10K Pulse Tube Cooler
A 3-stage pulse tube cooler has been designed to operate at 10¶K. The staged cooler uses the same compressor and parallel staging configuration for the 1 st and 2 nd stages as previously employed for our delivered High Capacity Cryocooler (HCC). The 2 nd and 3 rd stages are in a serial configuration. The addition of the third stage extends the performance of this cooler to lower operating temperatures below 10¶K.
A Three-Stage Stirling Pulse Tube Cryocooler Approaching 4
It is a great challenge for a Stirling Pulse tube cryocooler (PTC) to reach liquid-helium temperature, where there are promising applications such as superconducting digital electronics, midinfrared instrument, heterodyne detectors. Lockheed Martin first achieved a temperature below 4 K with a four-stage configuration with He-3 as working fluid. A single-stage Stirling PTC precooled by a self-made two-stage GM-type PTC has been constructed and tested to explore the loss mechanism of 4 K PTC working at high frequency at Zhejiang University. Temperature as low as 4.2 K has been successfully obtained with He-4 as working fluid by the end of 2008. In this paper, we report a newly-designed three-stage PTC, which aims to reach 4 K. The 4 K cooler is a thermalcoupled type, whose mass flows are easier t ocontrol and whose energy flows are more readily monitored. It will be working with He-4 instead of He-3. The first and second stages have been finished. A bottom temperature of 35 K and 9 W at 77 K with 300 We input has been achieved in the first stage. The bottom temperature of second stage is as low as 20.6 K, and the cooling power is measured as 1.0 W at 28.6 K. The test results are in good agreement with the model for both stages. The first and second stage is designed to couple with the a stage, which is expected to reach below 5.0 K at 30 Hz.
Investigations of dielectric gratings using electrodynamic models based on volume integral equations
Eigenmodes of planar and cylindrical dielectric gratings (DGs) and electromagnetic wave scattering from multiplayer DGs are investigated. The DG characteristics are calculated using numerical-analytical solution of integral equations (IEs).