Optically stimulated exoelectron emission processes in quartz: comparison of experiment and theory

DEFF Research Database (Denmark)

Pagonis, V.; Ankjærgaard, Christina; Murray, A.S.

2009-01-01

Recent experiments have demonstrated that it is possible to measure optically stimulated exoelectron emission (OSE) signals simultaneously with optically stimulated luminescence (OSL) from quartz samples. These experiments provide valuable information on the charge movement in quartz grains. Two...... data yield a value of χ1.2 eV for the work function of quartz. The experimental temperature dependence of the OSE signals is interpreted on the basis of a photo-thermostimulated (PTSEE) process involving the main OSL trap at 320 °C; this process takes place with a thermal assistance energy estimated...... at W(0.29±0.02) eV. Good quantitative agreement is obtained between theory and experiment by assuming a thermal broadening of the thermal depletion factor for the OSL traps, described by a Gaussian distribution of energies....

Development of a thermally stimulated exoelectron emission (TSEE) system for dosimetric applications

International Nuclear Information System (INIS)

Rocha, Felicia del Gallo

1997-01-01

A thermally stimulated exoelectron emission measuring system (TSEE) with a counting (reader) and a heating system was designed, constructed and tested for the dosimetry of weakly penetrating radiations, such as alpha and beta particles and low energy X rays. The counting system consists of a 271 windowless gas-flow proportional counter, while the heating system is composed by a temperature programmer that provides linear heating of the samples. The characterization of the proportional counter was done, as well as the tests to verify the performance of the counting system with reference TSEE materials, such as beryllium oxide (BeO) and magnesium oxide (MgO) single crystals. The dosimetric characteristics of some materials as pure calcium sulphate (CaS0 4 ) sintered pellets and with 10% of graphite in its composition, lithium fluoride doped with magnesium, copper and phosphor (LiF:Mg,Cu,P), lithium fluoride (LiF) thin films on aluminum and stainless steel substrates and BeO on graphite substrates were studied. As an application, the feasibility of the use of pure calcium sulphate sintered pellets and others with 10% of graphite in area monitoring of an electron accelerator with variable energy was studied. The obtained results show the usefulness of this system in the dosimetry of weakly penetrating radiations. (author)

Detection of oxygen-related defects in GaAs by exo-electron emission spectroscopy

International Nuclear Information System (INIS)

Hulluvarad, Shiva S.; Naddaf, M.; Bhoraskar, S.V.

2001-01-01

The influence of intentional introduction of oxygen, at the surface of GaAs, on its native surface states was studied. Oxygen was made to interact with the surface of GaAs by three different means: (1) by growing native oxides, (2) exposing to oxygen plasma in an electron cyclotron resonance (ECR) plasma reactor and by (3) high energy oxygen ion irradiation. Thermally stimulated exo-electron emission (TSEE) spectroscopy was used to estimate the relative densities and energies of the surface states induced by the three different modes of introducing oxygen. Out of the two native defect levels found in GaAs by TSEE; at 325 K (0.7 eV below E c ) and at 415 K (0.9 below E c ); the former is seen to get broadened or split into multiple peaks in each of the methods. Multiple peaks in TSEE signify the presence of a closely spaced band of defect levels. Therefore the results exclusively point out that oxygen-related complexes contribute to the formation of a band of defects centered at 325 K in TSEE which is correlated to an energy level 0.7 eV below E c known as the EL2 defect level. The results reported in this paper thus confirm that the TSEE peak at 0.7 eV below E c is related to oxygen induced defects whereas the peak at 0.9 eV is not affected by the presence of oxygen-related species

Detection of oxygen-related defects in GaAs by exo-electron emission spectroscopy

Science.gov (United States)

Hulluvarad, Shiva S.; Naddaf, M.; Bhoraskar, S. V.

2001-10-01

The influence of intentional introduction of oxygen, at the surface of GaAs, on its native surface states was studied. Oxygen was made to interact with the surface of GaAs by three different means: (1) by growing native oxides, (2) exposing to oxygen plasma in an electron cyclotron resonance (ECR) plasma reactor and by (3) high energy oxygen ion irradiation. Thermally stimulated exo-electron emission (TSEE) spectroscopy was used to estimate the relative densities and energies of the surface states induced by the three different modes of introducing oxygen. Out of the two native defect levels found in GaAs by TSEE; at 325 K (0.7 eV below Ec) and at 415 K (0.9 below Ec); the former is seen to get broadened or split into multiple peaks in each of the methods. Multiple peaks in TSEE signify the presence of a closely spaced band of defect levels. Therefore the results exclusively point out that oxygen-related complexes contribute to the formation of a band of defects centered at 325 K in TSEE which is correlated to an energy level 0.7 eV below Ec known as the EL2 defect level. The results reported in this paper thus confirm that the TSEE peak at 0.7 eV below Ec is related to oxygen induced defects whereas the peak at 0.9 eV is not affected by the presence of oxygen-related species.

Detection of oxygen-related defects in GaAs by exo-electron emission spectroscopy

International Nuclear Information System (INIS)

Hulluvarad, Shiva S.; Naddaf, M.; Bhoraskar, S.V.

