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Based on results from a measurement of weak decay branches observed following the β- decay of 94Y and on lifetime data from a study of 94Zr by inelastic neutron scattering, collective structure is deduced in the closed-subshell nucleus 94Zr. These results establish shape coexistence in 94Zr. The role of subshells for nuclear collectivity is suggested to be important.

A program of high-precision superallowed Fermi β decay studies is being carried out at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility at TRIUMF. Recent high-precision branching ratio measurements for the superallowed decays of 74Rb and 26Alm, as well as a half-life measurement for 26Alm that is the most precise half-life measurement for any superallowed emitter to date, are reported. These results provide demanding tests of the theoretical isospin symmetry breaking corrections in superallowed Fermi β decays.

The 8 π spectrometer, located at TRIUMF-ISAC, was the world’s most powerful spectrometer dedicated to β -decay studies until its decommissioning in early 2014 for replacement with the GRIFFIN array. An integral part of the 8 π spectrometer was the Pentagonal Array for Conversion Electron Spectroscopy (PACES) consisting of 5 Si(Li) detectors used for charged-particle detection. PACES enabled both γ − e − and e − − e − coincidence measurements, which were crucial for increasing the sensitivity for discrete e − lines in the presence of large backgrounds. Examples from a 124 Cs decay experiment, where the data were vital for the expansion of the 124 Cs decay scheme, are shown. With suffcient statistics, measurements of conversion coeffcients can be used to extract the E 0 components of J π → J π transitions for J ≠ 0, which is demonstrated for data obtained in 110 In→ 110 Cd decay. With knowledge of the shapes of the states involved, as obtained, for example, from the use of Kumar-Cline shape invariants, the mixing of the states can be extracted.

The highly-efficient and segmented TIGRESS gamma-ray spectrometer at TRIUMF has been used to perform a reorientation-effect Coulomb-excitation study of the 2(1)(+) state at 3.368 MeV in Be-10. This is the first Coulomb-excitation measurement that enables one to obtain information on diagonal matrix elements for such a high-lying first excited state from gamma-ray data. With the availability of accurate lifetime data, a value of -0.110 +/- 0.087 eb is determined for the diagonal matrix element, which assuming the rotor model, leads to a negative spectroscopic quadrupole moment of Q(S)(2(1)(+)) = -0.083 +/- 0.066 eb. This result is in agreement with both no-core shell-model calculations performed in this work with the CD-Bonn 2000 two-nucleon potential and large shell-model spaces, and Green's function Monte Carlo predictions with two-plus three-nucleon potentials.

A study of the ${\ensuremath{\beta}}^{+}$-electron capture decay of ${}^{110}$In into levels of ${}^{110}$Cd is combined with a reanalysis of data from a previous study of ${}^{110}$Cd with the $(n,{n}^{\ensuremath{'}}\ensuremath{\gamma})$ reaction with monoenergetic neutrons. The $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidences from the ${}^{110}$In decay leads to many new assignments of $\ensuremath{\gamma}$ rays observed in the $(n,{n}^{\ensuremath{'}}\ensuremath{\gamma})$ reaction, permitting the observation of weak low-energy transitions, and setting stringent upper limits on unobserved decay branches. The uncertainties on many of the lifetimes from the $(n,{n}^{\ensuremath{'}}\ensuremath{\gamma})$ reaction are significantly reduced, and limits are established for the lifetimes of levels too long for a direct measurement. The absence of enhanced transitions between the previously assigned phonon states and the deformed intruder states strongly suggests that mixing between the configurations is generally weak, refuting the strong-mixing scenario as an explanation of the decay pattern of the excited ${0}^{+}$ states in ${}^{110}$Cd. The decay pattern of the nonintruder states is suggestive of a $\ensuremath{\gamma}$-soft rotor, or O(6) nucleus, rather than a vibrational, or U(5), pattern. The existence of a four-particle--six-hole proton excitation in ${}^{110}$Cd is also suggested.

