Cosmic Rays for Environmental Sensing aims to make use of the waves and subatomic particles that shower down on earth in cosmic rays, by radiation detection to obtain data about the environment. The current focuses of CRES are obtaining the snow water equivalency (SWE) through gamma ray detection, and the soil moisture content over a 100 meter radius through detecting high and low energy neutrons. These are well known techniques, however the current technologies for these methods can cost around $30,000, for example the GMON3 from Campbell science. We are currently focused on building neutron detection instruments.
With radiation detection equipment like silicon photomultiplier emerging and replacing PMT Tubes, it is becoming easier to make cheap, compact, and robust radiation detection instruments. A silicon photomultiplier can be thought of like a photoresistor, but a diode. PMT Tubes and silicon photomultiplier are used with a scintillator, a crystal or plastic that emits light when it detects a particle or wave, to create a voltage pulse to get event counts and the intensity of the count.
To start understanding radiation detection systems we assembled Cosmic Watch Muon Detector, where multiple units can be put together in a muon telescope which can be used geological mapping of things like caves, volcanoes, or finding hidden rooms of the Pyramids of Egypt. This detector costed about $250, with many spare components to use for CRES.
Environmental Physics Motivation
Cosmic rays produce a flash of particles and electromagnetic energies. When the rays reach earth’s surface they interact with matter; detection these cosmic rays reveals valuable information about the environment.
water molecules in snow absorb gamma rays
In the mountains rocks considered non-radioactive give off constant gamma rays for the location. When snow falls on these rocks, the water molecules in the snow absorb some of the gamma rays which is exemplified in the image to the right.
Beer’s law is applied to calculate the maximum water content of the snow for forecasting. The equation used is: I(snow) = I(initial) × exp(α×Z). Where I is intensity of the waves, α is the attenuation coefficient, and Z is the path length or distance of the medium; which in this case Z will be the water content of the snow. With a gamma ray detector the only unknown variable we will have is the path length, so the equation is rearranged to be: Z = -ln( I(snow)/I(initial) ) × 1/α.
Soil MOISTURE found by neutron energy ratio
Neutrons have an atomic mass of 1, and start off with a high energy level. In the air above earth neutrons collide into other subatomic particles and elements which causes them to bounce around in the atmosphere, this bouncing around is called atmospheric scattering. Due to the mass of neutrons most of their collisions are inelastic which results in little energy loss. When a neutron collides with a hydrogen atom in a water molecule, it goes from high to low energy; this is called thermalization. Hydrogen causes energy loss to the neutron is because it also has an atomic mass of 1 which results in an inelastic collision. By obtaining the ratio of high to low energy neutrons we will know the the soil moisture for a 100 meter radius.
general muon detection applications
Muon detectors used in series together form a muon telescope, which is used for mapping out areas like caves, Egyptian Tombs, and to aid safe urban development.
Modify Cosmic Watch to detect gamma rays, and prevent other cosmic rays from interfering with gamma ray data.
Make use of scintillators to transform the Cosmic Watch to detect neutrons.
Work with the Radiation Detection Group at Oregon State to implement and to test our equipment against theirs to ensure ours is working accurately.
Muon, Gamma Ray, Neutrons, Detection, Arduino Nano, Cosmic Watch v2, scintillators, Water Density Sensing.
 “ARDUINO NANO–CHINA,” Sri Lakshmi Electronics, 01-Aug-2018. http://sle6.com/product/arduino-nano-china/.