Publications

Displaying 1 - 8 of 8

Dynamic acoustic optimization of pulse tube refrigerators for rapid cooldown

April 23, 2024

Author(s)

Ryan Snodgrass, Vincent Kotsubo, Scott Backhaus, Joel Ullom

Pulse tube refrigerators are a critical enabling technology for many disciplines that require low temperatures. These refrigerators dominate the total power consumption of most modern cryostats, including those that reach millikelvin temperatures using

Intermediate cooling from pulse tube refrigerator regenerators operating in the real-fluid regime

April 20, 2023

Author(s)

Ryan Snodgrass, Gregory Swift, Joel Ullom, Scott Backhaus

Under some circumstances, pulse tube refrigerator regenerators operating in the real-fluid regime can absorb a large amount of heat between their warm and cold ends without a decrease to cooling power at their cold heat exchanger. Experiments and analysis

Performance of a Miniature, Closed-Cycle Dilution Refrigerator at Tilt Angles between 0 and 30 Degrees

December 1, 2022

Author(s)

Ryan Snodgrass, Joel Ullom, Scott Backhaus

Closed-cycle dilution refrigerators (DRs) recirculate 3He from the still via condensation on a cooled surface; condensate from the cooled surface drips down toward the mixing chamber via gravity. Compact versions of these DRs are being considered for

Role of Non-Temperature-Gradient Power Flow Terms in Low-Temperature Regenerators

December 1, 2022

Author(s)

Ryan Snodgrass, Joel Ullom, Scott Backhaus

The total power flow through cryocooler regenerators is key to their performance because it reduces the cooling available at the cold heat exchanger. At temperatures near 4 K, the real-fluid properties of helium and the finite-heat-capacity of regenerator

Optimal absorption of distributed and conductive heat loads with cryocooler regenerators

July 13, 2022

Author(s)

Ryan Snodgrass, Joel Ullom, Scott Backhaus

The second-stage regenerators of pulse tube refrigerators are routinely used to intercept heat in cryogenic systems; however, optimal methods for heat sinking to the regenerator have not been studied in detail. We investigated intermediate cooling methods

Direct cooling from the regenerators of Gifford-McMahon cryocoolers, with comparison to pulse tube refrigerators

May 5, 2022

Author(s)

Ryan Snodgrass, Joel Ullom

The second-stage regenerators of pulse tube refrigerators (PTRs) are routinely used to intercept heat loads without disturbing cooling at their base temperatures, often near 4 K. Gifford-McMahon cryocoolers (GMCs) have not yet demonstrated a similar

A Temperature Instability in 4 K Cryocooler Regenerators Caused by Real Fluid Properties

April 1, 2021

Author(s)

Ryan Snodgrass, Vincent Y. Kotsubo, Joel Ullom, Scott Backhaus

We report temperature profile measurements from a densely instrumented, commercial pulse tube refrigerator. Azimuthal temperature differences of 15 K were measured across its 3 cm diameter regenerator which was operated at cold end temperatures below 10 K

Leveraging Real Fluid Effects as a Tool for Power Flow Measurements in 4 K Cryocooler Regenerators

April 1, 2021

Author(s)

Ryan Snodgrass, Vincent Y. Kotsubo, Joel Ullom, Scott Backhaus

The real fluid properties of helium have a major impact on the thermodynamics of pulse tube and Gifford-McMahon cryocoolers operating below about 30 K. For example, real fluid properties cause the temperature profile in low-temperature regenerator to be

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