Strategies for equivalent dose determination without heating, suitable for portable luminescence readers

Abstract

In recent years a number of portable instruments have been built for measuring the optically stimulated luminescence (OSL) signal from naturally occurring minerals. Some of these instruments have incorporated ionising radiation sources, giving the possibility of determining an equivalent dose (D e), but little use has been made of these. One challenge has been that heating samples in this type of equipment is a major engineering challenge, yet methods for D e determination use thermal pretreatments to remove charge from unstable traps, making signals arising from irradiation in nature and the laboratory comparable. This paper explores three strategies for obtaining accurate estimates of the D e of samples in situations where thermal treatments are not possible: (1) deriving a correction factor based on comparing D e values obtained using protocols with and without heating; (2) removing the contribution from the 110°C TL peak and other unstable defects by component fitting the unheated OSL signal; and (3) adding a small beta dose to the sample prior to measurement of the natural luminescence signal so that the 110°C TL peak is filled, making this measurement comparable with regeneration measurements where this peak is also populated. All three methods are promising when applied to quartz that has been physically separated from samples using standard laboratory procedures. The next step in

The potential of portable luminescence readers in geomorphological investigations: a review

“…Secondly, for those readers that may have an internal source, irradiated samples would need to be heated prior to measurement in order to eliminate charges in unstable traps. However, heating a sample in a portable OSL reader places challenges that would need to be overcome, ranging from excessive power demand to the possibility of combustion of organics in an untreated sample, and condensation of moisture from wet sediment (Roberts et al ., 2018). Heating of samples has been conducted outside the reader in some studies (e.g.…”

“…The beta dose fills the 110°C TL peak such that the measurement obtained would be comparable to a regeneration measurement that has not been heated and, hence, has the same peak. While these approaches have been tested on pure quartz separates using a Risø TL/OSL‐DA‐12 or a TL/OSL‐DA‐20 system (Robert et al, 2018), they still need to be tested using bulk samples, and portable OSL readers for that matter. Thus, overall, the approaches provide scope for future development of the technique going forward.…”

“…However, heating a sample in a portable OSL reader places challenges that would need to Portable OSL reader used to examine sediment in three sections along Wadi Suf in a study looking at the relationship between urban settlement and riverine systems in semi-arid environments. Results show that both IRSL and blue OSL signal intensities increased downstream suggesting increase in sensitivity due to repeated erosion-deposition cycles be overcome, ranging from excessive power demand to the possibility of combustion of organics in an untreated sample, and condensation of moisture from wet sediment (Roberts et al, 2018). Heating of samples has been conducted outside the reader in some studies (e.g.…”

“…Nonetheless, future technical advancements in the design of portable OSL readers may render this possible. Notably, Roberts et al (2018) have proposed three different methods for approximating D e that do not require heating of samples and could be used with portable OSL readers. The first approach requires the derivation of a correction factor that is obtained from comparing D e values determined using heating with those obtained using no heating.…”

A method for routinely monitoring the reproducibility of thermal pretreatment prior to optically stimulated luminescence measurements

“…A potential solution is to give a small dose to the sample prior to measurement of the natural. Adding a laboratory irradiation prior to measurement of De is not a new approach: Roberts et al (2018) describe experiments using such an approach, and Mejdahl and Figure 7: Data for quartz from the beach sample used for the inter-comparison exercise of Murray et al (2015) Bøtter-Jensen (1994) proposed the single aliquot regeneration of additive doses (SARA) method 25 years ago. SARA involves giving a range of different additive doses prior to measurement of De, and has been used in a number of studies since then (e.g.…”