Based on results from a measurement of weak decay branches observed following the β- decay of 94Y and on lifetime data from a study of 94Zr by inelastic neutron scattering, collective structure is deduced in the closed-subshell nucleus 94Zr. These results establish shape coexistence in 94Zr. The role of subshells for nuclear collectivity is suggested to be important.

A high-precision half-life measurement for the superallowed ${\ensuremath{\beta}}^{+}$ emitter $^{26}\mathrm{Al}^{m}$ was performed at the TRIUMF-ISAC radioactive ion beam facility yielding ${T}_{1/2}=6346.54\ifmmode\pm\else\textpm\fi{}{0.46}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}{0.60}_{\mathrm{syst}}\text{ }\text{ }\mathrm{ms}$, consistent with, but 2.5 times more precise than, the previous world average. The $^{26}\mathrm{Al}^{m}$ half-life and $ft$ value, 3037.53(61) s, are now the most precisely determined for any superallowed $\ensuremath{\beta}$ decay. Combined with recent theoretical corrections for isospin-symmetry-breaking and radiative effects, the corrected $\mathcal{F}t$ value for $^{26}\mathrm{Al}^{m}$, 3073.0(12) s, sets a new benchmark for the high-precision superallowed Fermi $\ensuremath{\beta}$-decay studies used to test the conserved vector current hypothesis and determine the ${V}_{ud}$ element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

Nucleon transfer experiments have in recent years begun to be exploited in the study of nuclei far from stability, using radioactive beams in inverse kinematics. New techniques are still being developed in order to perform these experiments. The present experiment is designed to study the odd-odd nucleus Na which has a high density of states and therefore requires gamma-ray detection to distinguish between them. The experiment employed an intense beam of up to 3×10 pps of Na at 5.0 MeV/nucleon from the ISAC-II facility at triumf. The new silicon array SHARC was used for the first time and was coupled to the segmented clover gamma-ray array TIGRESS. A novel thin plastic scintillator detector was employed at zero degrees to identify and reject reactions occurring on the carbon component of the (CD) target. The efficiency of the background rejection using this detector is described with respect to the proton and gamma-ray spectra from the (d,p) reaction. © Published under licence by IOP Publishing Ltd.

The stable Cd isotopes have long been used as paradigms for spherical vibrational motion. Extensive investigations with in‐beam γ spectroscopy have resulted in very‐well‐established level schemes, including many lifetimes or lifetime limits. A programme has been initiated to complement these studies with very‐high‐statistics β decay using the 8π spectrometer at the TRIUMF radioactive beam facility. The decays of 112In and 112Ag have been studied with an emphasis on the observation of, or the placement of stringent limits on, low‐energy branches between potential multi‐phonon levels. A lack of suitable 0+ or 2+ three‐phonon candidates has been revealed. Further, the sum of the B(E2) strength from spin 0+ and 2+ states up to 3 MeV in excitation energy to the assigned two‐phonon levels falls far short of the harmonic‐vibrational expectations. This lack of strength points to the failing of collective models based on vibrational phonon structures.

Recent experimental work at the TRIUMF‐ISAC radioactive ion‐beam facility in Vancouver Canada, has produced several new results related to precise experimental tests of fundamental symmetries. The nature of these programs range from campaigns using existing setups, to the development of new apparati to further the experimental reach. One of the primary goals has been the investigation of superallowed Fermi β‐decay, and its relation to Standard Model tests of CVC and CKM unitarity The extraction of experimental β‐decay ft values requires the measurement of three quantities: the half‐life, the superallowed branching ratio, and the parent‐daughter mass difference. TRIUMF‐ISAC has the ability to measure each of these values with very high precision, using a gas‐proportional‐counter, the 8π γ‐ray spectrometer, and TITAN, respectively. This report focuses on the recent experimental progress of the superallowed program, as well as highlighting some results from the successful halo‐nucleus mass‐measurement progra...