2004-01-01

The influence of intentional introduction of oxygen, at the surface of GaAs, on its native surface states was studied. Oxygen was made to interact with the surface of GaAs by three different means: (1) by growing native oxides, (2) exposing to oxygen plasma in an electron cyclotron resonance (ECR) plasma reactor and by (3) high energy oxygen ion irradiation. Thermally stimulated exo-electron emission (TSEE) spectroscopy was used to estimate the relative densities and energies of the surface states induced by the three different modes of introducing oxygen. Out of the two native defect levels found in GaAs by TSEE; at 325 K (0.7 eV below E c ) and at 415 K (0.9 below E c ); the former is seen to get broadened or split into multiple peaks in each of the methods. Multiple peaks in TSEE signify the presence of a closely spaced band of defect levels. Therefore the results exclusively point out that oxygen-related complexes contribute to the formation of a band of defects centered at 325 K in TSEE which is correlated to an energy level 0.7 eV below E c known as the EL2 defect level. The results reported in this paper thus confirm that the TSEE peak at 0.7 eV below E c is related to oxygen induced defects whereas the peak at 0.9 eV is not affected by the presence of oxygen-related species. (author)

Detection of oxygen-related defects in GaAs by exo-electron emission spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Hulluvarad, Shiva S.; Naddaf, M.; Bhoraskar, S.V. E-mail: svb@physics.unipune.ernet.in

2001-10-01

The influence of intentional introduction of oxygen, at the surface of GaAs, on its native surface states was studied. Oxygen was made to interact with the surface of GaAs by three different means: (1) by growing native oxides, (2) exposing to oxygen plasma in an electron cyclotron resonance (ECR) plasma reactor and by (3) high energy oxygen ion irradiation. Thermally stimulated exo-electron emission (TSEE) spectroscopy was used to estimate the relative densities and energies of the surface states induced by the three different modes of introducing oxygen. Out of the two native defect levels found in GaAs by TSEE; at 325 K (0.7 eV below E{sub c}) and at 415 K (0.9 below E{sub c}); the former is seen to get broadened or split into multiple peaks in each of the methods. Multiple peaks in TSEE signify the presence of a closely spaced band of defect levels. Therefore the results exclusively point out that oxygen-related complexes contribute to the formation of a band of defects centered at 325 K in TSEE which is correlated to an energy level 0.7 eV below E{sub c} known as the EL2 defect level. The results reported in this paper thus confirm that the TSEE peak at 0.7 eV below E{sub c} is related to oxygen induced defects whereas the peak at 0.9 eV is not affected by the presence of oxygen-related species.

Application of TSEE characteristics to high energy radiation dosimetry around an electron linear accelerator

International Nuclear Information System (INIS)

Yamamoto, T.; Nakasaku, S.; Kawanishi, M.

1986-01-01

The response of the exoelectron dosemeter to the absorbed dose has been investigated with the LiF sample irradiated with high energy electrons from a linear accelerator and γ rays from a 60 Co source. The energy absorbed in the thin surface layer, which can be related to the origins of exoelectron emission, is, in general, smaller than the energy liberated there by primary radiation. In this paper the surface dose is calculated by the Monte Carlo Code EGS4. It is pointed out that the air layer in front of the sample also plays an important role by supplying secondary electrons to the surface region of the sample. The emission density of exoelectrons from a LiF single crystal for unit absorbed dose is found to be 5 x 10 4 electrons.cm -2 .Gy -1 , and nearly constant independent of the low LET radiation type. (author)

TSEE from Fe-Cr alloy system and its application to the estimation of gasoline deterioration

International Nuclear Information System (INIS)

Shimada, H.; Nakajima, K.

1983-01-01

The exoelectron glow curves for oxide surface on Fe-Cr alloy were measured as a function of Cr content. It was seen that with increasing Cr content the total counts of thermally stimulated exoelectron emission (TSEE), threshold temperature for measuring the glow curve (starting temperature of the glow curve) and the activation energy clearly indicate a good coincidence with the oxidation process of the surface. The interaction of Fe-Cr alloy with gasoline was examined by applying the test for the oxidation induced period (ASTM D525). The induction period became minimum at about 4%Cr, and the deposit of gasoline gum was maximum at its composition. The results were compared with that of TSEE, and it was found that the catalytic effect of Fe-Cr alloy on the deterioration of gasoline is explained from the starting temperature of the glow curves. (author)

Panel Discussion on Origin of Imperfections

Science.gov (United States)

1991-11-01

ELECTRON MICROSCOPE D. POSITRON ANNIHILATION 7. PHOTOSTIMULATED EXO-ELECTRON EMISSION 8. SURFACE EXAMINATION A. OPTICAL HOLOGRAPHY 9. EDDY...during fracture of polycarbonate, alkali emission from NaCl, and 02 emission during microcracking in single crystal MgO . The results indicate that there

Possibilities and problems of modern dosimetry techniques in dentistry

International Nuclear Information System (INIS)

Regulla, D.F.

Basic requirement for an optimized application of radiation in dentistry is a qualified dosimetry. The paper introduces into new dosimetry techniques based on solid state phenomena, such as luminescence an exoelectron emission, which, in case of dentistry, appear superior to conventional methods such as film and ionization chamber dosimetry. Advantages of the TLDs dosimeters, such as miniature detector volume, dynamic detection range, tissue equivalence etc., and their dosimetric possibilities are described together with hints on operational problems with respect to achieving high dosimetric measurement accuracy. (orig.) [de

Ozone generation by rock fracture: Earthquake early warning?

Energy Technology Data Exchange (ETDEWEB)

Baragiola, Raul A.; Dukes, Catherine A.; Hedges, Dawn [Engineering Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

2011-11-14

We report the production of up to 10 ppm ozone during crushing and grinding of typical terrestrial crust rocks in air, O{sub 2} and CO{sub 2} at atmospheric pressure, but not in helium or nitrogen. Ozone is formed by exoelectrons emitted by high electric fields, resulting from charge separation during fracture. The results suggest that ground level ozone produced by rock fracture, besides its potential health hazard, can be used for early warning in earthquakes and other catastrophes, such as landslides or land shifts in excavation tunnels and underground mines.

