Recent results of beam loss mitigation and extremely low beam loss operation of J-PARC RCS

Saha, P. K.   ; Okabe, Kota  ; Nakanoya, Takamitsu  ; Shobuda, Yoshihiro   ; Harada, Hiroyuki  ; Tamura, Fumihiko   ; Okita, Hidefumi  ; Yoshimoto, Masahiro  ; Hotchi, Hideaki*

To reduce high residual radiation at the RCS injection are caused by the foil scattering uncontrolled beam loss during injection period, a smaller size foil by minimizing the injection beam size has been successfully implemented at 700 kW operation. The new scheme also gives a significant beam loss mitigation at the collimator and 1st arc sections by reducing the beam halos. A beam loss mitigation of 30% has been achieved at the injection and 1st arc sections, while it is more than 50% at the collimator section. The residual radiation at 700 kW operation was thus measured to be significantly reduced, which at the injection and 1st arc sections are especially important due frequent access to these areas for regular maintenance works. The new scheme has also been successfully in service for 800 KW operation at present. It gives a very stable operation of the RCS and will also be tested for 1 MW operation in June 2022.