Text of Jimmy McCarthy International Cosmic Ray Day 26 th September 2012 Detecting Cosmic Rays
Jimmy McCarthy International Cosmic Ray Day 26 th September 2012 Detecting Cosmic Rays
The Scintillation Counter Plastic scintillator Charged particle goes through scintillator. Light emitted in all directions. Light bounces around scintillator. Enters light guide. Directed into PMT
Photomultiplier Tube Photon hits cathode. Electron is emitted from cathode. Hits dynode and 2 or 3 electrons emitted. Amplified at each stage Electrical signal produced. Photon Anode Electron DynodesPhotocathode
The QuarkNet Card ddddfd Signal In Check for coincidences Counting cosmic rays Connect to computer
The Experiments Split into 3 groups 3 different experiments 11:00 12:15 Getting familiar with equipment 12:15 1:15 Lunch 1:15 2:15 Collecting Data 2:15 3:15 Analysing Data
Measuring Flux (All 3 experiments) Flux is the number of cosmic rays passing through the detector every second. Using the counter on the QuarkNet board. What errors might arise using this method? Using 6 people to get results. 1 person to keep time. 2 people to record and process counts 3 people to read the counter each minute Every 30 secs, 3 people shout out the number on the counter. Take an average of the 3 numbers, and work out how many cosmic rays were detected. Repeat for ~15 minutes (30 readings)
Exp1: Solid Angle Start with counters at fixed separation. Measure the flux of cosmic rays Change the separation Measure the flux again Discuss in groups: Do you expect to see a difference? If so, what difference? Why? Calculate theoretical predictions. Does it match your measurements?
Exp2: Zenith Angle Start at fixed separation. Measure the flux. Change the angle of the detector to the vertical. Keep the separation the same Discuss in groups: Do you expect to see a difference? If so, what difference? Why? Measure more angles (from 0 90 ) Does it follow a pattern?
Exp3: Altitude. Start with fixed separation. Measure flux. Put the detector on the trolley provided. Move to a different floor in the building. Measure the flux again. Discuss in groups: Do you expect to see a difference? If so, what difference? Why? Measure the flux on each floor of the building. Estimate the height difference between floors. Does the flux follow a pattern?