Status and prospects of the TAx4 experiment

The TAx4 experiment is a project to observe highest energy cosmic rays by expanding the detection area of the TA experiment with newly constructed surface detectors (SDs) and fluorescence detectors (FDs). The construction of both SDs and FDs is ongoing. New SDs are arranged in a square grid with 2.08 km spacing at the north east and south east of the TA SD array. Field of view of new FDs overlaps the detection area of new SDs to observe SD FD hybrid events. New SDs are planning to be deployed early next year. The first light with new FDs was already observed on February 2018. Especially the hotspot and energy spectrum anisotropy are expected to be understood in more detail from the implications obtained by the TA experiment. (author)