Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 22: Other Low Temperature Topics: Poster Session
TT 22.4: Poster
Monday, March 16, 2015, 15:00–18:00, Poster B
Pulse Tube Cryocoolers at 4 K: Optimized Design for Low Vibrations and Temperature Oscillations — •Jens Falter1, Bernd Schmidt1,2, Andreas Euler1, Marc Dietrich1,2, André Schirmeisen1,2, and Günter Thummes1,2 — 1TransMIT-Center for Adaptive Cryotechnology and Sensors, Giessen, Germany — 2Institute of Applied Physics (IAP), Justus-Liebig-University Giessen, Germany
Since their invention [1] two-stage 4 K pulse tube cryocoolers (PTCs) have evolved as an excellent technique for "dry" cooling of cryogenic experiments without need for liquid helium, operating even below 4 K. PTCs have no cold moving mechanical parts, which is a main advantage over conventional Gifford-McMahon coolers. This results in a lower vibration level and long operation times. These properties make PTCs very attractive as the main cooling system for applications with high demands for low vibrations and high temperature stability. However, PTCs still exhibit two intrinsic effects due to the cyclic compression and expansion of the working fluid (He) in the cold head: (a) a periodic elastic deformation ("breathing") of the thin walled pulse- and regenerator-tubes, which leads to residual vibrations and (b) a periodic variation in temperature. Here, we present optimized applications of two-stage 4 K PTC cold heads to reduce these effects. First, both intrinsic effects are minimized by adapting the input power of the compressor. Remaining vibrations are reduced by mechanical decoupling of the experiment from the cold flange. Also, a temperature damping unit is implemented for a reduction of the temperature variations.
[1] C. Wang, G. Thummes, C. Heiden, Cryogenics 37, 159-164 (1997)