Pressure wave induced sound measurement for diagnosing the operation status of the J-PARC pulsed spallation neutron source

Naoe, Takashi   ; Kogawa, Hiroyuki  ; Wakui, Takashi  ; Teshigawara, Makoto   ; Haga, Katsuhiro  ; Futakawa, Masatoshi  

A liquid mercury target for the spallation neutron source is installed in the J-PARC. The liquid mercury is enclosed with the multi-walled stainless steel vessel. At the time of highly intense proton beams hits the target at a repetition rate of 25 Hz, pressure waves, that causes cavitation erosion, are generated owing the rapidly thermal expansion of mercury. We have installed the target diagnostic system consisting of a laser Doppler vibrometer (LDV) and a dynamic microphone to remotely investigate the structural integrity of the target under high-radiation environment. In this study, aiming to understand correlation between the acoustic vibration and the operation conditions such as the proton beam power and beam profile, proton beam induced acoustic vibration was measured by parametrically changing the target operation conditions. The result showed that the sound is well correlated with the operation conditions.