Pulse Tube Cryocooler for Rapid Cooldown of A Superconducting Magnet

Published

June 9, 2008

Author(s)

Michael A. Lewis, Ryan P. Taylor, Peter E. Bradley, Isaac Garaway, Ray Radebaugh

Abstract

A single-stage pulse tube cryocooler was designed to provide rapid cooldown of a high temperature superconducting (HTS) magnet that is part of a gyrotron required for the generation of a high-power mm-wave (95 GHz) beams. These beams are used in the nonlethal weapons systems know as the Active Denial System. the optimized cryocooler is designed to provide 50 W of net refrigeration power at 50 K and is driven by a pressure oscillator that can produce up to 2.8 kW of acoustic power at 60 Hz. The rapid cooling technique makes use of a resonant phenomenon in the inertance tube and reservoir system to decrease the flow impedance and thereby increase the acoustic power through the system when the cold end is near room temperature. We use three different reservoir volumes at the end of the inertance tube with ball valves to select the optimum reservoir for any particular cold-end temperature. With the optimum reservoir connected, the cooler impedance at any temperature is better matched to that of the pressure oscillator, which allows for a greater input power and faster cooldown without hitting the end stops in the pressure oscillator. This paper discusses the construction and performance of the cryocooler. Initial measurements showed the presence of serious flow nonuniformities inside the pulse tube that led to poor performance. The steps taken to eliminate the nonuniformities and their effect on the cooler performance are discussed. The cooling rates for different reservoir volumes with a 20 kg copper mass attached, which simulates a HTS magnet, are compared and discussed.

Proceedings Title

Pulse Tube Cryocooler for Rapid Cooldown of a Superconducting Magnet

Conference Dates

June 9-12, 2008

Conference Location

Long Beach, CA

Conference Title

15th International Cryocooler Conference

Pub Type

Conferences

Keywords

acoustic power, cryocooler, fast cooldown, heat exchanger, inertance tube, pulse tube, regenerator

Citation

Lewis, M. , Taylor, R. , Bradley, P. , Garaway, I. and Radebaugh, R. (2008), Pulse Tube Cryocooler for Rapid Cooldown of A Superconducting Magnet, Pulse Tube Cryocooler for Rapid Cooldown of a Superconducting Magnet, Long Beach, CA (Accessed April 19, 2024)