Scintillators For Radiation Detection Research Articles

A Melt‐Quenched Luminescent Glass of an Organic–Inorganic Manganese Halide as a Large‐Area Scintillator for Radiation Detection

AbstractGlass is a group of materials with appealing qualities, including simplicity in fabrication, durability, and high transparency, and they play a crucial role in the optics field. In this paper, a new organic–inorganic metal halide luminescent glass exhibiting >78 % transmittance at 506–800 nm range together with a high photoluminescence quantum yield (PLQY) of 28.5 % is reported through a low‐temperature melt‐quenching approach of pre‐synthesized (HTPP)2MnBr4 (HTPP=hexyltriphenylphosphonium) single crystal. Temperature‐dependent X‐ray diffraction, polarizing microscopy, and molecular dynamics simulations were combined to investigate the glass‐crystal interconversion process, revealing the disordered nature of the glassy state. Benefiting from the transparent nature, (HTPP)2MnBr4 glass yields an outstanding spatial resolution of 10 lp mm−1 for X‐ray imaging. The superb optical properties and facility of large‐scale fabrication distinguish the organic–inorganic metal halide glass as a highly promising class of materials for optical devices.

Understanding Thermal and A‐Thermal Trapping Processes in Lead Halide Perovskites Towards Effective Radiation Detection Schemes

AbstractLead halide perovskites (LHP) are rapidly emerging as efficient, low‐cost, solution‐processable scintillators for radiation detection. Carrier trapping is arguably the most critical limitation to the scintillation performance. Nonetheless, no clear picture of the trapping and detrapping mechanisms to/from shallow and deep trap states involved in the scintillation process has been reported to date, as well as on the role of the material dimensionality. Here, this issue is addressed by performing, for the first time, a comprehensive study using radioluminescence and photoluminescence measurements side‐by‐side to thermally‐stimulated luminescence (TSL) and afterglow experiments on CsPbBr3 with increasing dimensionality, namely nanocubes, nanowires, nanosheets, and bulk crystals. All systems are found to be affected by shallow defects resulting in delayed intragap emission following detrapping via a‐thermal tunneling. TSL further reveals the existence of additional temperature‐activated detrapping pathways from deeper trap states, whose effect grows with the material dimensionality, becoming the dominant process in bulk crystals. These results highlight that, compared to massive solids where the suppression of both deep and shallow defects is critical, low dimensional nanostructures are more promising active materials for LHP scintillators, provided that their integration in functional devices meets efficient surface engineering.

Photo-Responses of Silicon Photodiodes with Different ARC Thicknesses for Scintillators

We designed and fabricated silicon positive-intrinsic-negative (PIN) photodiodes coupled with a scintillator for radiation detection. The photodiodes were fabricated on an n-type double-sided polished silicon wafer with a diameter of 6-in., a high resistivity ( orientation. To increase the quantum efficiency (QE) of the photodiode, an anti-reflection coating (ARC) was provided on the side where light entered. It is difficult to realize an ARC with an uniform thickness in the sensor fabrication process. The effect of changes in the ARC thickness on the QE of the fabricated sensors was studied in detail. We measured the electrical characteristics and compared their quantum efficiencies as a function of the incident light wavelength for the photodiodes with different ARC thicknesses. In this paper, we present the design of the photodiodes and their measured electrical characteristics and photo-responses for different ARC thicknesses. From measurements of the wavelength-dependent QE, we determined the refractive index of the ARC layer to be 2.25 ± 0.15. The ARC layer improved the QE up to 56% and 63% at the wavelengths of 550 and 475 nm, which correspond to the wavelengths of the scintillation light from CsI(Tl) and CdWO4, respectively.

