ANL/APS/TB-6

APS X-ray Optics Fabrication and Characterization Facility

by Steve Davey

The APS is in the process of assembling an X-ray Optics Fabrication and Characterization Facility. This report will describe its current (as of February 1993) design. The role of this facility is threefold:

(1) to develop fabrication techniques (mirror coating, multilayer fabrication, single crystal cutting and polishing, etc.) for new and/or improved x-ray optical components for use at the APS,
(2) to provide the capability for x-ray characterization of both single optical components (crystals, multilayers, zone plates, etc.) and complete systems (monochromators, crystal benders, etc.), and
(3) to provide the capability to measure surface figure and finish of components (mirrors, etc.).

Surveys of the APS Collaborative Access Teams (CATs) were conducted in 1992 that asked for specifications of expected optical needs. While not all of the optical needs of the CATs can be accommodated, these surveys provided guidance in how the APS might best fulfill the needs of the CATs. This facility will best serve the user community by providing for standard x-ray optical needs (e.g., on site x-ray diffractometers for orientation, etc.) and providing for some of the special optical needs of the APS user community (e.g., a mirror coating system for optics up to 1.5 m long). This facility will be operated by the staff of the APS and will compliment more standard optical shop facilities, such as the Argonne National Laboratory optics shop.

The surface metrology laboratory and the deposition system will be located in clean rooms in the APS Experiment Hall. The Experiment Hall floor will provide a mechanically stable environment for the labs. Figure 1 (see below) is the proposed layout of the deposition and the surface metrology labs.

The APS X-ray Optics Fabrication and Characterization Facility will be composed of the following:

(1) A deposition system for single metal coatings for mirrors and synthetic multilayer coatings
(2) A surface metrology laboratory equipped with:
a figure interferometer
a surface profiler interferometer
a long trace profilometer (LTP) or other large figure device
(3) Single crystal optics fabrication facilities equipped with:
a precision diamond slicing machine
a lapper-polisher
(4) X-ray characterization facilities equipped with:
sealed tube x-ray generators
diffraction equipment:
double crystal goniometer
triple axis diffractometer
back Laue camera
single axis goniometer for precision crystal orientation

Figure 1. Proposed deposition lab and surface metrology lab layout. These labs are located in the Experiment Hall of the APS between Sector 1, the main aisle, and the Early Assembly Area (EAA).

Deposition Facility

A deposition facility will be constructed in a clean room on the experimental floor adjoining the surface metrology laboratory, refer to Fig. 1. This will provide a clean and vibration-free environment for the coating chamber for single element metal coatings as well as synthetic multilayer coatings. A class 10,000 clean room or similar environment is planned. Based upon the results of a 1992 survey of the CATs' expected mirror requirements, most of the expected needs of the CATs could be accommodated with coating chambers that handle substrates that are:

1500 mm long x 150 mm wide x 125 mm thick for single element metal coatings, and
500 mm long x 50 mm wide x 125 mm thick for multilayer coatings.

The materials for single element coatings include nickel, rhodium, gold, and platinum.

The design of the deposition laboratory will be completed by the spring of 1993 and constructed by early 1994.

Surface Metrology Laboratory

The surface metrology laboratory will be used to characterize the figure and the finish of x-ray optics. This laboratory will have the facilities to measure surface features with lateral (in the surface) resolution from less than a micron to lengths greater than a meter and with a vertical (normal to the surface) resolution as small as an Ångstrom. It is currently planned to cover this entire range with three noncontact instruments, a surface profiling interferometer, a figure interferometer, and a long trace profiler. Each of these instruments is described in detail below.

Surface Profiler

A surface profiler is an instrument that will measure the 3D microscopic topography (finish) of optical surfaces. Vertical resolution of less than 1 nm is obtained using phase shifting interferometry. When operated with a low power objective, the field of view can be as wide as a few mm2, and, with a high power objective, submicron lateral resolution is obtained. Typically, an interferogram will contain more than 60,000 data points and will be analyzed in a few seconds time.

The profiler will be used in the surface metrology laboratory to characterize both diffraction crystals and reflecting mirrors. These optics can be quite large and heavy. A typical mirror may be larger than 1.5 m x 100 mm x 100 mm and made of copper alloy. In order to accommodate such optics, the phase shifting hardware must be located in the microscope head and cannot be located in the support stage.

