thick.
These x-ray transmission curves were compiled from the
data on the web site of Eric Gullikson at the Advanced Light Source at the
Lawrence Berkeley Laboratory:
http://henke.lbl.gov/optical_constants/filter2.html
This data is updated frequently and is the most
complete available. This site will quickly generate transmission or
absorption curves for virtually any material. We owe Eric, and all at ALS
that have contributed to this site, our sincerest thanks.
The transmission curve of a material is but the first
step in designing successful x-ray filters. Though Lebow Company is not
qualified to design filters, we can make the following suggestions:
All filter materials (except Au) oxidize. Some,
like Cu, very rapidly. Filter designs must allow for an appropriate amount
of oxygen. Most filter designs should include a layer of oxygen. We have
included the transmission of oxygen at the end of our curve sets for
reference.
Keep filters as small as possible. They will be
stronger, of better quality and be less costly. Often the cost saving of
only a 2-3 mm size reduction can more than pay for a custom frame.
Ultrathin foil is rarely "light tight."
Normal foil has an attenuation, in the visible, of 5 to 8 orders of
magnitude. Before demanding perfect foil, think carefully about the
requirements of the application and try to reduce the required attenuation
to a number. If an extraordinarily high light attenuation is truly
required it can often be achieved by using special fabrication techniques.
This compilation is an attempt to assist in the design
of x-ray filters and windows. It is our goal to make it as useful as
possible and we warmly welcome your suggestions and corrections.
Our sincerest thanks go to Marisol Torres for developing these curves.
