[en] With the NICOLE facility on-line to the isotope separator ISOLDE-3 at CERN we obtained on the gyromagnetic factors of ^{182,184m,184g}Au using the nuclear spin-lattice relaxation phenomena; this new method uses a radioactive pulsed beam and a time resolved detection. We developed an algorithm based on the relaxation theory which allows to calculate the time evolution of the angular distribution of γ-radiation emitted in radioactive decay of oriented nuclei. The possibilities for the ¹⁸²Au spin value were reduced to I=2,3,4; its half-life was reevaluated to T_1/2(¹⁸²Au) = 15.6(4)s. The first on-line experiment carried out at NICOLE on ¹⁸⁴Au showed the existence of an unknown long-lived isomeric state which decays to the short-lived ground state through an M3 transition. Our results indicate that the most probable spin sequence is 3⁺ and 6⁺ for the isomeric and ground state, respectively; the half-lives are T_1/2 (^184mAu) = 48(1)s and T_1/2 (¹⁸⁴Au)=19(1)s. Magnetic moments of ^91mY, ⁹⁵Zr and ⁹⁷Nb and quadrupole moments of ⁹⁵Zr and ⁹⁵Nb have been measured using the time-integral nuclear orientation and the nuclear magnetic resonance methods at low temperature. The measured magnetic moment |μ (⁹⁵Zr)| =1.131(20)μ_N gives a quadrupole deformation ε 0.06 - 0.07 for ⁹⁵Zr using the Nilsson model with a Coriolis mixing term. This deformation explains the observed value for the quadrupole moment Q(⁹⁵Zr) = +0.29(5) eb. The small oblate deformation of ⁹⁵ Nb is in agreement with the spectroscopic quadrupole moment Q (⁹⁵Nb) = -0.28(10) eb. (author). 120 refs., 43 figs., 13 tabs

[en] Precise hyperfine field value of zinc in iron has been determined by nuclear magnetic resonance on oriented nuclei (NMR/ON): B_hf (ZnFe)=-18.785(35) T at 7 mK. The relaxation constant of Zn in iron is established C_K=14(3) Ks. The new hyperfine field value of zinc in iron allows a more precise reevaluation of the magnetic moments of ^69mZn and ^71mZn measured with NMR/ON. (orig.)

[en] A first characterization of a 1100 g sapphire bolometer, performed at sea level and at a working temperature of 40 mK, is presented. Despite perturbations coming from the high-radioactive background and cosmic rays, calibration spectra could be achieved with an internal α source and a ⁵⁷Co γ-ray source: the experimental threshold is 25 keV, while the FWHM resolution is 17.4 keV for the 122 keV peak. Possible heat release effects are discussed, and a new limit of 9x10^-14 W/g is obtained for sapphire

[en] Magnetic moments around the Z=40 shell closure have been established using nuclear magnetic resonance on oriented nuclei (NMR/ON) in iron. From the resonance frequencies we established vertical strokeμ(⁹¹Y; 9/2⁺)vertical stroke=5.96(6)μ_N,vertical stroke μ(⁹⁵Zr; 5/2⁺)vertical stroke=1.103(23)μ_N, vertical strokeμ(⁹⁷Nb; 9/2⁺)vertical stroke=6.153(5)μ_N. From the electric quadrupole alignment of ⁹⁵Zr+⁹⁵Nb in a Zr single crystal Q(⁹⁵Zr)=+0.29(5)b and Q(⁹⁵Nb)<0 have been derived. The results obtained are discussed using the Nilsson deformed single particle model. It is shown that for certain deformation regions, a measurement of the magnetic moment can give information on the nuclear quadrupole deformation. (orig.)

[en] First experiments in the systematic study of the structure of ground states and isomeric states of Br isotopes as function of neutron number of ISOLDE, CERN are reported. The isotopes ^{74g,74m,77,78,84g,84m}Br have been implanted into iron and studied with the techniques of low temperature nuclear orientation and nuclear magnetic resonance of oriented nuclei (NMR/ON). The experiments were performed with the NICOLE on-line nuclear orientation set-up using the isotope separator ISOLDE-3. NMR/ON experiments were successful for ^74mBr with continuous on-line implantation and for ⁷⁷Br. Using as value of the hyperfine field B_hf(BrFe)=+81.35(3) T we obtain vertical strokeg(^74mBr)vertical stroke=0.455(3) and vertical strokeg(⁷⁷Br)vertical stroke=0.6492(3). Static nuclear orientation data have been measured for all above mentioned isotopes. From these data we derive vertical strokeμ(⁷⁸Br, I=1)vertical stroke=0.13(3) and vertical strokeμ(⁸⁴⁹Br, I=2)vertical stroke=1.9(7). The results are discussed within the systematics of the bromine isotopes. (orig.)

