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Recent developments in luminescence dating offer new ways to date exposure and burial durations of rocks. The new rock surface dating methods ideally require high-resolution data, faster sample preparation and measurement times, and field screening methods to select samples with appropriate luminescence characteristics and bleaching histories. Presented here is a demonstration of an EMCCD (electron multiplying charge coupled device) based system capable of imaging high-resolution Infrared stimulated luminescence (IRSL) and Infrared-photoluminescence (IRPL) from rock samples. The IRPL can be detected at both 880 nm and 955 nm. Using this instrument, the entire luminescence-depth profile can be reconstructed by imaging a single surface cut perpendicular to the exposed rock face. We demonstrate the possibility of reconstructing luminescence-depth profiles suitable for rock surface dating from large (cm-scale) rock samples, without using a regeneration dose for normalisation of the natural luminescence signals. Based on the different bleaching characteristics of the IRSL and IRPL emissions at 880 nm and 955 nm, we show that it is possible to gain reliable estimates of bleaching depths from measurement of as few as two images of the IRPL signal (one for each emission), or from measurement of the IRSL decay curve. We thus by-pass laborious sample preparations and the need for a gamma source to estimate the bleaching depth, thereby extending the 2D luminescence-depth profile imaging technique to other laboratories that lack access to ionising radiation facilities. This study also makes a significant progression towards development of a field instrument for in-situ relative exposure dating, and sample screening for rock surface burial dating.

In this study, we explored the potential of a NaI(Tl) scintillator-based gamma spectrometer for the accurate determination of burial dose rates in natural geological samples using a full spectrum analysis (FSA) approach. In this method, an iterative reweighted least-square regression is used to fit calibration standard spectra (40K, and 238U and 232Th series in equilibrium) to the sample spectrum, after subtraction of an appropriate background. The resulting minimum detection limits for 40K, 238U, and 232Th are 4.8, 0.4 and 0.3 Bq·kg−1, respectively (for a 0.23 kg sample); this is one order of magnitude lower than those obtained with the three-window approach previously reported by us, and well below the concentrations found in most natural sediments. These improved values are also comparable to those from high-resolution HPGe gamma spectrometry. Almost all activity concentrations of 40K, 238U, and 232Th from 20 measured natural samples differ by ≤5% from the high resolution spectrometry values; the average ratio of dose rates derived from our NaI(Tl) spectrometer to those from HPGe spectrometry is 0.993 ± 0.004 (n=20). We conclude that our scintillation spectrometry system employing FSA is a useful alternative laboratory method for accurate and precise determination of burial dose rates at a significantly lower cost than high resolution gamma spectrometry.

Metastable states form by charge (electron and hole) capture in defects in a solid. They play an important role in dosimetry, information storage, and many medical and industrial applications of photonics. Despite many decades of research, the exact mechanisms resulting in luminescence signals such as optically/thermally stimulated luminescence (OSL or TL) or long persistent luminescence through charge transfer across the metastable states remain poorly understood. Our lack of understanding owes to the fact that such luminescence signals arise from a convolution of several steps such as charge (de)trapping, transport and recombination, which are not possible to track individually. Here we present a novel coupled RPL(radio-photoluminescence)/OSL system based on an electron trap in a ubiquitous, natural, geophotonic mineral called feldspar (aluminosilicate). RPL/OSL allows understanding the dynamics of the trapped electrons and trapped holes individually. We elucidate for the first time trap distribution, thermal eviction, and radiation-induced growth of trapped electron and holes. The new methods and insights provided here are crucial for next generation model-based applications of luminescence dating in Earth and environmental sciences, e.g. thermochronometry and photochronometry., Manuscript accepted in Scientific Reports (https://www.nature.com/srep/)

