FLASH and the European XFEL are SASE-FEL user facilities. at which superconducting TESLA cavities are operated in a pulsed mode to accelerate long bunch-trains. Several cavities are powered by one klystron. While the low-level rf system is able to stabilize the vector sum of the accelerating gradient of one rf station sufficiently. https://homehardware4ues.shop/product-category/mirror-mastics/