Interior temperature monitoring of NaI(Tl) crystal in space environment by pulse width measurement

In this paper, we develop a direct and reliable method of monitoring the interior temperature of a NaI(Tl) crystal in space environment. This method employs the temperature-dependent pulse width measured with a new pulse shape analyzer (PSA). The temperature dependence of the scintillation properties of the NaI(Tl) crystal is measured three times in the temperature range −20 to 45 °C from August to December 2008. Those measurements show that the pulse width of the NaI(Tl) crystal monotonically depends only on the temperature of the crystal. The relation between pulse width and temperature of the NaI(Tl) crystal is calibrated with a third-order polynomial. We apply this relation to monitor the interior temperature of the NaI(Tl) crystal under thermal non-equilibrium environments. We found that the crystal's interior temperature is generally quite different from that of its surrounding locations. This method is then used to improve the energy resolution of the detector in a temperature varying environment, by correcting the signal amplitude of each recorded event based on its pulse width.