Exoelectron emission in determination of strength parameters of nickel

Energy Technology Data Exchange (ETDEWEB)

Dus-Sitek, M.; Olszowski, Z. (Technical Univ. of Czestochowa (Poland). Inst. of Physics); Sujak, B. (Wroclaw Univ. (Poland). Inst. of Experimental Physics)

1983-01-01

A correlation between the intensity of PhSEE curve as registered from nickel during continuous uniaxial plastic deformation and the S-S curve is derived. A relationship of surface concentration of vacancies with respect to the degree of specimen deformation is also discussed.

On the use of dental ceramics as a possible second-line approach to accident irradiation dosimetry

International Nuclear Information System (INIS)

Davies, J.E.

1979-01-01

Recent development in dental ceramic production has resulted in natural or depleted uranium, used for over half a century to mimic the fluorescence of natural teeth, being substituted in such ceramics by non-radioactive fluorescent materials. This creates the possibility of using dental ceramics incorporating the latter as second-line dosimeters in cases of accidental irradiation. This pilot study shows the feasbility of such an approach using both thermally stimulated exoelectron and thermoluminescent techniques. In conclusion, it is considered that it would be of interest to continue this investigation of dental ceramic materials as second-line accident dosimeters

Forward and backscatter dose profile to diagnostic X-rays at gold/tissue interfaces

International Nuclear Information System (INIS)

Rosa, Luiz A.R. da; Seidenbusch, Michael; Regulla, Dieter F.

1997-01-01

The radiological and clinical significance of dose distributions in the vicinity of media interfaces in radiotherapy and the complex nature of these dose distributions have long been recognised. A possible dosimetry method for dose profile assessment near interfaces is the use of the so-called thermally stimulated exoelectron emission (TSEE) dosemeter. In this work the possibility of using Be O/TSEE dosimeters to assess the forward and backscatter dose profile at the interface soft tissue/gold was investigated for diagnostic heavily filtered X-rays spectrum A-60 of ISO Standard A-quality. Dose and range profiles are presented. (author). 14 refs., 3 figs

Exoemission and thermoluminescence from human enamel and shark enameloid

International Nuclear Information System (INIS)

Davies, J.E.

1983-01-01

Simultaneous measurements of exoelectron emission and thermoluminescence from powdered biological apatites, which have not been chemically or thermally pretreated, are reported. Recycling, that is, consecutive irradiation and non-isothermal scanning, is shown to change both the form of the glow curves and emissivity of samples. Two biological apatites of the hydroxyapatite type (human enamel) and fluorapatite type (shark enameloid) are compared. Although their initial glow curves are different, recycling renders the glow curves similar suggesting that the defects involved are a product of the host lattice. The relevance of exoemission as a ''fingerprinting'' technique for biologically reactive material is discussed. (author)

Dosimetry of ionizing radiation

International Nuclear Information System (INIS)

Musilek, L.; Seda, J.; Trousil, J.

1992-01-01

The publication deals with a major field of ionizing radiation dosimetry, viz., integrating dosimetric methods, which are the basic means of operative dose determination. It is divided into the following sections: physical and chemical effects of ionizing radiation; integrating dosimetric methods for low radiation doses (film dosimetry, nuclear emulsions, thermoluminescence, radiophotoluminescence, solid-state track detectors, integrating ionization dosemeters); dosimetry of high ionizing radiation doses (chemical dosimetric methods, dosemeters based on the coloring effect, activation detectors); additional methods applicable to integrating dosimetry (exoelectron emission, electron spin resonance, lyoluminescence, etc.); and calibration techniques for dosimetric instrumentation. (Z.S.). 422 refs

Anomalous low-temperature desorption from preirradiated rare gas solids

International Nuclear Information System (INIS)

Savchenko, E.V.; Gumenchuk, G.B.; Yurtaeva, E.M.; Belov, A.G.; Khyzhniy, I.V.; Frankowski, M.; Beyer, M.K.; Smith-Gicklhorn, A.M.; Ponomaryov, A.N.; Bondybey, V.E.

2005-01-01

The role for the exciton-induced defects in the stimulation of anomalous low-temperature desorption of the own lattice atoms from solid Ar and Ne preirradiated by an electron beam is studied. The free electrons from shallow traps-structural defects-was monitored by the measurements of a yield of the thermally induced exoelectron emission (TSEE). The reaction of recombination of self-trapped holes with electrons is considered as a source of energy needed for the desorption of atoms from the surface of preirradiated solids. A key part of the exciton-induced defects in the phenomenon observed is demonstrated

'Hot particle' intercomparison dosimetry

International Nuclear Information System (INIS)

Kaurin, D.G.L.; Baum, J.W.; Charles, M.W.; Darley, D.P.J.; Durham, J.S.; Scannell, M.J.; Soares, C.G.

1996-01-01

Dosimetry measurements of four 'hot particles' were made at different density thickness values using five different methods. The hot particles had maximum dimensions of 650 μm and maximum beta energies of 0.97, 046, 0.36, and 0.32 MeV. Absorbers were used to obtain the dose at different depths for each dosimeter. Measurements were made using exoelectron dosimeters, an extrapolation chamber, NE Extremity Tape Dosimeters (tm), Eberline RO-2 and RO-2A survey meters, and two sets of GafChromic (tm) dye film with each set read out at a different institution. From these results the dose was calculated averaged over 1 cm 2 of tissue at 18, 70, 125, and 400 μm depth. Comparisons of tissue-dose averaged over 1 cm 2 for 18, 70, and 125 μm depth based on interpolated measured values, were within 30% for the GafChromic (tm) dye film, extrapolation chamber, NE Extremity Tape Dosimeters (tm), and Eberline RO-2 and 2A (tm) survey meters except for the hot particle with 0.46 MeV maximum beta energy. The results for this source showed differences of up to 60%. The extrapolation chamber and NE Extremity Tape dosimeters under-responded for measurements at 400 μm by about a factor of 2 compared with the GafChromic dye films for two hot particles with maximum beta energy of 0.32 and 0.36 MeV which each emitted two 100% 1 MeV photons per disintegration. Tissue doses determined using exoelectron dosimeters were a factor of 2 to 5 less than those determined using other dosimeters, possibly due to failures of the equipment. (author)

Exploring gamma radiation effect on exoelectron emission properties of bone

International Nuclear Information System (INIS)

Zakaria, M.; Dekhtyar, Y.; Bogucharska, T.; Noskov, V.

