How the Risø DA-20 TL/OSL Reader from DTU Physics enables luminescence dating of sediments, ceramics and archaeological materials, accident dosimetry and radiation protection research — and why Bangladeshi universities and geological institutes are investing in this capability.
Bangladesh sits at the confluence of the Ganges, Brahmaputra and Meghna rivers — one of the world's most active sedimentary environments. Understanding the timing of sediment deposition, floodplain evolution, coastal accretion and delta formation requires absolute dating techniques that can reach beyond the range of radiocarbon (approximately 50,000 years). Optically Stimulated Luminescence (OSL) and Thermoluminescence (TL) dating, performed on the Risø DA-20 TL/OSL Reader, fill this gap — dating quartz and feldspar grains from 100 years to over 500,000 years before present.
Mineral grains (quartz, feldspar) accumulate charge in crystal defects when exposed to natural ionising radiation (from uranium, thorium and potassium in the surrounding sediment). When the grains are exposed to light (bleaching event — e.g. transport by wind or water) or heat (firing of ceramics), the stored charge is released as light — the luminescence signal. After burial, the charge begins to accumulate again at a rate determined by the local dose rate. By measuring the stored charge (the equivalent dose, De) and the dose rate, the burial age can be calculated: Age = De / Dose Rate.
The Risø DA-20 is the world's most widely deployed luminescence measurement system — more than 400 units installed in leading research laboratories across 60 countries. Manufactured by DTU Physics (Technical University of Denmark), it features: an automated 48-position sample changer in a vacuum chamber (<0.2 mbar); a shaped Kanthal heater strip with endpoint temperature of 700°C; IR/green stimulation (870 nm, >135 mW/cm² at sample) and blue LED stimulation (470 nm, >80 mW/cm²) arrays with optical feedback servo; a 1.48 GBq ⁹⁰Sr/⁹⁰Y beta irradiator for in-situ dose calibration; and an EMI 9235QB15 photomultiplier tube (linear to 40×10⁶ cps). The system is controlled by the Sequence Editor software, which allows fully automated, user-defined TL/OSL measurement protocols.
Quaternary geology and delta research: OSL dating of Holocene and Pleistocene sediments from the Bengal Delta, Sylhet Basin and Chittagong Hill Tracts — establishing chronologies for river migration, tectonic uplift and sea-level change. Archaeological dating: TL dating of fired ceramics, burnt flint and brick from archaeological sites across Bangladesh — extending the chronological framework beyond the range of radiocarbon. Coastal geomorphology: OSL dating of beach ridges, aeolian dunes and tidal flat sediments along the Bay of Bengal coast and the Sundarbans — critical for understanding coastal vulnerability to sea-level rise. Radiation protection and accident dosimetry: The Risø reader's beta irradiator and high-sensitivity PMT make it suitable for retrospective dosimetry of building materials (bricks, tiles) after a radiation accident — a capability of direct relevance to Bangladesh's growing nuclear power programme (Rooppur NPP). Nuclear medicine physics: TL dosimetry of clinical radiation fields using LiF:Mg,Ti (TLD-100) and Al₂O₃:C (OSL) dosimeters — for quality assurance in radiotherapy and nuclear medicine departments.
A Risø TL/OSL laboratory requires a light-tight sample preparation room (red safelight only), a dedicated instrument room with stable temperature (20±2°C) and humidity (<60% RH), a compressed nitrogen supply for purging the sample chamber, and a radiation safety enclosure for the ⁹⁰Sr/⁹⁰Y beta source (licensed by the Bangladesh Atomic Energy Commission, BAEC). Vvon Technologies provides the complete laboratory design: room layout, light-tight construction specification, BAEC source licence application support, instrument installation, software configuration and operator training in SAR (Single Aliquot Regenerative) and SARA protocols.
DTU Physics provides after-sales service for all Risø TL/OSL readers through a network of trained engineers and scientists — the same team that designed and built the instrument. Vvon Technologies is the local service point in Bangladesh, providing first-line support, consumables (sample discs, cups, detection filters, heater strips) and coordination with DTU Physics for major repairs or upgrades. The Risø platform is modular and upgradeable: existing readers can be retrofitted with new attachments (IRSL head, single-grain OSL attachment, alpha irradiator) as research requirements evolve. Request a luminescence lab consultation →