8 research outputs found
Oscillations in radioactive exponential decay
Several older and recent reports provided evidence for the oscillatory character of the exponential decay law in radioactive decay and attempted to explain it with basic physics. We show here that the measured effects observed in some of the cases, namely in the decay of 226Ra, 32Si in equilibrium, and 36Cl, can be explained with the temperature variations
Further Evidence Suggestive of a Solar Influence on Nuclear Decay Rates
Recent analyses of nuclear decay data show evidence of variations suggestive
of a solar influence. Analyses of datasets acquired at the Brookhaven National
Laboratory (BNL) and at the Physikalisch-Technische Bundesanstalt (PTB) both
show evidence of an annual periodicity and of periodicities with sidereal
frequencies in the neighborhood of 12.25 year^{-1} (at a significance level
that we have estimated to be 10^{-17}). It is notable that this implied
rotation rate is lower than that attributed to the solar radiative zone,
suggestive of a slowly rotating solar core. This leads us to hypothesize that
there may be an "inner tachocline" separating the core from the radiative zone,
analogous to the "outer tachocline" that separates the radiative zone from the
convection zone. The Rieger periodicity (which has a period of about 154 days,
corresponding to a frequency of 2.37 year^{-1}) may be attributed to an r-mode
oscillation with spherical-harmonic indices l=3, m=1, located in the outer
tachocline. This suggests that we may test the hypothesis of a solar influence
on nuclear decay rates by searching BNL and PTB data for evidence of a
"Rieger-like" r-mode oscillation, with l=3, m=1, in the inner tachocline. The
appropriate search band for such an oscillation is estimated to be 2.00-2.28
year^{-1}. We find, in both datasets, strong evidence of a periodicity at 2.11
year^{-1}. We estimate that the probability of obtaining these results by
chance is 10^{-12}.Comment: 12 pages, 6 figures, v2 has a color corrected Fig 6, a corrected
reference, and a corrected typ
Power Spectrum Analysis of Physikalisch-Technische Bundesanstalt Decay-Rate Data: Evidence for Solar Rotational Modulation
Evidence for an anomalous annual periodicity in certain nuclear decay data
has led to speculation concerning a possible solar influence on nuclear
processes. We have recently analyzed data concerning the decay rates of Cl-36
and Si-32, acquired at the Brookhaven National Laboratory (BNL), to search for
evidence that might be indicative of a process involving solar rotation.
Smoothing of the power spectrum by weighted-running-mean analysis leads to a
significant peak at frequency 11.18/yr, which is lower than the equatorial
synodic rotation rates of the convection and radiative zones. This article
concerns measurements of the decay rates of Ra-226 acquired at the
Physikalisch-Technische Bundesanstalt (PTB) in Germany. We find that a similar
(but not identical) analysis yields a significant peak in the PTB dataset at
frequency 11.21/yr, and a peak in the BNL dataset at 11.25/yr. The change in
the BNL result is not significant since the uncertainties in the BNL and PTB
analyses are estimated to be 0.13/yr and 0.07/yr, respectively. Combining the
two running means by forming the joint power statistic leads to a highly
significant peak at frequency 11.23/yr. We comment briefly on the possible
implications of these results for solar physics and for particle physics.Comment: 15 pages, 13 figure
Solar Influence on Nuclear Decay Rates: Constraints from the MESSENGER Mission
We have analyzed Cs-137 decay data, obtained from a small sample onboard the
MESSENGER spacecraft en route to Mercury, with the aim of setting limits on a
possible correlation between nuclear decay rates and solar activity. Such a
correlation has been suggested recently on the basis of data from Mn-54 decay
during the solar flare of 13 December 2006, and by indications of an annual and
other periodic variations in the decay rates of Si-32, Cl-36, and Ra-226. Data
from five measurements of the Cs-137 count rate over a period of approximately
5.4 years have been fit to a formula which accounts for the usual exponential
decrease in count rate over time, along with the addition of a theoretical
solar contribution varying with MESSENGER-Sun separation. The indication of
solar influence is then characterized by a non-zero value of the calculated
parameter \xi, and we find \xi=(2.8+/-8.1)x10^{-3} for Cs-137. A simulation of
the increased data that can hypothetically be expected following Mercury orbit
insertion on 18 March 2011 suggests that the anticipated improvement in the
determination of \xi could reveal a non-zero value of \xi if present at a level
consistent with other data.Comment: Accepted for publication in Astrophysics and Space Science, 2011. 7
pages, 5 figures. Version 2 has corrected Figure 1, since Fig. 1 did not
appear correctly in Version
Avaliação do método de espectrometria por cintilação em meio líquido para a medida das atividades alfa e beta total em água: aplicação a águas de abastecimento público no estado de Goiás, Brasil
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A new look at reaction mechanisms with 4. pi. charged-particle and neutron multiplicity measurements
We have studied the excitation of target-like fragments produced in the reactions of 331.9 MeV /sup 28/Si + /sup 181/Ta. The light charged particles and intermediate mass fragments were detected in a small, highly segmented 4..pi.. phoswich detector system placed inside the spin spectrometer, a 4..pi.. NaI array which served as a neutron and ..gamma..-ray detector. All target emissions indicate that excitation ceases to increase with decreasing projectile-like fragment energy, as it should if the primary reaction is binary. Non-equilibrium neutron, proton and ..cap alpha..-particle emission and projectile fragmentation conspire and limit the conversion of kinetic energy into target excitation. This effect is more pronounced for PLF away from the injection point and for the largest kinetic energy losses. 8 refs., 10 figs