Detecting cosmic rays using CMOS sensors in consumer devices Matthew Plewa

Introduction What is a cosmic ray Stable Typically striped nucli Charged What is a secondary? Gammas, muons, protons, pions and electrons

Common Detections Methods Citizen Scientist Cloud Chambers Vapor condenses along the particle path (can visually see) Scintillator Panels When excited by ionizing particles they emit photons

Common Detection Methods CMOS Sensors When light is blocked from the sensor cosmic rays deposit a charge on the sensor. This charge is then interpreted as light in the image. The sensor must be capturing a frame at the time the cosmic ray enters it. Small active area

DECO (CMOS Sensor) Funded by American Physical Society Knight Foundation and Simon-Strauss Foundation Works on android phones (IPhones soonish) Great learning tool and is becoming a great scientific tool with upcoming upgrades

CMOS Sensor Benefits Easily attainable Most of us have them in our pocket Easily used CMOS sensor just needs to have light blocked Tools are being developed for detection in the frames

CMOS Sensors Due to the small area (~.15 cm^2) livetime is extremely important. For this reason we had to look at what method would increase livetime Video mode Still capture

Video vs Still Capture Still capture (8MP) Livetime ~5% 1 out of every 20 events detected High resolution (Low data rate ~1 a sec) Video mode (2MP) ~95% livetime Low resolution (High Data rate ~30 a sec)

Video vs Still What would work best for high altitude ballooning? The more events that can be captured the more analysis that can be done. Lower resolution means track analysis is less accurate More events seemed to be the best choice for initial testing

Using a GoPro Readily available device Knew the sensor size (.24 cm^2) so determining how many events that should be seen at ground level was easy. Fairly reliable hardware

Post Flight Processing Video needed to be decompiled into individual frames Current method of detecting events is a simple threshold cut of the R, G and B values for each pixel Altitude data was not recorded so events couldn’t be correlated accordingly

Results 66 “events” were detected in 2 hour span Electron worms and Alpha particles (decay on the surface of the sensor) Demonstrated the viability of detection using CMOS sensors Need better filtering parameters

Future work Raspberry Pi & Pi cameras Potentially larger surface area. Higher resolution Data logging Temperature Altitude GPS

Long Duration Exposure DECO V2 (full resolution) Android 5.0 + Camera2 api Able to set ISO Full exposure control up to 2 seconds Automatic datalogging Database collection Highly recommended for future ballooning

Track Analysis Need to determine how to reduce electron and alpha particle noise Track traceback and pointing of particle origin (path before entering sensor) Will be easier with higher resolution

Questions?