[en] We measured the thermal neutron capture cross section for the ¹⁸⁰W nucleus. There is only one previous measurement with regard to this cross section, and it yielded a value of 30 -100%+300% b. To determine whether ¹⁸¹W is an appropriate low energy neutrino source, the thermal neutron capture cross section should be measured more precisely to estimate the production rate of ¹⁸¹W inside a nuclear reactor. We measured the cross section of ¹⁸⁰W using a natural tungsten foil and obtained a value of 22.6±1.7 b

[en] We analyzed low-background data from the CRESST-II experiment with a total net exposure of 730 kg days to extract limits on double electron capture processes. We established new limits for ⁴⁰Ca with $T_{1/2}^{2\mathrm{\nu <!--\; ??\; -->}2\mathrm{K}}><!--\; >\; -->9.9\times <!--\; ??\; -->{10}^{21}$ y and $T_{1/2}^{0\mathrm{\nu <!--\; ??\; -->}2\mathrm{E}\mathrm{C}}><!--\; >\; -->1.4\times <!--\; ??\; -->{10}^{22}$ y and for ¹⁸⁰W with $T_{1/2}^{2\mathrm{\nu <!--\; ??\; -->}2\mathrm{K}}><!--\; >\; -->3.1\times <!--\; ??\; -->{10}^{19}$ y and $T_{1/2}^{0\mathrm{\nu <!--\; ??\; -->}2\mathrm{E}\mathrm{C}}><!--\; >\; -->9.4\times <!--\; ??\; -->{10}^{18}$ y at 90% CL. Depending on the process, these values improve the currently best limits by a factor of $\sim <!--\; ???\; -->1.4\text{--}30$. (paper)

No abstract available

[en] The small High Efficiency pulse tube Cooler (HEC) cooler, that has been produced and flown on a number of space infrared instruments, was originally designed to provide cooling of 10 W @ 95 K. It achieved its goal with >50% margin when limited by the 180 W output ac power of its flight electronics. It has also been produced in 2 stage configurations, typically for simultaneously cooling of focal planes to temperatures as low as 35 K and optics at higher temperatures. The need for even higher cooling power in such a low mass cryocooler is motivated by the advent of large focal plane arrays. With the current availability at NGAS of much larger power cryocooler flight electronics, reliable long term operation in space with much larger cooling powers is now possible with the flight proven 4 kg HEC mechanical cooler. Even though the single stage cooler design can be re-qualified for those larger input powers without design change, we redesigned both the linear and coaxial version passive pulse tube cold heads to re-optimize them for high power cooling at temperatures above 130 K while rejecting heat to 300 K. Small changes to the regenerator packing, the re-optimization of the tuned inertance and no change to the compressor resulted in the increased performance at 150 K. The cooler operating at 290 W input power achieves 35 W@ 150 K corresponding to a specific cooling power at 150 K of 8.25 W/W and a very high specific power of 72.5 W/Kg. At these powers the cooler still maintains large stroke, thermal and current margins. In this paper we will present the measured data and the changes to this flight proven cooler that were made to achieve this increased performance

[en] The rarest natural alpha activity observed in tungsten due to ¹⁸⁰W (0.12% of isotopic abundance) is discussed in the context of recent half-life measurements taken in the Solotvina and Gran Sasso Underground Laboratories and the evaluations based on a one-parameter, semiempirical model developed by us very recently. (comment)

No abstract available

[en] Highlights: • How geometrical features of tracks are affected by laser power and affect lack of fusion (LOF) have been revealed. • There is a small range of power within which increasing power rapidly reduces the amount of the normal LOF to a low value. • Above the referred power range, a low amount of LOF remains, due to the presence of a spatter related and large LOF defect. • Deeper penetration using high power aids the reduction of the spatter related LOF. There is a need to understand how selective laser melting (SLM) parameters affect the size and shape of tracks which are the predominant factor relating to the amount of lack of fusion (LOF) formed during SLM. This study is needed as severe LOF impacts quality. In this work on CoCrMo alloy SLM, experiments and analysis have been conducted to reveal how laser power (P) and thus energy, as other parameters are kept unchanged, affect the geometrical features of SLM tracks and the formation of LOF. It has been found that the track was insufficient to overlap and prevent LOF when the recommended condition (P = 180 W) was used. Increasing P increases the size and improves the shape stability of the tracks. It will be shown that there is a rapid decay in the amount of LOF as P increases from 180 W to 220 W, as the result of the geometrical effect of the track size on overlapping coverage. However, residual LOF has remained even when P has increased to > 300 W. Evidence of large size spatters causing this and of the high laser beam penetrating capability to reduce the spatter effect is presented and discussed.

[en] In the Moessbauer conversion spectroscopy the detection of the Moessbauer absorption is carried out by watching the conversion electrons afterwards emitted. In spite of the higher experimental efforts, the method is a real alternative to the usual transmission experiment. In a series of Mb-measurements at the E₂-transitions of the Os-, Hf-, and W-isotopes, the criteria developed for the applicability of the MBC could be ascertained. The two W-isotopes ¹⁸⁰W and ¹⁸²W tested in this study are located at the beginning of the transition of deformed nuclei to spherical ones. Deviations from the simple rotation model should be perceptible in the size of the electromagnetic moments and in the transition probabilities of the excited nuclear states. For the first excited rotational states, the proportion of the quadrupole moments can be determined with the help of Mb-measurements. The result does not show any deviations from the predictions of the rotational model. Further information about the structure of rotational states can be gained from Mb-isomeric shifts. In this essay the isomeric shift of the first rotational state in ¹⁸²W was determined for several joints. Limiting values for the negative Δ < r²> are given with an electron density calibration based on relativistic Hartree-Fock-calculations. (orig./WBU)

[en] The search for the ¹⁸⁰W α-decay is carried out within the frames of the study on the ¹¹⁶Cd 2β-decay through the ¹¹⁶CdWO₄ low-background scintillation detector with the mass of 330 g at the Solotvinskaya underground laboratory. The dependences of the α/β ratio and the scintillation signal form on the α-particles energy and the irradiation direction relative to the main crystallographic axes are measured. The first indications of the α-decay of the ¹⁸⁰W with the T_1/2 = 8_-2⁺⁶(stat.)_-2⁺⁸(syst.) x 10¹⁷ years are obtained after 975 hours of the measurement

No abstract available