The most recent isospin-symmetry-breaking corrections, δc, of Towner and Hardy for superallowed Fermi β-decay transitions, have included the opening of specific core orbitals. This change has resulted in significant deviations in some of the δc factors from their previous calculations, and an improved agreement of the individual corrected t values with the overall world average of the 13 most precise cases. While this is consistent with the conserved-vector-current (CVC) hypothesis of the Standard Model, these new calculations must be thoroughly tested, and guidance must be given for the improvement of calculations for the upper-pf shell nuclei. Using the (d,t) reaction mechanism to probe the single neutron wavefunction overlap, information regarding the relevant shell-model configurations needed in the calculation can be determined. An experiment was therefore performed with a 22 MeV polarized deuterium beam from the MP tandem Van de Graaff accelerator in Munich, Germany. Using the Q3D magnetic spectrograph, and a cathode-strip focal-plane detector, outgoing tritons were analyzed at 9 angles between 10° and 60°, up to an excitation energy of 4.8 MeV. This proceeding reports the motivational and experimental details for the 64Zn(d,t)63Zn transfer work presented.

The (3He, d) single-proton stripping reaction has been performed on targets of 185,187Re to investigate the structures of the 43+ states in 186,188Os. The experiment employed 30 MeV 3He beams, and the reaction products were analyzed with a Q3D spectrograph. Absolute cross sections were determined at nine angles between 5° and 50° for states up to approximately 3 MeV in excitation energy. Large 5/2+[402]π+3/2+[402]π two-quasiparticle components are deduced for the 43+ levels of both isotopes. Their magnitudes are in agreement with calculations performed using the quasiparticle phonon model, which predicts a coexistence of a large hexadecapole with a smaller, but sizable, γ-γ component in the 43+.

A high-precision half-life measurement for the superallowed β+ emitter 26Al(m) was performed at the TRIUMF-ISAC radioactive ion beam facility yielding T 1/2 6346.54 ± 0.46(stat) ± 0.60 (syst) ms, consistent with, but 2.5 times more precise than, the previous world average. The 26Al(m) half-life and ft value, 3037.53(61) s, are now the most precisely determined for any superallowed β decay. Combined with recent theoretical corrections for isospin-symmetry-breaking and radiative effects, the corrected Ft value for (26)Al(m), 3073.0(12) s, sets a new benchmark for the high-precision superallowed Fermi β-decay studies used to test the conserved vector current hypothesis and determine the V(ud) element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

The low-energy structure of the proton dripline nucleus {sup 20}Na has been studied using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. A 1.7-MeV/nucleon {sup 20}Na beam of {approx}5x10{sup 6} ions/s was Coulomb excited by a 0.5-mg/cm{sup 2nat}Ti target. Scattered beam and target particles were detected by the BAMBINO segmented Si detector while {gamma} rays were detected by two TIGRESS HPGe clover detectors set perpendicular to the beam axis. Coulomb excitation from the 2{sup +} ground state to the first excited 3{sup +} and 4{sup +} states was observed, and B({lambda}L) values were determined using the 2{sup +}{yields}0{sup +} de-excitation in {sup 48}Ti as a reference. The resulting B({lambda}L){down_arrow} values are B(E2;3{sup +}{yields}2{sup +})=55{+-}6 e{sup 2} fm{sup 4} (17.0{+-}1.9 W.u.), B(E2;4{sup +}{yields}2{sup +})=35.7{+-}5.7 e{sup 2} fm{sup 4} (11.1{+-}1.8 W.u.), and B(M1;4{sup +}{yields}3{sup +})=0.154{+-}0.030 {mu}{sub N}{sup 2} (0.086{+-}0.017 W.u.). These measurements provide the first experimental determination of B({lambda}L) values for this proton dripline nucleus of astrophysical interest.