Prasad et al. (2017) recently developed a new method of measuring the dosimetric signal in feldspar, based on a Stokes-shifted photoluminescence emission (excitation energy ∼ 1.40eV (885 nm), emission energy ∼ 1.30eV (955 nm)). The new signal, termed as infrared photoluminescence (IRPL), was shown to arise from radiative relaxation of the excited state of the principle trap (dosimetric trap), and allows non-destructive probing of the dosimetric information. Thus, IRPL provides a unique tool to study physical characteristics of these metastable states in feldspar, e.g., number density and spatial distribution, trap depth, photo-ionisation and capture cross-section, excited state lifetime, and tunneling probabilities. The IRPL emission is apparently related to the infrared radioluminescence (IR-RL) in K-feldspar (Trautmann et al., 1998); in the latter, however, the electrons relax after being trapped as a result of exposure to ionising radiation, rather than as a result of excitation within the trap. In this study, we report the discovery of a second IRPL emission centred at ∼ 1.41eV (880 nm) in a K-feldspar which arises in response to excitation with 1.49eV photons. Based on the temperature- and dose-dependent behaviour of IRPL and IR-RL, we conclude that the same defect(s) participates in these two emissions. However, IRPL emission is governed by the characteristics of the principle trap (defect) alone, whereas IR-RL depends additionally on thermally assisted transport within the band-tail states. Since IRPL is a site selective technique, it does not, unlike IR-RL, suffer from contamination from higher energy emissions (e.g. from Fe 3 + ). This lack of contamination, and the possibility for thermal/optical pre-treatments and repeated measurements of the same trapped electrons, suggest that IRPL is a robust alternative to IR-RL.

It is desirable to be able to establish the relationship between the spatial distribution of luminescence and chemical composition/mineralogy. This is especially true in complex, heterogeneous samples such as solid coarse-grained rock slices and separated feldspar grains, where the internal dose rate is very dependent on the effective size of luminescent regions of the sample. The addition of spectral information would then help to give further insights into luminescence production mechanisms. A high sensitivity imaging attachment to the Riso TL/OSL Reader for investigating the spatial distribution of OSL and TL from natural and artificial phosphors has recently been developed (Kook et al., 2015). When combined with a Bruker μ-XRF facility and a high sensitivity spectrometer attachment, it is possible to investigate the relationship between the spatial distribution of luminescence, the distribution of chemical composition/mineralogy and the associated excitation and emission spectra. Here laboratory measurements undertaken using solid rock samples are presented and the observed relationships and their dosimetric implications are discussed.

Optical dating has revolutionized our understanding of Global climate change, Earth surface processes, and human evolution and dispersal over the last ~500 ka. Optical dating is based on an anti-Stokes photon emission generated by electron-hole recombination within quartz or feldspar; it relies, by default, on destructive read-out of the stored chronometric information. We present here a fundamentally new method of optical read-out of the trapped electron population in feldspar. The new signal termed as Infra-Red Photo-Luminescence (IRPL) is a Stokes emission (~1.30 eV) derived from NIR excitation (~1.40 eV) on samples previously exposed to ionizing radiation. Low temperature (7–295 K) spectroscopic and time-resolved investigations suggest that IRPL is generated from excited-to-ground state relaxation within the principal (dosimetry) trap. Since IRPL can be induced even in traps remote from recombination centers, it is likely to contain a stable (non-fading), steady-state component. While IRPL is a powerful tool to understand details of the electron-trapping center, it provides a novel, alternative approach to trapped-charge dating based on direct, non-destructive probing of chronometric information. The possibility of repeated readout of IRPL from individual traps will open opportunities for dating at sub-micron spatial resolution, thus, marking a step change in the optical dating technology.

