The authors describe the development of the ``associated-particle`` imaging technique for producing low-resolution three-dimensional images of objects. Based on the t(d,n){sup 4}He reaction, the method requires access to only one side of the object being imaged and allows for the imaging of individual chemical elements in the material under observation. Studies were performed to (1) select the appropriate components of the system, including detectors, data-acquisition electronics, and neutron source, and (2) optimize experimental methods for collection and presentation of data. This report describes some of the development steps involved and provides a description of the complete final system that was developed.

We investigate a method for determining the elemental composition of biological samples that uses prompt gamma rays induced by 14,7-MeV neutrons. Alpha particles are produced simultaneously with the neutrons, which exit opposite the alpha detector through the vacuum chamber wall The sample under investigation is irradiated and emits gamma radiations in a spectral energy distribution characteristic of the material Barium-fluoride (BaF2) and high-purity germanium (HPGe) gamma detectors view the sample and record the spectrum of gamma radiation.

A simple method for the determination of the total width of the 9.17 MeV level in 14N is described. The method is based on the use of a resonant detector which contains nitrogen in its active volume. With the help of the resonant detector the ratio of Γγ0/ΓT was found to be 0.052 ± 0.004. This result together with the data from a conventional resonant absorption experiment yields for the total width of the level a value of 122±8 eV.

Particle-gamma-ray coincidence spectra from the /sup 110/Pd(t,p..gamma gamma..)/sup 112/Pd and /sup 100/Mo(t,p..gamma gamma..)/sup 102/Mo reactions were measured with enriched /sup 110/Pd and /sup 100/Mo targets bombarded by 16-MeV tritons to obtain more complete level structures for /sup 112/Pd and /sup 102/Mo. The resultant ground state band of /sup 112/Pd and that of /sup 120/Xe are used in the interpretation of coexistence in /sup 116/Sn. The possible observation of backbending in /sup 102/Mo is used to investigate the A dependence of backbending over a wider mass region.

We describe an ''associated particle'' method for producing three-dimensional images. Based on the t(d,n)/sup 4/He reaction, the method requires access to only one side of the object being imaged. A major advantage of the technique is that it is possible to produce separate images for individual chemical elements in the material under observation. Studies were performed to select alpha-particle and gamma-ray detectors, to optimize experimental parameters, and to evaluate the effect of intervening materials between the neutron sources and the object under observation. 9 refs., 22 figs., 5 tabs.

Conversion electrons have been measured for E0 transitions between the first excited ${0}^{+}$ states and the ground states of $^{100}\mathrm{Mo}$, $^{102}\mathrm{Mo}$, $^{106}\mathrm{Ru}$, $^{108}\mathrm{Pd}$, $^{110}\mathrm{Pd}$, and $^{112}\mathrm{Pd}$. The ${\ensuremath{\rho}}_{21}^{2}$ and ${X}_{\mathrm{ijk}}$ values are calculated from the measured E0/E2 branching ratios and level lifetimes that were either measured in this experiment or obtained from the literature. The results are discussed briefly in terms of neutron-proton interacting boson model mixed-configuration calculations and intruder states.

Charged particle spectroscopy using the (t,p) reaction has been employed for more than two decades to study the low-energy structure of nuclei. This reaction has contributed significantly to the elucidation of single-particle and collective phenomena for neutron rich nuclei in virtually every mass region. We have begun to use the (t,p) reaction in conjunctionuclei with in-beam ..gamma..-ray and conversion-electron spectroscopy to bring additional understanding to low-energy nuclear structure. In this report we briefly discuss the experimental considerations in using this reaction for in-beam spectroscopy, and present some results for nuclei with mass near 100.

The /sup 36/S(t,p..gamma..) /sup 38/S reaction was used to populate levels in /sup 38/S up to 3-MeV excitation. A definite 2/sup +/ assignment to the 1292-keV first-excited state was obtained from a (t,p..gamma..) angular correlation. Doppler shift information provided lower limits of 0.45 and 0.2 ps for the mean lifetimes of the 1291..--u003e..0 and 2825..--u003e..1291 transitions. Evidence for a possible new level at 2805 keV was obtained from p-..gamma.. coincidence data. The known level spectrum of /sup 38/S is compared to predictions of a shell-model interaction utilizing the full sdpf model space. The E2 and M1 transition rates predicted by this calculation are also presented.

The $\ensuremath{\gamma}$-ray decay of the ${J}^{\ensuremath{\pi}}={0}^{+}$ shape isomer at 2557.6 keV of excitation in $^{238}\mathrm{U}$ has been reinvestigated using the $^{238}\mathrm{U}(\mathrm{d},\mathrm{p}\mathrm{n})^{238}\mathrm{U}^{m}$ reaction with a new two-detector technique. A line at 2512.7\ifmmode\pm\else\textpm\fi{}0.5 and another possible one at 1877.6 keV are attributed to decay of the isomer. The cross section for production of the 2512.7-keV $\ensuremath{\gamma}$ ray by 18-MeV deuteron bombardment of $^{238}\mathrm{U}$ is 42\ifmmode\pm\else\textpm\fi{}12 \ensuremath{\mu}b, consistent with our earlier conversion-electron work on $^{238}\mathrm{U}^{m}$. The isomer decay is about 5% by fission and 95% by $\ensuremath{\gamma}$ rays and conversion electrons.

The quadrupole coupling constant of the $\ensuremath{\pi}{({h}_{\frac{11}{2}}^{\ensuremath{-}1} {s}_{\frac{1}{2}}^{\ensuremath{-}1})}_{{5}^{\ensuremath{-}}}$ isomer in polycrystalline $^{206}\mathrm{Hg}$ at 225 K has been measured by means of the perturbed angular distribution method. The result is $\frac{{e}^{2}\mathrm{Qq}}{h}=136.5\ifmmode\pm\else\textpm\fi{}3$ MHz, from which we deduce $eQ=65\ifmmode\pm\else\textpm\fi{}13 e$ ${\mathrm{fm}}^{2}$ and an effective charge ${e}_{\mathrm{eff}}(\ensuremath{\pi}{h}_{\frac{11}{2}}^{\ensuremath{-}1})=(2.2\ifmmode\pm\else\textpm\fi{}0.5)e$.

An electron spectrometer has been operated in coincidence with a thin annular Si(Au) proton detector to obtain conversion-electron spectra associated with the (t,p) reaction. Electrons are transported from the target to a Si(Li) detector through a solenoidal magnetic field in a two-loop baffle arrangement. Proton detection efficiencies of up to 14% were obtained with a 98Mo target by optimizing the forward-angle position of the Si(Au) detector.

A J/sup ..pi../ = (25/2)/sup +/ isomer in /sup 205/Tl has been observed using techniques of in-beam ..gamma..-ray spectroscopy and the /sup 204/Hg(t,2n)/sup 205/Tl reaction. The decay scheme firmly establishes the yrast levels: (J/sup ..pi../,E/sub x/ (keV)) (11/2)/sup -/, 1484.02; (15/2)/sup -/, 2054.57; (17/2)/sup -/, 2394.18; (19/2)/sup -/, 2551.56; and (25/2)/sup +/, 3290.7. A candidate for a 12/sup -/ state in /sup 204/Tl with the configuration (..pi..h/sub 11/2/ /sup -1/, ..nu..i/sub 13/2/ /sup -1/) is identified.