High-statistics $\ensuremath{\beta}$-decay measurements of $^{112}\mathrm{Ag}$ and $^{112}\mathrm{In}$ were performed to study the structure of the $^{112}\mathrm{Cd}$ nucleus. The precise energies of the doublet of levels at 1871 keV, for which the ${0}^{+}$ member has been suggested as a possible daughter state following neutrinoless double electron capture of $^{112}\mathrm{Sn}$, were determined to be 1871.137(72) keV (${0}_{4}^{+}$ level) and 1870.743(54) keV (${4}_{2}^{+}$ level). The nature of the ${0}_{4}^{+}$ level, required for the calculation of the nuclear matrix element that would be needed to extract a neutrino mass from neutrinoless double electron capture to this state, is suggested to be of intruder origin.

The low-energy structures of the radioactive nuclei 20, 21Na have been examined using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of ∼ 5×106 ions/s were accelerated to 1.7MeV/A and Coulomb excited in a 0.5mg/cm^2 natTi target. Two TIGRESS HPGe clover detectors perpendicular to the beam axis were used for $ \gamma$ -ray detection, while scattered nuclei were observed by the Si detector BAMBINO. For 21Na , Coulomb excitation from the 3/2+ ground state to the first excited 5/2+ state was observed, while for 20Na , Coulomb excitation was observed from the 2+ ground state to the first excited 3+ and 4+ states. For both beams, B ( $ \lambda$ L) values were determined using the 2+ $ \rightarrow$ 0+ de-excitation in 48Ti as a reference. The resulting B(E2) ↓ value for 21Na is 137±9 e^2fm^4, while the resulting B( $ \lambda$ L) ↓ values for 20Na are 55±6 e^2fm^4 for the 3+ $ \rightarrow$ 2+ , 35.7±5.7 e^2 fm^4 for the 4+ $ \rightarrow$ 2+ , and 0.154±0.030 μ_N^2 for the 4+ $ \rightarrow$ 3+ transitions. This analysis significantly improves the measurement of the 21Na B(E2) value, and provides the first experimental determination of B( $ \lambda$ L) values for the proton dripline nucleus 20Na .-1

The scattering of 30 MeV $^{3}\mathrm{He}$ from a $^{185}\mathrm{Re}$ target has been investigated. The measured elastic scattering is in disagreement with calculations using common optical model parameter sets found in the literature. A new optical model parameter set has been determined that reproduces the data for both the elastic and the inelastic scattering channels.

The TRIUMF‐ISAC Gamma‐Ray Escape Suppressed Spectrometer (TIGRESS) is a state‐of‐the‐art γ‐ray spectrometer being constructed at the ISAC‐II radioactive ion beam facility at TRIUMF. TIGRESS will be comprised of twelve 32‐fold segmented high‐purity germanium (HPGe) clover‐type γ‐ray detectors, with BGO∕CsI(Tl) Compton‐suppression shields, and is currently operational at ISAC‐II in an early‐implementation configuration of six detectors. Results have been obtained for the first experiments performed using TIGRESS, which examined the A = 20, 21, and 29 isotopes of Na by Coulomb excitation.

