Speaker
Description
Currently, we are developing a fleet of nano-satellites for detection and position determination of short gamma-ray bursts (SGRBs) for the proposing CAMEROT (Cubesats Applied for MEasureing and LOcalising Transients) mission. We synchronize time information of each satellite by using a global positioning system, and plan to use large-area CsI(Tl) scintillators which provide a high light output and readout by multi-pixel photon counters (MPPC), which have low power consumption that is suitable for nanosatellite platform.
We plan to use one of the latest-model MPPCs provided by Hamamatsu Photonics, namely, S13360-6050CS, which have an active area of $6\times6$ mm$^2$. We compared the performance of two scintillators of different sizes ($150\times75\times5$ mm$^3$, $100\times75\times5$ mm$^3$); the bigger one is the maximum size that can be mounted on a three-unit satellite we are planning to apply, and found the difference of light yield was only $\sim$13$\%$. We also tested two-MPPC readout to improve the energy threshold and uniformity by using signals from $^{241}$Am source. We confirmed the same energy threshold as one-MPPC readout of $\sim$10 keV at 25$^\circ\mathrm{C}$ and energy resolution got better by 7$\%$ thanks to the improved uniformity. Then we investigated the optimum position of two-MPPCs on the scintitllator by using ray-tracing Monte Carlo simulator, and found that symmetrical configurations against to the center of the scintillator gives the best performance of light yield.
