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The power-frequency magnetic field originating from an existing substation has been calculated using a two-dimensional finite-element model. With this model, the shielding effectiveness for different shielding materials and geometries has been simulated. Calculations were made using 5 mm thick shields on the ceiling and walls. The shield materials used were iron, aluminum and copper. The aluminum and copper shields gave the best average attenuation, 25 dB, while iron gave 10 dB attenuation of the magnetic flux density in the room above the substation. Studies of varying shield geometry in the substation showed that shielding of the switch-gears, containing the high current busbars, in combination with a shield on the ceiling give a calculated attenuation of the field comparable to that of a shield on the ceiling and walls. The calculations have been compared with measurements for one shielding case.

The magnitudes and signs of twenty eight E2 and three M1 matrix elements involving 17 low-lying excited states in 104Ru have been measured by Coulomb excitation using 208Pb, 136Xe and 58Ni ions. The completeness of the set of E2 matrix elements is sufficient to extract, directly from the data, the expectation values of the intrinsic-frame E2 moments that provide considerable insight into the underlying collectivity. The measured E2 properties strongly correlate with macroscopic quadrupole collective degrees of freedom. Detailed comparison of the experimental results and theoretical microscopic calculations within the general quadrupole collective Bohr Hamiltonian are presented. Very good agreement of calculations and experiment is achieved without any parameters fitted to the 104Ru experimental data. Results of phenomenological γ-unstable and γ-rigid models are also given.

E2 collective properties for the low-lying states in 186,188,190,192 Os and 194 Pt have been investigated experimentally by means of Coulomb excitation using 3.3–4.8 MeV/nucleon 40 Ca, 58 Ni, 136 Xe and 208 Pb beams. The deexcitation γ rays following Coulomb excitation were detected in coincidence with the scattered particles. Levels with excitation energies up to 3–4 MeV of the ground-state, γ and 4 + collective bands as well as excited 0 + states were populated in each nucleus studied. A semiclassical Coulomb-excitation least-squares search code GOSIA was used to extract E2 matrix elements from the measured γ-ray yields. For each nucleus studied, a unique and almost complete set of E2 matrix elements for the low-lying states has been determined, which includes both the magnitudes and signs of the transitional and diagonal matrix elements. The completeness of the set of measured E2 matrix elements makes it possible to determine the intrinsic quadrupole deformation for the low-lying states in these nuclei via a model-independent method. The results indicate clearly that the E2 properties for the low-lying states in these nuclei are correlated well using only the quadrupole collective degrees of freedom. The extracted E2 matrix elements are compared with the prediction of various collective models such as the asymmetric rigid rotor model, the γ-soft model of Leander, and the IBA-2 model. These particular models do not reproduce the data satisfactorily, however the general trends of the data are consistent with the descriptions of γ-soft type collective models through a prolate to oblate shape-transition region. That the enhanced B (E2) values between the I ,quasi- K π = 4,4 + state and members of the I ,quasi- K π = 2,2 + band are well reproduced by the γ-soft model is consistent with the interpretation of the I ,quasi- K π = 4,4 + state being a two-phonon γ-vibration excitation.

The nuclei 106 Pd and 108 Pd have been Coulomb excited using beams of 16 O, 58 Ni and 208 Pb. The data determined 25 and 31 E2 matrix elements in 106 Pd and 108 Pd, respectively. The experimental data are qualitatively in agreement with the spherical-harmonic quadrupole vibrational model, but quantitatively there are large discrepancies, even for the states generally accepted to be the two-phonon vibrational states. A sum-rule method was applied to the data, the result of which implies that the vibrational quadrupole strengths of the 0 + and 4 + two-phonon states are fragmented and shared between several E2 matrix elements. The E2 matrix elements imply appreciable quadrupole triaxiality with a γ-centroid of about 20°. A systematic comparison is made with neighbouring Pd-isotopes and with 114 Cd.

