The theory of zero-gradient crystal ovens

Crystal ovens designed to have zero or near-zero thermal gradients within the oven mass are described both from a theoretical viewpoint, and with actual examples. Thermal gains of well over 100,000 in a single oven with a height of only 19 mm. (¾ inch) have been demonstrated experimentally. Conventional ovens often have one or two point sources of heat and rely on high thermal conductance in the oven mass to achieve a temperature profile that is roughly isothermal. Unavoidable residual thermal gradients limit the achievable thermal gain to a few thousand, and in only a small area. By using distributed heaters that match the heat loss distribution, the overt mass can be maintained arbitrarily close to a zero gradient state with resultant high thermal gain over most of its volume. An idealized strawman oven with spherical symmetry is used to establish the basic principles of zero gradient ovens. These are then applied to a practical oven configuration having cylindrical symmetry. A finite element analysis of this oven is presented. Experimental results of actual ovens are given