2006-01-01

Gamma radiation is used for radiation therapy to treat carcinogenic diseases including bone cancer. Ionising radiation kills carcinogenic calls. However, there are side effects of the gamma radiation on the bone surface electron structure. One of the effects is in the form of altering electron density of states of bone that, with time, influences biomedical reactions on bone life condition. (authors)

Exploring gamma radiation effect on exoelectron emission properties of bone

Energy Technology Data Exchange (ETDEWEB)

Zakaria, M.; Dekhtyar, Y.; Bogucharska, T.; Noskov, V. [Riga Technical Univ., Biomedical Engineering and Nanotechnology Institute (Latvia)

2006-07-01

Gamma radiation is used for radiation therapy to treat carcinogenic diseases including bone cancer. Ionising radiation kills carcinogenic calls. However, there are side effects of the gamma radiation on the bone surface electron structure. One of the effects is in the form of altering electron density of states of bone that, with time, influences biomedical reactions on bone life condition. (authors)

Dosimetry of low-energy beta radiation

International Nuclear Information System (INIS)

Borg, J.

1996-08-01

Useful techniques and procedures for determination of absorbed doses from exposure in a low-energy β radiation field were studied and evaluated in this project. The four different techniques included were β spectrometry, extrapolation chamber dosimetry, Monte Carlo (MC) calculations, and exoelectron dosimetry. As a typical low-energy β radiation field a moderated spectrum from a 14 C source (E β , max =156 keV) was chosen for the study. The measured response of a Si(Li) detector to photons (bremsstrahlung) showed fine agreement with the MC calculated photon response, whereas the difference between measured and MC calculated responses to electrons indicates an additional dead layer thickness of about 12 μm in the Si(Li) detector. The depth-dose profiles measured with extrapolation chambers at two laboratories agreed very well, and it was confirmed that the fitting procedure previously reported for 147 Pm depth-dose profiles is also suitable for β radiation from 14 C. An increasing difference between measured and MC calculated dose rates for increasing absorber thickness was found, which is explained by limitations of the EGS4 code for transport of very low-energy electrons (below 10-20 keV). Finally a study of the thermally stimulated exoelectron emission (TSEE) response of BeO thin film dosemeters to β radiation for radiation fields with maximum β energies ranging from 67 keV to 2.27 MeV is reported. For maximum β energies below approximately 500 keV, a decrease in the response amounting to about 20% was observed. It is thus concluded that a β dose higher than about 10 μGy can be measured with these dosemeters to within 0 to -20% independently of the βenergy for E β , max values down to 67 keV. (au) 12 tabs., 38 ills., 71 refs

Electronic relaxations of radiative defects of the anion sublattice in cesium bromide crystals and exoemission of electrons

CERN Document Server

Galyij, P V

2002-01-01

The paper presents the results of investigations of thermostimulated exoelectron emission (TSEE) from CsBr crystal, excited by moderate doses (D <= 10 sup 4 Gy) of ultraviolet (h nu <= 7 eV) that selectively creates anion excitons and radiative defects in the anion sublattice. Having used the previously established connection between thermoactivated processes such as thermostimulated exoemission, electroconductivity, and luminescence in the irradiated crystal lattice, the concentrations of exoemission-active centers (EAC) and kinetics parameters of TSEE are calculated. The EAC concentration calculated on a base of the bulk, thermoactivated-recombinational, and band-gap Auger-like exoemission mechanisms, are in satisfactory agreement with the concentration of electron color centers in the irradiated crystals.

New luminescence measurement facilities in retrospective dosimetry

DEFF Research Database (Denmark)

Lapp, Torben; Jain, Mayank; Thomsen, Kristina Jørkov

2012-01-01

), this facility has been used to measure natural doses in feldspar using the decaying NIR RL signal.Secondly, we present a method for mapping radiation field of the built-in 90Sr/90Y β-source and estimating grain-location specific dose-rates. This is important for the accuracy of single grain results, when......This paper gives a review of recent developments in luminescence measurement facilities on the Risø TL/OSL reader including radio-luminescence (RL), exo-electron and violet stimulation attachments, and a method for characterising and if necessary correcting for beta irradiation source non...... radiation field is spatially non-uniform across the sample area. We document the effect of this correction method and further investigate on the effect of lifting the source to achieve a better dose-rate uniformity.Finally we summarise two recently-developed novel facilities to help investigate (i) the time...

Formation of (Xe2H)* centers in solid Xe via recombination: nonstationary luminescence and 'internal electron emission'

International Nuclear Information System (INIS)

Savchenko, E.V.; Khyzhniy, I.V.; Uyutov, S.A.; Gumenchuk, G.B.; Ponomarev, A.N.; Bondybey, V.E.; Beyer, M.K.

2010-01-01

The formation of excimers (Xe 2 H) * in solid Xe doped with molecular hydrogen under electron beam is studied using the original two-stage technique of nonstationary (NS) cathodoluminescence (CL) in combination with the current activation spectroscopy method - thermally stimulated exoelectron emission (TSEE). Charged species were generated using a high-density electron beam. The species produced were then probed with a low density beam on gradual sample heating. The near UV emission of the (Xe 2 H) * was used to monitor the neutralization process. It is found that the temperature behavior of the NS CL band of (Xe 2 H) * clearly correlates with the yield of TSEE measured after identical pre-irradiation of the sample. The fingerprints of the thermally stimulated detrapping of electrons - 'internal electron emission' in the spectrum of NS CL point to the essential role of neutralization reaction in the stability of the proton solvated by rare-gas atoms.

