Cryogenic Helium Flow Sensor System

K. Jordan, G. Biallas
Jefferson Science Associates,
United States

Keywords: helium, mass flow, cryogenics


Superconducting Radio Frequency (SRF) Cavities, key components in linear accelerators used for basic research in energy and matter, require measurement of system health in real-time in order to maintain proper operations. Conventional monitoring instruments do not support the typically extreme operating temperatures and pressures of these systems, and operators seldom use existing methods due to cumbersome and lengthy procedures which incur impractical operational downtimes, particularly for accelerators with large numbers of cryomodules. A DOE Small Business Innovative Research Grant (SBIR) Phase I showed that the Helium Flow Monitor System, developed jointly by Jefferson Lab and Hyperboloid LLC, provides an effective and efficient means of monitoring SRF cavity health parameters while simplifying diagnostic procedures and minimizing system downtimes. The Helium Flow Monitor System finds the extra heat generated by unhealthy cavities by measuring increased evaporation of helium from the 2 K, “wispy” pressure of ~0.03 atm, Super-fluid cooling bath surrounding the cavities. With push button ease, accelerator operators can schedule pinpointing changes in heat dissipation in the 8-cavity accelerating units (Cryomodule) during normal accelerated beam delivery. Operators can then isolate a problematic cavity, again using the Helium Flow Monitor System during beam-down-time, turning the cavity’s acceleration down and turning up healthy cavities and maintaining the rated beam energy of the accelerator. This turn-down reduces excess field emission from problematic cavities that causes radiation damage to other components and reduces excessive heat load on the Cryogenic Refrigerator Plant where one watt of dissipated power removed from 2 K requires >1000 W of refrigerator power. An SBIR Phase II will support the transition from prototype to commercial product, investigating changes necessary to adapt the Flow Monitor System to other cryogenic applications where instrumentation is typically scarce. Potential changes include thermal characteristics or switching to high-temperature superconductors. Applications include the use of helium at slightly higher temperatures and much greater pressures, hydrogen near its boiling point of 20 K, and liquid nitrogen and liquified natural gas. The emerging market for clean energy infrastructure suggests substantial demand for cryogenic control systems and technologies. This talk will discuss principles, benefits, and applications of the Flow Monitoring System.