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GAS-FILLED IONISATION DETECTORS

Physics

GAS-FILLED IONISATION DETECTORS

Principle of Operation:
1. Ions are created by the ionizing radiation entering the gas chamber.
2. Ions created by the ionisation of gas are collected by applying a voltage between two electrodes.
3. The accelerating voltage across the electrodes can be varied giving rise to several “modes of operation” for gas-filled detectors.
4. Ionisation chambers are used for survey meters (units: uSv/h).
5. Geiger-Muller tubes are usually used for contamination monitoring.
6. Output of G-M tube is not proportional to the absorbed energy: any radiation depositing energy in the gas leads to one ‘count’.
7. For a contamination monitor, the usual output is counts per second.


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REFERENCES

1. Bushberg, J. T. (2012). The essential physics of medical imaging. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. Find it at Amazon
2. Heggie, J. C., Liddell, N. A., & Maher, K. P. (1997). Applied imaging technology. Melbourne: St. Vincents Hospital.

Ⓒ A. Manickam 2018

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