| http://www.w3.org/ns/prov#value | - The wafer boat 50 is made of a material such as quartz which is highly resistive to heat and corrosion and comprises four poles 51 each provided with a large number of horizontal grooves 51A typically between 100 and 150, a pair of discs 52 for securely and rigidly holding the upper and lower ends of the four poles 51, an insulating cylinder 53 disposed below the lower disc 52 and a flange 54 fitt
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