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The Mulde River drains the former uranium mining areas in Saxony (Germany), which has led to a large-scale contamination of the river and the adjacent floodplain soils with radionuclides of the uranium decay series. The objective of the investigation is to quantify the long-term effect of former uranium mining activities on a river system. All of the investigated environmental compartments (water, sediment, soil) still reveal an impact from the former uranium mining and milling activities. The contamination of water has decreased considerably during the last 20 years due to the operation of water treatment facilities. The uranium content of the sediments decreased as well (on average by a factor of 5.6), most likely caused by displacement of contaminated material during flood events. Currently, the impact of the mining activities is most obvious in soils. For some of the plots activity concentrations of >200 Bq/kg of soil were detected for uranium-238. Alluvial soils used as grassland were found to be contaminated to a higher degree than those used as cropland. [ABSTRACT FROM AUTHOR]

The electric dipole strength distribution in 48Ca between 5 and 25 MeV has been determined at RCNP, Osaka from proton inelastic scattering experiments at forward angles. Combined with photoabsorption data at higher excitation energy, this enables the first extraction of the electric dipole polarizability αD(48Ca)=2.07(22) fm³. Remarkably, the dipole response of 48Ca is found to be very similar to that of 40Ca, consistent with a small neutron skin in 48Ca. The experimental results are in good agreement with ab initio calculations based on chiral effective field theory interactions and with state-of-the-art density-functional calculations, implying a neutron skin in 48Ca of 0.14-0.20 fm. [ABSTRACT FROM AUTHOR]

Background: The quenching of spin-isospin modes in nuclei is an important field of research in nuclear structure. It has an impact on astrophysical reaction rates and on fundamental processes like neutrinoless double- ß decay. Gamow-Teller (GT) and spin-flip M1 strengths are quenched. Concerning the latter, the Jp = 1+ resonance in the doubly magic nucleus 48Ca, dominated by a single transition, serves as a reference case. Purpose: The aim of the present work is to search for weak M1 transitions in 48Ca with a high-resolution (p, p') experiment at 295 MeV and forward angles including 0° and a comparison with results from a similar study using backward-angle electron scattering at low momentum transfers in order to estimate their contribution to the total B (M1) strength in 48Ca. Methods: The spin- M1 cross sections of individual peaks in the spectra are deduced with a multipole decomposition analysis (MDA) and converted to reduced spin- M1 transition strengths by using the unit cross-section method. For a comparison with electron-scattering results, corresponding reduced B (M1) transition strengths are extracted following the approach outlined in Birkhan et al. [Phys. Rev. C 93, 041302(R) (2016)]. Results: In total, 30 peaks containing a M1 contribution are found in the excitation energy region 7-13 MeV. The resulting B (M1) strength distribution compares well to the electron-scattering results considering different factors limiting the sensitivity in both experiments and the enhanced importance of mechanisms breaking the proportionality of nuclear cross sections and electromagnetic matrix elements for weak transitions as studied here. The total strength of 1.14(7) µ²N deduced assuming a nonquenched isoscalar part of the (p, p') cross sections agrees with the (e, e') result of 1.21(13) µ²N. A bin-wise analysis above 10 MeV provides an upper limit of 1.51(17) µ²N. Conclusions: The present results confirm the previous electron-scattering work that weak transitions contribute about 25% to the total B (M1) strength in 48Ca and the quenching factors of GT and spin- M1 strength are then comparable in f p -shell nuclei. Thus, the role of meson-exchange currents seems to be negligible in 48Ca, in contrast to sd -shell nuclei. [ABSTRACT FROM AUTHOR]

Inelastic proton scattering at energies of a few hundred million electron volts and extreme forward angles selectively excite the isovector spin-flip M1 (IVSM1) resonance. A method based on isospin symmetry is presented to extract its electromagnetic transition strength from the (p,p') cross sections. It is applied to 48Ca, a key case for an interpretation of the quenching phenomenon of the spin-isospin response, and leads to a M1 strength consistent with an older (e,e') experiment excluding the almost two times larger value from a recent (γ,n) experiment. Good agreement with electromagnetic probes is observed in 208Pb, suggesting the possibility of extracting systematic information on the IVSM1 resonance in heavy nuclei. [ABSTRACT FROM AUTHOR]

