  We have developed a novel procedure for constructing high surface area silver
sinter heat exchangers. Our recipe incorporates nylon fibers having a diameter
of ~ 50 microns and thin wires of bulk silver in the heat exchanger. In order
to increase the thermal conductance of liquid helium within the heat exchanger,
prior to sintering, the nylon fibers are dissolved with an organic acid leaving
a network of channels. In addition, the silver wires reinforce the structural
integrity, and reduce the resistance, of the silver sinter. We have constructed
a 3-He melting curve thermometer (MCT) with this type of heat exchanger and
measured the thermal time response of the liquid 3-He inside the MCT in the
temperature range T = 2-150 mK. We find a thermal relaxation time of ~ 490 s at
T ~ 1 mK. We have used scanning electron microscopy (SEM) to characterize the
heat exchanger and BET absorption for determination of the specific surface
area.
