Crystal Optics Fabrication

Crystal optics are a critical responsibility of the APS, as the premier hard x-ray synchrotron facility in the US. Comprehensive in-house infrastructure, capabilities and expertise for fabricating and developing almost all kinds of crystal-based X-ray optics, including crystal monochromators, beam splitters and analyzers, high-heat-load monchromators, mirror substrates, ultrahigh-resolution crystal optics systems, FEL crystal optics, etc., for APS beamlines as well as other DOE light sources, and neutron facilities.

Expertise includes:

Figure 1:Elina Kasman cutting grooves into optical pitch on 36" continuous polisher.

  1. Designing crystal optics with X-ray dynamical-theory calculations and modeling to achieve desired resolution, efficiency, acceptance, etc.,
  2. Fabricating ultrahigh-quality crystal optics, from precise orienting, cutting/dicing, grinding, etching, to strain-free polishing
  3. X-ray characterization and testing of crystal optics

Work requests can be submitted by filling the Optics Group's work request from at https://beam.aps.anl.gov/pls/apsweb/wam0002.owr_main_menu.

The crystal optics facilities are described below.

Slicing/Cutting Laboratory

The lab contains two dicing saws for cutting relatively thin wafers and plates into distinct pieces. A rotary diamond blade saw is used to cut large crystal boules. The diamond-wire saw is used to slice crystal boules of Si and Ge up to 8" in diameter and 12 inches long. The diamond-wire saw cuts crystals with minimal loss of valuable material and low stresses/strains.

Etching Laboratory

This facility is used to etch crystals using wet chemical methods to remove surface stresses/strains induced by machining processes.

Polishing Lab

The Polishing Laboratory utilizes the following lappers/polishers:

Hyprez LM28 Lapping Machine (Engis)

This machine is used for planarization and thinning of optical components up to 300mm diameter on hard pad or composite copper lapping plate.

Strasbaugh 6CM Continuous Polisher

This 36" table machine is set up with optical pitch for fine low-angstrom polishing of single crystal optical components and substrates using colloidal silica slurry. For best results, parts up to 200mm diagonal can be polished, in some cases parts up to 300mm diagonal can be accommodated.

Strasbaugh 6DF-1 Precision Polishmaster

This versatile overarm polisher can be outfitted with variety of plates and pads to perform intermediate and fine polishing steps, using diamond or colloidal silica slurries.

Inspection Equipment

Figure 2: Example of sapphire crystal (078) orientation: Superimposed Laue pattern and simulation results in red by LauePt - a software tool developed by X. Huang.

The Fabrication Laboratory is equipped with DIC microscope for immediate inspection during polishing process. Optics requiring more detailed inspection and accurate measurements are sent to the Metorology Laboratory.

Other Equipment (in collaboration with the ANL Central Shops)

Two midsize high-precision grinders; Blanchard precise grinder; several overarm polishers; core drill press; and Ultrasound mill.

X-ray Laboratory

Orienting crystals for fabrication, and characterization of crystal optics by double-crystal diffraction rocking curve measurements and topography imaging using laboratory x-ray generators. This laboratory is equipped with three main instruments:

Figure 3: Laboratory topography stations

  1. Two-axis Rigaku diffractometer (with Cu or Mo x-ray tube) for precisely orienting single crystals along required lattice planes with precision ≤0.1°.
  2. Back-reflection Laue camera (with Cu or Mo x-ray tube) for identification/verification of crystal orientations, equipped with the LauePt simulation software (developed in-house by Xianrong Huang) for studying the orientations of any single crystals with high precision up to 0.1°.
  3. Topo Unit, consisting of 18kW rotating-anode X-ray generator and a double-crystal diffractometer, can measure high-resolution double-crystal rocking curves of silicon, germanium, diamond, etc. and take topography images (with a CCD detector) on each point of the rocking curve. The X-ray beam size can be up to four inches in diameter, allowing to reveal macroscopic strains of large crystals (including X-ray monochromators mounted on fixtures).

Advanced X-ray characterization of crystal optics is carried out at the 1-BM Optics and Detectors Test Beamline.

Figure 4: Design of high-resolution (10 meV) crystal analyzer system using a Montel mirror and angular-dispersion optics for RIXS.

Crystal Optics Research and Development

R&D in crystal optics is carried out jointly with the APS beamline scientists and user community, independently or in collaboration with other facilities to keep the group at the state-of-the art in x-ray optics. Examples include high and ultrahigh resolution crystal monochromators and analyzers, strain-free; etc.