Control Systems Using Programmable Logic Controller and Analog Signal Filter Module for Pulse Modulators at PAL-XFEL

The pulse modulator control system of PAL-XFEL is composed of a programmable logic controller (PLC) and an analog signal filter module (ASFM). The interlocks can be roughly categorized into ‘static’ and ‘dynamic’ types. To speed up the dynamic interlocks, a relay switch was removed to modify the internal interface of the PLC and replaced with a photocoupler component; after debugging the program, the response time was < 2 ms after interlock events occurred. The ASFM is a noise-filtering module that converts noisy analog signals to clean signals. Electromagnetic (EM) noise is caused by thyratron switching. This noise causes signal distortion and may lead to failures of control device when it is mixed with modulator output signals. Broadband electromagnetic noise continues to degrade the stability of control devices. This paper describes the results of modifications of the internal circuit of the PLC and development of a noise-filtering module.