Miroslav Finger

Results from the OSQAR photon-regeneration experiment : No light shining through a wall

A new method to amplify the photon-axion conversions in a magnetic field is proposed using a buffer gas at a specific pressure in a photon-regeneration experiment. As a first result, new bounds for mass and coupling constant for laboratory experiments aiming to detect any hypothetical scalars and pseudoscalars, which can couple to photons were obtained, excluding with 95% confidence level, the recently withdrawn PVLAS result.

Low temperature nuclear orientation of nuclei far from beta stability Spin — Facility at JINR

The experimental facility for the study of the decay of oriented nuclei in a broad range of atomic and mass number and half-lives based on hyperfine interactions at ultralow temperatures — the SPIN facility at JINR — is described. High cooling power top loading 3He-4He dilution refrigerator of the system is capable of fast cooling of the sample inserted into the mixing chamber to the base temperature 10 mK for about 1–2 h. Detection system is designed for the study of angular distribution and temperature dependence of the anisotropy of gamma rays, linear polarisation of gamma rays and NMR/ON studies. Some results of nuclear orientation studies in off-line mode of radioactive nuclei with the half-live down to ∼1 h produced by spallation reaction with 660 MeV protons are presented. The project of nuclear orientation system on-line to the mass-separator and the new 600 MeV Dubna proton phasotron is described.

Multilayer Scintillator Responses for Mo Observatory of Neutrino Experiment Studied Using a Prototype Detector MOON-1

An ensemble of multilayer scintillators is discussed as an option of the high-sensitivity detector MOON (Mo Observatory of Neutrinos) for spectroscopic measurements of neutrinoless double beta decays. A prototype detector MOON-1, which consists of 6-layer plastic scintillator plates, was built to study the photon responses of the MOON-type detector. The photon responses, i.e., the number of scintillation photons collected and the energy resolution, which are key elements for high-sensitivity experiments, are found to be 1835 � 30 photoelectrons for 976 keV electrons and � ¼ 2:9 � 0:1% (� E=E ¼ 6:8 � 0:3% in FWHM) at the Q�� � 3 MeV region, respectively. The multilayer plastic scintillator structure with high energy resolution as well as a good signal for the background suppression of � –� rays is crucial for the MOON-type detector to achieve inverted-hierarchy neutrino-mass sensitivity. It will also be useful for medical and other rare-decay experiments as well.

The decay of 152Tb

Abstract The conversion electron spectrum, electron-gamma and β + -gamma coincidence spectra are investigated, and the gamma-ray spectrum is studied in two Ge(Li) semiconductor spectrometers. A decay scheme 152 Tb → 152 Gd is suggested, including many new levels among which two 0 + states at 1484.0 and 2720.7 keV. Relative intensities at 0.2 : 0.3 : 1 are found for positon branches from 152 Tb to the 615.6 keV (0 + ), 344.4 keV (2 + ) and to the ground state of 152 Gd. Spin 1 − is ascribed to the ground state of 152 Tb. Spin assignments are being made for the following excited levels: 755.6 keV 4 + , 1109.8 keV 2 + , 1123.8 keV 3 − , 1606.1 keV 2 + , 1643.9 keV 1 − , 1862.3 keV 2 + and 1942.5 keV 2 + .

Feasibility study of an experiment to measure the vacuum magnetic birefringence

The use of a recently decommissioned 15-meters long twin aperture LHC supercon-ducting magnet prototype having a transverse magnetic fieldB ≈ 9.5 T provides the unique opportunity for the construction of a new powerful experiment to measure the Vacuum Magnetic Birefringence (VMB). The values or the limit values of the mass and of the coupling constant to two photons of possible dark matter candidates such as axions are aimed to be deduced from such an experiment. In this article, the technical feasibility study of a new setup to measure the VMB will be presented. It is based on a linear optical resonant cavity house in the LHC superconducting dipole prototype. The mechanical integrations of the optical components inside the magnet aperture as well as the optical detection principles will be presented. A comparison of the expected performances with respect to the present reference results for this type of experiment will also be given.

