Optical absorption and luminescence for radiation defects in Bi4Ge3O12 crystals

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 52, No. 3, pp. 400–405, March, 1990.     

The effect of detector port radiation on the determination of insertion loss by Fourier transform spectrometry

It is demonstrated that the identification of the measured power insertion loss of a specimen with the power transmission or reflection of that specimen in conventional Fourier transform spectrometry using internal modulation is susceptible to systematic error. The error arises from the presence of radiation from the detector port of the interferometer in its interferometrically modulated output, and is particularly significant at millimetre and long submillimetre wavelengths and when the specimen temperature differs from that of the interferometer. It is shown that such an error is not present in the determination of complex insertion loss by dispersive Fourier transform spectrometry owing to the greater symmetry of the experimental configuration with respect to the various radiation fluxes passing through the interferometer. The effect is demonstrated by the results of transmission measurements on specimens of the polymers polystyrene and TPX.     

Study of the relationship between infrared stimulated luminescence and blue light stimulated luminescence for potassium-feldspar from sediments

In luminescence measurements of potassium-feldspar (K-feldspar), both infrared (IR) and blue light (BL) can be used as stimulation sources. Component analysis suggests that the blue light stimulated luminescence (BLSL) measured at 60 °C from K-feldspar can be fitted using three components, namely fast, medium and slow. In order to explore the relationship between the origin of the infrared stimulated luminescence (IRSL) signal and the different components of the BLSL, five sets of experiments were conducted, namely post-IR BLSL (pIR-BLSL), post-BL IRSL (pBL-IRSL), pulse annealing tests, dose response and laboratory fading rate tests. It is observed that most of the IRSL signal can be bleached by BL, while the BLSL signal can only be partially bleached by the IR. The sources for IRSL are mainly associated with the fast and medium components of the BLSL signal.     

A survey of the signal stability and radiation dose response of sulfates in the context of adapting optical dating for Mars

The Martian landscape is currently dominated by eolian processes, and eolian dunes are a direct geomorphic expression of the dynamic interaction between the atmosphere and the lithosphere of planets. The timing, frequency, and spatial extent of dune mobility directly reflects changing climatic conditions, therefore, sedimentary depositional ages are important for understanding the paleoclimatic and geomorphologic history of features and processes present on the surface of the Earth or Mars. Optical dating is an established terrestrial dosimetric dating technique that is being developed for this task on Mars. Gypsum and anhydrite are two of the most stable and abundant sulfate species found on the Earth, and they have been discovered in Martian sediments along with various magnesium sulfates and jarosite. In this study, the optical dating properties of various Ca-, Mg-, and Fe-bearing sulfates were documented to help evaluate the influence they may have on in-situ optical dating in eolian environments on Mars. Single-aliquot regenerative-dose (SAR) experimental procedures have been adapted to characterize the radiation dose response and signal stability of the Martian sulfate analogs. Jarosite was dosimetrically inert in our experiments. The radiation dose response of the Ca- and Mg-sulfates was monotonically increasing in all cases with characteristic doses ranging from ∼100 to ∼1000 Gy. Short-term signal fading also varied considerably in the Ca- and Mg-sulfates ranging from ∼0% to ∼40% per decade for these materials. These results suggest that the OSL properties of Ca- and Mg-sulfates will need to be considered when developing protocols for in-situ optical dating on Mars, but more enticingly, our results foreshadow the potential for gypsum to be developed as a geochronometer for Mars or the Earth.     

The spatial variation of dose-rate from 90Sr/90Y beta sources for use in luminescence dating

The spatial variation of dose-rate from a 1850 MBq (50 mCi) ⁹⁰Sr/⁹⁰Y Amersham International SIF type ceramic-substrate beta particle source (5 mm diameter active area) was measured and compared with that from a 1480 MBq (40 mCi) ⁹⁰Sr/⁹⁰Y Amersham International SIP type silver plaque type beta particle source (12 mm diameter active area), for a variety of source–target spacings. The radiation field intensities were mapped using the intensity of radioluminescence induced in a probe comprising an ≅1 mm diameter calcium fluoride grain attached to the end of a glass fibre optic cable, and detected by a photomultiplier. Both sources were found to have radially symmetric dose distributions with no significant local irregularities, and dose-rate radial profiles indistinguishable at the closest source–probe spacing used (15 mm). At the largest source–probe spacing, 25 mm, the ceramic-substrate source exhibited slightly lower centre-periphery dose-rate decrease.Further measurements, using in addition a 3700 MBq (100 mCi) ceramic-substrate source, found an apparently lower dose-rate/MBq from the ceramic-substrate sources than from the silver plaque. This somewhat negates the practical benefits arising from the increased source activity permissible on radiation safety grounds for ceramic-substrate sources for a given shielding configuration, as although a given shielding configuration can house a ceramic-substrate source delivering a greater dose-rate than can safely be achieved from a silver plaque source, a considerably higher source activity is required to do so.It was concluded that the overall suitability of both types of sources for luminescence applications differs little in that both are suitable, and the choice between types is best governed by case-to-case considerations, such as practical constraints on shielding.     

