Radiation-induced Absorption Coefficient Research Articles

Study of the V[formula omitted] state in neutron-irradiated silicon using photon-absorption measurements

Pieces of n-type silicon with 3.5kΩ cm resistivity have been irradiated by reactor neutrons to 1MeV neutron equivalent fluences of (1, 5 and 10)×1016cm−2. Using light-transmission measurements, the absorption coefficients have been determined for photon energies, Eγ, between 0.62 and 1.30eV for the samples as irradiated and after 15min isochronal annealing with temperatures between 80°C and 330°C. The radiation-induced absorption coefficient, αirr, has been obtained by subtracting the absorption coefficient for non-irradiated silicon. The Eγ-dependence of αirr shows a resonance peak, which is ascribed to the neutral divacancy, V20, sitting on a background, and αirr(Eγ) is fitted by a Breit–Wigner line shape on a parameterized background. It is found that at an annealing temperature of 210∘C the V20 intensity is reduced by a factor 2, and that at the meV level, the position and the width of the fitted Breit–Wigner do not change with irradiation dose and annealing.

Effects of high dose gamma irradiation on the optical properties of Eu3+ doped zinc sodium bismuth borate glasses for red LEDs

Interaction of 10ZnO-5Na2O-10Bi2O3–74.3B2O3-0.7Eu2O3 glasses exposed to high dose gamma rays were investigated using XRD, FTIR, absorption, photoluminescence followed by thermally and optically stimulated luminescence studies. XRD analysis confirmed the amorphous nature of glasses post-irradiation. Variation in FTIR spectra revealed, structural deformation of borate groups as a result of high dose gamma irradiation. Enhanced glass absorbance and red shift in absorption edge were observed with the increase in gamma dose. Further, radiation-induced absorption coefficient confirmed the trapped charges in the forbidden energy gap supported by Tauc's plot and Urbach energy. Photoluminescence (PL) study demonstrated quenching of luminescence intensity at higher gamma doses. Lifetime of metastable 5D0 state of Eu3+ ions were estimated by the decay curves and color purity was calculated using 1931 CIE chromaticity coordinates (x,y). Thermally and optically stimulated luminescence studies reassured the existence of charges in trap centers due to irradiation. TL glow curve exhibited two broad emission peaks with the corresponding temperature being at 490 K and 625 K. Distinct TL peaks of the material and their kinetic parameters (E, S, τ and b) were determined via Computerized Glow Curve Deconvolution (CGCD) method. Linear behaviour obtained through the dose response of the glass (0.25–3 kGy) proved their suitability for dosimetric application in the food irradiation zones in addition to red LEDs (< 1 kGy).

Gamma ray irradiation-induced variations in structure and optical properties of cerium/titanium-doped oxyfluoride transparent glass-ceramics

CeO2/TiO2-doped oxyfluoride transparent glass ceramics with a composition of 45SiO2–20Al2O3–10CaO–25CaF2 were synthesized and irradiated by gamma ray. The effects of CeO2/TiO2 on the structure and optical properties of the samples before and after irradiation were investigated. Doping with CeO2 causes network depolymerization and conversion of [AlO6] to [AlO4], enlarging the percolation region and promoting CaF2 crystallization. Co-doping with CeO2/TiO2 helps reduce the intrinsic coloring of transparent glass ceramics containing only CeO2, and the addition of TiO2 enhances network interconnectivity, suppressing CaF2 crystallization. Doping with CeO2 and/or TiO2 improves the structural stability of transparent glass ceramics upon irradiation and maintains the optical band gap and Urbach energy constant due to the defect saturation over the irradiation dose. Doping solely with CeO2 allows for a lower radiation-induced absorption coefficient than co-doping CeO2/TiO2 because of the enhanced crystallization induced by CeO2 and balanceable light absorption of polyvalent cerium ions.

Spectroscopic investigations on γ-irradiated Eu3+ and Dy3+ doped oxyfluoride glasses

Abstract Changes in the UV–visible spectra of undoped and Dy/Eu singly doped oxyfluoride glasses with varying PbF 2 /CdF 2 content were studied under high doses of gamma irradiation. The unirradiated undoped and doped glasses exhibited strong UV absorption and characteristic absorption bands due to the presence of rare earth ions. Gamma irradiation caused loss of transmission and red shift in the cut-off wavelength for the undoped and doped samples. The radiation induced absorption coefficient and energy band gap depicted variation due to the nature of rare earth as well as the host matrix. The rare earth addition affected the physical properties (density, refractive index, molar volume) and the structure of the studied glasses revealed by Fourier Transform Infrared Spectroscopy.