Metastable states created by electron or hole capture in crystal defects are widely used in dosimetry and photonic applications. Feldspar, the most abundant mineral in the Earth’s crust (> 50%), generates metastable states with lifetimes of millions of years upon exposure to ionizing radiation. Although feldspar is widely used in dosimetry and geochronometry, the creation of metastable states and charge transfer across them is poorly understood. Understanding such phenomena requires next-generation methods based on high-resolution, site-selective probing of the metastable states. Recent studies using site-selective techniques such as photoluminescence (PL), and radioluminescence (RL) at 7 K have revealed that feldspar exhibits two near-infrared (NIR) emission bands peaking at 880 nm and 955 nm, which are believed to arise from the principal electron-trapping states. Here, we map for the first time the electron-trapping states in potassium-rich feldspar using spectrally-resolved cathodoluminescence microscopy at a spatial resolution of ~ 6 to 22 µm. Each pixel probed by a scanning electron microscope provides us a cathodoluminescence spectrum (SEM-CL) in the range 600–1000 nm, and elemental data from energy-dispersive x-ray (EDX) spectroscopy. We conclude that the two NIR emissions are spatially variable and, therefore, originate from different sites. This conclusion contradicts the existing model that the two emissions arise from two different excited states of a principal trap. Moreover, we are able to link the individual NIR emission peaks with the geochemical variations (K, Na and Fe concentration), and propose a model that explains the quenching of the NIR emission by Fe4+. Our study contributes to an improved understanding of charge storage in feldspathic minerals, with implications for developing sub-single grain (micrometer scale) measurement techniques in radiation dosimetry.

Optically stimulated luminescence (OSL) dating of sediment, based on the accumulation of trapped charge in natural crystals since their last exposure to daylight, has revolutionised our understanding of the late Quaternary period. Recently, a complementary technique called luminescence rock surface dating (RSD), which uses differential spatial eviction of trapped charges in rocks exposed to daylight, has been developed to derive exposure and burial ages, and hard-rock erosion rates. In its current form, the RSD technique suffers from labour intensive sample preparation, uncertainties in the depth and dose rate estimates, and poor resolution of the luminescence-depth profile. Here, we develop a novel, 2D luminescence imaging technique for RSD of large rock slabs (3 × 5 cm) to overcome these challenges. We utilize the recently discovered infrared photoluminescence (IRPL) signal for direct, non-destructive imaging of the luminescence-depth profile in a sub-aerially exposed granitic rock, with an unprecedented spatial resolution of ~140 µm. We further establish a correlation between luminescence and geochemistry using micro X-ray fluorescence (µXRF) spectroscopy. Our study promises a substantial advancement in luminescence imaging and paves the path towards novel applications using 2D dating, micro-dosimetry in mixed composition samples, and portable instrumentation for in-situ luminescence measurements.

Infrared photoluminescence (IRPL) is a Stokes-shifted emission arising from radiative relaxation of the excited state of the principal dosimetric tap in feldspar. Recent investigations have revealed that there exist two IRPL emissions at 880 nm and 955 nm (for excitation using 830 nm laser). Since IRPL does not depend on the recombination centers, the signal can be read out non-destructively; this allows us to insert its measurement in a conventional IRSL (infrared stimulated luminescence) or post IR-IRSL single-aliquot regenerative (SAR) dose protocol. In this study, we focus on the development of a SAR protocol using the two different IRPL emission bands (~880 nm and ~955 nm) and test their potential for sediment dating with known-age samples. Our results show that accurate equivalent doses from 100 to 300 Gy (age range 20–128 ka) can be obtained using an IRPL-based SAR protocol without a fading correction.

In contrast to the detailed investigations on the dosimetric electron trap in feldspar only little has been done to understand the luminescence centers. We use a comparison of multiple spectroscopic techniques, site selective photoluminescence spectroscopy and time resolved measurements to further our understanding of the luminescence mechanisms and recombination sites, in a sample of Na rich plagioclase feldspar (oligoclase). Both the UV and violet–blue emissions show resonant excitations arising from a distribution of energy levels. We propose, contrary to the general understanding, that the green emission may not arise from Mn 2+ in our sample and that photoionisation of this centre may be possible by excitation to the band tail states. The deep red emission is tied to the Fe 3+ , and the exponential rise in the UV excitation efficiency of this centre is discussed in the context of the band-tail model.

The measurement of OSL/TL relies on the initial trapping and subsequent release and recombination of charge in a suitable crystal structure. These measurements allow us to estimate the dose which the crystal has been subjected to and its age. During such processes, however, electrons can be emitted from the sample surface; the ability to measure such exo-electrons can provide information regarding the trapping process, as well as an alternative method of measuring trapped charge. Ideally, TL/OSL can be measured alongside exo-electrons. We will present a new design for an exo-electron detector compatible with the classic Riso reader stimulation head featuring multiple anode configurations and the option for high-voltage modulation to reduce the UV component during TL/OSL measurements.

