Detecting Cosmic Radiation Levels in the Middle & Upper Atmosphere St Paul’s School Asgard- II Module

Asgard I We placed several dosimeters on board the BalloonSat. One dosimeter containing film was placed next to the electronics inside the BalloonSat. We also placed two thermoluminescence dosimeters (TLD, for measuring radiation at the finger tips) on the outside of the BalloonSat with a third was kept as a control.

Asgard I radiation results

Cosmic Rays The illustration at right shows that the detected cosmic ray flux peaks at about 15 km in altitude and then drops sharply (note the logarithmic scale on the altitude). This kind of variation was discovered by Pfotzer in It suggests that the detection method used was mainly detecting secondary particles rather than the primary particles reaching the Earth from space.

Ionisation Chamber The ionization chamber is the simplest of all gas-filled radiation detectors, and is used for the detection or measurement of ionizing radiation

Geiger-Muller Tube The GM tube we used was ZP1481 produced by Centronic Ltd. It contains a inert gas atmosphere The tube had a recommended working voltage at 430V with a mica window thickness of 2.5mg/cm 3 The window diameter is 17cm and has a maximum background count of 30 counts/min when shielded with 50mm of Lead. The optimum operating range is between -40 and +70C and we know that low humidity will not have an effect. The GM tube has a halogen quenched tube making it very sensitive to Beta and Alpha Radiation.

The High Voltage Supply It is based on a disposable camera’s high voltage flash unit. We modified the circuit by replacing the 80µF bulk storage capacitor with a 2.2nF on. Also we power the circuit with a 3.0VDC.

GM Tube output pulse detector There is a small issue relating to the fact that pulses coming from the GM tube are not sufficient enough to be registered by the Arduino. The series of Transistors shown below act to first amplify then invert the output into the 555 monostable shown. This monostable outputs pulses to the Arduino which counts them.

555 Monostable operation Once the time period has started further trigger pulses are ignored. The timing period is triggered (started) when the trigger input (555 pin 2) is less than 1/3 Vs, this makes the output high (+Vs) and the capacitor C1 starts to charge through resistor R1.

The Arduino The Arduino microcontroller is an open source family and uses a simplifies version of C++ Plug and Play system using an IC2 Bus thereby making it very easy to use.

Other measurements (Asgard I data)

EEPROM “Electrically Erasable Programmable Read-Only Memory” a type of non-volatile computer memory to store data that must be saved when power is removed

Detecting Cosmic Radiation Levels in the Middle & Upper Atmosphere St Paul’s School Asgard- II Module

Asgard II radiation results

Asgard II acceleration results

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