The exterior is made of SECC steel plate and treated with fine powder baking paint. The interior is made of SUS stainless steel. The operation procedures are simple, the temperature uniformity is good, and the vacuum resistance is high, up to 5x10-3 Torr. The air valve and intake valve use ball valves, which are easy to use and have high tightness. They provide high-temperature protection, overload protection, automatic power-off, and silicone packing. The circulation method includes thermal radiation and natural convection to strengthen the glass window