Heat and Light Measurement of a ${}^{40}{\rm Ca} {}^{100} {\rm MoO}_4$ Crystal for the AMoRE Double Beta Decay Experiment

The simultaneous measurement of heat and light signals from a ${}^{40}{\rm Ca} {}^{100} {\rm MoO}_4$ scintillating crystal was performed at temperatures of tens of milli-kelvin using a scintillating bolometric detector. The crystal was instrumented with a pair of low-temperature detectors, consisting of a metallic magnetic calorimeter for reading the phonon signals and a light detector based on a Ge light absorber, to simultaneously measure the scintillation light and phonon signals. This article presents the principle and performance, such as the event separation capability, of this simultaneous heat/light measurement system.