The award responds to US Department of Energy SBIR Topics FY 2022
Phase I, Release 1, Version 4, July 23, 2021, DE-FOA-0002554. The grant
is aimed a solution to Topic 34, b. Design and Operation of Radio
Frequency Beam Acceleration Systems, 3) devices and methods for
accurate in-situ measurement of SRF cavity Q0s.

The invention is a gas flowmeter used as a power meter (Watt meter). It
is used by operators of superconducting radio-frequency (SRF)
acceleration cavities in particle accelerators. By measuring the
evaporation of helium gas from 2 to 5 K liquid baths, it measures the
heat generated by individual SRF cavities at the Watt level. Increased
heat dissipation is an indication of a dysfunctional SRF cavity. This
Flowmeter satisfies a more than 30 year need to measure this parameter
in-situ in an SRF accelerator.
 
The instrument head is installed in a pipe that conveys cryogenic gas at
temperatures ranging from 2 K (-456°F) to 5 K (-451°F) at 1/30 atm to 1
atm. Its primary function is to measure gas flow. The head consists of a
superconducting material positioned adjacent to an electric resistance
heater. During operation, power to the heater is increased until the
superconductor transitions to a normal conducting state - a
phenomenon known as "quench" - while electric current flows through it.
 
The amount of heater power required to induce quench is directly
related to the cooling from the gas flow rate passing over the instrument
head. This relationship allows the device to serve as a precise flow
meter. The system includes heater current, superconductor current and
voltage detection elements, as well as a temperature sensor. These
components are connected to a remote electronics chassis equipped
with current sources and voltage detection circuitry.
 
Control and readout of the system components are managed by a
LabJack Analog-to-Digital and Digital-to-Analog (AtoD/DtoA) unit that
interfaces with a digital control system (DCS). Future versions of the

meter could be adapted to work with other cryogenic gases, such as
hydrogen, nitrogen, or possibly natural gas, by using different types of
superconducting materials.