The magnetic shielding effectiveness for closed and open shield structures is studied at extremely low frequencies. Analytical solutions are used for simple geometries, while more complex structures are evaluated using a finite-element method. Both highly conductive and ferromagnetic materials are studied, and their different shielding behavior is shown. Ferromagnetic shields give good results for small and closed shields and they also give a large field attenuation at close range to the source for open shield geometries. Highly conductive materials, on the other hand, are found to be suitable for large shield sizes. The attenuation is, however, reduced in the close vicinity of the source. Comparisons of numerical results with analytical calculations and measurements confirmed the high accuracy of the finite-element model. >

The finite element method (FEM) is used for analyzing the shielding effectiveness of an eddy current shield applied to a 10/0.4 kV substation. The influence of the shield extension is studied, and a calculated magnetic field attenuation of 30 dB is obtained for a 5 mm aluminum shield applied on the ceiling and the walls. With a 3D model, the eddy current distribution in the shield is studied, giving guidance for door positioning. Here, the insertion of a door in the shielded wall off the paths of the main eddy currents is found to create only a locally elevated magnetic field. With a simplified 2D model, the influence of shield conductivity is also analyzed. An increase of the conductivity over that of aluminum here gives a limited shielding improvement. >

The nucleus 72Ge has been Coulomb excited using 16O, 58Ni and 208Pb. Seventeen E2 matrix elements coupling the low-lying states have been determined. Based on these data, an interpretation of the structure of 72Ge has been proposed that includes an “intruder” 0+ state perturbing what the present work shows to be a triaxial quadrupole-deformed collective rotational structure.

A 3-D finite element model is used to analyze the shielding effectiveness of an eddy-current shield applied to a 10/0.4-kV substation. The influence of the shield extension is shown. Furthermore, the insertion of a door in the shielded wall was found to create a locally elevated B-field. The results show that the magnetic field from substations can be shielded so that disturbances on VDT (video display terminal) screens in the vicinity can be avoided. >

A direct determination of the sign of the interference term which arises in Coulomb excitation has been performed For the case of 102 Ru, this sign was found to be negative in agreement with the relevant model predictions.

The nucleus 114 Cd has been Coulomb excited using beams of 16 O, 40 Ca, 58 Ni and 208 Pb. Several new states have been observed and an almost complete set of reduced E2 matrix elements for the lowest-lying positive-parity states in 114 Cd have been measured. In total, about 40 E2 matrix elements have been determined in a model-independent way, including the static quadrupole moments of the 4 + 1 , 6 + 1 , 2 + 2 and 2 + 3 states. Large negative static quadrupole moments were found for the 4 + 1 and 6 + 1 states and a large positive quadrupole moment for the 2 + 2 state. All E2 matrix elements involved in the deexcitation of the quintuplet of states at an energy of about 1.2 Me V were determined. The data are compared with predictions by various models, including a configuration mixing calculation within the framework of the IBA model, the harmonic vibrator and a model in which the states of a near-harmonic vibrator are mixed with those of a rotational intruder band with a large deformation. Although no perfect match is obtained, the data favour a vibration-like structure involving levels up to the four-quadrupole phonon multiplet.

The reorientation precession technique, REPREC, for measurements of quadrupole moments is described. The application of REPREC to the measurement of the static electric quadropole moments of the first excited 2 + states in 108, 110 Pd is presented. The possibility to measure the sign of the matrix product P 4 = M 02 M 22′ M 02′ M 22 is also discussed. Such measurements are presented for 108, 110 Pd. The results of these measurements are P 4 108 Pd and 110 Pd. For 108 Pd the quadrupole moment of the first excited 2 + state was found to be −0.66±0.18 e ·b and for 110 Pd, −0.72±0.14 e ·b. Intrinsic nuclear properties for 106−110 Pd are derived using the sum rules suggested by Kumar.

The quadrupole moments of the first excited 2+ states in 96,100,104Ru have been measured using the reorientation precession technique. In 104Ru the sign of the Coulomb interference term P4 = M0+12+1 M0+12+2 M2+22+1 × M2+12+1 was determined and found to be P4 < 0. The quadrupole moment in 104Ru was determined to be -0.76 ± 0.19 eb. In 96Ru and 100Ru the measurements revealed quadrupole moments of -0.15 ± 0.27 eb and -0.40 ± 0.12 eb, respectively, independent of the sign of P4. The experimentally determined values are compared with theoretical calculations.

The directional correlations ofγ-γ andγ-electron cascades in119Sb are measured, in the decay of119mTe. Bothγ-γ andγ-electron directional correlation coefficients are determined for the cascades (energies in keV): 153.5-1212.7, 942.3-270.5, (976.2+979.3)-270.5, 1095.7-270.5 and 1136.8-270.5. For the cascades 912.6-1366.2, 2013.4-270.5 and 2089.9-270.5γ-γ directional correlations are measured. The mixing ratios evaluated are:δ(M2/E1, 153.5 keV)=0.0003±0.0023,δ(E2/M1, 270.5 keV)=-0.39±0.29,δ(E2/M1, 942.3 keV)= −0.26±0.12,δ(E3/M2,1095.7 keV)=−0.01±0.07, andδ(M3/E2,1212.7 keV) =0.004±0.007. The result is compared with theoretical predictions.

