| The Canadian Light Source (CLS), a particle accelerator experimental facility located in Saskatoon, Canada, uses a high energy electron beam to create synchrotron light, which is millions of times brighter than sunlight. A superconducting radio frequency (SRF) cavity, which is kept at 4.5 K by a liquid helium (LHe) bath, is used to maintain the momentum of the electron beam during operation. CLS engineers have questions about the operation and optimization of the LHe cryogenic system that provides this LHe bath, and a computer model of this system has been proposed.;The model is validated against data obtained at the CLS, and is then used to answer several questions posed by CLS staff. The void fraction of gas exiting the LHe supply line is found to be around 20%. Oscillations in LHe line boundary conditions are found to have little dynamic effect at the CLS due to small magnitudes, but it is demonstrated that steady-state or quasi-steady models for boiling two-phase flows are generally insufficient to describe the corresponding flow dynamics. It is found that increasing the pressure controller gains can improve performance. Also, a proposed new supply and return line configuration is examined, and it is found that these proposed line changes can not only improve control issues but can also increase the maximum LHe supply rate for the system.;In this work, a computer model of part of the LHe cryogenic system including the SRF cryostat and its supply and return lines, is constructed. A modular approach is taken, combining separate models of the LHe supply line, gaseous helium (GHe) return system, and the cryostat. The LHe supply line model is designed to accommodate two-phase flows, as some LHe boils before reaching the cryostat. Conservation of mass, momentum and energy are used along with modified equations of state in an iterative method to solve pipe flows. The cryostat model is based on an established boiling vessel model. Virtual PID controllers are implemented on the combined model to drive the level and pressure control valves in realistic fashion. |
