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| Aluminizing 2 |
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| This is the vacuum system a little "closer up"The first picture shows the various valves and connections that make the system work. I will also give an explanation of how I use the system. |
| To coat , a cleaned mirror or other item is placed in the chamber with a fresh filliment and some pure aluminum hanging on the filliment, the Belljar is clamped down. I close the lower "vent" Ball valve and open the upper Ball valve. The valve between the Diffusion pump and chamber is opened and the Backing pump and Roughing pump are turned on, the low vacuum guage is swtiched on also. I monitor the low vacuum guage until the pressure drops to between 10 -1 and 10 -2 torr then the fan and the diffusion pump are switched on. It takes a few minutes for the diffusion pump to heat up, All of a sudden the low vacuum guage starts to drop very quickly, once I see the low vacuum guage starting to drop quickly the upper ball valve is closed and the roughing pump is switched off. The pressure on the low vacuum guage is monitored until it almost "zero's out" then the high vacuum guage is switched on and I continue to pump the system down till the vacuum is about 10 -5 torr.Now I can turn on the filliment. The picture on the right shows the variable transformer, voltmeter and battery charger |
| I use a variable transformer to controll a large battery charger that powers the filliment. I ajust the transformer until the voltage output of the charger reads about 3.5 volts on my voltmeter then I watch the voltmeter untill the voltage drops all of a sudden then it starts to climb back up as the aluminum is being evaporated, after about 10 seconds the filliment is turned off, the mirror is now coated. I shut off the vacuum guages then I close the valve between the chamber and the diffusion pump, vent the chamber by opening the lower ball valve and then the upper ball valve. I open the chamber to see the coating and ohh and ahh a little :-) The diffusion pump is switched off, but the fan and the backing pump are left on until the diffusion pump has cooled down, this takes about 20 minutes. then the backing pump and fan are shut off. |
| Below are a couple of pictures of my "crane system" for raising and lowering the bell jar. |