Countermeasures against noise of inverter-controlled multi-stage root pumps in J-PARC LINAC beam dump

Kobayashi, Fuminori; Kamiya, Junichiro   ; Moriya, Katsuhiro  ; Miyao, Tomoaki*; Kotoku, Hirofumi*; Takano, Kazuhiro*

The L3BT beamline at J-PARC LINAC has beam dumps connected via vacuum partition windows to separate the ultra-high vacuum beamline from the low vacuum beam dumps. Roots pumps are used to evacuate each beam dump. The roots pump controllers have been installed away from the pump in the accelerator tunnel to avoid radiation damages. The special controllers, which have no inverter circuit inside, have been used to reduce the electrical noise on the beam loss monitors nearby. However, in this case, several problems have occurred such as the instability of the pumping performance. To solve such problems, the roots pump controller with the inverter circuit must be used after reducing the electrical noise. In this report, some countermeasures to reduce the electrical noise from the inverters were investigated. The noise reduction circuit was successfully optimized to the level where the beam loss monitors work unaffected.