Now That is an ERF!

[colinsk]

2.4.1. Front Window
The front window, the main purpose of which is to limit the heat input to the instrument,
is a 50 Å bandpass filter made by Andover Corporation. In the order in which the light
travels it consists of 6 mm of Schott BK7G18 radiation-resistant clear glass, 3 mm of Schott
GG495 green glass, a bandpass coating, an infrared rejection coating, and another 6 mm
of BK7G18 glass. The BK7G18 glass, among other things, serves as a radiation shield for
the non-radiation-resistant GG495 glass. The GG495 glass serves two important purposes:
One is to block the blue and ultraviolet light from reaching the bandpass filter, which can
be damaged by exposure to those wavelengths. Another is to cause the window to absorb
a small amount of light, thereby heating it up and limiting the center-to-edge temperature
gradient.

http://www.springerlink.com/content/r30 ... lltext.pdf

[marktownley]

That's an interesting doc Colin, thanks for that. One for a read over the weekend with a beer me thinks...

[swisswalter]

Hi Colin

thank you very much for digging that out. Could it be of any use to us down stream users?

[colinsk]

For me it reminded me that an ERF is a system that needs to be well thought out. This system removes a very large amount of the incoming radiation. It is only 50A wide! It took not an element but a system.