Operation of a Continuous Flow Liquid Helium Magnetic Microscopy Cryostat as a Closed Cycle System

TL;DR

This paper demonstrates a stable, closed-cycle liquid helium cryostat system for magnetic microscopy, achieving low vibrations and efficient cooling with a custom gas handling system.

Contribution

It introduces a novel modular cryocooling setup and detailed system analysis for continuous flow liquid helium magnetic cryostats.

Findings

Base temperature reached within 10 hours

Magnetic field ramping at 0.5 T/min

Vibration amplitudes around 5 nm

Abstract

We demonstrate successful operation of a continuous flow liquid helium magnetic cryostat (Oxford Instruments, Microstat MO) in closed cycle operation using a modular cryocooling system (ColdEdge Technologies, Stinger). For the system operation, we have developed a custom gas handling manifold and we show that despite the lower cooling power of the cryocooler with respect to the nominal cryostat cooling power requirements, the magnetic cryostat can be operated in a stable manner. We provide the design of the gas handling manifold, and a detailed analysis of the system performance in terms of cooling times, magnetic field ramping rates and vibrations at the sample. Base temperature can be reached within 10 hours while the superconducting magnet can be energized at a ramping rate of 0.5 T/min. Vibrations are measured interferometrically and show amplitudes with a root mean square on the order of 5 nm permitting the use of the system for sensitive magnetic microscopy experiments.