In the current paper, we analyzed the variation of cosmic radiation flux with elevation, time of the year and ambient temperature with the help of a portable cosmic muon detector, the construction of which was completed by a team from Southern Arkansas University (SAU) at Lawrence Berkeley National Laboratory (LBNL). Cosmic muons and gamma rays traverse two synchronized scintillators connected to two photomultiplier tubes (PMT) via light guides, and generate electronic pulses which we counted using a Data Acquisition Board (DAQ). Because muons are the product of collisions between high-energy cosmic rays and atmospheric nuclei, and therefore shower onto earth, the scintillators were arranged horizontally for detection. The elevation measurements were recorded at different locations, starting from 60 feet below sealevel at the Underground Radiation Counting Laboratory at Johnson Space Center, TX, to 4200 feet at Mt. Hamilton, CA. Intermediate locations included sea-level Galveston Bay, TX, and Mt. Magazine, AR (2800 feet). The data points showed a noticeable increase in flux as elevation increases, independent of latitude. Measurements investigating the dependence of cosmic rays on temperature and time of the year took place locally in Magnolia, AR. We found that cosmic muon flux is uniform, appears to be independent of conditions on earth, and is anticorrelative with temperature. We are convinced that the sun has minimal to zero effect on cosmic-ray flux; it cannot be a major contributing source of this background radiation. The source of cosmic radiation remains one of the biggest unanswered questions in physics today.
The xenon time projection chamber (TPC) promises a novel detection method for neutrinoless double-beta decay (0ν ββ) experiments. The TPC is capable of discovering the rare 0ν ββ ionization signal of a distinct topological signature, with a decay energy Q ββ = 2.458 MeV. However, more frequent internal (within TPC) and external events are also capable of depositing energy in the range of the Q ββ -value inside the chamber, thus mimicking 0ν ββ or interfering with its direct observation. In the following paper, we illustrate a methodology for background radiation evaluation, assuming a basic cylindrical design for a toy titanium TPC that is capable of containing 100 kg of xenon gas at 20 atm pressure; we estimate the background budget and analyze the most prominent problematic events via theoretical calculation. Gamma rays emitted from nuclei of 214 Bi and 208 Tl present in the outer-shell titanium housing of the TPC are an example of such events for which we calculate probabilities of occurrences. We also study the effect of alpha-neutron (α-n)-induced neutrons and calculate their rate. Alpha particles which are created by the decay of naturally occurring uranium and thorium present in most materials, can react with the nucleus of low Z elements, prompting the release of neutrons and leading to thermal neutron capture. Our calculations suggest that the typical polytetrafluoroethylene (PTFE) inner coating of 1Corresponding author.
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