Construction of J-PARC LINAC-RCS beam transport line vacuum system

Abstract

In J-PARC LINAC, the vacuum system is in place to maintain an ultra-high vacuum in the beam transport line (LINAC to 3GeV RCS beam transportation line: L3BT) between the LINAC to the 3-GeV synchrotron. The vacuum system is installed in the LINAC and L3BT buildings and consists of vacuum pumps, vacuum gauges, beam line gate valves (BLGVs), and other vacuum. Vacuum pumps and vacuum gauges are controlled by a Programmable Logic Controller (PLC) which provides the logic to safely transition from atmospheric to ultra-high vacuum conditions. On the other hand, the BLGV is controlled by the BLGV relay unit and VME controller using the Machine Protection System (MPS), which remotely opens and closes the BLGV and forcibly closes the BLGV when the beamline pressure exceeds a threshold value according to an interlock (ILK) logic. In the existing vacuum system, the vacuum equipments in each area between BLGV is independently controlled, and the vacuum system does not monitor the information on the equipments or vacuum pressure between nearby areas. This means that vacuum equipment can be operated regardless of the condition of adjacent areas, resulting in sudden deterioration of the vacuum in high vacuum areas, or injecting air into vacuum pumps that are in operation. In addition, when a vacuum deterioration occurs in the beam transport line, the vacuum deterioration ILK signal is transmitted to the BLGV relay unit via the MPS transmission signal, which causes the BLGVs to be forcibly closed. Because the ILK signal transmission range extends to all BLGVs in the L3BT, however, BLGVs in areas unaffected by vacuum deterioration are also forced to close. This could cause problems such as unnecessary open/close operations leading to more frequent maintenance cycles of the BLGVs. In addition, Since the BLGVs are operated using the MPS signal path, the open/close signal in the vacuum deteriorating ILK signal can only be sent uniformly to all BLGVs, and each individual control is not possible. Furthermore, maintenance of the vacuum control system also requires work involving the MPS signal path, making it difficult to maintain the vacuum control system alone and making the work complicated. To solve these problems, it is necessary to improve maintainability by separating the signal paths and automatically controlling BLGV separately. Therefore, the vacuum control system was modified and constructed with the aim of realizing a control system that takes into account the safety and efficient maintenance and operation of the L3BT vacuum system. This report summarizes the development and use of the L3BT vacuum system control system.