[en] Pulse-tube based dilution refrigerators are massively employed in low temperature physics. They allow to reduce the running costs and to be operated with unprecedented easiness. However, the main drawback of this technology is the mechanical vibrations induced by the pulse-tube cryocooler. These perturbations can cause extra-noises drastically affecting the detector performance. In this paper, we propose a solution to mitigate the impact of these vibrations by mounting the detectors in an elastic-pendulum based suspended tower. Based on vibration modeling and experimental tests, we show that the vibration levels are attenuated by up to two orders of magnitude at most frequencies, especially above ∼20 Hz, for both vertical and radial directions. Thanks to this passive isolation solution, vibration levels, both along vertical and radial directions, below 1 μ g/√Hz in the frequency range [1–1000] Hz are obtained. This provides a convenient environment to test the ultimate performance of low temperature detectors. As a result, we report an improvement by one to two orders of magnitude on the noise levels of massive cryogenic bolometers, leading to thermal energy resolutions improved by a factor 5 to 40. Finally, we conclude that the energy resolution of our cryogenic bolometers are no longer limited from any residual vibrations, hence allowing the perspective of further improving our bolometer performance in the context of low-mass dark matter searches and neutrino physics applications.

[en] A possibility to search for elementary particles as dark matter candidates is to detect elastic scattering with cryogenic detectors. For the interpretation of the data one has to determine the detector response to nuclear recoils, the so-called quenching factors. They can differ for the heat-, for the scintillation- and for the ionization-signal and can be measured by scattering of neutrons. The CRESST- and the EDELWEISS-collaborations have set up a neutron scattering facility for cryogenic detectors at the tandem-accelerator of the Munich 'Maier-Leibniz-Labor.' The scattering angle and the time-of-flight of the neutrons are measured by an array of liquid scintillator cells. The pulsed high energy (11 MeV) neutron beam is created by nuclear reaction of a ¹¹B on a H₂-gas target. The set-up and the results of first tests are presented

[en] Monoclinic Tb:CePO₄ nanophosphors with a spindle-like morphology and tailored size (in the nanometer and micrometer range) have been prepared through a very simple procedure, which consists of aging, at low temperature (120 °C), ethylene glycol solutions containing only cerium and terbium acetylacetonates and phosphoric acid, not requiring the addition of surfactants or capping agents. The influence of the heating mode (conventional convection oven or microwave oven) and the Tb doping level on the luminescent, structural and morphological features of the precipitated nanoparticles have also been analyzed. This study showed that microwave-assisted heating resulted in an important beneficial effect on the luminescent properties of these nanophosphors. Finally, a procedure for the functionalization of the Tb:CePO₄ nanoparticles with aspartic-dextran is also reported. The functionalized nanospindles presented negligible toxicity for Verocells, which along with theirs excellent luminescent properties, make them suitable for biomedical applications.

[en] The dry cryostat technology is based on pulse tube cryo-coolers and offers a good alternative to wet dilution cryostats. However, the main drawback is the production of vibrations induced by the pulse tube. These vibrations can be transmitted to the cryogenic detectors mounted in the cryostat and cause extra-noises dramatically affecting their performance. A solution to mitigate the impact of these vibrations is to mount the detectors on a suspended tower. For this purpose, vibrations in a dry cryostat were modeled and preliminary prototypes were investigated in the scope of R&D for the EDELWEISS-III experiment.

[en] The status of the EDELWEISS experiment is presented. First tests of a prototype detector of the '1 kg' stage show an event rate before rejection of ∼2 evt/kg/keV/day above E>20 keV, a factor ∼10 improvement compared to previous runs. An unexpected category of events is evidenced and used to interpret the 'bump' events observed by the UKDMC and Saclay NaI WIMP detection experiments. Finally, the short-term perspectives of the '1 kg' stage, which should allow to sample realistic SUSY models, and the main characteristics of the EDELWEISS-II experiment are described