Atacama sub-millimeter telescope experiment polarimeter (APol) I: design and lab-test result.

In this paper, the Atacama Submillimeter Telescope Experiment (ASTE) is presented. A 10-m aperture telescope hosts a camera equipped with a transition edge sensor (TES). We developed a fore-optics module-"APol," to convert the 271 pixels of the TES working at 350 GHz into a sensitive imaging polarimeter without sacrificing the image quality and the ${7.5}^\prime$7.5 field of view. Here, we describe the detailed optical design of APol and present the results of the preliminary test in a laboratory.