Element No. 102
By the use of a radically new method they have succeeded in identifying unambiguously an isotope of element 102. In other careful experiments conducted over a period of many months they find that they are unable to confirm the element 102 discovery work of Fields et al. reported in 1957. The experiments at Berkeley were performed with the new heavy ion linear accelerator (HILAC) over a period of several weeks and culinated the chemical identification of an isotope of fermium (Fm{sup 250}) as the daughter of an alpha-particle-emitting isotope of element 102 (102{sup 254}). The method used to detect the isotope of element 102 was essentially a continuous milking experiment wherein the atoms of the daughter element 100 were separated from the parent element 102 by taking advantage of the recoil due to the element 102 alpha particle decay. The target consisted of a mixture of isotopes of curium (95% Cm{sup 244} and 4.5% Cm{sup 246}) mounted on a very thin nickel foil. The target was approximately 0.5 mg/cm{sup 2} thick and was covered with 75 {micro}gm/cm{sup 2} aluminum to prevent curium 'knockover'. The curium was bombarded with mono-energetic C{sup 12} ions at energies from 60 to 100 Mev. The transmuted atoms were knocked into helium gas to absorb the considerable recoil energy. It was found that with a sufficient electric field strength practically all of these positively charged atoms could be attracted to a moving negatively charged metallic belt placed directly beneath the target. These atoms would then be carried on this conveyer belt under a foil which was charged negatively relative to the belt. Approximately half of the atoms undergoing alpha decay would cause their daughter atoms to recoil from the surface of the belt to the catcher foil. The catcher foil was cut transversely to the direction of the belt motion into five equal length sections after a time of bombardement suited to the half-life of the daughter atom to be examined. The five foils were then alpha-pulse-analyzed simultaneously in a multiplex assembly consisting of five Frisch grid chambers, amplifiers, a single Wilkinson type 'kick-sorter', and a printer. With this equipment it was easily possible to make all the desired measurements for identifying the atoms caught on the catcher foils and thus to measure the half-life of the parent of the recoiling atoms. The method was first successfully used in bombardments of Pu{sup 240} with C{sup 12} ions to identify a new isotope of element 100, Fm{sup 248}. It was shown to have a half-life of 0.6 minutes by analysis of the amounts of the 20-minute Cf{sup 244} caught on the catcher foils.
- Research Organization:
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USAEC
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 915472
- Report Number(s):
- UCRL-8314; TRN: US200817%%371
- Country of Publication:
- United States
- Language:
- English
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