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Jimmy McCarthy International Cosmic Ray Day 26 th September 2012 Detecting Cosmic Rays

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The Detector

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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

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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

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The QuarkNet Card ddddfd Signal In Check for coincidences Counting cosmic rays Connect to computer

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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

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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)

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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?

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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?

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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?