The Risø TL/OSL-DA-20 Luminescence Reader is designed for automated measurement of thermally and optically stimulated luminescence. The luminescence is detected by a photomultiplier (E<I 9235QA). Transmission filters consisting of Hoya U-340, Schott BG39 and Corning 7-59 are used to discriminate between the luminescence and scattering stimulating light. This limits the transmission band for the luminescence to 300 – 400 nm. Samples for both thermal and optical stimulation are placed on a 48 – sample carousel which can be rotated in position under the photomultiplier. The heating element located underneath the photomultiplier heats the sample and also lifts the sample to the measurement position. Samples can be heated up to 700 °C at rates from 0.1 to 10 °C/s. If necessary, the sample chamber can be flushed with nitrogen to improve thermal condition between sample disk and the heater and to prevent oxidation of the heating systems at high temperature. Optical stimulation is done using clusters of light-emitting diodes (870 nm infrared and 470 nm blue LEDs). 532 nm and 830 nm laser stimulation source are optional. The LEDs can be operated at constant intensity for continuous-wave optical stimulation. LM-OSL can be operated if the intensity of the LEDs are pulsed, then time-resolved spectra may be measured. Samples are excited using beta irradiation using a detachable beta irradiator fixed above the sample carousel. The irradiation source is a 1.48 GBq 90Sr/90Y beta source which emits beta particles with a maximum energy of 2.27 MeV. Optional sources are a 10.7 MBq 241Am foil alpha source and a Varian VF-50J X-ray tube.