When injecting charged particles into a radio frequency (RF) field at a phase, where the particles are decelerated instead of accelerated, the particles return energy to the RF field. This effect is called energy recovery. The beam-energy recovery efficiency is determined by the measurement of RF forward and reverse powers. At the S-DALINAC, no RF power detection system was available to permanently measure all cavities simultaneously for a full energy recovery characterization. In this paper, the new RF power measurement setup is described regarding design and characterization of this system. With an energy gain measurement, an additional application of the system is presented, which was done for the first time for 20-cell cavities using an RF power measurement. [ABSTRACT FROM AUTHOR]

Background: The B(E2) transition strength to the 22+ state in 94Zr was initially reported to be larger by a factor of 1.63 than the one to the 2+ state from lifetime measurements with the Doppler-shift attenuation method using the (n,n'y) reaction [Elhami et al., Phys. Rev. C 75, 011301(R) (2007)]. This surprising behavior was recently revised in a new measurement by the same group using the same experimental technique leading to a ratio below unity as expected in vibrational nuclei. Purpose: The goal is an independent determination of the ratio of B(E2) strengths for the transitions to the 21,2+ states of 94Zr with inelastic electron scattering. Method: The relative population of the 21,2+ states in the (e,e') reaction was measured at the S-DALINAC in a momentum transfer range q = 0.17-0.51 fm-1 and analyzed in plane-wave Born approximation with the method described by Scheikh Obeid et al. [Phys. Rev. C 87, 014337 (2013)]. Results: The extracted B(E2) strength ratio of 0.789(43) between the excitation of the 21+ and 22+ states of 94Zr is consistent with but more precise than the latest (n,n'y) experiment. Using the B(E2) transition strength to the first excited state from the literature a value of 3.9(9) Weisskopf units is deduced for the B(E2; 22+➔01+)transition. Conclusions: The electron scattering result independently confirms the latest interpretation of the different (n,n'y) results for the transition to the 22+ state in 94Zr. [ABSTRACT FROM AUTHOR]

The technique of self absorption has been applied for the first time to study the decay pattern of low-lying dipole states of 140 Ce. In particular, ground-state transition widths Γ 0 and branching ratios Γ 0 Γ to the ground state have been investigated in the energy domain of the pygmy dipole resonance. Relative self-absorption measurements allow for a model-independent determination of Γ 0 . Without the need to perform a full spectroscopy of all decay channels, also the branching ratio to the ground state can be determined. The experiment on 140 Ce was conducted at the bremsstrahlung facility of the superconducting Darmstadt electron linear accelerator S-DALINAC. In total, the self-absorption and, thus, Γ 0 were determined for 104 excited states of 140 Ce. The obtained results are presented and discussed with respect to simulations of γ cascades using the DICEBOX code. [ABSTRACT FROM AUTHOR]

A direct measurement of the decay width of the excited 0+1 state of 6Li using the relative self-absorption technique is reported. Our value of Γγ,0+1→1+1=8.17(14)stat.(11)syst. eV provides sufficiently low experimental uncertainties to test modern theories of nuclear forces. The corresponding transition rate is compared to the results of ab initio calculations based on chiral effective field theory that take into account contributions to the magnetic dipole operator beyond leading order. This enables a precision test of the impact of two-body currents that enter at next-to-leading order. [ABSTRACT FROM AUTHOR]

The E2/M1 multipole mixing ratio δ1→2 of the 1sc+→21+ γ-ray decay in 156Gd and hence the isovector E2 transition rate of the scissors mode of a well-deformed rotational nucleus has been measured for the first time. It has been obtained from the angular distribution of an artificial quasimonochromatic linearly polarized γ-ray beam of energy 3.07(6) MeV scattered inelastically off an isotopically highly enriched 156Gd target. The data yield first direct support for the deformation dependence of effective proton and neutron quadrupole boson charges in the framework of algebraic nuclear models. First evidence for a low-lying Jπ=2+ member of the rotational band of states on top of the 1+ band head is obtained, too, indicating a significant signature splitting in the K=1 scissors mode rotational band. [ABSTRACT FROM AUTHOR]