X ray questions:What material is suitable in windows for hard X-rays?


by runnerwei
Tags: material, questionswhat, suitable, windows, xrays
runnerwei
runnerwei is offline
#1
Dec8-11, 12:08 PM
P: 9
What material is suitable in windows for hard X-rays?

What material would you choose as reflective coating of X-rays mirrors for radiation at 200 eV? Why?
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M Quack
M Quack is offline
#2
Feb24-12, 03:26 PM
P: 638
Hmm, 200 eV is very very soft. The only window you can use for that is a free-stainding SiN membrane one a Si frame (substrate with a small window etched into it). These are commercially available, up to maybe a few window mm size.

A window is always a compromise of thickness and the material's absorption length. The latter depends on Z. Generally speaking you want Z as low as you can get, but the material has to withstand possible radiation damage.

For x-rays above 3.5keV or so you can use Beryllium (Z= 4 for large pieces) or CVD diamond (Z=6 for smaller pieces). For hard x-rays above 20keV or so you can use Al, plastics or even Si wafers.

For 200 eV I would use a naked Si mirror without any coating. The critical angle at 200 eV is large enough, and Si you can get in excellent quality.

Check out the Center for X-Ray Optics. There you can calculate transmission and reflectivity of softish X-rays.

http://henke.lbl.gov/optical_constants/


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