Search For Superheavy Elements Research Articles

Search for Superheavy Elements in Natural and Proton-irradiated Materials

WE have used an improved method of measuring low levels of spontaneous fission to establish limits for postulated super-heavy elements in natural materials. The apparatus has also been used to give an approximate measure of the rate of cosmic ray-induced fission of lead. Our result for lead agrees with theoretical predictions and satisfactorily explains observations of fission events in Pb glass that had previously been attributed to superheavy element decay1. Measurements on a lead target irradiated with 29 GeV protons were carried out as a comparison with the latest results of Marinov et al.2, which would have predicted 15 counts in our experiment. Our sample yielded no counts.

Search for Superheavy Elements in Nature

The results of a search for elements in the region of atomic number 114 are reported. More than 40 large samples of ores, naturals minerals, and other possible sources have been investigated. The method of detection made use of a large liquid scintillator to detect spontaneous fission events in which unusually large numbers of neutrons are emitted. The apparatus was located in a tunnel under about 250 m of earth shielding in order to reduce the interfering effects of cosmic rays. The limit set for the ratio of half-life/concentration for all the materials tested was greater than ${10}^{23}$ yr/concentration. If the half-life were ${10}^{9}$ yr this limit would correspond to a concentration of less than ${10}^{\ensuremath{-}14}$ moles of superheavy elements per mole of sample.

Search for super-heavy elements produced by secondary reactions in uranium

Thick targets of U were irradiated with 24 GeV protons, the volatile reaction products were isolated from the molten target matrix by vacuum distillation, and finally an electromagnetic isotope separation was performed. Upper limits are set on the production cross section of super-heavy elements decaying by spontaneous fission. The transuranium elements were chemically isolated from the distillation residue and cross sections are given for the production of isotopes of Pu, Am, Cm and Cf.

Production of actinides and the search for super-heavy elements using secondary reactions induced by GeV protons

A search for actinide and super-heavy elements produced by means of secondary reactions during the irradiation of tungsten and uranium targets with 12 and 28 GeV protons has been made. Yields for production of many actinide isotopes in uranium targets are given up to and including 248Cf. Upper limits have also been established for spontaneous fission activities which could be attributed to the decay of possible super-heavy elements produced by means of secondary reactions.

Search for Superheavy Elements in Uranium Irradiated with High-Energy Protons

Search for Superheavy Elements in Uranium Irradiated with High-Energy Protons

Neutron multiplicity counter

A neutron multiplicity counter assembly has been constructed to enable a search for superheavy elements in natural samples and in accelerator targets. The detector consists of twenty 3He counters placed in a paraffin moderator. These counters surround a central sample cavity with a capacity of about 20 1, capable of accomodating samples up to 100 kg in weight, depending on the density. A particular feature of this counter is its relative insensitivity to gamma rays. The efficiency for detecting a single neutron is ≈ 30%. An estimate of v, the number of neutrons emitted per fission in a sample, may be obtained from the observed multiplicity distribution P(n), where n is the number of neutron counts in an event. More accurate values of v may be obtained for small, isolated samples of spontaneously fissioning isotopes, where the neutron counters may be gated by a fission fragment detector. The design of the counter and an analysis of its properties are presented.

Implications of the hypothesis of extinct fissioning isotope in the primitive meteorites

It is shown that if the carbonaceous chondrite xenon anomaly was really caused by fission, its progenitor was the longest living isotope of superheavy elements (SHE) with a half-life of 2 × 10 6 y < T 1 2 ⪅ 6 × 10 7 y . Then the search for SHE synthesized prior to the solar system formation would be fruitless.

Search for Superheavy Elements in Terrestrial Matter

Search for Superheavy Elements in Terrestrial Matter

Search for Superheavy Elements in Terrestrial Matter

Negative results have been obtained in a search for spontaneously fissioning super-heavy nuclei by neutron counting of a large variety of samples. An upper limit of about ${10}^{\ensuremath{-}11}$ g/g is estimated for the presence of such nuclei with a half-life of about ${10}^{9}$ yr.