27 research outputs found
Second T = 3/2 state in B and the isobaric multiplet mass equation
Recent high-precision mass measurements and shell model calculations~[Phys.
Rev. Lett. {\bf 108}, 212501 (2012)] have challenged a longstanding explanation
for the requirement of a cubic isobaric multiplet mass equation for the lowest
isospin quartet. The conclusions relied upon the choice of the
excitation energy for the second state in B, which had two
conflicting measurements prior to this work. We remeasured the energy of the
state using the reaction and significantly disagree
with the most recent measurement. Our result supports the contention that
continuum coupling in the most proton-rich member of the quartet is not the
predominant reason for the large cubic term required for nuclei
α Clustering in Si 28 probed through the identification of high-lying 0+ states
Background: Aspects of the nuclear structure of light α-conjugate nuclei have long been associated with nuclear clustering based on α particles and heavier α-conjugate systems such as C12 and O16. Such structures are associated with strong deformation corresponding to superdeformed or even hyperdeformed bands. Superdeformed bands have been identified in Ca40 and neighboring nuclei and find good description within shell model, mean-field, and α-cluster models. The utility of the α-cluster description may be probed further by extending such studies to more challenging cases comprising lighter α-conjugate nuclei such as Mg24, Si28, and S32. Purpose: The purpose of this study is to look for the number and energy of isoscalar 0+ states in Si28. These states are the potential bandheads for superdeformed bands in Si28 corresponding to the exotic structures of Si28. Of particular interest is locating the 0+ bandhead of the previously identified superdeformed band in Si28. Methods: α-particle inelastic scattering from a Sinat target at very forward angles including 0 has been performed at the iThemba Laboratory for Accelerator-Based Sciences in South Africa. Scattered particles corresponding to the excitation energy region of 6 to 14 MeV were momentum-analysed in the K600 magnetic spectrometer and detected at the focal plane using two multiwire drift chambers and two plastic scintillators. Results: Several 0+ states have been identified above 9 MeV in Si28. A newly identified 9.71 MeV 0+ state is a strong candidate for the bandhead of the previously discussed superdeformed band. The multichannel dynamical symmetry of the semimicroscopic algebraic model predicts the spectrum of the excited 0+ states. The theoretical prediction is in good agreement with the experimental finding, supporting the assignment of the 9.71-MeV state as the bandhead of a superdeformed band. Conclusion: Excited isoscalar 0+ states in Si28 have been identified. The number of states observed in the present experiment shows good agreement with the prediction of the multichannel dynamical symmetry
Isospin mixing and the cubic isobaric multiplet mass equation in the lowest <i>T</i>=2, <i>A</i>=32 quintet
The isobaric multiplet mass equation (IMME) is known to break down in the
first T = 2, A = 32 isospin quintet. In this work we combine high-resolution
experimental data with state-of-the-art shell-model calculations to investigate
isospin mixing as a possible cause for this violation. The experimental data
are used to validate isospin-mixing matrix elements calculated with newly
developed shell-model Hamiltonians. Our analysis shows that isospin mixing with
nonanalog T = 1 states contributes to the IMME breakdown, making the
requirement of an anomalous cubic term inevitable for the multiplet
Volume reduction of water samples to increase sensitivity for radioassay of lead contamination
The World Health Organisation (WHO) presents an upper limit for lead in drinking water of 10 parts per billion ppb. Typically, to reach this level of sensitivity, expensive metrology is required. To increase the sensitivity range of low-cost devices, this paper explores the prospects of using a volume reduction technique of a boiled water sample doped with Lead-210 (210 Pb), as a means to increase the soluteâs concentration. 210Pb is a radioactive lead isotope and its concentration in a water sample can be measured with e.g. High Purity Germanium (HPGe) detectors at the Boulby Underground Germanium Suite. Concentrations close to the WHO limit have not been examined. This paper presents a measurement of the volume reduction technique retaining 99±(9)% of 210Pb starting from a concentration of 1.9Ă10â6 ppb before reduction and resulting in 2.63Ă10â4 ppb after reduction. This work also applies the volume reduction technique to London tap water and reports the radioassay results from gamma counting in HPGe detectors. Among other radio-isotopes, 40K, 210Pb, 131I and 177Lu were identified at measured concentrations of 2.83Ă103 ppb, 2.55Ă10â7 ppb, 5.06Ă10â10 ppb and 5.84Ă10â10 ppb in the London tap water sample. This technique retained 90±50% of 40K. Stable lead was inferred from the same water sample at a measured concentration of 0.012 ppb, prior to reduction
Characterization of germanium detectors for the first underground laboratory in Mexico
This article reports the characterization of two High Purity Germanium detectors performed by extracting and comparing their efficiencies using experimental data and Monte Carlo simulations. The efficiencies were calculated for pointlike Îł-ray sources as well as for extended calibration sources. Characteristics of the detectors such as energy linearity, energy resolution and full energy peak efficiencies are reported from measurements performed on surface laboratories. The detectors will be deployed in a Îł-ray assay facility that will be located in the first underground laboratory in Mexico, Laboratorio Subterr'aneo de Mineral del Chico (LABChico), in the Comarca Minera UNESCO Global Geopark [1]
A focus on selected perspectives of the NUMEN project
The use of double charge exchange reactions is discussed in view of their application to extract information that may be helpful to determinate the nuclear matrix elements entering in the expression of neutrinoless double beta decay half-life. The strategy adopted in the experimental campaigns performed at INFN - Laboratori Nazionali del Sud and in the analysis methods within the NUMEN project is briefly described, emphasizing the advantages of the multi-channel approach to nuclear reaction data analysis. An overview on the research and development activities on the MAGNEX magnetic spectrometer is also given, with a focus on the chosen technological solutions for the focal plane detector which will guarantee the performances at high-rate conditions