Particle parameters for the highly hindered 84.2 keV transition in 231 Pa have been shown to be influenced by dynamic nuclear structure effects. According to the theory by Pauli 1 ) the nuclear current parameter η is found to be η > 4.

A simple method for designing parallel plate electron multipliers is described. Semiconducting and secondary emitting layers are deposited onto glassplates by rf-sputtering, and by placing two plates face to face with a separation of 0.6 mm a parallel plate multiplier is formed. The multipliers have a high gain (>10 9 ) and give output pulses with a very narrow pulse height distribution. The multipliers are used as detectors in electron spectrometers. The small dimensions imply that a large number of multipliers may be placed in the focal plane and used simultaneously.

Transitions in the decay of 168Tm to 168Er have been studied by measurements of electron-gamma directional correlations. The M1-contributions of the 632-, 731- and 816-keV transitions between the gamma-vibrational band and the ground state rotational band have been determined to amount to less than 0.8%. The 99-, 198- and 830-keV transitions depopulating the 1094-keV state have been determined to be of predominantly E1-character. A pure E1-multipolarity for the 99-keV transition is however possible only if a penetration effect is present in the internal conversion process characterized by a nuclear current parameter ? = 303-8+7 or ? = -12.2-2.0+2.0

Four transitions in 133 Cs have been studied by measurements of relative conversion electron intensities and electron-gamma directional correlations. The transitions studied, 276, 223, 161 and 80 keV respectively, all feed and de-excite the 161 keV level in 133 Cs. In addition the L-subshell ratios for the 81 keV transition have been measured and analysed. The 161 and 223 keV transitions show penetration effects in the internal conversion process. The penetration effects in the 223 keV transition are reported for the first time.

Directional correlations of the cascade in 123 Te involving K, L and M electrons from the 89 keV M4 transition have been measured in order to determine the δ (E2/M1) value for the 159 keV transition. The result agrees with that from older correlation measurements, but is in conflict with values derived from Coulomb excitation and lifetime measurements as well as from L subshell ratios.

The γ-ray and internal conversion spectra of the decay of 131 Ba to levels in 131 Cs were investigated using a Ge(Li) detector and a double-focussing β-ray spectrometer. Accurate transition energies and internal conversion coefficients were deduced using the internal conversion data of Horen et al . 1 ) in conjunction with the results obtained here. Gamma-gamma and electron-γ directional correlation measurements were performed. Unique spin-parity assignments were obtained for all levels in a compiled level scheme using the deduced conversion coefficients, the results from angular correlation measurements and the deduced log ft values. Nuclear penetration effects were found to be present in the 92 keV transition characterized by λ = 23 −11 +7 .

The sign of the matrix product P 3 = M 0 1 + 2 1 + M 2 1 + 2 1 + M 2 2 + 0 1 + is determined for 194 Pt and found to be negative. A suggestion is made that single particle degrees of freedom in the wavefunctions will be important for the sign of P 3

The transuranium nucleus 248 Cm has been Coulomb excited using 641 MeV 136 Xe and 260 MeV 58 Ni projectiles. Only the ground band was excited with measurable cross sections. The E2 transition matrix elements involving the ground-band states up to spin 24 + have been extracted from these Coulomb excitation data using a new semiclassical Coulomb-excitation least-squares search code. The extracted E2 transition matrix elements agree with the spheroidal rigid rotor relation to within the experimental errors. In addition static electric quadrupole moments have been measured up to spin 20 + for the first time for a strongly deformed nucleus, uniquely determining the prolate shape of the ground band of 248 Cm.

It is well-known that the stable isotopes of Ru and Pd belong to a transitional region between a spherical and deformed shape of the potential surface. This is clearly reflected in the energy systematics of the positive parity states presented in fig. 1. In this figure only states with highly reliable spin assignments are given. Thus a number of states with positive parity are omitted especially in the energy region 1–2 MeV.

The level scheme of 131 Cs has been troublesome to interpret both theoretically and experimentally1,2,3,4). The angular correlation measurements of Fechner et al.4), however, provided unique spin assignments for some of the lower lying states for which previously reported results had been contradictory.