Two-photon excited luminescence in POPOP under pulse-periodic laser excitation

Scintillators with pulse-shape discrimination (PSD) capability are of great interest to many fields in the scientific community. The ability to discern a gamma ray from a neutron using PSD varies between different types of scintillator materials and dopants. A new generation of organic scintillator materials with PSD capability were studied to determine their radiation hardness to ionizing and non-ionizing radiation. The PSD capability, average pulse shapes, and light output of four types of organic scintillator were characterized before and after neutron and gamma-ray irradiation. The main goal of this investigation is to study the effects of long-term irradiation that may be experienced in space applications on the light output and particle discriminating capabilities of each material. EJ-270, EJ-276, organic glass, and Stilbene were tested. Damage due to non-ionizing (neutron) radiation was not observed in any of the scintillators up to $2.56\times10^{11}$ n/cm$^2$, except for Stilbene which showed a small (12$\%$) decrease in light output. All scintillators presented some light output reduction after ionizing (gamma-ray) irradiation, with reductions of 17$\%$ (EJ-276 and OGS), 32$\%$ (EJ-270), and 42$\%$ (Stilbene) observed immediately after 100 kRad.

Performance Evaluation of Pulse Shape Discrimination Capable Organic Scintillators for Space Applications

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Performance evaluation of pulse shape discrimination capable organic scintillators for space applications

The energy of the two-photon-excited luminescence has been studied experimentally as a function of the energy of the monochromatic pump—a giant ruby laser pulse—in a molecular stilbene crystal. At pump power densities up to 108 W/cm2 this dependence is quadratic. Above 108 W/cm2, the behavior deviates from the quadratic law; the two-photon-excited luminescence signal increases sharply with a further increase in the pump power density. The efficiency of the conversion of the laser light (λ = 694.3 nm) into UV two-photon-excited luminescence is η = 0.1%. The coefficient of two-photon absorption is estimated from the experimental data on the transition from spontaneous two-photon-excited luminescence to stimulated luminescence. The result agrees satisfactorily with data in the literature. Conditions for raising the efficiency of the conversion of radiation on the basis of two-photon-excited luminescence in condensed molecular media are analyzed.

https://iopscience.iop.org/article/10.1070/QE1993v023n06ABEH003113/pdf

A. I. Sokolovskaya

Papers

Stimulated two-photon-excited luminescence in stilbene crystals