Charge recombination processes in minerals studied using optically stimulated luminescence and time-resolved exo-electrons

DEFF Research Database (Denmark)

Tsukamoto, Sumiko; Murray, Andrew; Ankjærgaard, Christina

2010-01-01

electron concentration in the conduction band. In this study, TR-OSE and time-resolved optically stimulated luminescence (TR-OSL) were measured for the first time using quartz, K-feldspar and NaCl by stimulating the samples using pulsed blue LEDs at different temperatures between 50 and 250 °C after beta...... irradiation and preheating to 280 °C. The majority of TR-OSE signals from all the samples decayed much faster than TR-OSL signals irrespective of the stimulation temperatures. This suggests that the lifetime of OSL in these dosimeters arises mainly from the relaxation of an excited state of the recombination...

Irradiation effects of swift heavy ions on gallium arsenide, silicon and silicon diodes

International Nuclear Information System (INIS)

Bhoraskar, V.N.

2001-01-01

The irradiation effects of high energy lithium, boron, oxygen and silicon ions on crystalline silicon, gallium arsenide, porous silicon and silicon diodes were investigated. The ion energy and fluence were varied over the ranges 30 to 100 MeV and 10 11 to 10 14 ions/cm 2 respectively. Semiconductor samples were characterized with the x-ray fluorescence, photoluminescence, thermally stimulated exo-electron emission and optical reflectivity techniques. The life-time of minority carriers in crystalline silicon was measured with a pulsed electron beam and the lithium depth distribution in GaAs was measured with the neutron depth profiling technique. The diodes were characterized through electrical measurements. The results of optical reflectivity, life-time of minority carriers and photoluminescence show that swift heavy ions induce defects in the surface region of crystalline silicon. In the ion-irradiated GaAs, migration of silicon, oxygen and lithium atoms from the buried region towards the surface was observed, with orders of magnitude enhancement in the diffusion coefficients. Enhancement in the photoluminescence intensity was observed in the GaAs and porous silicon samples that, were irradiated with silicon ions. The trade-off between the turn-off time and the voltage, drop in diodes irradiated with different swift heavy ions was also studied. (author)

Review of present beta dosimetry problems in radiation protection; to day's answers and future trends

International Nuclear Information System (INIS)

Fracas, P.

1986-01-01

The large use of pure beta radionuclides needs to be develop beta dosimetry methods for radiation protection. The different types of present dosimetry assessments are reviewed. In all the cases the quantity to take into account is the absorbed dose rate in human tissus and more particularly in skin. In the case of point sources of known nature and activity this quantity can be worked out. This calculation is achieved either by incident beta spectrum analysis or theoretical considerations based on Kernel point. The absorbed dose rate can also be measured by extrapolation ionization chamber which characteristics and working are detailed here. All present survey meter were not initially planned for such a beta dosimetry, as this performed with the extrapolation ionization chamber which is taken here as a reference. So responses of usual dosimeters compared to this reference need to be estimated. Responses of personal film badges used in CEA, portable ionization chambers as babyline, pocket dosimeters SEQ7 and the thermoluminescent dosimeters TLD700 are exposed here. Results show that all these survey meters are not completely suitable for routine beta dosimetry. Consequently other operational dosimetry techniques have to be pursued. In particular some thermoluminescence dosimeters for instance boron diffused in surface layer and multi-elements, and furthermore Thermally Stimulated Exoelectron Emission (TSEE) and surface barrier detectors are described [fr

Characterization of natural topaz for dosimetric applications in the therapeutic range

International Nuclear Information System (INIS)

Souza, Divanizia do Nascimento

2002-01-01

The thermoluminescence (TL) and the thermally stimulated exoelectron emission of Brazilian natural topaz samples from Minas Gerais were analysed aiming the use of this mineral for dosimetric applications. Topaz is an aluminium fluorosilicate with a fairly constant chemical composition of Al 2 SiO 4 (F,OH) 2 . The major variation in the structure among different samples is related to the OH/F concentration ratio. In the present work, samples cut from rolled pebbles, powdered samples and composites were used. The composites (dosimeters) were prepared with powdered topaz embedded in powdered Teflon or glass. The dosimetric characterization of the composites showed that the dosimeters present a linear response in the range of therapeutic doses, slow isothermic fading and a strong TL dependence with radiation energy. The TL was also combined with the X-ray diffraction, infrared and Raman spectroscopic techniques to identify the charge carrier traps and those of the recombination centres, that are essential aspects to understand the processes of light emission in natural colourless topaz. It was observed that the main charge trapping centers in the topaz are due to various OH-related defects, and that the thermal treatments can change the concentration of the recombination centers. Implantations with chromium, aluminium and iron ions into colourless samples were performed, and they were efficient to produce TL modifications in topaz. (author)

Oxidation/reduction effects on sapphire thermoluminescent detectors

International Nuclear Information System (INIS)

Molnar, G.; Borossay, J.; Suevegh, K.; Vertes, A.

