Launch and operation of the PIKACHU experiment to search for double beta decay in 160Gd

¹⁶⁰Gd is a candidate for double beta decay with relatively high natural abundance (21.9%). However, its low Q-value (1.73 MeV) makes the observation of even the two-neutrino double beta decay (2ν2β) extremely challenging. The most sensitive search used a 2 inch Gd₂SiO⁵ (GSO) scintillator. However, they was not able to observe 2ν2β due to significant background from intrinsic radioactive impurities which are uranium and thorium decay chains. Consequently, they established a lower limit of 1.9×10¹⁹ years on the 2ν2β half-life (T2ν1/2). Theoretical prediction suggests T2ν1/2 of approximately 7.4×10²⁰ years. The PIKACHU experiment was designed to observe ¹⁶⁰Gd 2ν2β by employing large Gd₃Ga₃Al₂O₁₂ (GAGG) single crystals. GAGG offers several advantages over GSO: higher light yield, possibility of pulse shape discrimination, and a higher ¹⁶⁰Gd content by increasing in size. We planned two phases: Phase 1 aims to search 2ν2β in ¹⁶⁰Gd with the best sensitivity in the world, and then, Phase 2 is intended to achieve a sensitivity approximately an order of magnitude better than previous study, with the goal of observing the decay. In this conference, I introduced the concept of the PIKACHU experiment, present on the development of high-purity GAGG crystals, and report the current status of data acquisition and analysis for Phase 1.