The low-energy structures of the mirror nuclei {sup 21}Ne and radioactive {sup 21}Na have been examined by using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of {approx}5x10{sup 6} ions/s were accelerated to 1.7 MeV/A and Coulomb excited in a 0.5 mg/cm{sup 2} {sup nat}Ti target. Scattered beam and target particles were detected by the segmented Si detector BAMBINO, while {gamma} rays were observed by using two TIGRESS HPGe clover detectors perpendicular to the beam axis. For each isobar, Coulomb excitation from the (3/2){sup +} ground state to the first excited (5/2){sup +} state was observed and B(E2) values were determined by using the 2{sup +}{yields}0{sup +} de-excitation in {sup 48}Ti as a reference. The {phi} segmentation of BAMBINO was used to deduce tentative assignments for the signs of the mixing ratios between the E2 and M1 components of the transitions. The resulting B(E2){up_arrow} values are 131{+-}9 e{sup 2} fm{sup 4} (25.4{+-}1.7 W.u.) for {sup 21}Ne and 205{+-}14 e{sup 2} fm{sup 4} (39.7{+-}2.7 W.u.) for {sup 21}Na. The fit to the present data and the known lifetimes determined E2/M1 mixing ratios and B(M1){down_arrow} values of {delta}=(-)0.0767{+-}0.0027 and 0.1274{+-}0.0025 {mu}{sub N}{sup 2} and {delta}=(+)0.0832{+-}0.0028 and 0.1513{+-}0.0017 {mu}{sub N}{sup 2} more » for {sup 21}Ne and {sup 21}Na, respectively (with Krane and Steffen sign convention). By using the effective charges e{sub p}=1.5e and e{sub n}=0.5e, the B(E2) values produced by the p-sd shell model are 30.7 and 36.4 W.u. for {sup 21}Ne and {sup 21}Na, respectively. This analysis resolves a significant discrepancy between a previous experimental result for {sup 21}Na and shell-model calculations. « less

A high-precision branching ratio measurement for the superallowed ${\ensuremath{\beta}}^{+}$ decay of $^{62}\mathrm{Ga}$ was performed at the Isotope Separator and Accelerator (ISAC) radioactive ion beam facility. The 8\ensuremath{\pi} spectrometer, an array of 20 high-purity germanium detectors, was employed to detect the \ensuremath{\gamma} rays emitted following Gamow-Teller and nonanalog Fermi ${\ensuremath{\beta}}^{+}$ decays of $^{62}\mathrm{Ga}$, and the SCEPTAR plastic scintillator array was used to detect the emitted \ensuremath{\beta} particles. Thirty \ensuremath{\gamma} rays were identified following $^{62}\mathrm{Ga}$ decay, establishing the superallowed branching ratio to be $99.858(8)%$. Combined with the world-average half-life and a recent high-precision $Q$-value measurement for $^{62}\mathrm{Ga}$, this branching ratio yields an $\mathit{ft}$ value of $3074.3\ifmmode\pm\else\textpm\fi{}1.1$ s, making $^{62}\mathrm{Ga}$ among the most precisely determined superallowed $\mathit{ft}$ values. Comparison between the superallowed $\mathit{ft}$ value determined in this work and the world-average corrected $\overline{\mathcal{F}t}$ value allows the large nuclear-structure-dependent correction for $^{62}\mathrm{Ga}$ decay to be experimentally determined from the CVC hypothesis to better than 7$%$ of its own value, the most precise experimental determination for any superallowed emitter. These results provide a benchmark for the refinement of the theoretical description of isospin-symmetry breaking in $A\ensuremath{\geqslant}62$ superallowed decays.

The branching ratio for the superallowed ${\ensuremath{\beta}}^{+}$ decay of $^{38}\mathrm{K}^{m}$ was measured at TRIUMF's ISAC radioactive ion beam facility. The $M3$ internal transition between the isomer and the ground state of $^{38}\mathrm{K}^{m}$ was observed with a branching ratio of 330(43) ppm. A search for the nonanalogue $\ensuremath{\beta}$-decay branch to the first excited ${0}^{+}$ state in $^{38}\mathrm{Ar}$ was also performed and yielded an upper limit of $\ensuremath{\le}12\text{ }\text{ }\mathrm{ppm}$ at 90% C.L. These measurements lead to a revised superallowed branching ratio for $^{38}\mathrm{K}^{m}$ of 99.967(4)%, and increase the $^{38}\mathrm{K}^{m}$ $ft$ value by its entire quoted uncertainty to $ft=3052.1(10)\text{ }\text{ }\mathrm{s}$. Implications for tests of the nuclear-structure dependent corrections in superallowed $\ensuremath{\beta}$ decays and the extraction of the Cabibbo-Kobayashi-Maskawa matrix element ${V}_{\mathrm{ud}}$ are discussed.

