Development of the GEM-TPC X-ray Polarimeter with the Scalable Readout System Takao Kitaguchi, Asami Hayato, Wataru Iwakiri, Yoko Takeuchi, Megu Kubota, Kazuki Nishida, Teruaki Enoto and Toru Tamagawa EPJ Web Conf., 174 (2018) 01015 Published online: 21 February 2018 DOI: 10.1051/epjconf/201817401015