Effects of CuO co-doping on γ-ray irradiation resistance of active ions doped phosphate glasses

The effect of copper ion doping on the γ-ray irradiation resistance of Mn2+ and Pr3+ doped phosphate glasses has been studied. UV–visible transmission spectra and photoluminescence spectra have been measured before and after γ-irradiation to characterize the radiation-induced defects. The electron paramagnetic resonance spectra of the irradiated samples with, and without Cu ions have been compared to show the ability of Cu ions to suppress the generation of radiation-induced color centers. The differential transmission spectra and the radiation-induced absorption coefficients have also been calculated for discussion of the observed phenomena. The much improved γ-irradiation resistance of Mn2+ and Pr3+ doped phosphate glasses has been demonstrated through CuO co-doping.

Effect of Gamma‐Ray Irradiation on the Optical Properties of PbO–B2O3–SiO2 and Bi2O3–B2O3–SiO2 Glasses

Irradiation treatments on glasses in both PbO–B2O3–SiO2 and Bi2O3–B2O3–SiO2 systems were carried out under the 60Co γ‐ray radiation at a dose of 5.0 kGy. Ultraviolet and visible (UV–Vis) transmission spectra were used to compare the optical transmittance before and after irradiation in the wavelength range of 300–800 nm. The radiation‐induced absorption coefficient (RIAC), the optical mobility gap (E0), and the width of the energy tail above the gap (ΔE) were calculated by optical transmittance. The variation of these parameters indicated that the structure of glasses changed due to irradiation. The differences in the optical properties of the two glass systems were explained from the viewpoint of glass chemistry.

Gamma irradiation effects on ZnO-based scintillating glasses containing CeO2 and/or TiO2

Irradiation resistance of as-studied scintillating glass samples were tested under the 60Co γ-ray radiation at doses between 60 and 700Gy. Photoluminescence properties of glasses with and without cerium ions were investigated to show the effect of cerium (III) on the luminescence of ZnO. Ultraviolet and visible optical transmittance spectra were compared before and after irradiation treatment. The so-called radiation-induced absorption coefficient (RIAC) was introduced to compare more effectively the radiation damage on glass samples. The much reduced transmittance change and decreased RIAC value in UV–Vis region indicate that the density of electron centers and hole centers caused by radiation decreased, which helps to confirm that the reduction and oxidation reaction of cerium ions took place in radiation process. From RIAC curves, it can be seen that TiO2 enhances the irradiation resistance of sample in UV region. However, high TiO2 content has negative effect on visible transmittance of glasses after the higher dose irradiation (700Gy).

A Study on Correlations Between the Initial Optical and Scintillation Properties and Their Radiation Damage for Lead Tungstate Crystals

This paper presents a study of correlations between the initial optical and scintillation properties and their radiation damage for mass produced lead tungstate crystals. A correlation was observed between crystal's initial light outputs and the values of its initial longitudinal transmittance at 360 nm. A strong correlation was found between the emission weighted radiation induced absorption coefficients and the relative losses of the longitudinal transmittance at 440 nm. Correlations were also observed between the relative losses of crystal's light output and the relative losses of its longitudinal transmittance at 440 nm, or the emission weighted radiation induced absorption coefficients. No correlations were observed between crystal's radiation hardness and its initial longitudinal transmittance or the slope of the initial longitudinal transmittance across the band edge

Radiation sensitivity of GSO and LSO scintillation detectors

Radiation resistance of 4×4×30 mm 3 GSO and LSO imaging scintillation detectors has been studied for low-energy gamma-ray doses of 10 4 Gy (10 6 rad) and 10 5 Gy (10 7 rad). Radiation hardness was determined by the measurement of optical transmission through GSO and LSO scintillation crystals before and after irradiations with 60Co gamma-rays. The results have been analysed in terms of the radiation-induced absorption coefficients and compared with radiation sensitivity measurements of small BGO scintillation crystals. The recovery time of irradiated small GSO and LSO crystals has also been determined.

Evaluation of mass-produced lead tungstate crystals

Because of broad interest in high-energy and nuclear physics community, mass production capacities of lead tungstate (PWO) crystals have been established. The optical and scintillation properties of PWO crystals, 20 each from two major vendors, were evaluated. The transmittance, emission and excitation spectrum, light output, decay kinetics and light response uniformity, as well as their degradation under γ-ray irradiations, were investigated. The radiation-induced color centers and the emission weighted radiation-induced absorption coefficients were measured. It was found that currently mass-produced PWO crystals are radiation hard enough for radiation environment where dose rates of up to a few hundreds rad/h is expected.

