Cathodoluminescence Study of Undoped and Mn Doped Lithium Tetraborate Crystals Being Developed for Neutron Detection (original) (raw)
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MRS Proc., 2011
Photoemission spectroscopy using synchrotron radiation was used to determine the energy level structure of Mn doped 2 4 7 Li B O crystals. Photoemission studies provided evidence of Mn in the bulk crystal at 47.2 eV. Valence band analysis provided the presence of surface states but no acceptor sites. Cathodoluminescence studies were also made on undoped and Mn doped 2 4 7 Li B O using various beam energies from 5 to 10 KeV at room temperature. Self trapped exciton emission states are evident in the undoped and Mn doped Li 2 B 4 O 7 sample ranging in energies from 3.1 to 4.1 eV.
Neutron flux measurements with a Li2B4O7 crystal
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007
The effect of neutron irradiation on a lithium tetraborate (Li 2 B 4 O 7 , LBO) single crystal has been investigated. The crystals of high optical quality are found to be quite stable under high neutron fluence. This study shows that LBO crystals can be used as a proportional counter for neutron fluxes of the order 10 9 cm À2 s À1 and higher. The detectors fabricated were found to have a sensitivity of $3 Â 10 À18 A (nv) À1 .
Analysis of neutron induced defects in silver doped lithium tetraborate
2012
Neutron-induced defects in silver doped lithium tetraborate (Li2B407:Ag) are identified and characterized using electron paramagnetic resonance (EPR) spectroscopy and thermoluminescence (TL). Neutron irradiation induced two unique defects detectable by EPR. Both of these neutron-induced defects are substantially more thermally stable than as-grown crystal defects. Models for the neutron-induced defects are proposed.
In this paper, the thermoluminescence (TL) dosimetric characteristics under beta-ray, x-ray and gamma-ray excitations of powder and pellet Mn-doped lithium tetraborates (LTB) which were produced by solution combustion synthesis technique were investigated, and the results were compared with that of TLD-100 chips. The chemical composition and morphologies of the obtained LTB and Mn-doped LTB (LTB: Mn) were confirmed by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) and scanning electron microscopy (SEM) with EDX. LTB:Mn was studied using luminescence spectroscopy. In addition, the effects of sintering and annealing temperatures and times on the thermoluminescence (TL) properties of LTB:Mn were investigated. The glow curves of powder samples as well as pellet samples exposed to different beta doses exhibited a low temperature peak at about 100 °C followed by an intense principal high temperature peak at about 260 °C. The kinetic parameters (E, b, s) associated with the prominent glow peaks were estimated using T m –T stop , initial rise (IR) and computerized glow curve deconvolution (CGCD) methods. The TL response of integral TL output increased linearly with increasing the dose in the range of 0.1–10 Gy and was followed by a superlinearity up to 100 Gy both for powder and pellet samples using beta-rays. Powder and pellet LTB:Mn were irradiated to a known dose by a linear accelerator with 6 and 18 MV photon beams, 6–15 MeV electron beams and a traceable 137 Cs beam to investigate energy response. Further, TL sensitivity, fading properties and recycling effects related with beta exposure of LTB:Mn phosphor were evaluated and its relative energy response was also compared with that of TLD-100 chips. The comparison of the results showed that the obtained phosphors have good TL dose response with adequate sensitivity and linearity for the measurement of medical doses.
2015
Single crystals of Ce doped Li 6 Y(BO 3 ) 3 have potential applications to be used as a scintillator to detect thermal neutrons. These single crystals having an optimum Ce concentration been successfully grown using the Czochralski technique. The crystals have been characterized for optical and scintillation properties. A portable detectors set-up that works from a USB port of a laptop has been developed to detect thermal neutrons. The detection efficiencies in excess of 80% have been achieved even for thin slices of the crystal (1 mm thick) mounted on a photo-multiplier tube (PMT).
