Cryogen-free one hundred microkelvin refrigerator

Area of Science:

• Low-temperature physics
• Condensed matter physics
• Cryogenics

Background:

• Achieving and maintaining ultra-low temperatures is crucial for fundamental physics research.
• Nuclear demagnetization is a powerful technique for reaching millikelvin and microkelvin regimes.
• Cryogen-free systems offer advantages in terms of operational simplicity and cost.

Purpose of the Study:

• To demonstrate a cryogen-free system capable of reaching sub-100 microkelvin temperatures.
• To investigate the stability and duration of ultra-low temperatures in such a system.
• To enable experiments requiring stable ultra-low magnetic fields.

Main Methods:

• Utilized a customized cryogen-free dilution refrigerator.
• Employed a copper-nuclear demagnetization stage.
• Measured electron temperature using pulsed platinum nuclear magnetic resonance thermometry.
• Integrated a coaxial room-temperature-bore cryogen-free magnet for independent field control.

Main Results:

• Achieved and maintained a conduction electron temperature below 100 microkelvin (µK).
• Sustained this ultra-low temperature for over 10 hours.
• Demonstrated independent control of demagnetization (up to 9 T) and research (up to 12 T) magnetic fields.

Conclusions:

• The developed cryogen-free system reliably achieves and sustains ultra-low temperatures below 100 µK.
• This technology opens new possibilities for experiments in quantum physics and materials science at microkelvin temperatures.
• The independent magnetic field control enhances experimental flexibility in ultra-low temperature regimes.