ESR measurements are performed with two spectrometers: (1) Bruker EMXmicro 6/1 (X-band) equipped to work from room (300 K) to liquid nitrogen temperature (77 K); (2) Bruker Elexsys E500 (Q and X band) equipped to work from room (300 K) to liquid helium temperature (4 K). The stability of the experimental conditions is ensured by a ThermoFlex3500 chiller connected to the EMXmicro spectrometer and a Rieden PC100.02-KE chiller connected to the Elexsys E500 spectrometer. Both chillers control and precisely stabilize the temperature (±0.1 °C) of the water cooling the magnets. An air conditioning system regulates the temperature of the room. A programmable goniometer ensures tube rotations inside the resonator with a precise angular resolution and reproducibility which allows checking angular variation of the ESR signal. The natural radioactivity of geological/archaeological samples is assessed with two Canberra high-purity germanium detectors (Extended Range Coaxial –Xtra and well-type detectors). Sample irradiations are performed using a Gammacell-1000 irradiator with a 137Cs source (approx. dose rate: 8 Gy/min) (Best Theratronics). Sample preparation is carried out in a dark laboratory under controlled lighting conditions to obtain pure quartz and feldspars from sediments or separate different dental tissues from fossil teeth. This laboratory is fully equipped (saws, dentist's drills, agate mortars, sieves, mills, hot plates, scales, magnetic separator, etc.) to optimally treat samples prior to chemical preparation. The chemical preparation laboratory is equipped with fume hoods to prevent hazardous and odorous chemical exposure. It is also furnished with all other laboratory material necessary for acid attacks or the separation of minerals through dense liquids. In order to bleach quartz samples, it is used a Hönle solar simulator (UVACube400 + SOL500). CENIEH has all of the necessary field material to carry out sampling campaigns: PVC tubes, Minigrip® Anti UV opaque bags, hammer, GPS, tape measures and two Canberra portable gamma spectrometers: an Inspector1000 multichannel analyzer connected to a NaI(Tl) probe and an Inspector1000 multichannel analyzer connected to a LaBr3(Ce) probe.
Potential Results
ESR is a highly versatile dating method which can produce ages mainly on fossil remains, quartz grains and speleothems. Although this method cannot reach a level of precision similar to other isotopic dating methods, it is applicable in almost any archaeological context over the last 2.6 Ma. In many cases, it is the only numerical method that can be used at a given site. ESR dating shows great potential for Quaternary Geochronology and is characterized by a large variety of possible applications in Archaeology.