Optically stimulated luminescence of MgB 4 O 7 :Ce,Li for gamma and neutron dosimetry
Journal of Luminescence, 2017
The objective of this work was to develop a new optically stimulated luminescence (OSL) material for dosimetry applications that is tissue equivalent and has high sensitivity to ionizing radiation, fast lumi-nescence lifetime, and intrinsic neutron sensitivity. To achieve this combination of properties, we started with a host material with low effective atomic number, MgB 4 O 7 (Z eff ¼ 8.2) , with an appropriate dopant characterized by short luminescence lifetime (Ce 3 þ). The samples were synthesized using Solution Combustion Synthesis with excess boric acid to achieve the correct crystallographic phase and Li co-doping to enhance its sensitivity. We investigated the thermoluminescence (TL) and OSL properties as a function of annealing temperature, radiation dose, dopant concentration, and time elapsed after irradiation (i.e., signal fading). We also applied a step-annealing procedure to investigate the depth of the trapping centers associated with the OSL signal. The samples obtained are characterized by a dominant TL peak at $ 210 °C with intensity comparable to LiF:Mg,Ti. The OSL intensity is $ 50% of that from Al 2 O 3 :C when using Hoya U-340 filters and shows no saturation up to almost 1 kGy. The OSL signal seems to originate from trapping center with stability 4 150 °C, which means that the OSL fading is expected to be small. After the first day, in which fading associated with shallow traps is observed, fading of the total OSL signal was o4% within 6 days. The possibility of enhancing the neutron sensitivity was also demonstrated by synthesizing the material with enriched 10 B. Although further development and characterization of the material may be needed, this work demonstrates that this host/dopant combination can be a viable alternative in OSL do-simetry, particularly for 2D dose mapping and neutron dosimetry applications.
Inorganic scintillation crystals for neutron detection
2013 3rd International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications (ANIMMA), 2013
Inorganic scintillators play an important role in the detection and spectroscopy of gamma and X-rays, as well as in neutrons and charged particles. For a variety of applications, new inorganic scintillation materials are being studied. New scintillation detector applications arise continuously and, consequently, the interest in the introduction of new fast scintillators becomes relevant. Scintillation crystals based on cesium iodide (CsI) have relatively low hygroscope, easy handling and low cost, features that favor their use as radiation detectors. In this work, lithium and bromine doped CsI crystals were grown using the vertical Bridgman technique. In this technique, the charge is maintained at high temperature for 10 h for the material melting and complete reaction. The temperature gradient 21° C/cm and 1 mm/h descending velocity are chosen as technique parameters. After growth is finished, the furnace is cooled at a rate of 20° C/h to room temperature. The concentration of the lithium doping element (Li) studied was 10-3 M and the concentration of the bromine was 10-2 M. Analyses were carried out to evaluate the scintillators developed concerning the neutron from the AmBe source, with energy range of 1MeV to 12 MeV. Lithium can capture neutrons without gamma-ray emission, thus, reducing the background. The neutron detection reaction is 6 Li(n,α) 3 H with a thermal neutron cross section of 940 barns. In this paper, it was investigated the feasibility of the CsI:Li and CsI:Br crystals as neutron detectors for monitoring, due to the fact that in our work environment there are two nuclear research reactors and calibration systems.
Radiation effects in Li2B4O7 oxide crystals
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
The lithium tetraborate single crystal has been irradiated by neutrons and the optical properties of these crystals are studied. Irradiation induces optical absorption bands at 42 000, 33 000, and 20 000 cm À1. The intensities of these bands depend on the energy of the neutrons, on the irradiation temperature, and on the presence of an external electric ®eld. An applied electric ®eld induces the displacement of charged particles, creating the micrononhomogeneous regions in the crystal leading to a decrease of the intensities of the absorption bands. It has been established that the irradiation damages not only the surface of the crystal but also the deeper layers.
Production and identification of rare-earth doped lithium triborate
Journal of Alloys and Compounds, 2006
Research in the field of non-linear optical (NLO) devices lead to an increasing interest in new borate compounds, capable of expanding the frequency range provided by common laser sources. Lithium triborate (LBO) is a newly developed ideal non-linear optical crystal used in laser weapon, welder, radar, tracker, surgery, communication, etc. In this study, synthesis and identification of rare-earth doped lithium triborate was carried out. Borates containing rare-earth elements are of great interest since they are found to be superior in non-linear optical applications. Lithium triborate was produced from the solid-state reaction. Lithium triborate was then doped with some rare-earth elements (Gd, La, Y, etc.) in several different concentrations. In this study, LBO samples doped with Gd are presented. Characterization of the new products was done by X-ray diffraction (XRD) and infrared (IR) analysis. Differential thermal analysis (DTA) was used for examination of the thermal properties of the compounds, morphology of new compounds was observed by scanning electron microscopy (SEM). The compounds are then subjected to thermoluminescence (TL) studies. From the XRD studies, no change related to addition of the rare-earth elements was observed. IR analysis showed that there is no change related to B-O link with the addition of rare-earth elements. DTA studies showed that the melting point of LBO decreases with the addition of rare-earth elements. In the SEM images, particles of rare-earth elements and lithium triborate were observed clearly.