Superconducting Gas Flow Meter for Cryogenic Low-Pressure Helium
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Solution Overview
Problem
Accurate measurement of mass flow of gaseous helium at cryogenic temperatures and low pressures from vacuum bottles containing superconducting radio frequency (SRF) cavities is critical for determining power boiling and quality factor (Q0) of superconducting cavities, with existing methods lacking effective solutions.
Innovation Solution
A gas flow meter using a superconducting material adjacent to an electric resistance heater, calibrated as a power meter, measures gas flow by detecting the power required to quench the superconductor, with remote electronics for data processing and calibration, suitable for helium and other cryogenic gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional flow meters are used to measure gas flow at cryogenic temperatures and low pressures, then the measurement system is simple and familiar, but the measurement precision and reliability are insufficient for accurate mass flow determination
Solution Approach 1:
The patent replaces conventional mechanical flow meter components with a superconducting-based measurement system. The core mechanism uses a superconducting material that transitions to normal conducting state when heated by an electric resistance heater, creating a detectable voltage signal. This substitution of mechanical sensing with superconducting quantum effects enables precise mass flow measurement at cryogenic temperatures where conventional mechanical sensors fail.
Solution Approach 2:
The invention exploits the dramatic change in electrical resistance parameter of superconducting material when transitioning from superconducting state to normal conducting state. By controlling the heater power to induce this phase transition, the system creates a measurable voltage signal that correlates directly with gas mass flow rate. This parameter change approach provides high sensitivity and precision for flow measurement in cryogenic environments.
2Measurement precision
If a superconducting material with electric resistance heater is used to measure gas flow, then measurement precision is improved, but device complexity and electronics requirements increase
Solution Approach 1:
The patent divides the measurement system into distinct functional modules: the instrument head containing the superconducting material and heater, the electronics chassis with power supply and detection circuits, and the data processing system. This segmentation allows each component to be optimized independently and facilitates remote operation where the electronics can be housed separately from the cryogenic environment, reducing thermal management complexity.
Solution Approach 2:
The superconducting material acts as an intermediary between the thermal field (heater) and the electrical field (voltage detection). It converts thermal energy from the heater into electrical signals that can be measured and processed. This intermediary function enables precise measurement while isolating the complex electronics from the extreme cryogenic environment, simplifying overall system integration.
3Ease of operation
If remote electronics chassis with AtoD DtoA units are used for control and readout, then ease of operation and data processing are improved, but device complexity increases
Solution Approach 1:
The system implements self-service through automated feedback control where the detection circuits monitor the voltage across the superconducting material and automatically adjust the heater power to maintain the superconductor at the threshold of transitioning to normal conducting state. This self-regulating mechanism eliminates the need for manual calibration and adjustment, simplifying operation while the complexity is managed through standardized electronic control circuits.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables precise determination of gas flow and heat dissipation in SRF cavities, providing early warning of heat load increases and maintaining cavity health by measuring power dissipation directly, overcoming limitations of conventional flow meters.
Implementation Method 1
The instrument head consists of a superconducting material adjacent to an electric resistance heater. The power in the heater is increased until the superconductor exhibits 'normal' conducting voltage (known as 'quench') while an electric current passes through it.
Implementation Method 2
The power in the heater is increased until the superconductor exhibits 'normal' conducting voltage (known as 'quench') while an electric current passes through it. The heater power (and thus the heater current) required to drive the superconductor to quench is a function of the gas flow passing the instrument head.
Data Source
AI summary
A gas flow meter for all pressures, including fractions of an atmosphere, and for cryogenic temperature systems such as cryomodules for cooling superconducting radio frequency cavities in a particle accelerator. An accurate measurement is critical to determine the quality factor (Q0) of the superconducting cavities. The instrument head, including a superconducting material adjacent to an electric resistance heater, measures gas flow. The power in the heater is increased until the superconductor exhibits ‘normal’ conducting voltage (quench) while an electric current passes through it. The heater power required to drive the superconductor to quench is a function of the gas flow passing the instrument head. Digital control and readout of all critical elements are supplied by a digital control system interfacing to an analogue to digital, digital to analogue (AtoD DtoA) module.