Trends, technologies and the future of indirect radiation sensing materials

Pr:LuAG has interesting properties of high density, high light yield and a very fast 5d-4f emission decay time. Recently we have develop 2-inch-diameter Pr:LuAG single crystal for scintillator applications such medical imaging and high-energy physics. In this report, we study uniformity of the light yield, energy resolution, decay time and gamma-ray response in the range from 59.5 keV (241Am) to 1.4 MeV (241Am).

High-energy physics (HEP) experiments have employed many new types of scintillators. Specifically, bismuth germanate, thallium-doped cesium iodide, and lead tungstate (PbWO4, PWO) have been used for the L3 experiment; CLEO II, Belle and BES-III; and CMS, respectively. PWO has particularly beneficial properties, such as high density, fast decay time, short radiation length and radiation hardness. In this study, we tested the PWO crystals at low temperatures to determine their applicability in future calorimeters. Various crystals from the Proton Antiproton Annihilations at Darmstadt (PANDA) experiment in Giessen, the Bogoroditsk Techno-Chemical Plant (BTCP) in Russia and by Shanghai Institute of Ceramics, Chinese Academy of Sciences (SICCAS) in China were investigated. We studied the scintillation properties of PWO crystals, such as their X-ray luminescence, relative light yields, absolute light yields, energy resolutions, decay times and longitudinal uniformities of their light yields. In addition, we measured the temperature dependences of the light yields and decay times by using a 137Cs γ-ray source.

The effect of crystal surface finish on the performance of radiation detector has been studied many times mostly focused on a single isolated crystal coupled to a single photosensor. In this paper, we studied roughen crystal effect on light sharing crystal arrays using LYSO crystals of 3.95 × 5.3 × 25mm3. Four different types of crystal arrays were built: no light sharing and light sharing arrays with all polished crystals, and no light sharing and light sharing arrays with crystals of one surface lapped. ESR films were placed in between crystals to make no light sharing arrays. Each array of 2×3 crystals was coupled to a monolithic SiPM of 2×3 anodes and evaluated for light output and timing resolution. For no-light sharing, no-light sharing arrays with one surface lapped showed 14% more light output and 7% improvement in timing resolution compared to no-light sharing with polished crystals. For light sharing, lapped crystal array showed 27% more light output and 14% improvement in timing resolution than its counterpart with polished crystals. Light sharing array with polished crystals collected 16% more light output than no-light sharing array with polished crystals, however, it's increased light output did not manifest as better timing resolution. When light sharing array with lapped crystals was compared to no-light sharing array with polished crystals, it showed a surprising 47% more light output with 11% better timing resolution. In short, lapped crystals showed a big improvement in both light output and timing resolution, and more improvement was observed with light sharing array.

Characterization of Ca co-doped LSO:Ce scintillators coupled to SiPM for PET applications

Characterization of BaCl 2 scintillation crystal at low temperature

Measurement of LYSO crystal light output and energy resolution improvement with acid etching

Background: CeBr3 Inorganic scintillator is a favorite scintillator in various fields, especially in medical imaging and X-rays/gamma rays detectors. One is important before being applied in any application is the fundamental properties that it has to measure such as energy resolution, PTR, PCR, and light yield. Objectives: In this research, a CeBr3 crystal was carried out trial for calculating the energy resolution, peak to total (PTR), and peak to Compton (PCR) values. Materials and methods: When high photon energy undergoes with the CeBr3 crystal, the crystal will occur to interact with photon energy by energy’s absorptions via the interaction ternary as the photoelectric absorption, Compton scattering, and pair production. The nuclear instrument module (NIM) was used in this experiment. The crystal will generate light and come into a photomultiplier tube (PMT 9256 KB) for amplifying the light signal via the radiation sources as Ba-133, Na-22, Cs-137, and Co-60, which generated the energies at 0.356 MeV, 0.511 MeV, 0.662 MeV, 1.173 MeV, and 1.332 MeV, respectively. Results: The result found that the energy resolution of CeBr3 showed the energy resolution of CeBr3 crystal showed a linear pattern of inverse the square root of the energy and found the energy resolution values were increased when the photon energy decreased. The PTR and PCR values decreased with increasing energy ranges via experiment of each full energy peak of radiation sources. Conclusion: From the fundamental properties of CeBr3 crystal showed a good energy resolution and is a possible candidate to apply for any application such as radiation detection and high-energy physics. Anywise, other properties should be also considered, for example, light yield, decay time, and nonproportionality of light yield.

Europium concentration effects on the scintillation properties of Cs4SrI6:Eu and Cs4CaI6:Eu single crystals for use in gamma spectroscopy

In this study, we demonstrated a drastic improvement in energy resolution of (Lu0.75Y0.25)3Al5O12:Pr (LuYAG) single crystal scintillators from 4.8% to 4.1% at 662 keV upon Li+ codoping, which is the best value ever reported in the class of oxide single crystal scintillators. Li+ codoping can also significantly enhance its scintillation yield from 16 000 to 25 000 photons MeV−1, but slightly prolong the scintillation decay time. As Li+ codoping was found to have a negligible effect on the light yield non‐proportionality, we attributed the significant improvement in energy resolution to the reduced statistical variance in the number of photoelectrons produced in the photomultiplier tube (Rstat).

