|
Previous
|
Copyright © 2007 Gerardo A. Sanchez, All Rights Reserved
| Mérida360
Vacuum Chamber Atmosphere is the general name for a layer of gases that surround a celestial body of sufficient mass to hold them. The gases are attracted by the gravity of the body, and are retained for a longer duration if the gravity is high and the atmospheric temperature is low. But ... is it possible to remove the atmosphere temporarily? Almost: There is a neat piece of engineering called a Vacuum Chamber which can mimic an atmosphere-less world. This chamber removes all traces of atmospheric gases that could be found in it, reducing the inside pressure to less than 100.000.000 times that of the external pressure. This chamber is used to restore the aluminium coating on the main mirrors at the National Observatory in Venezuela. Due to dust, humidity and oxidation the mirrors reflectivity is lost, and once every two years or so the aluminium coating is removed and a new one applied. The chamber is two meters in diameter. It takes about two hours for several vacuum pumps to create such an environment. Three tungsten bars are used to burn a small amount of pure aluminium. Due to the low pressure inside the chamber the aluminium is deposited in a fine even layer over the glass. During the process the round plate is spinning which helps to produce a homogeneous reflective surface. The round plate and the triangular plate on the upper part of the chamber are also used as electrodes. A high electric current is applied over them to create a magnetic field, which draws small particles (as a light dots) from the lower round plate to the upper electrodes cleaning the glasses. This process, called efluvium, creates a nice blue light that can be observed through the windows on the chamber. After several hours of work the "new" mirrors are taken out from the chamber and put back again inside the telescopes. This panorama shows the chamber a few minutes before the process of burning the aluminium began; there are nine small mirrors ready to get new reflective layers. Can you see them all? (the answer is in this picture!) Other Pictures: - One meter mirror after getting a new aluminium layer - Taken out from the chamber - From the basement to the dome top, where the telescope is - One tonne mirror hanging 10 meters and swinging over my head!! - Workers after finishing a very good job Cámara de Vacío (Texto en español)
Shortcut to this page: http://geoimages.berkeley.edu/wwp_rss/go/n3319
|
