Embedded Active Vibration Cancellation of a Piston-Driven Cryocooler for Nuclear Spectroscopy Applications

Abstract

High Purity Germanium (HPGe) Detectors are the gold-standard sensor for nuclear spectroscopy applications. In order to make spectroscopic measurements, the detectors must be maintained at cryogenic temperatures. Cryogenic temperatures can be achieved using either liquid nitrogen or piston driven cryocoolers. Because of the bulky and transient nature of liquid nitrogen, the piston driven cryocoolers are preferable for remote, long term, or portable detector applications. These cryocoolers are a promising alternative due to the fact they only require a power source and heat dissipation for continuous operation. A major drawback however is that microphonic noise induced by the vibration of the piston reduces the resolution of the spectroscopic measurements. Passive damping techniques have been applied to this problem, An active damping control system is under development to significantly reduce the vibrations of the cryocooler by adapting to changes in boundary conditions and mass loading through time. Mitigating these vibrations will increase the resolution of portable HPGe detectors and facilitate the identification of nuclear materials.