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Polyethylene naphthalate (PEN) is an industrial plastic which is interesting to the physics community as a wavelength-shifting scintillator. Recently, PEN structures with excellent radiopurity have been successfully produced using injection compression molding technology. This opens the possibility for the usage of optically active structural components with wavelength shifting capabilities in low-background experiments. Thus, PEN holders will be used to mount the germanium detectors in the LEGEND-200 experiment. In this contribution the ongoing R&D on PEN is outlined with a focus on the evaluation of its optical properties. In addition, the ongoing efforts for further application of PEN in the LEGEND-1000 experiment are presented.

Many international low-background experiments are showing increasing interest in the use of different plastic scintillation detectors. Based on our experience in the field of quality improvement of the polystyrene (PS) based plastic scintillation detectors, this work is focusing on a further enhancement of the scintillator light output and the associated energy resolution crucial for the detection of a very rare nuclear processes. To produce PS scintillators from liquid styrene various stabilization additives and conditions of polymerization process are commonly used. These factors, i.e. stabilization additives and atmospheric oxygen, have a negative impact on above mentioned optical properties of the scintillation detectors. Within this study, several samples under different conditions, e.g. concentrations of luminescent additives; presence of stabilization additives; air and inert atmosphere, were prepared and tested using a unique tunable electron spectrometer providing a monoenergetic electron beam ranging from 200 keV to 1.5 MeV.

The discovery of scintillation in the blue regime from polyethylene naphthalate (PEN), a commonly used high-performance industrial polyester plastic, has sparked considerable interest from the physics community as a new type of plastic scintillator material. This observation in addition to its good mechanical and radiopurity properties makes PEN an attractive candidate as an active structure scintillator for low-background physics experiments. This paper reports on investigations of its potential in terms of production tests of custom made tiles and various scintillation light output measurements. These investigations substantiate the high potential of usage of PEN in low-background experiments.

In recent years, much attention has been focused on neutrino research because it can shed new light on greatest mysteries in physics. A new experiment devoted to detection and investigation of reactor antineutrinos is being performed at the Institute of Experimental and Applied Physics, Czech Technical University in Prague using a highly segmented scintillating detector S3. This detector is polystyrene based and does not contain any dangerous or flammable materials and is absolutely safe to be placed in the close vicinity of the reactor. The most important feature of plastic scintillators for this experiment is the amount of photoelectrons per deposited energy, which defines the final energy resolution of the detector and a lot of effort has been put into improvement of detector element overall quality. The detector has been constructed as a result of these optimization experiments.