Quality of mass-produced lead tungstate crystals

Because of the broad interest in high energy and nuclear physics community, mass production capacities of lead tungstate crystals have been established. The optical and scintillation properties of lead tungstate crystals, 20 each from two major vendors, were evaluated. The transmittance, emission and excitation spectra, light output and light response uniformity of these samples were measured. The degradations of these properties under irradiation, and the emission weighted radiation induced absorption coefficient (EWRIAC) were also studied. It was found that currently mass-produced lead tungstate crystals are radiation hard enough for radiation environments where expected dose rates do not exceed a few hundred rad/h.

Scintillating fibers for particle physics experiments—on-line-induced absorption measurements in gamma radiation field

Changes in the radiation-induced transparency of scintillating and wavelength-shifting fibers were studied by means of on-line-induced absorption coefficient measurement during and after gamma irradiation. It was found that the main contribution to radiation damage was caused by reactions between luminescent molecules. The time dependence of the radiation-induced absorption coefficient was analyzed in the broad spectral range (420–735nm) and compared with kinetic models of the processes of absorption center build-up and recovery. The latter has been recently published for these fibers and a lower dose rate in the range of 0.002–0.01Gys−1. Good agreement was reached between the low-dose and the presented high-dose measurements (dose rate 4.2Gys−1). The parameters calculated in this kinetic model are applicable to prediction of the fiber behavior in particle physics experiments.

Radiation hardness of PbWO 4 Cherenkov radiators heavily doped with trivalent rare-earth ions

PbWO 4 single crystals heavily doped with trivalent rare-earth (RE) ions were proposed a few years ago as one of the heaviest Cherenkov radiators. We have found that their radiation damage due to 60Co γ-rays are almost saturated at 10 3 Gy (1 Gy=100 rad). The radiation-induced absorption coefficient μ ir at 420 nm slightly above the short-wavelength cutoff was 3.1, 5.4 and 7.2 m −1 at 10 5 Gy in PbWO 4:Gd 3+(3 at%), PbWO 4:La 3+(5 at%) and PbWO 4:La 3+(8 at%), respectively.

The origin of radiation instability in yttrium-ion-doped lead tungstate crystals

Abstract Some Y3+-doped PbWO4 (PWO:Y3+) crystals grown by the modified Bridgman method showed exceptional behaviours, namely the increase in the light yield after low-dose-rate irradiation and also the improvement in the optical transmission at around 430 nm. In this paper, we studied the influences of high-temperature annealing in an oxygen-rich atmosphere on the stability of scintillation properties and radiation hardness of PWO: Y3+. The results show that annealing in oxygen enhances the absorption band at around 430 nm and makes optical transmission unstable at this wavelength after irradiation. After high-temperature annealing, the radiation-induced absorption coefficient is also negative around 430 nm. The 430 nm absorption band introduced by high-temperature annealing in oxygen has the same characteristics as the pre-existing bands in as-grown PWO: Y3+ crystals. So it decreases the stability of scintillation properties and radiation hardness of PWO: Y3+ crystals. The radiation instability relates t...

The origin of radiation instability in yttrium-ion-doped lead tungstate crystals

Abstract Some Y3+-doped PbWO4 (PWO:Y3+) crystals grown by the modified Bridgman method showed exceptional behaviours, namely the increase in the light yield after low-dose-rate irradiation and also the improvement in the optical transmission at around 430 nm. In this paper, we studied the influences of high-temperature annealing in an oxygen-rich atmosphere on the stability of scintillation properties and radiation hardness of PWO: Y3+. The results show that annealing in oxygen enhances the absorption band at around 430 nm and makes optical transmission unstable at this wavelength after irradiation. After high-temperature annealing, the radiation-induced absorption coefficient is also negative around 430 nm. The 430 nm absorption band introduced by high-temperature annealing in oxygen has the same characteristics as the pre-existing bands in as-grown PWO: Y3+ crystals. So it decreases the stability of scintillation properties and radiation hardness of PWO: Y3+ crystals. The radiation instability relates to the formation of interstitial oxygen ions (Oi”) during high-temperature annealing. The results reveal that the oxygen-rich atmosphere during the crystal growth and annealing procedure is the origin of the exceptional irradiation behaviours in PWO: Y3+ crystals.

