Optically stimulated luminescence dating laboratory
The methods through which dose rates are calculated vary between different laboratories worldwide.
The radiation dose rate is also measured in grays, but as we calculate the dose rate per thousand years, it is grays per thousand years (Gy/ka). A robust feldspar luminescence dating method for Middle and Late Pleistocene sediments.
Measuring the environmental dose rate for an OSL sample from Glen Tulla, Scotland.
The gamma spectrometer has been put into the sample hole (see the lead going from the gamma spectrometer crystal to the control box).
OSL works because all sediments have some natural radioactivity, caused by the presence of uranium, thorium and potassium isotopes in heavy minerals such as zircons.
In addition to radiation from the surrounding sediment, OSL samples are affected by a cosmic dose rate, which reduces as the amount of sediment the sample is buried under increases.
The cosmic dose is useful in other situations, as it can be used to determine how long rocks, for example, have been exposed on the Earth’s surface using Cosmogenic Nuclide Dating.
Luminescence dating depends on the ability of minerals to store energy in the form of trapped charge carriers when exposed to ionising radiation.
Stimulation of the system, by heat in the case of thermoluminescence (TL), or by light in the case of photo-stimulated luminescence (PSL), or optically stimulated luminescence (OSL).