Previous work has been unable to establish a relationship between K concentration and De in single-grains of feldspar. Here we use four well-bleached sediments with low external dose rate (typically ≤1.5 Gy ka−1) to investigate this relationship. Single and multi-grain pIRIR measurements and μ-XRF analyses are made on Na- and K-rich extracts; μ-XRF is directly applied to grains sitting in single-grain discs to minimise uncertainty in grain identification. Micro-XRF is shown to be sufficiently precise and accurate and luminescence instrument reproducibility is confirmed using dose recovery measurements on heated feldspar. We are again unable to establish any correlation between single-grain De and K concentration, even in feldspar grains for which the internal dose rate should dominate. We also measure highly variable Rb concentrations in these grains and are unable to detect, at the single-grain level, the correlation between K and Rb previously observed in multi-grain investigations. Nevertheless, these results are unable to explain the lack of De correlation with K. Finally, we investigate the dependence of De on grain size (isochrons). Linear correlations are observed but slopes are inconsistent with model prediction. We conclude that this surprising absence of the expected relationships between dose and K concentration and grain size does not arise from analytical precision, incomplete bleaching, sediment mixing or fading. It appears that we cannot measure feldspar doses in these samples as accurately as we thought.

A facility for the measurement of infrared photoluminescence (IRPL) has been developed for the Riso TL/OSL reader. The new IRPL measurement system uses an external laser light source at 1.49 eV (830 nm) and two photomultiplier tubes (PMT) for detecting emissions at ∼1.41 eV (880 nm) and ∼1.3 eV (955 nm) and an EMCCD. Pulsed IRPL measurement ensures a low background count rate by allowing the rejection of breakthrough from excitation light. We present the results of integrated IRPL measurements on both multiple- and single-grain aliquots, and finally demonstrate the potential of imaging natural K-feldspar samples and a granite rock slice.

In optically stimulated luminescence (OSL) dating and other retrospective dosimetry studies there is considerable demand for the ability to measure luminescence from individual dosimeters in the size range 50–500 μm diameter, either as separate grains or as part of a matrix. This work tests the potential of an electron multiplying charge-coupled device (EMCCD), providing extremely low level light detection. We characterize the performance of the device by discussing reproducibility and evaluating uncertainties in OSL signals. Finally we derive a typical single grain natural dose distribution with associated uncertainties.

In recent years opercula of the snail species Bithynia tentaculata have been shown to emit thermoluminescence (TL) signals that can be used to determine equivalent dose, and may be capable of dating events throughout the entire Quaternary period. Concentric growth lines are a notable feature of almost all B. tentaculata opercula, but it is not known whether the luminescence emitted by the opercula is influenced by these structures. This study uses a newly developed EMCCD imaging system to measure the TL signals from opercula. A combination of microscopic analysis of the opercula using visible imagery, and measurement of the TL using the EMCCD system has been undertaken. Variations in TL intensity and equivalent dose (De) are seen, but the two are not correlated. Changes in TL intensity broadly mimic the concentric growth structures, but the largest variations in intensity are between different margins of the opercula, not individual growth bands. The EMCCD system makes it possible to produce a two dimensional map of the De measured from an operculum. Dose recovery experiments give De values that are consistent with each other across the whole opercula. Measurement of the De arising from irradiation in nature shows significant variability across a single operculum, but at present the reason for this variability is unknown.

Here we compare the performance of an EMCCD-based imaging system with the standard laser-based single-grain Riso attachment. We first compare gamma dose distributions and the relative sensitivity of the two instruments is investigated using a single sample, by comparing the number of grains accepted into a dose distribution. EMCCD cross-talk is shown to be of concern at low light levels. We also make use of the fact that the EMCCD can observe TL signals from individual grains to examine the use of the correlation between the quartz 110 °C TL peak and the fast component OSL signal to correct for sensitivity change. Finally, we present the OSL dose distributions from a set of both well-bleached and poorly-bleached sedimentary samples. From a comparison of the measured doses, we conclude that the two instruments give indistinguishable dose estimates and dispersions, despite the fact that the laser-based system is effectively about four times as sensitive as the EMCCD.

