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Title: Search for possible solar influences in Ra-226 decays

Measurements of Ra-226 activity from eight HPGe gamma ray detectors at the NC State University PULSTAR Reactor were analyzed for evidence of periodic variations, with particular attention to annual variations. All measurements were made using the same reference source, and data sets were of varying length taken over the time period from September 1996 through August 2014. Clear evidence of annual variations was observed in data from four of the detectors. Short time periodograms from the data sets suggest temporal variability of both the amplitude and frequency of these variations. The annual variations in two of the data sets show peak values near the first of February, while surprisingly, the annual variations in the other two are roughly out of phase with the first two. Three of the four detectors exhibited annual variations over approximately the same time period. A joint statistic constructed by combining spectra from these three shows peaks approximating the frequencies of solar r-mode oscillations with ν R = 11.74 cpy, m = 1, and l = 3, 5, 6. The fact that similar variations were not present in all detectors covering similar time periods rules out variations in activity as the cause, and points to differingmore » sensitivities to unspecified environmental parameters instead. In addition to seasonal variations, the modulation of environmental parameters by solar processes remains a possible explanation of periodogram features, but without requiring new physics.« less
Authors:
 [1] ;  [2] ;  [3] ;  [2]
  1. North Carolina State Univ., Raleigh, NC (United States). Dept. of Electrical and Computer Engineering
  2. North Carolina State Univ., Raleigh, NC (United States). Dept. of Physics
  3. North Carolina State Univ., Raleigh, NC (United States). Dept. of Statistics
Publication Date:
Grant/Contract Number:
FG02-97ER41041
Type:
Published Article
Journal Name:
Results in Physics
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2211-3797
Publisher:
Elsevier
Research Org:
North Carolina State Univ., Raleigh, NC (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; nuclear beta decay; solar oscillation modes; time series analysis
OSTI Identifier:
1338625
Alternate Identifier(s):
OSTI ID: 1467066

Stancil, Daniel D., Balci Yegen, Sümeyra, Dickey, David A., and Gould, Chris R.. Search for possible solar influences in Ra-226 decays. United States: N. p., Web. doi:10.1016/j.rinp.2016.12.051.
Stancil, Daniel D., Balci Yegen, Sümeyra, Dickey, David A., & Gould, Chris R.. Search for possible solar influences in Ra-226 decays. United States. doi:10.1016/j.rinp.2016.12.051.
Stancil, Daniel D., Balci Yegen, Sümeyra, Dickey, David A., and Gould, Chris R.. 2017. "Search for possible solar influences in Ra-226 decays". United States. doi:10.1016/j.rinp.2016.12.051.
@article{osti_1338625,
title = {Search for possible solar influences in Ra-226 decays},
author = {Stancil, Daniel D. and Balci Yegen, Sümeyra and Dickey, David A. and Gould, Chris R.},
abstractNote = {Measurements of Ra-226 activity from eight HPGe gamma ray detectors at the NC State University PULSTAR Reactor were analyzed for evidence of periodic variations, with particular attention to annual variations. All measurements were made using the same reference source, and data sets were of varying length taken over the time period from September 1996 through August 2014. Clear evidence of annual variations was observed in data from four of the detectors. Short time periodograms from the data sets suggest temporal variability of both the amplitude and frequency of these variations. The annual variations in two of the data sets show peak values near the first of February, while surprisingly, the annual variations in the other two are roughly out of phase with the first two. Three of the four detectors exhibited annual variations over approximately the same time period. A joint statistic constructed by combining spectra from these three shows peaks approximating the frequencies of solar r-mode oscillations with νR = 11.74 cpy, m = 1, and l = 3, 5, 6. The fact that similar variations were not present in all detectors covering similar time periods rules out variations in activity as the cause, and points to differing sensitivities to unspecified environmental parameters instead. In addition to seasonal variations, the modulation of environmental parameters by solar processes remains a possible explanation of periodogram features, but without requiring new physics.},
doi = {10.1016/j.rinp.2016.12.051},
journal = {Results in Physics},
number = ,
volume = 7,
place = {United States},
year = {2017},
month = {1}
}