Thermo-acoustical oscillations in cryogenic

systemsJoel Fuerst

Magnetic Devices Group/Accelerator Systems Division/Advanced Photon Source/ANL

PIP-II meetingFermilab

18 April 2017

Thermoacoustics: the interaction between temperature, density, and pressure variations of acoustic waves- Wikipedia

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Gupta & Rabehl, “Design Guidelines for Avoiding Thermo-Acoustic Oscillations in Helium Piping Systems,” FERMILAB-PUB-14-292-TD

“Thermoacoustic Oscillations” article courtesy Meyer Tool & Mfg., Inc.

TADOPTR

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TADOPTR (ThermoAcoustic Driver/Orifice Pulse Tube Refrigerator)- R. Radebaugh, NIST

www.lanl.gov/thermoacoustics

Liquid Helium Level Measurement

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From the Oxford Instruments “Cryogenic Spares & Accessories” website:

“This simple, yet effective dipstick provides accurate indication of liquid helium depth. Stainless steel construction with a fine rubber diaphragm, held in place by an ‘O’ ring over the cup-shaped upper end of the dipstick.

The thermal gradient created in the tube leads to thermal oscillations, which are felt by the vibration of the membrane. The frequency of the oscillation with the lower end in liquid helium is noticeably lower in comparison to that when in cold gas, allowing the liquid level to be easily determined (in most cases).

The dipstick should not be left in the cryostat when it is not in use because it introduces a large amount of heat.”

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“Thermally Driven Acoustic Oscillations, Part II: Stability Limit for Helium”Nikolaus Rott, ETH Zurich, J Appl Math Phys (ZAMP) Vol. 24, 1973.

• discontinuous temperature jump

• Parameters:• Temperature ratio α = Twarm/Tcold• Length ratio ξ = (L-lh)/lh• Yc relates radius and Stokes BL thickness

• Lower asymptote: choose α, calculate Ycusing eq. 18

• Upper asymptote: choose Yc, calculate αusing eq. 28

• Curve: calculate Yc and α using eqs. 9 & 12

BR refrigerator, FNAL1990

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Gu & Timmerhaus, UC-Boulder

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“Thermal Acoustic Oscillations in Cryogenic Systems,” PhD Thesis 1993 UC-Boulder under Klaus Timmerhaus

Subsequent work (see Advances, Vols. 37 p.265*, 39 p.1733, 41 p.163…*CEC student meritorious paper award

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Mitigation

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• Reduce driving force• Change temperature ratio• Change length ratio

• Increase viscous damping(Reduce tube radius)

• Increase inertial damping• Increase tube radius• Change temperature gradient

Christie & Hartwig, NASA Glenn Research Center, “Thermal Acoustic Oscillation: Causes, Detection Analysis, and Prevention,” Thermal & Fluids Analysis Workshop (TFAWS), 2014.

• Block line• Check valve• Filter

• Connect fill with vent• Resonator/ballast volume

• Tube Inserts

Gupta & Rabehl, “Design Guidelines for Avoiding Thermo-Acoustic Oscillations in Helium Piping Systems,” FERMILAB-PUB-14-292-TD

Expander pressure taps: ballast volumes

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Dewar neck insert:warm end vent

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