A new automated Detection And Stimulation Head (DASH) has been developed for the Riso TL/OSL luminescence reader to provide easy access to new technologies, new signals and new measurement methods. The automated DASH includes a filter changer and a detector changer that makes it possible to change stimulation filters (4 × 4 filter combinations possible) and detectors (3 detectors possible) as part of a measurements sequence. The new automated DASH with dedicated driver electronics does not affect the use of other attachments, and can be retrospectively fitted to existing Riso TL/OSL readers.

We extend the localised transition model based on randomly varying recombination distances (Jain et al., 2012) to include Arrhenius analysis and truncated nearest neighbour distributions. The model makes important predictions regarding a) the physical understanding of the linear intercepts in the Arrhenius analysis for localised recombination systems and b) the relationship between charge depletion and shape of the luminescence decay curves; these predictions are successfully tested by experimental investigations. We demonstrate that this model successfully describes the kinetic behaviour, both thermal and optical, of the infrared stimulated luminescence signal from feldspar. Based on the application of this model, it is concluded that different infra-red stimulated luminescence emissions (UV, blue, yellow and far-red) follow the same kinetics, and, therefore, involve participation of the same electron (dosimetric) trap. The differences in thermal stabilities of the different emissions results from differences in number densities of the recombination sites. The results have implications for understanding the mechanism of the far-red emission, and the spatial distributions of recombination sites in feldspar.

The reconstruction of thermal histories of rocks (thermochronometry) is a fundamental tool both in Earth science and in geological exploration. However, few methods are currently capable of resolving the low-temperature thermal evolution of the upper ∼2 km of the Earth's crust. Here we introduce a new thermochronometer based on the infrared stimulated luminescence (IRSL) from feldspar, and validate the extrapolation of its response to artificial radiation and heat in the laboratory to natural environmental conditions. Specifically, we present a new detailed Na-feldspar IRSL thermochronology from a well-documented thermally-stable crustal environment at the German Continental Deep Drilling Program (KTB). There, the natural luminescence of Na-feldspar extracted from twelve borehole samples (0.1–2.3 km depth, corresponding to 10–70 °C) can be either (i) predicted within uncertainties from the current geothermal gradient, or (ii) inverted into a geothermal palaeogradient of 29±2 °C km−1, integrating natural thermal conditions over the last ∼65 ka. The demonstrated ability to invert a depth–luminescence dataset into a meaningful geothermal palaeogradient opens new venues for reconstructing recent ambient temperatures of the shallow crust (200 °C Ma−1 range). Although Na-feldspar IRSL is prone to field saturation in colder or slower environments, the method's primary relevance appears to be for borehole and tunnel studies, where it may offer remarkably recent (

Magnetic nanoparticles (MNPs) are considered promising for biomedical applications such as hyperthermia treatment and disease diagnosis owing to their distinctive thermal properties. For these applications, it is essential to screen the temperature distribution in the targeted disease site. This study aimed to investigate and observe the thermal properties of a small amount of MNPs used as highly sensitive biomarkers for disease diagnosis by microthermography. Toward this end, we used polyacrylamide and agarose phantoms containing a small amount of MNPs (30 mg Fe−1). In phantoms, the increasing temperature was observed using lock-in thermography for a small amount of MNPs distributed around the lesion. This suggests that the proposed microthermography technique can be used for diagnosis and screening in the early stage of a disease.

In nowadays, the infrared optics is frequently employed to various fields such as military, aerospace, industry and medical. To develop the infrared optics, special glasses which can transmit infrared wave are required. Ge(Germanium), Si(silicon), and fluoride glasses are typically used for material of the infrared optics. Compared with Ge and Si glasses, fluoride glasses have high transmittance in infrared wavelength range. Additionally, UV(ultraviolet) and visible light can be transmitted through fluoride glasses. There characteristics of fluoride glasses makes it possible to evaluate optical performance with generally used visible testing equipment. In this paper, we used design of experiment to find ultra precision machining characteristic of Ge and fluoride glasses and optimized machining process to obtain required form accuracy of PV(Peak to Valley) 0.2 ㎛.

