Quote:
Originally Posted by zenith2134
Something tell me that this would be a good thread. So far you guys have made me realize the more obvious answer; that ambient heating from the rest of the set heats the thing too....didn't even consider that. Also, it is neat to hear that the supports can actually compensate for the heating/expansion of the mask.
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The heating is from the electron beam. The mask sits in vacuum and being thin doesn't conduct heat very well along the surface. The only way it cools itself, except for the edge, is by blackbody radiation. 70 deg C is pretty warm, it's about 158 deg F.
The Stefan Boltzmann law is of the form P=k(T1**4-T2**4). In this case T1 is the temperature of the mask and T2 is the ambient temperature of the glass around the mask. P is the power radiated. It has to come into equilibrium with the power being deposited by the electron beam. So you could solve it for the temperature of the mask. The temperature would go as the fourth root of the power so it wouldn't change a lot with a change in beam current. If you doubled the current the temperature would increase by a factor of 1.19
The increase in temperature of the CRT bulb from the set heating it contributes, but isn't a major factor in the temperature of the mask since the faceplate is usually near room temperature.
John