Detecting Cosmic Rays Jimmy Mc Carthy International Cosmic
- Slides: 10
Detecting Cosmic Rays Jimmy Mc. Carthy International Cosmic Ray Day 26 th September 2012
The Detector
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 Electron Photocathode Dynodes Anode �Photon hits cathode. �Electron is emitted from cathode. �Hits dynode and 2 or 3 electrons emitted. �Amplified at each stage �Electrical signal produced.
The Quark. Net Card �ddddfd Counting cosmic rays Connect to computer Check for coincidences Signal In
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 Quark. Net 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 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)
Exp 1: 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?
Exp 2: 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?
Exp 3: 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?