Radiation hardness of Ce 3+-doped heavy germanate glasses

In the present work Ce 3+-doped germanate glasses containing Gd 2O 3 and BaO or La 2O 3 were developed. The UV and VIS transmission spectra of these glasses were measured before and after irradiation at doses ranging between 3 and 277 Gy. The radiation induced absorption coefficient μ was calculated on the basis of the measured transmission spectra. From these results the cerium ions doping turns out to be effective in improving the radiation hardness of glasses with respect to their undoped matrices.

The influences of monovalent ions on the stability of scintillation properties and radiation hardness of PbWO 4:Y 3+ crystals

Some Y 3+-doped PbWO 4 crystals grown by modified Bridgmann method showed exceptional behaviors, namely, light yield increased after low dose rate irradiation, and the radiation-induced absorption coefficient was negative around 430 nm. In this paper, the influences of monovalent ion impurities (Na + and K +) on the stability of scintillation properties and radiation hardness were studied. The experimental results show that Na + ion enhances the absorption band at cut-off edge and at 430 nm, while K + ion only makes optical transmission unstable around 430 nm when the crystals were annealed at high temperatures. The contamination by Na + and K + ions makes scintillation properties and radiation hardness more unstable in the temperature range from 50°C to 350°C. The radiation-induced absorption coefficient is also negative around 430 nm. The charge compensation mode of K + ion along the crystal does not change, but those of Na + ion are different along the crystal. The concentrated Na +, K + and Y 3+ ions, which occupied Pb sublattice, lead to the shortage of Pb vacancies ( V Pb″). Thus instead of the formation of [2(Y 3+ Pb) — V Pb″] ((Y 3+ Pb) stands for the Y 3+ ion occupying the Pb sublattice), Na + and K + ions compel the defect (Y 3+ Pb) to form cluster [2(Y 3+ Pb) —O i″] or [(Y 3+ Pb) —O i″+hole] in which the interstitial oxygen (O i″) was considered to be the origin of light yield increase after low dose rate irradiation.

Effect of γ irradiation on optical properties of Ce 3+-doped phosphate and silicate scintillating glasses

A set of Ce 3+ activated silicate- and phosphate-based scintillating glasses were submitted to γ irradiation in the 60Co radioisotope source “Calliope” (ENEA-Casaccia in Rome, Italy) in the dose range between 1 and 250 Gy (3.7 Gy/h). The effect of ionising radiation was probed by transmission measurements performed before and after each irradiation on all analysed samples. From these data, the radiation-induced absorption coefficient was calculated, proportional to the density of colour centres induced by irradiation in the solid matrix. Results are discussed by taking into account the possible dependence of radiation hardness on the composition of glass matrix.

La-doped PbWO 4 scintillating crystals grown in large ingots

We achieved a significant increase in the ingot size of La-doped PbWO 4 single crystals to 65 mm in diameter and 300 mm in length by using the Czochralski technique and three times of recrystallization. Four blocks each with a typical size of 20×20×230 mm 3 were taken from an ingot. The optical as well as the scintillation characteristics of the large-size crystals, including the radiation hardness, were found to be similar to or even better than those of smaller crystals. The radiation-induced absorption coefficient μ ir was as small as 0.5–1 m −1 at 10 7 rad of 60Co γ-ray irradiation.

Pulsed X-ray induced transient absorption in LiNbO/sub 3/, TiO/sub 2/:LiNbO/sub 2/, and MgO:LiNbO/sub 3/ at 1061 nm

Characteristics of pulsed X-ray induced transient absorption at 1061 mm have been determined for LiNbO/sub 3/, TiO/sub 2/:LiNbO/sub 3/, and MgO:LiNbO/sub 3/. The addition of the dopants TiO/sub 2/ and MgO reduces the induced absorption significantly. The two materials, LiNbO/sub 3/ and TiO/sub 2/:LiNbO/sub 3/, decay with an approximate 1/t/sup 1/4/ time dependence for the time interval 0.01 to 8 ms. After 8 ms, the decay rate for LiNbO/sub 3/ is faster than 1/t/sup 1/4/, and the decay rate for TiO/sub 2/:LiNbO/sub 3/ is slower than that initial rate. A low-intensity absorption which lasts for about 20 /spl mu/s is observed for the MgO:LiNbO/sub 3/. Peak radiation induced absorption coefficients for LiNbO/sub 3/, TiO/sub 2/:LiNbO/sub 3/, and MgO:LiNbO/sub 3/ have been determined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>