G.T. Ewan

The Sudbury neutrino observatory

The Sudbury Neutrino Observatory is a second-generation water Cherenkov detector designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. The detector is unique in its use of D2O as a detection medium, permitting it to make a solar model-independent test of the neutrino oscillation hypothesis by comparison of the charged- and neutral-current interaction rates. In this paper the physical properties, construction, and preliminary operation of the Sudbury Neutrino Observatory are described. Data and predicted operating parameters are provided whenever possible.The Sudbury Neutrino Observatory is a second generation water Cherenkov detector designed to determine whether the currently observed solar neutrino deficit is a result of neutrino oscillations. The detector is unique in its use of D2O as a detection medium, permitting it to make a solar model-independent test of the neutrino oscillation hypothesis by comparison of the charged- and neutral-current interaction rates. In this paper the physical properties, construction, and preliminary operation of the Sudbury Neutrino Observatory are described. Data and predicted operating parameters are provided whenever possible.

A one-meter-radius iron-free double-focusing π√2 spectrometer for β-ray spectroscopy with a precision of 1:105

Abstract This high resolving power, high luminosity π√2 spectrometer employs a novel coil geometry which leaves ample room for large, accessible source and detector assemblies. The exact coil diameters and spacings used to achieve axial focusing up to the fourth order were specified by Lee-Whiting after a detailed theoretical study of the electron optical focusing properties of the coil arrangement. Four pairs of precisely manufactured coils generate the cylindrically symmetrical field whose shape closely approximates a 1 √r form near the optic circle, ro = 100 cm. The largest pair has 560 turns per coil and a mean diameter of 395.1 cm. The temperature control arrangements for this all-aluminum spectrometer ensure a constancy in the calibration ratio, gauss cm per ampere, of better than 1 part in 105 for electron energies up to 4 MeV. At resolution settings of 0.01%, 0.1%, and 1.0%, transmission values of 0.08%, 0.26%, and 1.1% respectively, can be used. At resolution settings of 0.1%, or better, the luminosity (source area times transmission) is larger than the luminosities of other precision spectrometers. The degaussing system, iron-free building, source, baffle and detector arrangements, current-regulating and measuring systems, automatic controls, and readout system are discussed briefly. Several examples of the performance at resolution settings in the range 0.1% to 0.01% are given which illustrate this instruments luminosity, ultimate resolution in momentum of 1 part in 104, and inherent precision of 1 part in 105.

A Heavy Water Detector to Resolve the Solar Neutrino Problem

Abstract The observation of the following three reactions: νed→ppe; νxe→νxe; and νxd→νxpn (where νx is any left- handed neutrino) in a heavy water Cerenkov detector which is being designed, allows the solar 8B ve flux, spectrum and direction to be measured. In addition, the total solar 8 Bν c neutrino flux, direction and integral spectrum, independent of neutrino flavor, may be determined to provide several independent methods to resolve the solar neutrino problem.

A high resolution lithium-drift germanium gamma-ray spectrometer

The performance of a Ga-doped, Li-drifted Ge detector (resolution = about 0.5%) used as a gamma spectrometer is detailed. Results obthined on the gamma spectrum of /sup 177/Yb are reported. (T.F.H.)

Measurement of lifetimes in 152Sm, 154Gd and 156Gd by doppler-shlft recoil-distance techniques

Abstract The following lifetimes (in ps) have been measured for the states in 152 Sm : 4 g : 82.8 ± 1.2, 6 g : 14.6 ± 0.4, 8 g : 4.3 ± 0.65, 0 β : 8.92 ± 0.55; in 154 Gd: 4 g : 66.3 ± 2.2, 6 g : 11.2 ± 0.6, 0 β : 5.7 ± 0.9; and in 156 Gd : 4 g : 163 ± 7 and 6 g : 20.5 ± 1.75 . The Doppler-shift recoil-distance method was used in which the states were populated by Coulomb excitation using 100 MeV 35C1 ions. Gamma rays were detected in coincidence with back-scattered 35C1 ions. The results for the 0β lifetimes are discussed in terms of the monopole matrix elements between the ground state and β-vibrational bands. Deviations from rotational behaviour in the ground state band transition probabilities are found to be consistent with the simple band-mixing picture assuming the β-ground mixings as given by Rud, Nielsen and Wilsky.

