Control Mechanism for Attenuation of Thermal Energy Pulses Using Cold Circulators in the Cryogenic Distribution System of Fusion Devices in Tokamak Configuration.

Operation and control of superconducting (SC) magnets in the fusion devices having tokamak configuration opens up the domain of varying peak thermal energy environment as a function of time, commensurate with the plasma pulses. The varied thermal energy environment, thus propagated to upstream of the cooling system, is responsible for the system level instability of the overall cryogenic system. The cryogenic distribution system, the regime of first impact point, therefore, has to be tuned so as to stay at the nearly stable zone of operation. The configuration of the cryogenic distribution system, considered in the present study, involves a liquid helium (LHe) bath as a thermal buffer, LHe submerged heat exchangers and cold circulator apart from the valves for implementations of the precise controls. The cold circulator supplies the forced flow supercritical helium, used for the cooling of SC magnets. The transients of the thermal energy pulses can be attenuated in the cryogenic distribution system by various methodologies. One of the adopted methodologies in the present study is with the precise speed control of the cold circulators. The adopted methodology is applied to various configurations of arrangements of internal components in the distribution system for obtaining system responses with superior attenuation of energy pulses. The process simulation approach, assumptions, considered inputs and constraints, process modeling with different configuration as well as results to accomplish the control scheme for the attenuation of the thermal energy pulses are described. [ABSTRACT FROM AUTHOR]