Practically, all modern x-ray diffractometers, SAXS, TXRF systems and many other laboratory X-ray instruments are equipped with multilayer X-ray optics. It is due to a much higher flux these instruments have comparing with those having no optics or having a grazing incidence optics without multilayer coatings. There are variety of the multilayer optics designs – from one bounce collimating parabolic mirror to four corners double bounce focusing mirrors. Design of multilayer optics depends on application, X-ray source parameters, requirements on divergence, focal spot, available room for the optics, manufacturing capability and cost. Key characteristics of the optics, requirements on multilayers d-spacing accuracy, optics slope errors, and substrates surface roughness are discussed in the paper. Different optics designs are considered including recently developed optics for a laboratory topography system and a Hybrid optics combining multilayer and crystal optics for XRR and XRD.
Johansson crystals have been known for many decades as x-ray optical elements with a high resolving power and small
foci. However, in the past their use in applications requiring a small focus and a narrow band pass were limited by
imperfections caused by the technologies applied to their manufacture. While high performance Johansson crystals
might have been achieved in some research facilities, such crystals were not commercially available. RIT has developed
a process for fabricating precision Johansson crystals. The fabrication maintains the crystal structure intact. The angular
precision of the bending process of atomic planes and the reflecting crystal surface is better than four arc seconds. In
this paper, we will present the basic aspects of the technology and the achievements with Silicon and Germanium
crystals.
Two-dimensional multilayer optics have been widely used for enhancing and monochromatizing x-ray beams for various diffraction applications. However, when they are applied to Mo Kα radiation, the performance suffers from the fact that multilayer optics can use only a very small portion of the source. This is because the rocking curve of a multilayer becomes narrower at higher energy. Comparing to the optics for the Cu Kα radiation, the throughput of the optics for Mo Kα depends heavily on how small the source is. Based on the theoretical ray-tracing study, we have designed, fabricated and tested a system combining a microfocusing x-ray source and a side-by-side multilayer optic. Initial test results agree well with the theoretical expectation. The flux gain for a sample smaller than 100 micrometers is about 9 fold compared to a system composing of 2 kW sealed tube and graphite monochromator. The resolution of a diffractometer can also be improved by configuring the optical path. This paper will discuss the system design, detailed comparison between this system and a sealed tube-graphite monochromator based system, and possible applications such as small molecule diffraction system. A theoretical comparison to a rotating anode based system will also be discussed.
W-B4C multilayers with single d-spacing period of 2.2 nm have been deposited on 330 long by 50 mm wide Si substrates to be used as monochromators for a computed tomography application. Using magnetron sputtering and a substrate masking technique, d-spacing uniformities of +/- 0.86% and +/- 1% were obtained over a 180 mm by 100 mm area for 2.2 nm and 4.2 nm d-spacings respectively. Two separate processes were used to coat the 330 mm long substrate, wherein half of the substrate was coated in each process. A similar process was used to deposit depth graded W-B4C supermirrors on Si and CVD SiC substrates for a beamline pre-mirror application. The 330 mm long by 50 mm wide Si and 300 mm long by 79 mm wide SiC substrates were coated with 20 bi-layer supermirrors with d-spacings ranging from 4.4 nm to 10.8 nm. For an angiography research application laterally graded W-B4C multilayers were deposited on 150 mm by 120 mm silicon substrates. A strong nonlinear d-spacing gradient, from 1.6 nm to 3.8 nm was achieved across the mirror's surface in an attempt to provide uniform intensity over the reflected area. The maximum and minimum d-spacing gradient was 0.06 nm/mm and 0.003 nm/mm, respectively. We measured and mapped the d-spacing gradient using a custom Cu-Ka diffraction system. The measured d-spacings were within +/- 1.5% of the intended d-spacings.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.