1998-01-01

Complete text of publication follows. The thermoluminescence (TL) and thermally stimulated exoemission (TSEE) properties of Al 2 O 3 has been extensively studied during the past 40 years. It has been suggested as a dosemeter for both ultraviolet light and ionising radiation. Nevertheless the connection between the structure (point defects) of alumina and thermally stimulated relaxation processes has not yet been clearly explained. In this work α-Al 2 O 3 single crystal samples were studied in order to determine the mechanism of electron-hole processes of thermoluminescence and thermally stimulated exoelectron emission peaks. Single crystals prepared in highly reducing conditions were treated in different atmospheres (reducing/oxidising) and their optical absorption (after isochronous annealing), fluorescence, positron-annihilation and TL properties were investigated. Changes of optical absorption and positron annihilation spectra of oxidised samples suggest that Schottky-type defect formation occurred - the concentration of Al-vacancies increased while that of O-vacancies decreased. Also we observed the oxidation of Ti 3+ to Ti 4+ . The reduction of an oxidised sample led to the diminution of Al-vacancy concentration while that of O-vacancies has not been changed. This suggest a Frenkel-type cationic defect. We also tried to correlate these changes to changes of TL glow curves and to explain the origin of some TL peaks

Influence of the mechanical sample treatment on the thermally stimulated exoelectron emission in aspect of the application for sample dating

International Nuclear Information System (INIS)

Zastawny, Andrzej; Bialon, Jan

1999-01-01

The examination was focused on a typical, contemporary produced ceramics, irradiated by the beta particles 90 Sr- 90 Y source. According to measurements, the mechanical treatment of the sample in the form of abrading and washing in alcohol did not affect the glow curve of the TSEE above the temperature 130 deg. C. Because the peaks of the TSEE, which can be taken full advantage for the dating must lie above 300 deg. C, the mechanical and washing preparing of the samples should not affect the measurements

Neutron personnel dosimetry considerations for fusion reactors

International Nuclear Information System (INIS)

Barton, T.P.; Easterly, C.E.

1979-07-01

The increasing development of fusion reactor technology warrants an evaluation of personnel neutron dosimetry systems to aid in the concurrent development of a radiation protection program. For this reason, current state of knowledge neutron dosimeters have been reviewed with emphasis placed on practical utilization and the problems inherent in each type of dosimetry system. Evaluations of salient parameters such as energy response, latent image instability, and minimum detectable dose equivalent are presented for nuclear emulsion films, track etch techniques, albedo and other thermoluminescent dosimetry techniques, electrical conductivity damage effects, lyoluminescence, thermocurrent, and thermally stimulated exoelectron emission. Brief summaries of dosimetry regulatory requirements and intercomparison study results help to establish compliance and recent trends, respectively. Spectrum modeling data generated by the Neutron Physics Division of Oak Ridge National Laboratory for the Princeton Tokamak Fusion Test Reactor (TFTR) Facility have been analyzed by both International Commission on Radiological Protection fluence to dose conversion factors and an adjoint technique of radiation dosimetry, in an attempt to determine the applicability of current neutron dosimetry systems to deuterium and tritium fusion reactor leakage spectra. Based on the modeling data, a wide range of neutron energies will probably be present in the leakage spectra of the TFTR facility, and no appreciable risk of somatic injury to occupationally exposed workers is expected. The relative dose contributions due to high energy and thermal neutrons indicate that neutron dosimetry will probably not be a serious limitation in the development of fusion power

Some methods for calibration and beta radiation dosimetry

International Nuclear Information System (INIS)

Caldas, Linda V. Ehlin

1980-01-01

The calibration of beta radiation was studied from the point of view of primary and secondary standardization, using extrapolation chambers and examining several effects. The properties of a commercial ionization chamber were investigated, and the possibility of its use in calibration and dosimetry of 90 Sr- 90 Y beta radiation was demonstrated . A secondary standard calibration facility was developed and the results obtained with this facility were compared with those obtained from a primary system directly or indirectly. Nearly energy independent response was obtained in.the range 60 keV to 0,8 MeV with this secondary standard. Two solid state techniques namely thermoluminescence (TL) and thermally stimulated exoelectron emission (TSEE) were also used for beta dosimetry. Various characteristics like reproducibility, response with dose,energy dependence, etc. were studied for the materials: LiF, CaF 2 ,Li 2 B 4 O 7 , Be O, CaSO 4 and Al 2 O 3 . TL detectors of thickness 0,9 mm underestimate the dose 60 μm thick CaSO 4 :Tm embedded on a thin aluminium plate gave energy independent response behind skin layers of 7 mg/cm 2 . Mixed field of beta, X and gamma radiation was analysed using this detector. Quartz based Be O and graphite based alpha beta-Al 2 O 3 were found to be good beta radiation detectors when the TSEE technique is used. Energy independent CaSO 4 :Tm TL dosimeters were used in international comparison for dose measurements and the results obtained were in agreement with the actual given doses within 10%. The TL detectors were also used for dose rate measurements from glazed painted tiles used in construction industry and a 85 Kr source used in textile and metal industries. Results obtained in the later case were Q compared with those using the secondary standard facility. (author)

Alpha alumina exoemissive and thermoluminescent properties. Application to the dosimetry of ionizing radiations in case of accident

International Nuclear Information System (INIS)

Alessandri, M.F.

1989-06-01

This work consists of two parts. In the first part, a phenomenon of phototransfer in Thermostimulated Exoelectronic Emission (T.S.E.E.) is pointed out. Study of intrinsic T.S.E.E. of alpha alumina exposed to ultraviolet (U.V.) excitation of energy superior to 4 eV shows three T.S.E.E. peaks situated at 240, 325, 535 0 C (heating rate of 2 0 C.s -1 ). The phototransfer phenomenon is then characterized notably by the lowering of the U.V. excitation threshold to 3.5 eV and the increasing of T.S.E.E. response for U.V. energies between 3.5 and 6 eV. Discussion and interpretation of the results obtained are based on the perfect analogy with the phototransfer of Thermoluminescence (T.L.) observed on a similar type of alpha alumina. The second part describes the application of alpha alumina dosimetric properties to accidental irradiation dosimetry and cartography. The material is bound to a textile support to be used for clothes manufacturing for irradiation risking workers. T.S.E.E. and T.L. properties of the selected fabric have been studied. - T.S.E.E. response to a beta irradiation of strontium 90 covers the region [0.01 - 10 Gy], with a dispersion of ± 20%, a non significant thermic fading beyond 72 hours after irradiation and a very important optical fading; - the region in T.L. extends from 0.25 to 10 Gy with X irradiation (45 kV) and from 0.5 to 10 Gy with gamma irradiation of cobalt 60 and caesium 137; the dispersion is ± 20%, the thermic fading is weak and the optical fading is negligible in artificial light or does not vary any more after 5 days of sunlight exposition [fr

