Conducting materials having narrow impurity conduction bands can reduce the number of high energy excitations, and can be prepared by a sequence of plasma treatments. A cushioning material 25 is interposed in the gap to fix the cooling block 22 relatively to the magnetic yoke 20 by screws. The Original Bubble Nails eliminates other forms of drying wet fingernails because it encloses and totally protects wet fingernails in a protective form so wet nails can dry flawlessly.