UROP Proceedings 2020-21

School of Science Department of Physics 72 Basics on Dark Matter Supervisor: LIU Tao / PHYS Student: LI Weiran / PHYS Course: UROP1100, Summer For centuries, dark matter has been one of the most attractive topics among physicists, because it seems to be essential for the explanation of various current cosmological observations. In this report, I first introduce some basic concepts that are essential for the understanding of dark matter. Then some important observational facts are briefly summarized and alternative approaches in order to rule out dark matter are introduced. Detailed discussions on the nature of dark matter with observational evidence and researching methods are followed where basics concepts are revised and extended. Finally, a concise introduction of different categories of dark matter candidates is provided. Basics on Dark Matter Supervisor: LIU Tao / PHYS Student: ZHU Jundong / SSCI Course: UROP1100, Summer This report first reviews the basics of cluster algebra. We recall the basic structure of cluster algebra like cluster variables, exchange matrix, mutation, coefficient and so on. And we also recall an important feature of cluster algebra, the Laurent Phenomenon, as well as Caterpillar Lemma which can prove the phenomenon. Secondly, the report talks about the content of the paper. We associate an unpunctured surface with a cluster algebra with principle coefficients and then use the theorem introduced in the paper to give the expansion formula of some cluster variables which are related to arcs on the surface. At the end, an original example of a decagon is given to illustrate the idea above. Setup of an Automated Telescope System as Sensor Testbench Supervisor: SMOOT George F. / PHYS Student: CHAN Yan Yan / PHYS-IRE Course: UROP2100, Fall This report presents the preliminary design of a focal plane cooling system for the automated telescope testbench. The cooling system aims to reduce the dark count noise of a single photon imaging detector which is based on positionsensitive silicon photomultiplier (PS-SiPM). To maintain the photodetector at a low temperature, it is attached to a thermoelectric peltier cooler module, which is further attached to a CPU cooler. A 3D-printed plastic enclosure is also designed to reduce heat gain and disturbance from the external environment. Preliminary testing of the cooling system will be done afterwards.