Characterization of silicates and calcium carbonates applied to high-dose dosimetry

International Nuclear Information System (INIS)

Vila, Gustavo Barreto

2012-01-01

The predominant isomorphous form in the biominerals studied in this work (oyster shell, coral, mother of pearl and shell) was aragonite. The appearance of the calcite phase occurred at 500 deg C at a heating rate of 10 deg C /s for all samples except for the coral sample, which was 400 deg C, independent of the heating rate. The most abundant element in the biominerals samples was Ca in the CaO form, and in the silicates (tremolite, diopside and rhodonite) Si in the SiO form. The most common trace element observed in the biominerals samples was Fe. The analyses of electron paramagnetic resonance showed lines of Mn 2+ in the coral and mother-of-pearl samples before irradiation. In the case of the irradiated samples, the defects found were CO 2 - , CO 3 3- , CO 3 - and SO 2 - , in the g range between 2.0010 and 2.0062. In the analyses by optical absorption of biominerals, transitions due to the presence of Mn in the samples were found. A thermoluminescent (TL) peak at approximately 140 deg C was found for the biominerals and at 180 deg C for silicates, which intensity depends directly on the dose. For samples exposed to different types of radiation, the TL peak occurred at lower temperatures. From the dose-response curves obtained for these materials, it was possible to determine a linear range for which their application in high dose dosimetry becomes possible. Taking into account the radiation type, among biominerals and silicates, the lowest detectable dose (40mGy) to gamma radiation was achieved for oyster shell samples using the measuring technique of optically stimulated luminescence (OSL). Using beta radiation, for diopside and tremolite samples the lowest detectable dose of 60mGy was obtained. For all samples, using the TL, OSL and thermally stimulated exoelectron emission (TSEE) techniques in alpha, beta and gamma radiation beans a good response reproducibility was obtained. Therefore, the samples characterized in this work are suitable to be used as high

Characterization of silicates and calcium carbonates applied to high-dose dosimetry; Caracterizacao de silicatos e carbonatos de calcio aplicados a dosimetria de doses altas

Energy Technology Data Exchange (ETDEWEB)

Vila, Gustavo Barreto

2012-07-01

The predominant isomorphous form in the biominerals studied in this work (oyster shell, coral, mother of pearl and shell) was aragonite. The appearance of the calcite phase occurred at 500 deg C at a heating rate of 10 deg {sup C}/s for all samples except for the coral sample, which was 400 deg C, independent of the heating rate. The most abundant element in the biominerals samples was Ca in the CaO form, and in the silicates (tremolite, diopside and rhodonite) Si in the SiO form. The most common trace element observed in the biominerals samples was Fe. The analyses of electron paramagnetic resonance showed lines of Mn{sup 2+} in the coral and mother-of-pearl samples before irradiation. In the case of the irradiated samples, the defects found were CO{sub 2}{sup -}, CO{sub 3}{sup 3-}, CO{sub 3}{sup -} and SO{sub 2}{sup -}, in the g range between 2.0010 and 2.0062. In the analyses by optical absorption of biominerals, transitions due to the presence of Mn in the samples were found. A thermoluminescent (TL) peak at approximately 140 deg C was found for the biominerals and at 180 deg C for silicates, which intensity depends directly on the dose. For samples exposed to different types of radiation, the TL peak occurred at lower temperatures. From the dose-response curves obtained for these materials, it was possible to determine a linear range for which their application in high dose dosimetry becomes possible. Taking into account the radiation type, among biominerals and silicates, the lowest detectable dose (40mGy) to gamma radiation was achieved for oyster shell samples using the measuring technique of optically stimulated luminescence (OSL). Using beta radiation, for diopside and tremolite samples the lowest detectable dose of 60mGy was obtained. For all samples, using the TL, OSL and thermally stimulated exoelectron emission (TSEE) techniques in alpha, beta and gamma radiation beans a good response reproducibility was obtained. Therefore, the samples characterized

Understanding optically stimulated charge movement in quartz and feldspar using time-resolved measurements

International Nuclear Information System (INIS)

Ankjaergaard, C.

2010-02-01

Thermoluminescence (TL) and optically stimulated luminescence (OSL) from quartz and feldspar are widely used in accident dosimetry and luminescence dating. In order to improve already existing methods or to develop new methods towards extending the current limits of the technique, it is important to understand the charge movement within these materials. Earlier studies have primarily focussed on examination of the trap behaviour; however, this only tells half of the story as OSL is a combination of charge stimulation and recombination. By using time-resolved OSL (TR-OSL), one can directly examine the recombination route(s), and thus obtain insight into the other half of the process involved in luminescence emission. This thesis studies the TR-OSL and optically stimulated phosphorescence signals from quartz and feldspars spanning several orders of magnitude in time (few ns to the seconds time scale) in order to identify various charge transport mechanisms in the different time regimes. The techniques employed are time-resolved OSL, continuous-wave OSL, TL, optically stimulated exo-electron (OSE) emission and time-resolved OSE. These different techniques are used in combination with variable thermal or optical stimulation energy. The thesis first delves into three main methodological developments, namely (i) research and development of the equipment for TR-OSL measurements, (ii) finding the best method for multiple-exponential analysis of a TR-OSL curve, and (iii) optimisation of the pulsing configuration for the best separation of quartz OSL from a mixed quarts-feldspar sample. It then proceeds to study the different charge transport mechanisms subsequent to an optical stimulation pulse in quartz and feldspars. The results obtained for quartz conclude that the main lifetime component in quartz represents an excited state lifetime of the recombination centre, and the more slowly decaying components on the millisecond to seconds time scale arise from charge recycling

Understanding optically stimulated charge movement in quartz and feldspar using time-resolved measurements

Energy Technology Data Exchange (ETDEWEB)

Ankjaergaard, C.

