Two-stage high frequency pulse tube cooler for refrigeration at 25 K

A two-stage Stirling-type U-shape pulse tube cryocooler driven by a 10 kW-class linear compressor was designed, built and tested. A special feature of the cold head is the absence of a heat exchanger at the cold end of the first stage, since the intended application requires no cooling power at this intermediate temperature. Simulations where done using Sage-software to find optimum operating conditions and cold head geometry. Flow-impedance matching was required to connect the compressor designed for 60 Hz operation to the 40 Hz cold head. A cooling power of 12.9 W at 25 K with an electrical input power of 4.6 kW has been achieved up to now. The lowest temperature reached is 13.7 K

The superfluid vortex cooler

In this contribution a superfluid vortex cooler (SVC) is described. A SVC is a cooling device, the operation of which is based on the special properties of superfluid helium (He II). The SVC is small, simple, has no moving parts, and is gravity independent. It is capable of reaching temperatures as low as 0.65 K. First we have carried out a number of experiments, using a liquid-helium bath as a precooler for the SVC. Various geometries of the cooler components as well as the influence of the working pressure and the base temperature on the performance of the cooler have been investigated. Temperature below 1 K have been reached with a base temperature of 1.4 K. The next step has been combining the SVC with a pulse-tube refrigerator. In a preliminary experiment a lowest temperature of 1.19 K has been reached. Several ways to improve the system are suggested

THE RADIO-FREQUENCY SIZE EFFECT IN COPPER WHISKER BLADES : EXPERIMENTAL TECHNIQUE, LINE SHAPES

L'effet de taille en radiofréquence, a été mesuré sur des filaments lamellaires de cuivre orientés en avec un champ [MATH] parallèle à . La technique expérimentale se distingue des techniques habituelles. On a calculé numériquement les formes des raies et on a trouvé une bonne concordance pour la forme, la largeur et l'amplitude des raies. De plus, nous avons calculé l'amplitude en fonction du libre parcours des électrons.The parallel field RFSE ([MATH] ≥ ) has been measured in copper whisker blades. The expérimental technique differs from the conventional methods. For comparison the line shapes have been calculated by a numerical method. Good agreement is found as to the shape, width and amplitude of the lines. In addition the mean free path dependence of the amplitude has been calculated

Pilotstudie zu Pulsroehrenkuehlern Schlussbericht

Available from TIB Hannover: F95B2389+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

The superfluid vortex cooler

In this contribution a superfluid vortex cooler (SVC) is described. A SVC is a cooling device, the operation of which is based on the special properties of superfluid helium (He II). The SVC is small, simple, has no moving parts, and is gravity independent. It is capable of reaching temperatures as low as 0.65 K. First we have carried out a number of experiments, using a liquid-helium bath as a precooler for the SVC. Various geometries of the cooler components as well as the influence of the working pressure and the base temperature on the performance of the cooler have been investigated. Temperature below 1 K have been reached with a base temperature of 1.4 K. The next step has been combining the SVC with a pulse-tube refrigerator. In a preliminary experiment a lowest temperature of 1.19 K has been reached. Several ways to improve the system are suggested