The half-life of the superallowed {beta}{sup +} emitter {sup 62}Ga has been measured at TRIUMF's Isotope Separator and Accelerator facility using a fast-tape-transport system and 4{pi} continuous-flow gas proportional counter to detect the positrons from the decay of {sup 62}Ga to the daughter {sup 62}Zn. The result, T{sub 1/2}=116.100{+-}0.025 ms, represents the most precise measurement to date (0.022%) for any superallowed {beta}-decay half-life. When combined with six previous measurements of the {sup 62}Ga half-life, a new world average of T{sub 1/2}=116.121{+-}0.021 ms is obtained. This new half-life measurement results in a 20% improvement in the precision of the {sup 62}Ga superallowed ft value while reducing its mean by 0.9{sigma} to ft=3074.3(12) s. The impact of this half-life measurement on precision tests of the CVC hypothesis and isospin symmetry breaking corrections for A{>=}62 superallowed decays is discussed.

Levels in 186,188Os have been investigated using the (3He,d) reaction with 30 MeV 3He beams. Absolute level‐population cross sections have been determined, and angular distributions measured between 5° and 50°. The 43+ levels are observed to be some of the strongest populated states below 2 MeV excitation energy, and the magnitudes of the 5/2+[402]π+3/2+[402]π configuration extracted are in line with quasiparticle‐phonon model predictions which state that the lowest‐lying Kπ = 4+ band is predominantly a hexadecapole excitation.

The branching ratio for the superallowed beta(+) decay of (38)K(m) was measured at TRIUMF's ISAC radioactive ion beam facility. The M3 internal transition between the isomer and the ground state of (38)K(m) was observed with a branching ratio of 330(43) ppm. A search for the nonanalogue beta-decay branch to the first excited 0(+) state in (38)Ar was also performed and yielded an upper limit ofor =12 ppm at 90% C.L. These measurements lead to a revised superallowed branching ratio for (38)K(m) of 99.967(4)%, and increase the (38)K(m) ft value by its entire quoted uncertainty to ft=3052.1(10) s. Implications for tests of the nuclear-structure dependent corrections in superallowed beta decays and the extraction of the Cabibbo-Kobayashi-Maskawa matrix element V(ud) are discussed.

The 8 pi spectrometer, installed at the TRIUMF-ISAC facility, was the world's most sensitive gamma-ray spectrometer dedicated to beta-decay studies. A description is given of the 8 pi spectrometer and its auxiliary detectors including the plastic scintillator array SCEPTAR used for beta-particle tagging and the Si(Li) array PACES for conversion electron measurements, its moving tape collector, and its data acquisition system. The recent investigation of the decay of Cs-124 to study the nuclear structure of Xe-124, and how the beta-decay measurements complemented previous Coulomb excitation studies, is highlighted, including the extraction of the deformation parameters for the excited 0(+) bands in Xe-124. As a by-product, the decay scheme of the (7(+)) Cs-124 isomeric state, for which the data from the PACES detectors were vital, was studied. Finally, a description of the new GRIFFIN spectrometer, which uses the same auxiliary detectors as the 8 pi spectrometer, is given.

The DESCANT array (D euterated S cintillator A rray for N eutron T agging) consists of up to 70 detectors, each filled with approximately 2 liters of deuterated benzene. This scintillator material o_ers pulse-shape discrimination (PSD) capabilities to distinguish between neutrons and γ -rays interacting with the scintillator material. In addition, the anisotropic nature of n – d scattering allows for the determination of the neutron energy spectrum directly from the pulse height spectrum, complementing the traditional time-of-flight (ToF) information. DESCANT can be coupled either to the TIGRESS (T RIUMF-I SAC G amma-R ay E scape S uppressed S pectrometer) γ -ray spectrometer [1] located in the ISAC-II [2] hall of TRIUMF for in-beam experiments, or to the GRIFFIN (G amma-R ay I nfrastructure F or F undamental I nvestigations of N uclei) γ -ray spectrometer [3] located in the ISAC-I hall of TRIUMF for decay spectroscopy experiments.

