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LEAF is a heavy ion experimental facility with low energy, high intensity and high charge state. It belongs to the strong current linear accelerator, and its maximum beam power can reach 10 kW. High-power beams can pose a great risk of damaging field devices in continuous beam mode due to high-power beam bombardment. In order to ensure the safe operation of field devices and key equipment, an interlocking control system for LEAF is designed by using the control board of FPGA and PLC controller. The FPGA-based interlock system mainly implements the real-time monitoring of the arc fault signals from the RFQ cavity, a few fast fault signals from LLRF system and beam diagnostic system. When a valid fault signal is detected, the system will send its protection instruction to the chopper power supply to cut off the beam rapidly. The PLC-based interlock system mainly handles the fault state detection and safety operation of field devices with a slower protective action, and the action time is in a millisecond range. The protective action time of the FPGA interlock system has been achieved within 10 µs. This system adopts two sets of control and protection logic, which are implemented in the control board of FPGA and the PLC controller. It can ensure the safety of the core devices through the double-redundant beam-cutting actions if the key equipment fails or the beam parameters are abnormal. The complete system has a simple structure. The redundant technique is used in the design of the control protection logic and data transmission path. This provides a reliable safety measure for beam commissioning and physical experiment of the LEAF facility.

Additional file 1: Table S1. The effects of different hydrolyzate on the germination of rice and wheat seeds. Fig. S1. Construction of pHBM905M-ChiA recombinant plasmids. AOX1: d1 + 2 × 201 AOX1 promoter; α-factor: MF4I-SS signal peptide; TT: AOX1 terminator. Fig. S2. Construction of multi-copy the target gene expression cassettes based on the pHBM905BDM vector. (A) Schematic diagram of constructing recombinant plasmids containing two copy ChiA expression cassettes. (B) SalI digestion of multi-copy expression plasmids. lane M: λ-EcoT14 digestion marker; lane 1-5: The plasmids pHBM905M-ChiA-1copy, -2copy, -3copy, -4copy, and -6copy by SalI digestion, respectively. Fig. S3. Construction of pGAPZB-HAC1/ERV29/SEC16/COG5/TRM1 recombinant plasmids. PGAP: GAP promoter; AOX1 TT: AOX1 terminator; PTEF1: TEF1 promoter; PEM7: EM7 promoter; CYC1TT: CYC1 terminator. Fig. S4. Relationship between copy number and enzyme activity. The data used is the highest enzyme activity in per copy number.

LEAF is a complicated and integrated facility, which includes several different subsystems. In order to realize the remote control of field equipment and meet the requirements of the beam commissioning, a LEAF control system has been designed. The developed control system includes the following sub-systems: timing systems, data archiving systems, personnel safety systems, and machine protection systems. The control system for LEAF is developed using the EPICS software toolset and the distributed control architecture. This is designed in a three-layer structure. At the equipment layer, the control of the low-level equipment is mainly done by various industrial controllers, including programmable logic controllers, controllers for serial devices, and motion controllers based on EtherCAT fieldbus. At the middle layer, the Ethernet switches are used to implement a Gigabit local area network. At the operation layer, high-level application software has been developed for the beam commissioning and the operation of the accelerator. The designed system can realize remote monitoring and control of field devices, provide synchronous timing and machine protection for key equipment, and automatically archive historical data for on-site running equipment. The complete system has a clear structure and stable operation and has been successfully applied to beam commissioning and operation of the LEAF facility.