsenic), the sum of iAs (As
III
+As
V
(pentavalent arsenic))+MMA (monomethylarsonic acid) concentration in urine and As levels in the air.
Conclusions
The results of the study demonstrate that occupational exposure to inorganic arsenic levels exceeding hygiene standards (TLV, BEI) generates disorders typical of peripheral neuropathy.
The 30P(p,γ)31S reaction plays an important role in understanding the nucleosynthesis of A≥30 nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure 31Cl ...β-delayed proton decay through the key Jπ=3/2+, 260-keV resonance. The intensity I260βp=8.3+1.2-0.9×10-6 represents the weakest β-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of Γp/Γ=2.5+0.4-0.3×10-4. By combining this measurement with shell-model calculations for Γγ and past work on other resonances, the total 30P(p,γ)31S rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of 30Si:28Si excesses in presolar nova grains and the calibration of nuclear thermometers.
25Siβ+-decay spectroscopy Sun, L. J.; Friedman, M.; Budner, T. ...
Physical review. C,
01/2021, Volume:
103, Issue:
1
Journal Article
Peer reviewed
Open access
Background: β-decay spectroscopy provides valuable information on exotic nuclei and a stringent test for nuclear theories beyond the stability line. Purpose: To search for new β-delayed protons and γ ...rays of 25Si to investigate the properties of 25Al excited states. Method: 25Si β decays were measured by using the Gaseous Detector with Germanium Tagging system at the National Superconducting Cyclotron Laboratory. The protons and γ rays emitted in the decay were detected simultaneously. Here, a Monte Carlo method was used to model the Doppler broadening of 24Mg γ-ray lines caused by nuclear recoil from proton emission. Shell-model calculations using two newly developed universal sd-shell Hamiltonians were performed. Results: The most precise 25Si half-life to date has been determined. A new proton branch at 724(4) keV and new proton-γ-ray coincidences have been identified. Three 24Mg γ-ray lines and eight 25Al γ-ray lines are observed for the first time in 25Si decay. The first measurement of the 25Si β-delayed γ-ray intensities through the 25Al unbound states is reported. All the bound states of 25Al are observed to be populated in the β decay of 25Si. Several inconsistencies between the previous measurements have been resolved, and new information on the 25Al level scheme is provided. An enhanced decay scheme has been constructed and compared to the mirror decay of 25Na and the shell-model calculations. Conclusions: The measured excitation energies, γ-ray and proton branchings, log $ft$ values, and Gamow-Teller transition strengths for the states of 25Al populated in the β decay of 25Si are in good agreement with the shell model calculations, offering gratifyingly consistent insights into the fine nuclear structure of 25Al.
The radionuclide 22Na is a target of γ-ray astronomy searches, predicted to be produced during thermonuclear runaways driving classical novae. The 22Na (p, γ) 23Mg reaction is the main destruction ...channel of 22Na during a nova, hence, its rate is needed to accurately predict the 22Na yield. However, experimental determinations of the resonance strengths have led to inconsistent results. In this Rapid Communication, we report a measurement of the branching ratios of the 23Al β-delayed protons as a probe of the key 204-keV (center-of-mass) 22Na (p, γ) 23Mg resonance strength. We report a factor of 5 lower branching ratio compared to the most recent literature value. The variation in 22Na yield due to nuclear data inconsistencies was assessed using a series of hydrodynamic nova outburst simulations and has increased to a factor of 3.8, corresponding to a factor of ≈ 2 uncertainty in the maximum detectability distance. Finally, this is the first reported scientific measurement using the Gaseous Detector with Germanium Tagging system.
GADGET: a Gaseous Detector with Germanium Tagging Friedman, M.; Pérez-Loureiro, D.; Budner, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2019, Volume:
940
Journal Article
Peer reviewed
Open access
The Gaseous Detector with Germanium Tagging (GADGET) is a new detection system devoted to the measurement of weak, low-energy β-delayed proton decays relevant for nuclear astrophysics studies. It is ...comprised of a new gaseous Proton Detector equipped with a Micromegas readout for charged particle detection, surrounded by the existing Segmented Germanium Array (SeGA) for the high-resolution detection of the prompt γ-rays. In this work we describe in detail for the first time the design, construction, and operation of the GADGET system, including performance of the Proton Detector. We present the results of a recent commissioning experiment performed with 25Si beam at the National Superconducting Cyclotron Laboratory (NSCL). GADGET provided low-background, low-energy β-delayed proton detection with efficiency above 95%, and relatively good efficiency for proton-gamma coincidences (2.7% at 1.37 MeV).
The $^{30}$P$(p,\gamma)^{31}$S reaction plays an important role in
understanding nucleosynthesis of $A\geq 30$ nuclides in oxygen-neon novae. The
Gaseous Detector with Germanium Tagging was used to ...measure $^{31}$Cl
$\beta$-delayed proton decay through the key $J^{\pi}=3/2^{+}$, 260-keV
resonance. The intensity $I^{260}_{\beta p} = 8.3^{+1.2}_{-0.9} \times 10^{-6}$
represents the weakest $\beta$-delayed, charged-particle emission ever measured
below 400 keV, resulting in a proton branching ratio of $\Gamma_p / \Gamma =
2.5^{+0.4}_{-0.3} \times 10^{-4}$. By combining this measurement with
shell-model calculations for $\Gamma_{\gamma}$ and past work on other
resonances, the total $^{30}$P$(p,\gamma)^{31}$S rate has been determined with
reduced uncertainty. The new rate has been used in hydrodynamic simulations to
model the composition of nova ejecta, leading to a concrete prediction of
$^{30}$Si/$^{28}$Si excesses in presolar nova grains and the calibration of
nuclear thermometers.
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