International audience; States in 26Na were populated in the (d, pγ) reaction, induced by bombarding deuterium target nuclei with an intense reaccelerated beam of 25Na ions from the ISAC2 accelerator at TRIUMF. Gamma-rays were recorded in coincidence with protons and used to extract differential cross sections for 21 states up to the neutron decay threshold of 5 MeV. Results for levels below 3 MeV are discussed in detail and compared with shell model calculations and with previous work. The angular distributions of decay gamma-rays were measured for individual states and are compared to theoretically calculated distributions, highlighting some issues for future work.

International audience; TIGRESS is a new generation gamma-ray spectrometer designed for use with radioactive beams from ISAC. This paper gives an overwiew of the project and presents results from the first radioactive beam experiment with TIGRESS, the Coulomb excitation of 20,21Na.

A neutron tagging array based upon liquid deuterated scintillators is being developed for the study of neutron-rich systems. The DEuterated SCintillator Array for Neutron Tagging, or DESCANT, will serve as an auxiliary detector for both the TIGRESS and GRIFFIN γ -ray spectrometers located at TRIUMF’s ISAC radioactive ion beam facility. DESCANT is comprised of 70 pseudohexaconical detectors of five varieties. The array is fully close-packed, subtends a downstream angle of θ = 65° and covers 92.6% of this solid angle or 1.08 π sr. Each detector is 150 mm thick and filled with Bicron BC-537 liquid deuterated scintillator. The white, red and blue detectors are viewed by 127 mm diameter Hamamatsu R4155 photomultiplier tubes while the yellow and green detectors are viewed by 78 mm diameter ET Enterprises 9822B photomultiplier tubes. The aim of this work is to report on the mechanical design of DESCANT and the performance of a prototype detector measured using mono-energetic neutrons.

A study of the 110 In β + /EC decay was performed at the TRIUMF Isotope Separator and Accelerator (ISAC) facility to probe the nuclear structure of 110 Cd. The data were collected in scaled-down γ -ray singles, γ − γ coincidence, and γ -electron coincidence mode. The data were sorted and a random-background subtracted γ − γ matrix was created containing a total of 850 million events. We expanded the level scheme of 110 Cd significantly by identifying 75 levels under 3.8 MeV, including 12 new ones, and increased the number of previously observed transitions from these levels to 273. The γ -ray branching intensities have been extracted through an analysis of the coincidence intensities. The branching ratios were combined with a reanalysis of lifetimes measurements obtained in an ( n, n'γ ) reaction with monoenergetic neutrons for the calculation of B(E2) values and these results have lead to the proposal of a γ -soft rotor, or O(6) nucleus, rather than a vibrational, or U(5) pattern for the nature of the low-lying, low-spin levels in 110 Cd.

Cadmium isotopes have been presented for decades as excellent examples of vibrational nuclei, with low-lying levels interpreted as multi-phonon quadrupole, octupole, and mixed-symmetry states. A large amount of spectroscopic data has been obtained through various experimental studies of cadmiumisotopes. In the present work, the 111Cd(d→$\overrightarrow {\rm{d}} $,p)112Cd reaction was used to investigate the single-particle structure of the 112Cd nucleus. A 22 MeV beam of polarized deuterons was obtained at the Maier-Leibnitz laboratory in Garching, Germany. The reaction ejectiles were momentum analyzed using a Q3D spectrograph, and 130 levels have been identified up to 4.2 MeV of excitation energy. Using DWBA analysis with optical model calculations, spin-parity assignments have been made for observed levels, and spectroscopic factors have been extracted from the experimental angular distributions of differential cross section and analyzing power. In this high energy resolution investigation, many additional levels have been observed compared with the previous (d,p) study using 8 MeV deuterons [1]. There were a total of 44 new levels observed, and the parity assignments of 34 levels were improved.

