Heater for high vacuum optical view port
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A heated view port for in-situ optical observation of a deposition chamber in a vessel under high vacuum application comprising a plurality of superimposed layers arranged in the shape of an annular band mounted around the view port substantially at the outer periphery thereof. The band includes a first layer of pyrolytic boron nitride, a second layer of pyrolytic graphite covering at least one surface of the pyrolytic boron nitride layer, an outer layer of pyrolytic boron nitride and two electrical contact terminals in contact with the pyrolytic graphite layer in an arrangement forming parallel resistive paths between the contact terminals. The terminal contacts are connected to an external source of electrical power.