Magnetic dipole moments of the145–149Eu ground states

Nuclear orientation measurements at low temperatures have been carried out on radioactive isotopes of145–149Eu in Fe and of147,149Eu in Gd. The initial-state orientation coefficients determined from the measured gamma-ray anisotropies yield the magnetic dipole moments of the europium nuclei with A=145, 146, 147, 148 and 149 to be 3.2(5), 1.7(3), 3.1(4), 2.1(3) and 2.5(5), ΜN, respectively. The values obtained for odd-A nuclei follow the systematics of the 5/2+ state magnetic moments of the nuclei in this region and are close to the values given by the single-particle model.

Nuclear orientation study of the decay of 169Lu

The level structure of 169Yb and the nature of the linking transitions have been studied by radioactive decay of 169Lu polarised at low temperatures in a gadolinium host. Anisotropies of 112 gamma rays in 169Yb have been measured. Unambiguous spin assignments have been made for a number of levels below 2 MeV and multipole mixing ratios of about 90 transitions have been deduced. In particular, it has been found that the 1070.8 keV 7/2+ to 7/2+ transition has delta =0.74-0.13+0.11 or 10.3-4.5+50.1 and from the experimental alpha K value an E0:E2 mixing ratio of mod q mod =5.8+or-0.8 or 3.55+or-0.16, respectively, has been obtained. The energy and structure of individual levels, reduced E2 and M1 transition probabilities and E2:M1 mixing ratios have been calculated using the quasiparticle-phonon model including a Coriolis interaction. In general, good agreement is obtained between the theoretical predictions and the experimental results.

Nuclear orientation of156Tb in gadolinium matrix

The anisotropy of the angular distribution of gamma-rays from the decay of156Tb, oriented in a gadolinium matrix at low temperatures, has been measured at the angles of 0 and π/2 with respect to the applied magnetic field direction in the range of temperatures from 14·6 to 68·4 mK. The temperature dependence of anisotropy was measured for the first time. The parameters of hyperfine magnetic dipole and electric quadrupole splittings have been determined and the values of the magnetic dipole moment ¦Μ156¦=(9·6±1·3)×10−27 J/T and the electric quadrupole momentQ156=(2·9±0·9)×10−28 m2 of the156Tb ground state have been calculated. Multipole mixing ratios andB(E2) branching ratios of many gamma-ray transitions occurring in156Gd have been found and the results have been discussed in terms of the rotational-vibration and pairing-plus-quadrupole models.

Multipole mixing ratios of electromagnetic transitions in 152Gd

Abstract Using γ-γ(θ), γ(θ) (nuclear orientation) and e k -γ(θ) directional correlation techniques, we have determined the multipole character of some transitions connecting the quadrupole and octupole quasi-vibrational bands to the ground state quasi-rotational band in 152 Gd following the decay of 152 Tb. For the γ-γ directional correlation measurements a high-energy resolution system employing a Ge(Li) and a NaI(Tl) detector was used while for the e k -γ correlation we used a NaI(Tl) and magnetic lens spectrometer system. The nuclear orientation measurements were carried out at low temperatures obtained with a 3 He- 4 He dilution refrigerator. The results show that the 2 + → 2 + transition between the β-vibrational and the ground state bands contains ≈ 10% Ml admixture, δ = − 3.05 ± 0.14, and a large E0 contribution while the similar transition from the γ-vibrational band has δ = 4.3 ± 0.7. These results are compared with Kumars predictions for similar transitions in 152 Sm. Three other mixing ratios were also determined.

Nuclear orientation of154EuFe,166TmGd and169YbFe and169YbGd

Nuclear orientation measurements at low temperatures have been carried out on radioactive isotopes of154Eu and169Yb in Fe and of166Tm and169Yb in Gd. Gamma-rays from169YbGd, obtained by the decay of implanted and melted sample of169IuGd, were observed to have smaller anisotropies of opposite signs compared with those from169YbFe. This may indicate that for Yb polarized in Gd electric quadrupole interaction is comparable with magnetic dipole one. Mixing ratios of the transitions in154Gd,166Er and169Tm have been made for two levels in166Er. Our analysis showed that the 3− to 3+ beta decay to the 1128 keV level in154Gd has 65(20)% Δjβ=0.