A superconducting magnet apparatus includes superconducting coils in a vacuum vessel. The vacuum vessel is provided with a refrigerator for cooling the superconducting coils. The refrigerator includes a motor drive, displacers, and a cooling cylinder accommodating the displacers such that the displacers may reciprocate therein. The vacuum vessel has a sleeve for accommodating the cooling cylinder while isolating them from its vacuum area, the sleeve having an opening near the wall of the vacuum vessel. A first flange is provided at an opening in the cooling cylinder for inserting the displacers therein. The motor drive is attached to the first flange, with the displacers being inserted therein. The first flange has a cylindrical portion to be inserted in the sleeve to seal the space in the sleeve. The motor drive and the displacers can be removed, while leaving the first flange and the cooling cylinder unremoved.
System for controlling crystal growth in a Czochralski crystal growing apparatus. A magnetic field is applied within the crystal growing apparatus and varied to control a shape of the melt-solid interface where the ingot is being pulled from the melt. The shape of the melt-solid interface is formed to a desired shape in response to the varied magnetic field as a function of a length of the ingot.
