Ripple‐free liquid‐nitrogen level controller for long‐term operation

This article describes the design features, construction, and operation of a liquid‐nitrogen level controller which can be used continuously over a period of several weeks. Liquid level is sensed by pairs of thermistors mounted on a dip stick. Replenishing of liquid nitrogen is achieved as a result of self‐pressurization of a tank containing the cryogen. The transfer system ensures a ripple‐free liquid surface during the replenishing operation. This level controller has been a part of a cryostat for diffusion measurements in liquefied inert gases.