The importance of U-series disequilibrium of sediments in luminescence dating: A case study at the Roc de Marsal Cave (Dordogne,France)

A multidisciplinary study of the Roc de Marsal Cave gave us the opportunity to re-examine the known problem posed by U-series disequilibria in sediments in the field of palaeodosimetric dating. Apart from burnt flints and heated limestones, the material being dated, THAT IS our principal concern here, is made of burnt sediment samples collected from a reddish layer that forms the very base of the Roc de Marsal Mousterian sequence (Couche B). U-series disequilibria of long life nuclides in sediments were observed: as a general trend, the activity of ²³⁸U is greater than that of ²²⁶Ra. Important discrepancies in age determination can occur according to the origin of the disequilibrium and its kinetics. To characterise these ancient modifications of radioactivity and constrain the range of possible variations of annual doses, a statistical study of ²³⁸U, ²²⁶Ra and ²³²Th activities, measured by gamma spectrometry, was carried out. It shows that the sediment was mainly enriched in mobile uranium. This conclusion is in accordance with the results of complementary measurements of ²³⁰Th and ²³⁴U performed by alpha spectrometry. On the kinetics side, two models of time-variation of U and daughter concentrations are compared, taking experimental data into account. A detailed presentation of the methodology and the method of calculation of dose rates, and particularly time-averaged dose rates in such a situation, is given.     

Development of a portable analyzer using solid-phase microextraction coupled with thermal desorption digitally-controlled plasma optical emission spectrometry for the determination of mercury volatile compounds released from sediments

Novel multi-species analyzer based on thermal desorption and digitally-controlled plasma optical emission spectrometry followed by solid-phase microextraction has been developed for determining various organometallics in sediment samples. A helium plasma source operating at 10?kHz and an integrated small-sized spectrometer with a charge-coupled device detector is installed for cost-effective atomic emission measurement and signal acquisition. Moreover, the analyzer size of a portable device is achieved, while the system is capable of absorbing large amounts of measurement data. Specifically, the analyzer has been applied for the speciation of mercury species in sediments. Method detection limits for MeHg and Hg²⁺ are 35.4 and 9.6?ng L^?1. Thus, sediments containing above 0.2 µg kg^?1 of mercury can be analyzed with precision 1–3.5% of RSD. The developed methods are validated by the analysis of estuarine sediment certified reference material ERM CC580, GBW 07405 Chinese soil. [AQ1]     

Studying variations in the elemental composition of annual layers in microsections of lake teletskoye sediments by means of scanning X-ray fluorescent microanalysis using synchrotron radiation

SR scanning XRF is used to analyze the annual elemental layers of bottom sediments from Lake Teletskoye. Scanning is conducted with a pitch of 0.1 mm at energies of 16, 24, and 38 keV. The content of more than 15 elements are determined: K, Ca, Ti, Mn, Fe, V, Cr, Ni, Cu, Zn, As, Rb, Sr, Y, Zr, Cd, Sn, I, and Ba (range of concentrations, 0.005–10%). A cross section containing (1) the upper part of an underlying layer, (2) the total annual layer, (3) one more complete layer, and (4) the lower part of an overlapping layer is measured. Geochemical indicators reflecting the rhythm of annual precipitation are found.     

X-ray spectrum determination from the angular dispersion of radiation in a diamond prism

The X-ray spectrum of hard polychromatic radiation with energies of up to 40 keV was obtained from the angular dispersion of the radiation beam in a diamond prism. In contrast to the classical optical scheme, the beam to be analyzed is passed through the entrance face of the prism without refraction and is directed onto the exit face at a glancing angle ～(2δ)^1/2, where δ is the real part of the decrement of the refractive index for the short-wavelength edge of the spectrum. The spectrum distortions caused by the intersection of the reciprocal lattice points by the Ewald sphere at a fixed number of wavelengths λ are minimized by the use of the angular divergence of the beam of ～10′ in the plane perpendicular to the refraction plane. In the energy range of 8–9 keV, an energy resolution of less than 100 eV was obtained, which exceeds the corresponding parameter for cooled semiconductor detectors. The measuring scheme suggested makes it possible to solve the problem of the analysis of spectra of directional X-ray beams when studying fast nonstationary generation processes.     

