Low level RF system for Jefferson Lab Cryomodule Test Facility

The Jefferson Lab Cryomodule Test Facility (CMTF) has been upgraded to test and commission SNS and CEBAF Energy Upgrade cryomodules. Part of the upgrade was to modernize the superconducting cavity instrumentation and control. We have designed a VXI based RF control system exclusively for the production testing of superconducting cavities. The RF system can be configured to work either in phase locked loop (PLL) or self excited loop (SEL) mode. It can be used to drive either SNS 805 MHz or CEBAF Energy Upgrade 1497 MHz superconducting cavities and can be operated in pulsed or continuous wave (CW) mode. The base design consists of RF-analog and digital sections. The RF-analog section includes a voltage control oscillator (VCO), phase detector, I&Q modulator and "low phase shift" limiter. The digital section controls the analog section and includes ADC, FPGA, and DAC. We will discuss the design of the RF system and how it relates to the support of cavity testing.