2010-02-15

Thermoluminescence (TL) and optically stimulated luminescence (OSL) from quartz and feldspar are widely used in accident dosimetry and luminescence dating. In order to improve already existing methods or to develop new methods towards extending the current limits of the technique, it is important to understand the charge movement within these materials. Earlier studies have primarily focussed on examination of the trap behaviour; however, this only tells half of the story as OSL is a combination of charge stimulation and recombination. By using time-resolved OSL (TR-OSL), one can directly examine the recombination route(s), and thus obtain insight into the other half of the process involved in luminescence emission. This thesis studies the TR-OSL and optically stimulated phosphorescence signals from quartz and feldspars spanning several orders of magnitude in time (few ns to the seconds time scale) in order to identify various charge transport mechanisms in the different time regimes. The techniques employed are time-resolved OSL, continuous-wave OSL, TL, optically stimulated exo-electron (OSE) emission and time-resolved OSE. These different techniques are used in combination with variable thermal or optical stimulation energy. The thesis first delves into three main methodological developments, namely (i) research and development of the equipment for TR-OSL measurements, (ii) finding the best method for multiple-exponential analysis of a TR-OSL curve, and (iii) optimisation of the pulsing configuration for the best separation of quartz OSL from a mixed quarts-feldspar sample. It then proceeds to study the different charge transport mechanisms subsequent to an optical stimulation pulse in quartz and feldspars. The results obtained for quartz conclude that the main lifetime component in quartz represents an excited state lifetime of the recombination centre, and the more slowly decaying components on the millisecond to seconds time scale arise from charge recycling

Realization of radiobiological in vitro cell experiments at conventional X-ray tubes and unconventional radiation sources

International Nuclear Information System (INIS)

Beyreuther, Elke

2010-01-01

More than hundred years after the discovery of X-rays different kinds of ionizing radiation are ubiquitous in medicine, applied to clinical diagnostics and cancer treatment as well. Irrespective of their nature, the widespread application of radiation implies its precise dosimetric characterization and detailed knowledge of the radiobiological effects induced in cancerous and normal tissue. Starting with in vitro cell irradiation experiments, which define basic parameters for the subsequent tissue and animal studies, the whole multi-stage process is completed by clinical trials that translate the results of fundamental research into clinical application. In this context, the present dissertation focuses on the establishment of radiobiological in vitro cell experiments at unconventional, but clinical relevant radiation qualities. In the first part of the present work the energy dependent biological effectiveness of photons was studied examining low-energy X-rays (≤ 50 keV), as used for mammography, and high-energy photons (≥ 20 MeV) as proposed for future radiotherapy. Cell irradiation experiments have been performed at conventional X-ray tubes providing low-energy photons and 200 kV reference radiation as well. In parallel, unconventional quasi-monochromatic channeling X-rays and high-energy bremsstrahlung available at the radiation source ELBE of the Forschungszentrum Dresden-Rossendorf were considered for radiobiological experimentation. For their precise dosimetric characterization dosimeters based on the thermally stimulated emission of exoelectrons and on radiochromic films were evaluated, whereas just the latter was found to be suitable for the determination of absolute doses and spatial dose distributions at cell position. Standard ionization chambers were deployed for the online control of cell irradiation experiments. Radiobiological effects were analyzed in human mammary epithelial cells on different subcellular levels revealing an increasing amount

Realization of radiobiological in vitro cell experiments at conventional X-ray tubes and unconventional radiation sources

Energy Technology Data Exchange (ETDEWEB)

Beyreuther, Elke

2010-09-10

More than hundred years after the discovery of X-rays different kinds of ionizing radiation are ubiquitous in medicine, applied to clinical diagnostics and cancer treatment as well. Irrespective of their nature, the widespread application of radiation implies its precise dosimetric characterization and detailed knowledge of the radiobiological effects induced in cancerous and normal tissue. Starting with in vitro cell irradiation experiments, which define basic parameters for the subsequent tissue and animal studies, the whole multi-stage process is completed by clinical trials that translate the results of fundamental research into clinical application. In this context, the present dissertation focuses on the establishment of radiobiological in vitro cell experiments at unconventional, but clinical relevant radiation qualities. In the first part of the present work the energy dependent biological effectiveness of photons was studied examining low-energy X-rays (≤ 50 keV), as used for mammography, and high-energy photons (≥ 20 MeV) as proposed for future radiotherapy. Cell irradiation experiments have been performed at conventional X-ray tubes providing low-energy photons and 200 kV reference radiation as well. In parallel, unconventional quasi-monochromatic channeling X-rays and high-energy bremsstrahlung available at the radiation source ELBE of the Forschungszentrum Dresden-Rossendorf were considered for radiobiological experimentation. For their precise dosimetric characterization dosimeters based on the thermally stimulated emission of exoelectrons and on radiochromic films were evaluated, whereas just the latter was found to be suitable for the determination of absolute doses and spatial dose distributions at cell position. Standard ionization chambers were deployed for the online control of cell irradiation experiments. Radiobiological effects were analyzed in human mammary epithelial cells on different subcellular levels revealing an increasing amount