Date published: Jan. 26, 2026

Summary:

A coaxial cable that detects local temperature changes by sensing variations in its electrical impedance. This enables precise, distributed temperature monitoring in cryogenic environments.

Applications: 

• Quantum computing thermal management
• High-Temperature Superconducting (HTS) cable quench detection for fusion energy, medical imaging (NMR/MRI) machinery

Advantages/Benefits: 

• High-resolution cryogenic temperature sensing
• Precise hot spot and power dissipation detection
• Flexible, robust, and strain-insensitive
• Cost-effective compared to fiber-optic methods
• Distributed calorimetric measurement capability

Background: 

Precise temperature monitoring is critical for optimizing performance and preventing failures in cryogenic and superconducting systems, particularly in extreme low-temperature environments. There is a significant need for sensitive, localized thermal detection. Current temperature sensing methods, like fiber-optic sensors, often lack adequate sensitivity and localization accuracy at deep cryogenic temperatures. They can also be costly and susceptible to mechanical strain, limiting their effectiveness. Ultrasonic sensors may be adversely affected by bending, and can be problematic at long lengths.

Technology Overview: 

Scientists at Berkeley Lab have developed a distributed cryogenic temperature sensing system that combines the best features of fiber-optic and ultrasonic sensing. The invention integrates a novel material as the dielectric in a radio-frequency transmission line or coaxial cable. Local temperature changes alter the material’s permittivity and loss tangent, affecting the line’s characteristic impedance. These impedance variations generate reflectometry signals, detectable by a vector network analyzer, which are then transformed into time-domain profiles to localize temperature fluctuations along the cable. 

In addition to temperature mapping, distributed calorimetry can be performed by sending DC current down the cable and measuring the thermal response.

This technology addresses a critical gap in high-sensitivity temperature monitoring at deep cryogenic temperatures, where existing methods like fiber-optic sensors lack adequate performance. It offers a flexible, strain-insensitive, and lower-cost alternative to fiber-optic methods, providing superior sensitivity. Local temperature variations as low as 40 mK at 77 K background and power dissipation down to 20 mW at 7.5 K background have been detected successfully using this technique. 

Development Stage: Proof of concept

Inventor:

Maxim Martchevskii

Opportunities: Available for licensing and / or collaborative research