Joseph Cerny

Production of an Accelerated Oxygen-14 Beam

BEARS is an ongoing project to provide a light-ion radioactive-beam capability at the 88-Inch Cyclotron at LBNL. Light radioactive isotopes are produced at a 10 MeV proton medical cyclotron, transported 350 m via a high-speed gas transport capillary, cryogenically separated, and injected into the 88-Inch Cyclotrons ion source. The first radioactive beam successfully accelerated was Carbon-11 and beams of intensity more than 108 ions/sec have been utilized for experiments. Development of Oxygen-14 as the second BEARS beam presented considerable technical challenges, both due to its short half-life of 71 seconds and the radiation chemistry of oxygen in the target. The usual techniques developed for medical uses of Oxygen-15 involve the addition of significant amounts of carrier oxygen, something that would overload the ion source. As a solution, Oxygen-14 is produced as water in a carrier-free form, and is chemically converted in two steps to carbon dioxide, a form readily usable by the BEARS. This system has been built and is operational, and initial tests of accelerating an Oxygen-14 beam have been performed.

Evidence for the Identification of 178Pb

With the use of the Berkeley Gas‐filled Separator, the α decay of 178Pb was identified in 78Kr irradiations of 102Pd. Following their separation from the incident beam particles, reaction products were implanted in a position‐sensitive silicon detector. Two events with Eα of 7602 and 7629 keV were observed and assigned to 178Pb because they were position‐correlated with known descendants in the 174Hg α‐decay chain. The half‐life of 178Pb was calculated with the maximum likelihood method to be 122−50+290 μs. A mass excess of 3608(39) keV and a proton separation energy of 362(48) keV were deduced for 178Pb based on the known masses of 174Hg and 177Tl.

DEVELOPMENT AND CHARACTERIZATION OF A LOW-ENERGY PARTICLE-IDENTIFICATION TELESCOPE ARRAY FOR PROTON AND ALPHA SPECTROSCOPY

Abstract Six improved low-energy gas- ΔE /gas- ΔE /Si- E particle-identification telescopes have been incorporated into an array. Calibration experiments have shown that these telescopes are capable of detecting and identifying protons with energies as low as ∼180 keV and alpha particles with energies as low as ∼450 keV, even when operating in a high-radiation environment. Methods of calibration at very low energies have been developed and tested. A survey of the beta-delayed proton emitters 21 Mg, 29 S, 40 Sc and 41 Ti revealed no new intense proton groups at low energies.

Delayed proton emission from nuclei: A historical perspective

Early experiments observing proton emission are reviewed, with an emphasis on the initial discovery. Beta-delayed proton emission (1963), direct proton radioactivity (1970), and beta-delayed two-proton emission (1983) have all been observed, while direct two-proton radioactivity is still being sought. This historical overview concludes in 1990.

Recent studies of proton drip-line nuclei using the Berkeley Gas-filled Separator

The Berkeley Gas-filled Separator provides new research opportunities at Lawrence Berkeley National Laboratorys X-Inch Cyclotron. The use of this apparatus for the study of proton drip-line nuclides is discussed. Preliminary results of {sup 78}Kr bombardments of {sup 102}Pd targets at mid-target energies of 360, 375 and 385 MeV are presented. Improvements planned partially as a result of this measurement are also discussed.

Exotic Decays at the Proton Drip Line

In this paper we review the general physics learned at the proton drip line. The extraordinary experimental problems which must be overcome are discussed in addition to several novel solutions. Finally, results of several recent experiments to look for ground state one-and two-proton emission are discussed.