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Scintillation Detectors and Materials Scintillation Detectors and Materials
Published in Douglas S. McGregor, J. Kenneth Shultis, Radiation Detection, 2020
Douglas S. McGregor, J. Kenneth Shultis
There are many benefits to adding a wavelength shifting fluor to the cocktail [Schram 1963]. First, the emission wavelengths of many primary fluors have sufficient energy to be significantly reabsorbed in the cocktail solution. The wavelength shifter converts light to lower energies, thereby reducing the probability of reabsorption. Second, a wavelength shifter can be selected that emits photons that match well to the light collection device such as a PMT. For instance, a solution with p-terphenyl as the primary scintillator with λmax near 340 nm may have a wavelength shifter added, such as POPOP with λmax near 410 nm and this improves transparency with a better match to a common bi-alkali PMT. Third, the longer wavelength photons are less likely to be absorbed by the container structure, such as the vial walls that contain the cocktail. Fourth, the longer wavelength photons (λ > 400 nm) are more effectively reflected by TiO2, a Lambertian reflector often used in scintillation counting. Typically, wavelength shifting fluors have lower solubility in the solvent than the primary fluor, hence the reason for their exclusion as a primary fluor. However, the energy transfer process between fluors requires only a small fraction of wavelength shifter, on the order of 1% concentration of the primary fluor. Energy lost during the energy transfer process between primary and wavelength shifting fluors is more than made up for by the improved luminescent transparency in the cocktail and efficient light coupling to the PMT (or other light sensitive device).
Novel X- and Gamma-Ray Detectors Based on Metamaterials
Published in Salah Awadalla, Krzysztof Iniewski, Solid-State Radiation Detectors, 2017
In a way, a scintillator can be defined as a wavelength shifter. It converts the energy (or wavelength) of an incident particle or energetic photon (ultraviolet [UV]-, x-, or γ-ray) into a number of photons of much lower energy (or longer wavelength) in the visible or near-visible range, which can be easily detected by current photomultipliers, photodiodes, or avalanche photodiodes.
Development of a water Cherenkov neutron detector for the active rotation method and demonstration of nuclear material detection
Published in Journal of Nuclear Science and Technology, 2023
Kosuke Tanabe, Masao Komeda, Yosuke Toh, Yasunori Kitamura, Tsuyoshi Misawa, Ken’ichi Tsuchiya, Norimitsu Akiba, Hidetoshi Kakuda, Kazunari Shibasaki, Hiroshi Sagara
As described in Section 2.2, the number of photons of Cherenkov light is dominant in the short wavelength region. However, the light collection and detection efficiency decreases in the region due to the decrease in water transmission and the quantum efficiency of the PMT. In particular, because acrylic windows do not transmit light below 400 nm, the use of a wavelength shifter (Amino-G-salt), which converts light in the ultraviolet region to light in the sensitive region of the PMTs, was examined. The optical absorption wavelength peaks of Amino-G-salt were at 255.0, 307.0, and 351.0 nm, and the maximum fluorescence wavelength was at 450.0 nm. Figure 11(a) shows the pulse height spectra for Amino-G-salt concentrations of 0.0 and 20 mg/L. The addition of the Amino-G-salt increased the number of detected photons dramatically for both neutrons and gamma-rays, which was expected to improve the neutron/gamma-ray discrimination. Figure 11(b) shows the correlation between the detection efficiency and Amino-G-salt concentration at the threshold of 100 channels. The effect of the wavelength shifter became saturated at approximately 30 mg/L. Comparing the neutron detection efficiencies at concentrations of 0.0 and 30 mg/L at the threshold of equal gamma-ray efficiency showed that the addition of Amino-G-salt increased the efficiency by approximately 1.3 times.
Effect of fluorescent dyes on the scintillation efficiency, improved light yield and radiation hardness of polystyrene-based plastic scintillator: a comparative study
Published in Radiation Effects and Defects in Solids, 2023
Lizbeth Alex, Rajesh Paulraj, Mohit Tyagi
All the materials such as styrene (Sty), p-Terphenyl (p-TP), 2-(4-tert-Butylphenyl)-5-(4-biphenyl)-1,3,4-oxadiazole (b-PBD), 1,4-diphenyl-1,3-butadiene (DPB), 1,4-bis-[2-(5-phenyl)oxazolyl]benzene (POPOP) used in the experiment were purchased from Sigma Aldrich with 99.5% purity. The amorphous aromatic plastic base polystyrene, the UV-emitting primary fluorescent dyes (p-TP, b-PBD, DPB) and the blue-emitting wavelength shifter (WLS) POPOP can improve the scintillation performance and help in efficient energy transfer mechanism in the plastic scintillator (9). Figure 1 shows the molecular structure of the monomer and the scintillating solutes involved in the formation of the plastic scintillator.