W.H. Kelly

Coincidence-anticoincidence gamma-ray spectroscopy with a NaI(TI) split annulus and a Ge(Li) detector☆

Abstract A versatile gamma-ray spectrometer system consisting of a Ge(Li) detector surrounded by a large (20.3 cm × 20.3 cm) split NaI(Tl) annulus is described, and experimental results are presented as examples of its use in a number of coincidence and anticoincidence experiments. The annulus as a whole was used as an anti-Compton spectrometer and was found to reduce the Compton backgrounds in the Ge(Li) detector considerably. When the optically-isolated halves of the annulus were used separately, the system was found to be very efficient for triple-coincidence experiments and as a pair spectrometer. As the latter, it yielded double-escape spectra having essentially no underlying backgrounds, even when used with complex gamma-ray emitters such as 56Co. It was also very effective in determining relative β+ feedings to various levels in the decay of position emitters. When the system was used as a coincidence spectrometer with narrow gates set on the pulses from the annulus, the Compton backgrounds of coincident gamma-rays detected in the Ge(Li) detector were reduced significantly.

A single crystal Ge(Li) Compton spectrometer

Abstract A single crystal Ge(Li) Compton spectrometer has been tested showing considerable promise as a device for detecting γ-rays in the presence of strong Compton and neutron backgrounds.

Fast aqueous chemistry on-line with cyclotron-produced activities using a helium-jet recoil-transport system

Abstract A relatively simple system is described that can be used to perform fast on-line chemical separations (≤ 1 s) on activities transported to low background areas in the relatively short times provided by a helium-jet recoil-transport system. The helium-jet recoil-transport system is run with its low-pressure end at atmospheric pressure, thereby eliminating the need for vacuum pumps and their associated apparatus.

An improved and modular helium-jet recoil-transport system for the study of short-lived nuclei

Abstract An improved, modular helium-jet-recoil-transport system for the study of short-lived (t 1 2 ⪅ 0.2 s ) is described. Its target irradiation assembly consists of modular pieces, allowing the interchanging of different target holders, different recoil-thermalizing chambers, etc., for economical and convenient setting up of each experiment. A remote-control degrader package allows rapid control of accelerator beam energies. Improved target-preparation techniques are described, including compacting oxides onto foils with a hydraulic press. Auxilliary equipment such as gas supplies, capillaries, pumping equipment, and a stepping tape drive for the counting chamber are described. Different detector arrays and assemblies are used for different kinds of nuclear spectroscopy, and data are presented for some of these, including γ-ray, γ-γ megachannel (multiparameter) coincidence, and β-delayed proton spectroscopy.

Nuclear data sheets for A = 104

Nuclear structure data available through January 1976 are compiled, and adopted level properties are given. The bulk of the data is presented pictorially for easy comparison. Experimental details, references, and additional comments, where required, are given in the text. All drawings, tables, and comments are reproduced from the computerized Evaluated Nuclear Structure Data File (ENSDF). Any additions or corrections desired by the users should be addressed to the compilers for maintenance and updating of the computer file.

States in 163Ho and 167Tm populated through the (p, t) reaction on 165Ho and 169Tm

Abstract The (p, t) reaction at 30 MeV on the deformed nuclei, 165 Ho and 169 Tm, strongly populates collective states in the residual nuclei. Indirect multiple-step processes evidently play an important role, and the reaction is a powerful tool for populating higher-lying rotational band members.

On improving Ge detector energy resolution and peak-to-Compton ratios by pulse-shape discrimination

Abstract The rise-time discrimination of pulses from Ge detectors can be used to improve the spectra on two levels: first, by discriminating against slower-rising pulses, both the energy resolution and peak-to-Compton ratios can be improved significantly, especially for detectors that have suffered neutron damage. Second, by adding a pulse-height correction to compensate for effects of varying rise-time, an improved composite spectrum can be obtained without significant loss in detector efficiency.

Nuclear data sheets for A = 102

Nuclear structure data available through January 1976 are compiled, and adopted level properties are given. The bulk of the data is presented pictorially for easy comparison. Experimental details, references, and additional comments, where required, are given in the text. All drawings, tables, and comments are reproduced from the computerized Evaluated Nuclear Structure Data File (ENSDF). Any additions or corrections desired by the users should be addressed to the compilers for maintenance and updating of the computer file.

Ultra-fast chemical separations (“plasma chemistry”) with a helium-jet recoil-transport system

Abstract The transport efficiency through a long-capillary He-jet recoil-transport system can be changed for different elements by altering the nature and/or the concentration of the impurities in the He. Thus, it appears that a form of “plasma chemistry” is taking place in the formation of the “macromolecules” that transport the radioactive recoils through the system and the attachment of the recoils to chemically specific sites on these macromolecules. We describe some experimental results and point out the advantages of such a system; also, we note that it is possible to obtain information about the Z of a nuclide from these experiments.

Spurious peaks produced by compton scattering in Ge(Li)-Ge(Li) coincidence gamma-ray spectrometer systems

We present results from our investigations of Compton scattering between Ge(Li) γ-ray detectors in coincidence experiments. Such scattering can generate false peaks that can be mistaken for photopeaks. The effects of varying gate position, gate width, background subtraction, and angle between detectors are discussed, and suggestions an: made for recognizing and minimizing spurious effects.