Studying the mechanism of gamma quantum radiation in cosmic gamma-ray bursts using data from the Swift,CGRO, and FERMI spacecraft

Light curves of 115 bright gamma-ray bursts with known cosmological distances z from sources detected by the BAT telescope on board the Swift spacecraft in four energy channels are analyzed. An averaged curve describing the shift of the light curves is obtained that depends on the energy of the channels in the coordinate system associated with the source. The results are compared to similar detailed curves for individual gamma-ray bursts detected in a wider range of energies by the BATSE (CGRO) and GBM (FERMI) telescopes. The divergence of curves in the region of low energies for some gamma ray bursts indicates the existence of an additional radiation source.     

Evaluation of the radiation dose to a phantom for various X-ray exposure factors performed using the dose area product in digital radiography

The aim of this study is to measure the dose area product (DAP) in digital radiography by using a DAP meter to determine the X-ray exposure. Pediatric X-ray examinations can be obtained for any radiographic examinations using the selected radiographic examination parameters (kVp and mAs), the DAP information recorded. The best peak signal-to-noise ratio (PSNR) at a fixed tube voltage of 70 kVp was obtained at tube currents of 20 and 32 mA, whereas the best PSNR at a fixed tube current of 25 mA was obtained at a tube voltage of 73 kVp. The fixed tube voltage of 70 kVp and the fixed tube current of 25 mA could help to obtain the best image quality and depict the spatial resolution of an anthropomorphic torso phantom radiographic examination. The normalized data over the DAP were provided to determine the patient dose from radiography.     

INAA for determination of trace elements in bottom sediments of the Selenga river basin in Mongolia

Instrumental neutron activation analysis (INAA) was used for the determination of major, minor and trace elements in samples of bottom sediments of the inflows of the Selenga river basin to assess the impact of the contamination from the industrial complex Erdenet and other industrial enterprises in Mongolia. A total of 42 elements (Na, Mg, Cl, K, Ca, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Sr, Rb, Sr, Zr, Nb, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Tb, Dy, Tm, Hf, Ta, W, Au, Hg, Th, and U) was determined by combination of conventional and epithermal neutron activation analysis at the IBR-2 reactor, FLNP JINR, Dubna. For the first time such a large set of elements was used for characterization of the bottom sediments as accumulating media which may reflect industrial contamination of the water basin. The concentrations of heavy metals and other trace elements in the samples from three inflows of the Selenga river basin were compared with data from the previous studies. It was shown that the industrial zone of the Erdenet Mining Corporation (EMC) and gold mining zone Zaamar are the sources of strong environmental contamination. The concentrations of Cu and Sb determined in sediment samples of the River Khangal and Govil near the EMC exceed average crustal rock and soil values by factors of 50 and 15, respectively. In the area of the gold mining zone Zaamar concentrations of Au, As, and Sb exceed crustal rock and soil values by factors of 4, 25, and 6, respectively. The relatively high levels of As, V, Zn, V, and Sr in the sediments of the studied rivers are obviously due to the discharges of untreated wastewater of desalination plant, electrical power station, textile industry and mining activities as well as domestic wastewater.     

Experimental determination of the production mechanism for noncharacteristic radiation in swift heavy-ion collisions

Absolute differential cross sections of non-characteristic radiation emitted in energetic heavy-ion collisions (E _P =3.92–48 MeV,Z=11–22) can only be explained in the framework of quasimolecular radiation. All other processes, particularly bremsstrahlung mechanisms are found to be negligible. For high projectile and photon energies the one-step quasimolecular radiation is dominant in solid targets, whereas the two-step process contributes mainly at low projectile and photon energies.     

On the dependence of equivalent dose on temperature of OSL measurements for sediment quartz grains and its implication in dating practice

The dependence of the equivalent dose (D_e) on the temperature used at stimulation when the standard OSL dating protocol (SAR) is applied has been investigated for sediment quartz samples. A considerable change in this value appears in the temperature region from 80 to 140 °C that is known for high complexity in OSL processes in quartz. Our observations suggest that the variation in the obtained results at least partly is caused by the laboratory procedure used when the natural OSL signal is measured. Directions for further investigations concerning this undesirable effect are indicated.     

A fingerprint technique using Mössbauer spectroscopy for the determination of individual chemical iron species in young sediments

Mössbauer spectroscopy was used in order to identify and quantify individual iron species in geochemically immature, anoxic sediments. A large number of counts per channel were allowed to accumulate for each spectrum so that “fine structures” could develop in the spectra. These could be attributed to individual spectral lines. By means of their positions in the Mössbauer spectrum, the spectral lines were identified as corresponding to definite sedimentary iron species. Mathematical simulation then permitted the quantitative determination of the identified chemical forms.