Luminescence dating of quartz using an improved single-aliquot regenerative-dose protocol

Single aliquot protocols are now widely used as a means of measuring the equivalent dose (D_e) in quartz and feldspar optical stimulated luminescence (OSL) dating of both heated and sedimentary materials. The most recent of these is the single-aliquot regenerative-dose (SAR) protocol, first suggested by Murray and Roberts (Radiation Measurements 29, 503–515, 1998). In this approach, each natural or regenerated dose OSL measurement is corrected for changes in sensitivity using the OSL response to a subsequent test dose (10–20% of D_e). If the sensitivity correction is adequate, then the corrected OSL response should be independent of prior dose and thermal/optical treatment, i.e. there should be no change in the sensitivity-corrected dose–response curve on remeasurement. Here we examine the interpretation of the sensitivity corrected growth curve as a function of dose, and the effect of changing measurement conditions (e.g. preheat temperature, size of test dose, stimulation temperature) on the estimation of D_e. The dependence of the dose response on prior treatment is tested explicitly, and the significance of thermal transfer discussed. It is concluded that a robust SAR protocol is now available for quartz, and that it is applicable to a wide range of heated and unheated materials.     

The single-aliquot regenerative-dose (SAR) protocol applied to coarse-grain feldspar

The application of the single-aliquot regenerative-dose (SAR) protocol to equivalent dose determination in coarse-grain feldspar is investigated. An outline of the protocol is presented, and basic tests of its performance are discussed. It is shown that the method is robust and yields results similar to those obtained with a single-aliquot additive-dose (SAAD) procedure. The use of the SAR procedure for fading tests is also discussed. We conclude that the SAR protocol for coarse-grain feldspar yields several advantages over previously used multiple-aliquot and single-aliquot methods. The method is fast and precise, the equivalent dose is obtained by interpolation, and the method corrects for sensitivity changes. The luminescence age obtained by SAR and additive-dose dating of the coarse-grain feldspar separates used in this study do, however, underestimate the independently estimated geological age of the samples.     

Application of the single-aliquot regenerative-dose protocol to the 375°C quartz TL signal

We report on investigations into the suitability of a single-aliquot regenerative-dose (SAR) protocol applied to the isothermal TL signal obtained from quartz held at 330°C. Samples are first thermally and optically pretreated to remove any signal from the 325°C TL trap. It is shown that the regenerated TL decay curve has the same shape as the natural one, and that recuperation is negligible. Examination of the TL glow curve before and after isothermal measurement suggests that the isothermal signal comes mainly from the 375°C TL peak, and a pulse anneal experiment is used to confirm this. This signal is bleached by simulated sunlight, with a fast component (making up about 60% of the total natural signal) bleaching about 30 times faster than a slower component. The SAR protocol is then applied to 9 samples from various depositional environments, and it is shown that the resulting data satisfy the internal checks of reliability, i.e., independence of prior treatment, and absence of recuperation. Examination of the sensitivity-corrected growth curve shows that the applicable age range for this signal may be only slightly greater than that from the OSL signal derived from the 325°C peak. This limited advantage is offset by the much greater difficulty of bleaching.     

Using the OSL single-aliquot regenerative-dose protocol with quartz extracted from building materials in retrospective dosimetry

We report on the application of the single-aliquot regenerative-dose (SAR) protocol to the optically stimulated luminescence signal from quartz extracted from fired bricks and unfired mortar in retrospective dosimetry. The samples came from a radioactive materials storage facility, with ambient dose rates of about 0.1 mGy/h. A detailed dose-depth profile was analysed from one brick, and compared with dose records from area TL dosemeters. Small-aliquot dose-distributions were analysed from the mortar samples; one associated with the exposed brick, and one from a remote site exposed only to background radiation. We conclude that unfired materials have considerable potential in retrospective dosimetry.     

探究式学习在物理实验课的应用

通过探究式实验教学与传统教学模式的比较,论证了探究式实验教学的必要性,并指出了探究性物理实验教学的实施空间和时间应该具有相对的开放性,即突破狭义的课堂教学的封闭环境,建构起以教科书为载体、以教室为实验空间的小环境和以所有媒介为补充、以日常生活乃至宏观世界为大环境的高中物理实验教学体系,同时本文还举例说明了探究式教学实施的途径.     

Optically stimulated luminescence production in the single-aliquot regenerative dose protocol

When using a single-aliquot regenerative dose (SAR) protocol for luminescence dating of sedimentary quartz grains, the fundamental assumption is that the sensitivity of the optically stimulated luminescence (OSL) produced by the regenerative doses can be monitored by their following test dose OSL response. Using well-bleached coarse quartz grains, OSL production in a SAR protocol was studied in detail when dose response curves were constructed using both single and multiple aliquot regenerative dose procedures. During application of the SAR protocol, two preheats are applied, each ahead of an OSL measurement that is produced by the regenerative dose and test dose, respectively. It is shown that sensitivity changes caused by heating were well corrected for using the OSL response to the test dose. However, these preheats are shown to result in thermally stimulated OSL signals that contribute both to the OSL response from the regenerative doses used to construct the dose response curve and to the OSL response from the test dose used to monitor OSL sensitivity changes as the quartz grains are repeatedly measured. A simple test is proposed to identify the contribution of the latter signal.     

Excel软件在物理实验中的应用

结合两个实例介绍了Ｅｘｃｅｌ函数和图表功能在最小二乘法作参数估计中的用法。     

Developing a single-aliquot protocol for measuring equivalent dose in biogenic carbonates

Exploiting biogenic carbonates as thermoluminescence dosimeters requires an understanding of trap kinetics and an appropriate sequence with which to measure equivalent dose. The trap kinetics of two high temperature peaks (peaks II and III) from calcitic snail opercula have been investigated resulting in the calculation of lifetimes of 7.4 × 10⁷ and 1.4 × 10¹¹ years for the two peaks respectively. Two measurement sequences, based upon changes in the application and measurement of a test dose, have been applied to peaks II and III, and though both methods were equally successful in dose recovery and production of a dose response curve some differences were observed. Primarily, the use of method 1 lead to dose dependant sensitivity change implying competition effects occurring during irradiation; method 2 did not experience this phenomenon. As a consequence method 2 was chosen as the most appropriate protocol for single-aliquot dating of this material.When assessing the TL behaviour of the two peaks, peak II performed poorly in dose recovery experiments recovering a dose 60–100% larger than that applied. Disproportionate growth of peak II in response to a beta dose applied prior to measurement, compared to growth following regeneration doses indicated that peak II was not suitable for use in single-aliquot protocols. However, dose recovery results for peak III were all within errors of unity of the given dose, and peak III was therefore chosen as the most appropriate peak for TL dosimetry in these single-aliquot procedures. The lifetime of charge in peak III is sufficient to date over many millions of years, and furthermore using the chosen method 2 the dose response curve has a D₀ of 3,250 ± 163 Gy allowing dating to over 3 million years.     

发展性评价在大学物理实验教学中的应用

针对当前大学物理实验评价中存在的问题,建议在实验教学中引入发展性评价,提出了两种具体实施模式.模式一采用在平时实验中学生自评、同伴评价与教师评价相结合的方式,模式二采用在操作考试中将工作单和观察法相结合的方式,并进行了对比试验.试验结果表明,发展性评价较有效地改善了实验效果.