Materials for Gamma-Ray Spectrometers: Inorganic Scintillators

Abstract

Scintillation detectors constitute an important branch of radiation detection instrumentation. The discovery of the inorganic scintillating compound thallium-activated sodium iodide (NaI:Tl) in 1948 was key to the production of the first practical gamma-ray spectrometer. Since that time, numerous inorganic scintillators have been discovered and studied. Many of the more successful inorganic scintillators are described, including discussion of their properties and performance, in this article.

Record-high positive refractive index change in bismuth germanate crystals through ultrafast laser enhanced polarizability

“…contrast) but the positive index in the core could not be explained as it shows as a rarefied zone (darker zones) 20 . The increase of refractive index in the core due to the migration of elements that exhibit a higher electronic polarizabiliy ( α e ), as for instance observed in the case of chalcogenide glass 25 , can be ruled out since the discrepancy of polarizability between Ge ( 0.137 × 10 −24 cm 3 ) and Bi(1.508 × 10 −24 cm 3 ) is more than one order of magnitude 26 . This indicates the possible formation of a large number of non-bridged oxygen in the core.…”

“…This indicates the possible formation of a large number of non-bridged oxygen in the core. Non-bridging oxygen possesses a significantly higher polarizability www.nature.com/scientificreports/ ( 3.88 × 10 −24 cm 3 ) compared to bridged oxygen 27,28 . This is underpinned by the migration of oxygen towards the core observed using EPMA (Fig.…”

“…Due to the wealth of publications based on Si compared to relatively few on Ge, the discussion here is based on Si as it is isochemical to Ge. No PL relating to interstitial O 2 , O 3 29 , oxygen deficiency related centers (ODC) 30 or Ge based non-bridging oxygen ( ≡ Ge−O − ) 31 was detected. The excess availability of oxygen in the core due to migration can induce the formation of nonbridging oxygen hole centers (NBOHCs) and/or interstitial molecular oxygen, which are generally found and reported in oxygen excess silica.…”

“…It is possible that O 2 and O 3 are formed, but their existence might be a transient phase before they are converted to other defects. PL due to oxygen deficiency related centers (ODC) 30 was absent or could not be observed with any of the excitation wavelengths. Since the core is enriched by the influx of oxygen, PL from the oxygen excess defects 30 is expected, such as Ge based non-bridging oxygen ( ≡ Ge-O − , ex = 590−656 nm , em = 666 nm, FWHM =∼ 58 nm) 31 and/or peroxy linkage or peroxy radical center based defects.…”

“…PL due to oxygen deficiency related centers (ODC) 30 was absent or could not be observed with any of the excitation wavelengths. Since the core is enriched by the influx of oxygen, PL from the oxygen excess defects 30 is expected, such as Ge based non-bridging oxygen ( ≡ Ge-O − , ex = 590−656 nm , em = 666 nm, FWHM =∼ 58 nm) 31 and/or peroxy linkage or peroxy radical center based defects. Of all the excitation wavelengths, only 785 and 830 nm laser wavelength gave a PL spectra centered between 890 and 900 nm for different waveguides, as shown in Fig.…”