Montana Instruments awarded patent on low drift design
Symmetric bellows to reduce effects of thermal contraction
The Montana Instruments Cryostation has seen quick acceptance as the standard for high performance applications requiring closed-cycle optical cryostats. Part of their success is based on their innovative design for low drift and low vibration.A few of the classic challenges for an optical cryostat system are thermal contraction of components that change from room temperature to low temperature. As well as the movement of thermal components due to contraction of flexible elements such as bellows under vacuum, and force transmission across vibration isolating components.
The displacement of the sample due to thermal contraction of components from room temperature to low temperature, can be minimized by a cryogenic sample support, which uses alternating nested materials. Due to equally balanced thermal contraction the total displacement of the sample stage is cancelled to near zero.
To address the challenges of moving components due to vacuum, the Cryostation product uses symmetric bellows. This creates a net zero force on the sample chamber inside the flexible bellows, see figure 1. In the center is the tall cryo-cooler assembly, with a horizontal copper rod reaching into the sample chamber on the right. Two bellows are placed symmetrically at the base of the cooler support in the direction of the cold finger axis. If the system had a single bellows on the right, the drop in pressure to a vacuum would compress the bellows and exaggerate the motion of the cold finger laterally. This not only would cause a displacement of thermal components, but would also require an equal and opposite force from springs or dampers, which only add to the force transmission across the bellows and increases vibration of the sample chamber. With two bellows in place, the pressure differential is balanced such that there is no lateral force on the sample chamber, no displacement of thermal components even when vacuum levels change, and minimal force transmission across thin bellows.
The patent claims are detailed more in US patent 8746008 B1, “Low vibration cryo-cooled system for low temperature microscopy and spectroscopy applications.”
This is one of several innovative design elements included in Montana Instruments products to drastically reduce drift. The benefit to the user is that they can setup their experiment at room temperature, and once the system has reached cryogenic temperatures and vacuum, their sample has remained solidly in the field of view of their optical experiment. Contact us to find out how these products solve the tough challenges of stability and vibration for researchers.
