Muon spin spectrometer at MLF MUSE U1A; Commissioning results and upgrade plans

神田 聡太郎*; 池戸 豊*; 大石 裕*; 下村 浩一郎*; 髭本 亘  ; 伊藤 孝   ; 中沢 雄河*; 林 幹稀*; 足立 匡*

Kanda, Sotaro*; Ikedo, Yutaka*; Oishi, Yu*; Shimomura, Koichiro*; Higemoto, Wataru; Ito, Takashi; Nakazawa, Yuga*; Hayashi, Motoki*; Adachi, Tadashi*

Muons serve as a highly sensitive local magnetic probe in materials science. While traditional SR relies on 4 MeV surface muons, investigations of thin films and interfacial phenomena demand precisely controlled low-energy muon beams. At J-PARC MLF MUSE, the U1 beamline delivers ultra-slow muons (USM) via laser ionization of thermal muonium. In the U1A experimental area, a muon spin spectrometer has been installed for USM-SR measurements. The spectrometer is mounted on a high-voltage platform for implantation energy control from nearly zero to 30 keV. Comprehensive beam characterization has demonstrated a spatial beam profile of 4 mm FWHM and a temporal width of 2 ns at the spectrometer's sample position. Commissioning of the spectrometer has demonstrated stable beam alignment and high time resolution in positron detection. In this work, we report these commissioning results and discuss potential upgrades for expanding the instrument's capabilities for future user programs.