(Invited) Ionic Liquid Enables Technologies for Winning Rare Earth Elements

Rare earth elements are amongst the most critical materials, they are crucial for a number of energy related technologies relying on the superior catalytic, optical or magnetic properties that can be achieved in their compounds. As catalysts they find application in fluidic catalytic cracking (FCC) catalysis, one of the most important processes in petrochemistry where they are used to convert the high-molecular weight hydrocarbon fraction of crude oil into more useful lower-weight hydrocarbons. Rare earth based phosphors are the key part for energy conversion in compact fluorescent lamps (CFLs) and light emitting diodes (LEDs) which are currently the most important energy efficient lighting devices. As phosphors rare earth based materials find also application in scintillators for radiation detection (as used by Homeland Security) or for medical imaging. As security makers they can be found in passports and banknotes. Currently an increased consumer demand for rare earth materials arises from the increased use of cell phones and tablets. The exceptional properties of rare earth elements are particularly used in alloys for permanent magnets. The properties of SmCo5 and Nd2Fe14B are unsuperseded. Because of their high field strength Nd2Fe14B magnets are used in hard drives, motors for hybrid cars or wind turbines. SmCo5 is less used as it not only has a weaker field strength, but is also more expensive because it contains two critical elements, samarium and cobalt. However, as the Curie temperature of SmCo5 is higher than that of Nd2Fe14B is used in applications where high field strengths at high temperatures are needed. However, the stable economic supply of rare earth elements is not guaranteed and, thus, the pproduction and use of rare earth compounds constitute an important strategic and dynamic segment of the electronic, chemical and energy industries. The presentation will discuss the importance and criticality of rare earth elements and will give insights into how ionic liquids can provide technology solutions for rare earth recycling, separation and production, most importantly, the electrodeposition from ionic liquids as an alternate, greener process to the currently used high temperature process.

Structural and crystal chemical properties of alkali rare-earth double phosphates

When appropriately activated, alkali rare-earth double phosphates of the form: M3RE(PO4)2 (where M denotes an alkali metal and RE represents either a rare-earth element or Y or Sc) are of interest for use as inorganic scintillators for radiation detection at relatively long optical emission wavelengths. These compounds exhibit layered crystal structures whose symmetry properties depend on the relative sizes of the rare earth and alkali-metal cations. Single-crystal X-ray and powder neutron diffraction methods were used here to refine the structures of the series of rare-earth double phosphate compounds: K3RE(PO4)2 with RE = Lu, Yb, Er, Ho, Dy, Gd, Nd, Ce, plus Y and Sc – as well as the compounds: A3Lu(PO4)2, with A = Rb, and Cs. The double phosphate K3Lu(PO4)2 was reported and structurally refined previously, and it exhibited two lower-temperature phases. The compound K3Yb(PO4)2 reported here also exhibits a new second phase that occurs at T = 120 °C with a transformation to hexagonal P-3 space group symmetry and a Yb-ion coordination number reduction from seven to six. This latter result was confirmed using EXAFS. Comprehensive structural data and structural systematics are reported here for a number of alkali rare-earth double phosphates. Additionally, single-crystal growth methods for the preparation of large single crystals of these compounds are described, and the thermal expansion properties of the present series of alkali rare-earth double phosphates, as determined by both X-ray and neutron diffraction methods, are presented. These data represent a structural and thermal characteristics basis for continuing research on the use of alkali rare-earth double phosphates as scintillators for radiation detection – as well as for future studies of the fundamental phase properties of these compounds at elevated pressures.

Luminescence of La0.2Y1.8O3 nanostructured scintillators.

For the first time, transparent La0.2Y1.8O3 nanostructured polycrystalline scintillators were fabricated by sintering nanoparticle powders at high temperatures and their scintillation properties are reported. La0.2Y1.8O3 is a host material that has never been investigated as scintillators for radiation detection. Our observations found that La0.2Y1.8O3 has an intense scintillation luminescence, a detection efficiency higher than that of YAG:Ce and a comparable energy resolution to NaI and CsI scintillators. In addition, La0.2Y1.8O3 is stable and has luminescence decay lifetime in the picosecond range which is favorable for radiation detection. The luminescence of La0.2Y1.8O3 has a large Stokes-shift and a large emission bandwidth, and the luminescence is highly temperature dependent. Different from most doped scintillators, the luminescence of La0.2Y1.8O3 is most likely from the self-trapped excitons. The discovery of La0.2Y1.8O3 scintillators opens a new door for the research of new materials for radiation detection.

Evaluation of the Detection Efficiency of LYSO Scintillator in the Fiber-Optic Radiation Sensor

The aim of this study was to develop and evaluate fiber-optic sensors for the remote detection of gamma rays in areas that are difficult to access, such as a spent fuel pool. The fiber-optic sensor consists of a light-generating probe, such as scintillators for radiation detection, plastic optical fibers, and light-measuring devices, such as PMT. The (Lu,Y)2SiO5:Ce(LYSO:Ce) scintillator was chosen as the light-generating probe. The (Lu,Y)2SiO5:Ce(LYSO:Ce) scintillator has higher scintillation efficiency than the others and transmits light well through an optical fiber because its refraction index is similar to the refractive index of the optical fiber. The fiber-optic radiation sensor using the (Lu,Y)2SiO5:Ce(LYSO:Ce) scintillator was evaluated in terms of the detection efficiency and reproducibility for examining its applicability as a radiation sensor.