300 mK He-3 Cryostat for UHV STM

April 2008

The Janis Research next generation model HE-3-BLSUHV-STM cryostat is a bottom loading He-3 system for Scanning Tunneling Microscopy (STM) with sample in UHV environment. The system incorporates a number of design enhancements for improved performance and ease of use as compared with the previous generation.

The cryostat bottom flange is designed to mate with a user supplied UHV sample preparation chamber; the user can then lower the He-3 insert and STM into the UHV chamber for sample change via an integrated linear motion manipulator. Cooled spring loaded radiation shutters are installed on the cryostat at several critical flange locations. The shutters are pushed open by the He-3 insert during sample exchange, and then close automatically when the He-3 insert is returned to the experimental position.

A sophisticated "helium-only" dewar (no LN2) with dual helium vapor cooled radiation shields was developed specifically for this system in order to completely eliminate the vibrations associated with boiling liquid nitrogen; no LN2 is used during operation.

An independent "isolation" helium reservoir separates the UHV sample space from the dewar vacuum space. This independent reservoir enables the UHV space to be reduced in diameter and volume, which in turn improves the pumpdown time and ultimate pressure of the sample region. In addition, this design eliminates the need to bake out the entire cryostat; the UHV space can be baked without affecting the magnet.

A self-contained UHV compatible He-3 insert is included and integrated with this system. Multiple measurements are made during fabrication and testing in order to guarantee the precise alignment of this insert when changing samples and when operating normally. A high field superconducting magnet is included.

Performance specifications:

The system includes:

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HE-BLSUHV-STM UHV Compatible Cooled Shutters 

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HE-3-BLSUHV-STM System Test

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