Earthtech's Proposed Design

(for scale, the sample ring is 150mm (6") in diameter)

The basic cryostat design is based upon the Liquid-Flow Cryostat described on p. 24 in "Experimental Techniques for Low-Temperature Measurement", Jack Ekin, Oxford U. Press, 2006.   LHe flows continuously into the chamber depicted above from a storage Dewar (not shown).  A control valve regulates the flow rate to achieve the desired temperature in the chamber.  Note that the LHe delivery tube is significantly off-center.  To prevent undesirable thermal gradients in the ring, we can rotate the ring slowly while cooling down.

A thermal analysis of this design predicts the total heat leak rate to be about 2 watts, requiring only 3 liters of LHe per hour....when NOT spinning.  We don't know what heat load will result from the spinning yet.

In this design we maintain the same size and shape of spinning ring, the same angular velocity of the ring, same temperature of the ring, same geometric relationship between ring and FOGs, and similar materials between the ring and FOG as Martin Tajmar's design.   Martin's "above ring" FOG is "below ring" in this design but that should not matter as the field is surely symmetrical about the horizontal plane through the ring.

However, there are some important differences:

No cryogenic bearing.  This design uses a stiff cantilevered shaft so that a lower bearing is not required.  The shaft has been designed with sufficient stiffness to keep the rotor operating well in the subcritical regime.  It will be necessary to balance the rotor carefully to achieve satisfactorily quiet operation at 5000 rpm.

Only the spinning ring is in the Dewar.  The FOGs are out in the room air where they can be moved around freely, connected to easily, and maintained at room temperature more easily.

This design permits an in-plane FOG to be placed quite close to the outside of the spinning ring, as shown above.  If the field has the shape and distribution of a real gravitomagnetic field, it will have the opposite sign in this location compared to the sign inside the ring.  If this can be observed it will greatly strengthen the case that the Tajmar effect is due to a real field.

The Dewar in this design must have a relatively thin, flat bottom in order to permit the FOG-ring geometry to be achieved.  It appears from these calculations that 3mm thick bottom plates will be sufficient for this unusual design.