Cosmic rays are high energy atomic nuclei travelling near the speed of light that collide with atoms and molecules in Earth’s upper atmosphere (primarily with nitrogen and oxygen), breaking down into a shower of particles of various energies in the stratosphere. As they travel earthward, these particles continue to break down and lose energy which results in relatively little ionizing radiation reaching the surface. Due to the scattering of cosmic rays, the angle at which the rays enter the atmosphere can affect the number and energies of ionizing particles detected at various altitudes. When using a standard Geiger counter on a high altitude balloon flight, cosmic rays of all energies and orientations are counted in the same manner making it impossible to determine the origin and history of a particular detection. To improve cosmic ray measurements at Trevecca Nazarene University’s Near Space Research Program, an “off the shelf” Geiger-Muller tube (ranged from .5 to 50 mR/hour and referenced to Cs-137) was modified to restrict peripheral ionizing radiation detection. The tube, which was 1.5 inches long and .5 inches in diameter, was fitted with a lead casing measuring 3 inches in length. This would ideally restrict the detection field for lower energy particles to a range of 0o to 18.5o along the tube axis. Due to the instability of the Geiger counter’s position during high altitude flights, the data from the restricted detection field required a method of determining which direction the Geiger counter was pointing relative to the zenith. During the flights, the Geiger counter was logging its data on a micro-SD card through a “Pic Pod” circuit board created at Trevecca. This board was also fitted with a 3-axis gyroscope, accelerometer, and magnetometer. By housing the circuit board and Geiger counter in fixed positions relative to each other during the flights, it was possible to use the data from the circuit board to determine the orientation of the Geiger counter. A LabVIEW program was created to translate the gyroscope, accelerometer, and magnetometer data into a three dimensional orientation. It is expected that rays coming in from a small zenith angle would contain a higher level of energy since they would have travelled through less atmosphere. Early results showed that when data from the modified counter was compared against the data from a flight with an unaltered Geiger counter, the total counts were considerably less than with the standard Geiger tube. This suggests that the lead column was successful in blocking some, if not all, of the peripheral radiation. Unfortunately, due to a launch failure in the spring, we have limited data so far with the modified Geiger counter. We will present the current results from our collimated and uncollimated data and explain the direction of future research.
How to Cite:
Van Nest, J. D., (2016) “High Altitude Cosmic Ray Detection”, Academic High Altitude Conference 2016(1). doi: https://doi.org//ahac.9765