Low Terminal Voltage Research Articles

Measurements of 10Be and 26Al in some meteorites with internal beam monitor method

Using the technique of “internal beam monitor method”, 26Al measurement of accelerator mass spectrometry with a low terminal voltage has been developed at the University of Tokyo tandem accelerator. Negative ion mixtures of 26Al − and 10B 16O − beams were accelerated with terminal voltages as low as 2.5 MV, and separated into a “main beam” ( 26Al 3+, 10 MeV) and a “monitoring beam” ( 16O 2+) by the magnet. The 26Al 27Al ratio was obtained by the simultaneous measurements of 26Al 3+ and 16O 2+, and measurement of negative ion current ratio ( 10B 16O − 27Al − ). The reproducibility in this method was found to be better than 7% by the measurements of a series of standard samples of 10 −9 to 10 −12 in 26Al 27Al ratio. The sensitivity was estimated to be about 1 × 10 −13. Using this technique, 26Al and 10Be in meteorites were measured. Preliminary results were obtained in four iron meteorites and in the metal phase and the whole rock of two chondrites. The 26Al 10Be activity ratios in Odessa, Henbury, Grant, ALH762, Peace River (Metal) and Bruderheim (Metal) meteorites were found to be 0.52, 0.67, 0.58, 0.68, 1.17 and 1.15, respectively.

The 12CH 22+ molecule and radiocarbon dating by accelerator mass spectrometry

The 12CH 2 2+ molecule has been studied and it was found that the molecule can be effectively eliminated thus allowing detection of 14C 2+ at low terminal voltages of a tandem accelerator. Some implications of this discovery for radiocarbon dating are discussed.

Mortalities Among Developing Trout and Salmon Ova Following Shock by Direct-Current Electrical Fishing Gear

Two units of direct-current fishing gear, providing terminal potentials of 550 and 150 volts, were used to give shocks of different severities to trout and salmon ova in various stages of development. The purpose of the tests was to establish precautionary measures to prevent damaging eggs when using similar apparatus, in waters of similar conductivity, in the vicinity of natural redds containing live eggs. High terminal voltage caused heavy losses among pre-eyed eggs, considerably fewer losses among eyed eggs, and no losses to eggs that were near hatching. There were no losses among eyed or pre-eyed eggs with low terminal voltage. Eggs that had been buried in the gravel of a stream apparently received some protection from electric shock. Salmon alevins were killed by prolonged severe shock, but not by a similar shock of shorter duration. The alevins showed greatly increased activity and swam about sporadically when in the electric field, but did not exhibit galvanotropic responses of a directional character.