Fusion Science and Technology / Volume 40 / Number 2 / September 2001 / Pages 147-151
The 3He and 4He concentrations in 2- to 6-mg samples of palladium-black from the interior of Arata-style cathodes were investigated using a tungsten wire furnace on-line to an ultrahigh sensitivity static mass spectrometer. The detection limit of the mass spectrometer was ~104 atoms 3He and 108 atoms 4He, and the mass resolution of 1 part in 620 was sufficient to cleanly resolve 3He from H3 and HD. Three specimens of palladium-black (A, B, and C) were from hollow Pd cathodes that had generated excess heat in D2O electrolysis experiments carried out by Arata and Zhang in their laboratory. One specimen of Pd-black (D) had not been used in any electrolysis experiment. A total of twelve samples, three from each specimen, were analyzed. The 3He and 4He concentrations were variable as if due to sample inhomogeneity. Two samples (C-1 and B-1) showed apparent 4He of 4.4 × 109 atoms/mg and 6.6 × 109 atoms/mg, respectively, and three (A-3, B-2, and D-3) showed excess 3He from 77 to 1096 × 103 atoms/mg relative to the atmospheric 3He/4He ratio. Seven samples showed no apparent excess of 3He or 4He. Five samples of the aluminum foil used to wrap Pd-black samples were also analyzed and gave mean values of 13 ± 18 × 103 atoms/mg and 1.50 ± 0.66 × 109 atoms/mg for 3He and 4He, respectively. The values for Al and Pd-black are comparable to the 1978 results of Mamyrin, Khabarin, and Yudenich, who examined helium isotopes in many ordinary metals and other materials including Al and Pd. At present, there is no evidence for the very much larger concentrations (1016 to 1017 atoms/mg) of 3He and 4He that Arata and Zhang claim to have detected in similar specimens of Pd-black from Pd cathodes subjected to D2O electrolysis.