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Temperature quenching in LAB based liquid scintillator
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The effect of temperature changes on the light output of LAB based liquid scintillator is investigated in a range from $-5$ to $30\,^{\circ }$ C with $\alpha $ -particles and electrons in a small scale setup. Two PMTs observe the scintillator liquid inside a cylindrically shaped aluminum cuvette that is heated or cooled and the temperature dependent PMT sensitivity is monitored and corrected. The $\alpha $ -emitting isotopes in dissolved radon gas and in natural Samarium (bound to a LAB solution) excite the liquid scintillator mixtures and changes in light output with temperature variation are observed by fitting light output spectra. Furthermore, also changes in light output by compton electrons, which are generated from external calibration $\gamma $ -ray sources, is analysed with varying temperature. Assuming a linear behaviour, a combined negative temperature coefficient of ${(-0.29 \pm 0.01)}{\,\%/^{\circ }}\hbox {C}$ is found. Considering hints for a particle type dependency, electrons show ${(-0.17 \pm 0.02)}{\,\%/^{\circ }}\hbox {C}$ , whereas the temperature dependency seems stronger for $\alpha $ -particles, with ${(-0.35 \pm 0.03)}{\,\%/^{\circ }}\hbox {C}$ . Due to a high sampling rate, a pulse shape analysis can be performed and shows an enhanced slow decay component at lower temperatures, pointing to reduced non-radiative triplet state de-excitations.