Inorganic scintillators are commonly used in various radiation detection applications due to their excellent energy resolution, reliable performance, relatively low cost, and high detection efficiency. However, many inorganic scintillators have high refractive indices and experience significant light losses at the collection surface caused by total internal reflection (TIR). This project employs optimized periodic nanostructures, known as photonic crystals (PHCs), to recover some of the light losses. A PHC layer creates an improved optical pathway between the scintillator and the photosensor for the trapped photons through constructive light interference. Enhancing the light extraction from an inorganic scintillator improves its energy resolution, time resolution, and the overall detection efficiency. In this work, the effects of an optimized PHC coupling with a LYSO scintillator are experimentally demonstrated. The PHC geometry is optimized through tailored simulations, manufactured with electron beam lithography, and characterized with radiation measurements to quantify improvements in light output and energy resolution. A 10 x 10 x 3 mm 3 LYSO sample shows an improvement of 28% in light output and 13% in energy resolution with an optimized 2D block structure Si 3 N 4 PHC structure. Future work will focus on expanding the experimental framework to other inorganic scintillators such as NaI and LaBr 3 , which are expected to have even greater light output improvements owing to their higher refractive index and total internal reflection.

All available imaging devices in nuclear medicine have finite energy resolution. This leads to inclusion of scattered radiation, which in turn degrades the image quality. Different scatter correction schemes therefore try to eliminate the effect of scattered radiation. On the other hand, improvement of the camera's intrinsic energy resolution would reduce the amount of detected scattered radiation as well. A simple model was developed in order to stimulate the influence of the energy resolution on the camera response. It is shown that improvement of the energy resolution and scatter correction schemes have a similar effect on the point spread function. On this basis, it is suggested that 'effective energy resolution' be used as a new measure for the effectiveness of scatter correction schemes. As an example, this is done for energy-weighted acquisition, a scheme wherein each event contributes imaging information according to a real-valued, energy-indexed weighting function.

In the time-of-flight measurement of high energy neutrons, the time resolution is often required to be as good as possible. For improvement of the energy resolution, the time-of-flight study was made by the use of Li (p, n) reaction at forward angles. Two types of detectors were tested. One was a liquid organic scintillator NE-213 5 inches (127 mm) in diameter and 127 mm thick connected with three Hamamatsu H2431 photomultipliers 2 inches (51 mm) in diameter. The other was NE-213 of the same size with a Hamamatsu R1250 127 mm in diameter. The experiment was made at /spl pi/2 beam line of 12 GeV proton synchrotron in High Energy Accelerator Research Organization (KEK). The incident proton energy was 800 MeV, and the flight path was 5 m. Two neutron detectors were set at 0 and 5 degrees, respectively. The time resolutions for prompt gamma rays were 0.5 ns for NE-213 with three H2431 s and 1.0 ns for NE-213 with R1250. The energy resolutions for 800 MeV neutrons were derived from these values were 70 and 100 MeV, respectively.

This paper investigates the effects of boron and calcium co-doping on the measured energy resolution of Gd3Ga3Al2O12:Ce (GGAG: Ce). For this study, three samples of GAGG were grown using the Czochralski method. The first sample was doped with Ce3+ and was used as a reference for comparison. The next two samples were additionally doped with either B3+ or Ca2+. The boron co-doped sample was found to have an overall improved performance when compared to the reference sample. The light output of the GGAG:Ce,B was measured to be 10% greater than the reference sample. In addition, the sample was found to have less charge trapping and a more linear relative light yield response. These factors led to an observed improvement in energy resolution from 9% in the reference sample to 7.8% in the B 3+ co-doped sample. Co-doping with Ca2+ led to an overall reduction in charge trapping; however, the sample suffered a 30% reduction in light output, and it was found to have a less linear relative light yield than the reference sample. Its energy resolution was measured to be 10.1%. The relationship between the measured energy resolution and the other measured properties in these samples is discussed.

Fabrication and characterization of cubic SrI2(Eu) scintillators for use in array detectors

Scintillator crystal detectors form the basis for many radiation detection devices. Therefore, a search for high light yield single crystal scintillators with improved energy resolution, large volume, and the potential for low cost, is an ongoing process that has increased in recent years due to a large demand in the area of nuclear isotope identification. Alkaline earth halides, elpasolites and rare earth halides are very interesting because many compositions from these crystal families provide efficient Ce3+/ Eu2+ luminescence, good proportionality and good energy resolution. They also have small band-gap leading to higher light yields. Ce3+and Eu2+ are efficient, and the emission wavelengths in the 350-500 nm region matches well with PMTs and a new generation of Siphotodiodes. In this presentation, we will the present progress made in the crystal growth of these compositions, and scintillator properties of large diameter SrI2:Eu2+ single transparent crystals. The crystals were grown successfully using the vertical Bridgeman technique. Crystals with different diameters of 1”, 1.3”, and 1.5” will be discussed. SrI2:Eu was discovered a half century ago, and was recently found to be an outstanding material for gamma ray-spectroscopy with high light yield, very good non-proportionality, and excellent energy resolution. We will also discuss growth and properties of larger Cs2LiYCl6 (CLYC) crystals. Recently, it has been shown that crystals from the elpasolite family, including CLYC, can be successfully employed for a dual gamma ray and neutron detection, which is possible with the help of pulse shape discrimination (PSD). PSD allows for recognition of an incident particle’s nature based on the shape of the corresponding scintillation pulse. CLYC has the potential to minimize the cost and complexity of dual sensing gamma ray and neutron spectrometers. We also address progress in growth of CLYC crystals with large diameters (1” and 2”) that are transparent and crack free.