**1.2 Vacuum vessel classification**

	- 1.Welded vacuum vessels
	- 2. Forged vacuum vessels
	- 3. Formed (extrude) vacuum vessels
	- 4. Blow mold vacuum vessels
	- 1. Plate to plate (square) vacuum vessels
	- 2. Cylindrical vacuum vessels
	- 3. Spherical vacuum vessels
	- 4. Monocopue vacuum chambers
	- 1.Low vacuum vessels (25–760 Torr)
	- 2. Medium vacuum vessels (10<sup>−</sup><sup>3</sup> –760 Torr)
	- 3. High vacuum vessels (10<sup>−</sup><sup>9</sup> –10<sup>−</sup><sup>3</sup> Torr)
	- 4. Ultra-high vacuum vessels (10<sup>−</sup>12–10−<sup>9</sup> Torr)
