An5 Radiation Detectors and Dosimetry

Aims Studying this chapter should give you some appreciation of the variety of radiation detectors available and equip you with some practical knowledge about their characteristics and uses. This chapter also contains practical knowledge about the description and measurement of the effects of radiation on humans. You should learn how the problem of measuring doses is currently handled in terms of physical concepts, such as energy absorption, and empirical constructs, such as quality factors and equivalent dose rates. Although you should study the detailed information about the sources of radiation in the environment, there is no point in trying to memorise detailed statistics. Use the data to develop your appreciation of the problems and the precautions which need to be taken. Minimum learning goals When you have finished studying this chapter you should be able to do all of the following. 1. Explain, use and interpret the terms gas-filled detector, gas amplification, ionisation chamber, proportional counter, Geiger counter, multi-wire detector, scintillation counter, scintillator, fluorescence, photomultiplier, image intensifier, solid state detector, semiconductor detector, film badge, stochastic process, specific ionisation (exposure), absorbed dose, gray, background, dose equivalent, sievert, quality factor (relative biological effectiveness), dose rate, annual intake, annual limits on intake (ALI), background radiation, cosmic radiation, dose limit. 2. Outline the operating principles of ionisation chambers, proportional counters, Geiger counters, scintillation counters, photomultipliers, semiconductor detectors and film badges. 3. Describe uses of various types of radiation detector. 4. (a) Describe and explain ways of specifying radiation doses. (b) State and apply the relation between dose equivalent and absorbed dose. 5. (a) Describe and discuss the significance of various sources of natural background radiation. (b) Describe how radionuclides can enter the body from the environment. 6. Describe and discuss the principles of dose limits.