An experiment is being developed at TRIUMF to search for a time-reversal violating electric dipole moment (EDM) in odd-A isotopes of Rn. Extensive simulations of the experiment are being performed with GEANT4 to study the backgrounds and sensitivity of the proposed measurement technique involving the detection of γ rays emitted following the β decay of polarized Rn nuclei. GEANT4 developments for the RnEDM experiment include both realistic modelling of the detector geometry and full tracking of the radioactive β, γ, internal conversion, and x-ray processes, including the γ-ray angular distributions essential for measuring an atomic EDM.

Effective renal plasma flow (ERPF) and linear cardiac output (aortic blood velocity) were measured in 15 patients who received halothane, enflurane or isoflurane in oxygen. All three agents caused a significant reduction in ERPF (P less than 0.05) and the effect was greater at 1.25 MAC than at 0.75 MAC. No significant difference was demonstrated between the agents. Linear cardiac output did not change significantly during the study, suggesting that the observed reduction in ERPF was not caused by cardiovascular depression.

Summary Gastric emptying half-times and small intestinal transit times were measured in a double-blind crossover study of 17 volunteers who received an intravenous injection of nalbuphine (5 or 10 mg), morphine (5 mg) or placebo. Both times were monitored using a gamma camera after a radioactive test meal and gastric emptying half-time was calculated. Small intestinal transit time was measured by the appearance of radioactivity in the caecum and also of hydrogen in end tidal air. Gastric emptying was prolonged over placebo by nalbuphine 10 mg, which had more effect than nalbuphine 5 mg or morphine 5 mg: morphine 5 mg had less effect than nalbuphine 5 mg. Small intestinal transit time was prolonged over placebo by nalbuphine 10 mg more than by nalbuphine 5 mg or morphine 5 mg, which had approximately equal effects. In these respects, the potency ratio of nalbuphine appears roughly equivalent to morphine. Small intestinal transit times measured by end tidal hydrogen concentration and gamma camera showed close agreement.

A method of assessing spleen size from splenic scintigraphs obtained using autologous heat damaged "Tc m labelled red cells is described. The method depends on a "computed volume" estimate. The method has a correlation coefficient of 0-989 with the exsanguinated weight of the spleen after splenectomy and has been shown to have an accuracy superior to methods previously described. The involvement of the spleen in human disease is poorly understood and descriptions of changes in the spleen are usually based on those found in morbid anatomical or surgical specimens. Dynamic changes in specific functions such as red-cell destruction can be observed but probably reflect red-cell abnormalities rather than changes in the spleen. In many disease states there is a need to be able to monitor changes, especially in spleen size, in relation to the course of the disease. Changes in spleen size in animals have been reported in association with immunological phenomena (Congdon and Makinodan, 1961; Old et al., 1961; Simonsen, 1961). Accurate monitoring of spleen size in man would allow observations of dynamic changes in relation to an immunological stimulus or in diseases which may have an immunological component. Clinical examination can monitor changes in truly massive splenomegaly but in general, spleens have to be larger than 750 g before half of them are palpated (Fischer and Leon, 1969). To detect lesser degrees of splenic enlargement an alternative method is required. Unfortunately, invariably many methods do not demonstrate the spleen. Radiography is successful in only 17 per cent of abdominal films (Rosenbaum, Leiber and Pellegrino, 1964) and although gas insufflation into the gastrointestinal tract or peritoneum can improve on this, invariably the spleen is not demonstrated (Zelman, 1958; Rosch, 1965). Radiographs taken at specific times during intravenous pyelography or coeliac arteriography (which is not without risk) can demonstrate the spleen so that its size can be assessed (Blendis, Williams and Kreel, 1969). However, Blendis made no comment as to the certainty with which the spleen could be demonstrated and the size was calculated from a single two-dimensional image of the organ.