This paper addresses the problem of computing grasp stability of the object for two-fingered robots in two dimensions. The concepts of force-closure and dual space are introduced and discussed in novel point of view, and we transform friction cones in a robot work space to line segments in a dual space. We newly define a grasp stability index by calculating intersection condition between line segments in dual space. Moreover, we propose a method to find the optimal grasp points of the given object by comparing the defined grasp stability index. Its validity and effectiveness are investigated and verified by simulations for quadrangle object and elliptic objects.

A method of measuring the precise temperature distribution of GaN-based light-emitting diodes (LEDs) by quantitative infrared micro-thermography is reported. To reduce the calibration error, the same measuring conditions were used for both calibration and thermal imaging; calibration was conducted on a highly emissive black-painted area on a dummy sapphire wafer loaded near the LED wafer on a thermoelectric cooler mount. We used infrared thermal radiation images of the black-painted area on the dummy wafer and an unbiased LED wafer at two different temperatures to determine the factors that degrade the accuracy of temperature measurement, i.e., the non-uniform response of the instrument, superimposed offset radiation, reflected radiation, and emissivity map of the LED surface. By correcting these factors from the measured infrared thermal radiation images of biased LEDs, we determined a precise absolute temperature image. Consequently, we could observe from where the local self-heat emerges and how it distributes on the emitting area of the LEDs. The experimental results demonstrated that highly localized self-heating and a remarkable temperature gradient, which are detrimental to LED performance and reliability, arise near the p-contact edge of the LED surface at high injection levels owing to the current crowding effect.

Cancer is increasing fast nowadays through all over the world. Early diagnosis of cancer is a desirable subject as it can significantly improve the patient's chances of survival. In most cases the cancer is diagnosis using MRI, CT, PET. But, there are several disadvantages associated with high cost, low sensitivity and specificity, and health risks from radioactive. For that reason, significant efforts are being invested to improve the current imaging system. Thermography can offer some advantages. Chief among these are the contact free and low cost for detect cancer. But thermography has some disadvantages associated with low sensitivity for small tumors. In this research develops non contact, safe, high sensitivity, and low cost infrared imaging technique. Experiments were performed using lock in thermography with a small amount of magnetic nanoparticle (MNP) and radiofrequency generator. As a result, highly sensitive infrared thermography can a small amount of MNP be detected by the technique.

We describe a portable luminescence reader suitable for use in remote localities in the field. The instrument weighs about 8 kg and is based around a 30 mm bialkali photomultiplier detecting signals through a glass filter centered on 340 nm. Stimulation is by 470 nm blue LEDs (24 W in total) operating in both continuous wave and pulsed mode; photon counting can be gated such that it is active only during the pulse off-period. There are also two bleaching light sources (470 nm, 5 W and 940 nm, 3 W), and the luminescence signals can be regenerated using a cold-cathode 30 kV X-ray tube, delivering ∼0.06 Gy.s−1. The three position sampling device has a heating element under each sampling position, able to heat the sample at 3 °C.s−1 up to at least 250 °C. The sampler can be inserted into unconsolidated sediments, and is designed to prevent exposure of the mineral grains to ambient light during sampling. The performance of the instrument in terms of sensitivity and reproducibility is comparable to that of the standard bench-top laboratory TL/OSL Riso reader. We show that the portable luminescence reader is able to measure accurately an ∼20 Gy quartz burial dose in a natural (unpretreated, no mineral separation) sandy sediment. We also show that, because of the configuration of the measurement head, the portable reader can be used to measure radioluminescence at elevated temperature in the presence of stimulation light; this facility is not available on conventional bench-top instruments. It is concluded that the portable luminescence reader can be used to accurately determine the quartz burial dose in loose sandy sediments in the field, without sample preparation or darkroom facilities.