INTRODUCTION

The design of soft x-ray filters and windows is a blend of physics and art. These x-ray  transmission curves for the ultrathin foils made by Lebow Company are compiled as an aid to filter design. The foil thickness, 0.2µ, is arbitrary and most materials are available from 0.1µ or less to 25µ 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.

Copyright Lebow Company, 2000, all rights reserved.