Flux Variation of Cosmic Muons

TL;DR

This study measured cosmic muon flux variations with elevation, temperature, and time, using a portable detector, and found flux increases with elevation but is unaffected by latitude or solar activity.

Contribution

It presents a portable cosmic muon detector setup and provides new empirical data on flux variation with elevation, temperature, and seasonal changes.

Findings

Muon flux increases with elevation

Flux is independent of latitude and solar activity

Flux is anti-correlated with temperature

Abstract

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 sea-level 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 anti-correlative 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.