Conversion electron spectrum from Ce144 decay

Abstract The internal conversion electron spectrum following the β decay of Ce144 has been studied in the Chalk River iron-free π√2 β spectrometer at a momentum resolution of ≈ 0.1%. The 33 conversion lines observed are identified with 7 transitions of energies (in keV) and multipolarities 33.57±0.03, M1; 40.93±0.03, M1; 53.41±0.03, M1; 59.03±0.03, M3; 80.12±0.03, Ml; 99.95±0.03, E2; and 133.53±0.03, M1. The multipolarity assignment for each transition was obtained by comparing the observed conversion line intensity ratios with the theoretical line intensity ratios of Sliv. The intensity of the K conversion line of the 133.53 keV transition has been measured relative to the total intensity of the Pr144 β spectrum; IK 133/IPr β sp. = 0.053±0.002. The momentum ratio of the Ce144 K 133.53 and Cs137 K 661.6 lines, corrected for electron energy loss in the Ce course, is BρK 133/BρK 661 = 0.31495±0.00003. Intensity limits are placed on all previously reported Ce114 conversion lines not presently observed. Relative quantum intensities and total transition intensities are deduced from the conversion line data. A decay scheme for Ce144 is given which satisfactorily accounts for all the results of this investigation and is compatible with the results of earlier workers when some line reassignments are made. Interpretations of the Pr144 levels, established in this work, are discussed in terms of both the shell model and the unified model. With δ ≈ +0.07, the unified model accounts for the experimental evidence in a simple but convincing fashion.

Pionic 4f → 3d transition in 181Ta, natural Re, and 209Bi And the strong interaction level shift and width of the pionic 3d state

Abstract Owing to a powerful Compton-suppression technique it was possible to observe for the first time the pionic 4f → 3d X-ray transition in elements heavier than A = 150. The strong interaction monopole shifts e 0 and widths Γ 0 as well as the quadrupole splitting of the 3d levels have been measured in Ta, Re and Bi. Thus in addition to the strongly shifted and broadened 5g → 4f transitions, a second, strongly affected line is available for these elements. For the pionic 4f levels, standard optical potentials fit the strong interaction shifts and broadenings quite well. The now observed, deeper-lying 3d states in Ta, Re and Bi have shifts and widths that differ by a factor of 2 or more from the standard optical potential predictions. From the observed relative X-ray intensities of the pionic cascade we also extract the strong interaction widths of the 5g and 4f levels.

Study of the giant gamow-teller resonance in nuclear β-decay: The case of 32Ar

Delayed proton and gamma emissions following the β-decay of 32Ar have been studied. The half-life of 32Ar is 98 ± 2 ms, and the T = 2 analogue state in 32Cl lies at the excitation energy 5036 ± 12 keV. From the intensity of the feeding to this state the proton intensities can be converted to an absolute scale leading to a total proton branching ratio of (43 ± 3)%. From proton-gamma coincidence measurements it emerges that (1.9 ± 0.2)% of the protons lead to the first-excited state in 31S. A level scheme up to 8.75 MeV excitation in 32Cl has been constructed and the Gamow-Teller strength function has been deduced. The result is a renormalization of the axial-vector strength to (49 ± 5)% of the free-nucleon value.

Application of high resolution lithium-drift germanium gamma-ray spectrometers to high energy gamma-rays

A description is given of the use of Li-drifted Ge detectors for high- resolution gamma spectroscopy. The detectors are used in the following manner: the photon enters the detector and annihilates into an electron-positron pair; the annihilation quanta escape from the detector; and the total energy of the electron-positron pair is lost in the detector. The detector thus reconds a peak at E -- 2m/sub 0/c/sup 2/, where E is the photon energy and mo is the electron rest mass. The method is useful only at high photon energies. The detectors in this application have energy resolutions of about 0.13%. (T.F.H.)

Negative parity levels in the even-even nucleus Dy160

Abstract The conversion electron spectrum of Tb160 has been studied in the Chalk River air-cored ρ√2 β-ray spectrometer at resolution settings of 0.04 % to 0.1 %. Gamma-conversion electron coincidence experiments have been made to establish the positions of the levels in Dy160. The level scheme based on the present results is 0(0+), 86.7 (2+), 283.6 (4+), 965.8 (2+), 1048.8 (3+), 1264.4 (2-), 1286.5 (3-), 1358.2 (2-), and 1398.5 keV (3-). This is similar to that of Nathan in the positive parity levels but differs in the negative parity levels. Particular attention has been paid to determining the intensities of weak transitions in the decay scheme. The relative quantum transition probabilities have been deduced from the conversion line measurements using Slivs theoretical conversion coefficients. The agreement between the observed transition probabilities from the positive parity levels and the theoretical predictions of the Unified Model is greatly improved if a small amount of K = 0 band is assumed mixed in the K = 2 gamma-vibrational band. The relative transition probabilities from the negative parity levels are not consistent with K being a good quantum number in discussing these levels. The possibility of interaction between the negative parity levels is briefly discussed.