Beam loss mitigation for operation beyond 1 MW beam power of the J-PARC RCS

J-PARC RCSにおける1MWを超えるビーム出力の運転でのビーム損失の軽減

Saha, P. K.   ; 原田 寛之  ; 田村 文彦   ; 菖蒲田 義博   ; 小島 邦洸 ; 吉本 政弘  ; 沖田 英史  ; 岡部 晃大  ; 畠山 衆一郎; 仲野谷 孝充  ; 守屋 克洋  ; 地村 幹   ; 山田 逸平 ; 高柳 智弘   

Saha, P. K.; Harada, Hiroyuki; Tamura, Fumihiko; Shobuda, Yoshihiro; Kojima, Kunihiro; Yoshimoto, Masahiro; Okita, Hidefumi; Okabe, Kota; Hatakeyama, Shuichiro; Nakanoya, Takamitsu; Moriya, Katsuhiro; Chimura, Motoki; Yamada, Ippei; Takayanagi, Tomohiro

The RCS (Rapid Cycling Synchrotron) of the J-PARC has already started 1 MW routine operation by minimizing the beam loss. However, to ensure always net 1 MW beam power at the present MLF targets, RCS has to achieve more than 1 MW beam power in a near future. This is needed to overcome the RCS duty to the MLF reduced by gradually getting faster operation cycle of the Main Ring. Achieving this goal strongly relies on the significant beam loss mitigation which increase nonlinearly due to the space charge effect (Coulomb repulsion) of beam particles being same charge. Recently we have performed systematic beam studies and detail numeral beam simulations by optimizing many parameters of the injection beam as well as RCS parameters in both transverse and longitudinal directions. We achieved a considerable beam loss mitigation at 1.5 MW resulting in a beam loss rate even lower than present operation at 1 MW. The beam loss occurs only at lower beam energies well controlling and perfectly localizing at the collimator section. The beam loss power is estimated to be only 70 W, sufficiently smaller than the collimator capacity of 4 kW, demonstrating RCS capability to operate at 1.5 MW with minimum machine activation.