W Vanderpoorten

Nicole: New on-line orientation facility at ISOLDE/CERN

This paper presents off-line and on-line orientation results obtained with the new on line nuclear orientation device NICOLE in CERN. Magnetic moments of187,185Ptg and186Irm, electric quadrupole moment ratios between Pt isotopes with mass number 185, 187 and 189, the spin of the 2 h isomer of186Ir and a new decay scheme of184Au involving a metastable state are established. The shape variation versus mass number of the Pt isotopes leads to sign change of the spectroscopic quadrupole moment between A=187 and 185.

Shape transition in light Pt isotopes: Magnetic moments and electric quadrupole moment ratios for185,187,189Pt

Nuclear orientation and nuclear magnetic resonance experiments were performed on185, 187, 189Pt isotopes oriented in Fe and single crystal Zn at temperatures down to about 6 mK. The hyperfine splitting frequencies of185Pt and187Pt in iron were determined to be 164.9(2) and 261.1(2) MHz, respectively. With the hyperfine field of −126.1(2.5) T, the g-factors are deduced to be |g(185Pt)|=0.172(3) and |g(187Pt)|=0.272(5).The spectroscopic quadrupole moment of187Pt was found to be negative with magnitude similar to that of189Pt, indicating a predominantly oblate ground state deformation for both isotopes. The spectroscopic quadrupole moment of185Pt was found to be positive, with the ratio Q(185Pt)/Q(189Pt)=−3.6(9), clearly indicating a change to prolate ground state deformation.

Hyperfine interaction aspects of cold implantation of francium in iron

The hyperfine field of Fr in Fe and a highly substitutional occupancy in host Fe after cold implantation (T<1 K) — although Fr is the largest atom in nature —have been deduced from experiment. These aspects are treated in relation to other alkalines and 6sp elements.

On line nuclear orientation: From technique to new physics

ConclusionSince the first results continuous improvements and further developments of OLNO have been carried out; e.g. the sensitivity has been increased by the realization of particle detection. On—line nuclear orientation has evolved to a unique technique to study a broad range of physics topics from very fundamental interactions to applied material science. This has been proven by the results that already have been obtained. Apart from the well established low temperature NO technique, also the development of in—beam polarization methods is taking place. At NICOLE fine opportunities exist to work out specific and unique physics problems. Benefit can be taken of the high production rates at ISOLDE as compared to the other OLNO systems.

First on-line β-decay asymmetry measurements of oriented nuclei

We report the first on-line β-anisotropy measurements with nuclear orientation. Particle detectors operating at 4K are used. The first results were obtained on the mirror nuclei15O,17F and19Ne and on69As. All isotopes were implanted in iron. With the same set-up85KrFe was also measured. Important information on hyperfine fields, site occupancy, spin-lattice relaxation and magnetic moments was obtained.

Anisotropic alpha-emission in the223Ra decay chain

Anisotropic α-emission from nuclei in the decay chain from223Ra to207Tl has been observed using low temperature nuclear orientation in combination with high resolution α-detection at 4.2 K. Information on partial wave amplitudes as well as hyperfine interactions has been extracted.

Particle-detection from oriented nuclei

A survey is given of particle emission from nuclei that have been spin oriented by cryogenical means. Experiments and recent developments with detectors in the low temperature environment and their on-line application are reviewed. The most recent results are mentioned. Some phenomena to be unraveled in future studies are pointed out.

Magnetic moments close to208Pb from on-line no

The nuclear magnetic moments of the shortlived isotopes199mPo,201mPo,201Po and203Po have been determined with on line nuclear orientation. Together with other recently measured moments in this region, the variations with Z and N may represent a clue to an understanding of the quenching of nuclear magnetism around208Pb.

Enhanced performance of a bolometric detector at mK temperatures in high magnetic fields

Results on the operation of a bolometer detector in high magnetic fields and at very low temperatures are presented. We tested a diamond absorber on a Ge thermistor in magnetic fields up to 8 Tesla and temperatures down to 10 mK using an55Fe X-ray and109Cd electron source. Heavily doped Ge shows a giant magnetoresistance effect. This was used to tune the thermistor impedance to an optimal value.

The interaction of low-energy secondary radioactive beams and magnetic-surfaces

A system was constructed to polarize on-line mass separated radioactive ion beams. They can be either transmitted through very thin foils or be reflected under a grazing incidence angle from a very flat ferromagnetic surface. It will be used to study both nuclear parameters of the ions polarized as well as the magnetic properties of the surfaces.