Reactive thermo elastic cryostat

摘要

A cryostat (12) with an actuator (40) which reacts to sensed temperature changes via externally controlled thermal heating generated therein. The actuator (40) is constructed with material having a high coefficient of thermal expansion. A flexible heating element (44) is embedded in the actuator material. A temperature sensor (62) provides a signal to cryostat control electronics. Responding to the temperature signal, the control circuitry (60) regulates current to the heating element (44) in the actuator (40). As the actuator temperature increases due to the heat generated by the heating element (44), it expands and moves open an attached needle (50) relative to an orifice (30), thereby increasing cryogen flow and regulating cooling. When the desired cold temperature is attained, current and heating are stopped. Flowing cryogen cools the actuator which shortens the actuator and pulls the attached needle into the orifice to regulate flow. The heating and cooling cycle repeats itself when the sensed temperature rises to an unacceptable value. The heating element (44) provides the ability to control actuator heating. It provides greater sensitivity and travel by inducing actuator temperature change rates and magnitude significantly larger than cryogen changes in temperature, which limit passive actuator designs.