The surface profiler delivery is needed early in 1993 so that the finish of cut and polished x-ray optical components can be measured. This information will provide feedback for developing the crystal polishing techniques.

Preliminary APS surface profiler description (2/93):

Phase shifting figure interferometer, optics, and computer:

Phase Shifting Optics

Mirau objectives X 2.5 and X 100

Field of view >2.5 mm x 2.5 mm minimum

Vertical resolution <0.05 nm for all magnifications

Lateral resolution <0.5 µm

Repeatability <0.2 nm rms difference of 2 measurements
<0.05 nm rms 16 averages w/ null
<0.1 nm rms 16 averages w/ 5 fringes rms for 2 sigma of 100 sets of measurements, each set is the average of 16 profile measurements

Reproducibility sigma of 20 measurements will be less than 0.15 Å, each measurement consists of 4 intensity averages with the instrument refocused between each measurement

Computer HP 382/16+2 workstation or equivalent
DOS floppy disk data transfer for compatibility with DOS PC
Interferometer operation and analysis software

Microscope column detachable from base for optical table mounting

Accessories:

Precision Reference Standard
Vibration Isolation Optical Table (large enough to handle the profiler and the large optics, 4' x 8')
Optical Table Mounting Plate to replace standard profiler base

Additional desirable features:

Vertical steps >2 µm
Turret-mounted objectives
Parfocal objectives
Turret less than or equal to 3" dia.
Objective working distances are maximized

Figure Interferometer

A figure interferometer characterizes the shape (figure) of optical surfaces and will be used to measure both diffraction crystals and reflecting mirrors. The APS digital phase-shifting figure interferometer was delivered in January 1993, and its specifications are provided in Appendix 1.

The figure interferometer will overlap the resolution and length scales probed by the surface profiler and a long trace profiler. The APS figure interferometer has a 6-inch clear aperture and has a 6:1 continuous zoom. The digitization resolution of 256 x 240 elements yields a lateral resolution of a fraction of a mm. A second port is available on which beam expander optics can be installed.

The phase shifter in this laser interferometer changes the relative optical path length of beams reflected from the test piece and an internal reference. The surface topography of the test piece is determined by calculating the optical path difference between the two beams. The data can them be plotted or analyzed fro a variety of optical characteristics. The computer platform makes the measurements on a timely basis. Data acquisition and display take a few seconds.

Figure Interferometer Decription:

Phase shifting figure interferometer, optics, and computer

Phase Shifting Optics

Aperture 150 mm (6-inch aperture)
[with the flexibility for larger aperture (e.g., 450 mm)]

Accuracy better than lambda/100 peak-valley (P-V) at lambda =632.8 nm
Value for accuracy reflects the overall accuracy for absolute testing. System accuracy for relative testing is dependent on the quality of the reference optic.

Precision better than lambda/1300 rms (6-inch aperture)
Instrument precision is the residual rms error that reflects the difference of two consecutive measurements, each consisting of an average of 16 sets of data. The specification is derived from a sample of 100 measurements and represents the mean value plus 2 sigma (98% confidence).

Repeatability better than lambda/100 P-V (6-inch aperture)
better than lambda/8000 rms (6-inch aperture)
Repeatability of the quoted statistic for 100 measurements, in which each sample consists of an average of 16 sets of data. The specifications are for the 2 sigma (95%) repeatability of the data. P-V calculated over 97% clear aperture; rms calculated over 100% clear aperture.

Maximum Slope better than 60 fringes

Zoom Range 6 X

Computer IBM-compatible DOS 486 PC platform processor

Accessories:

6-inch diameter transmission flat lambda/20
attenuation filter
sample mount, 3 translations and 2 rotations

composed of a base support with x-y-z translation, a tip tilt adapter and a self centering three jaw chuck
shelf mount that can be used in place of the three jaw chuck.

The mounts described in these last two items are intended for use with smaller optics (e.g., monochromator crystals)

Long Trace Profiler

The APS is planning to procure a long trace profiler (LTP), which is available from Continental Optical Corporation or other measurement device that will characterize optical figures over lengths of at least 1 m. The desired large figure device shall be able to measure surfaces up to 1 - 2 m long with a lateral resolution on the order of 1 mm. For a slope-measuring device, such as the LTP, an accuracy of less than 2 µrad will be expected.

Single Crystal Optics Fabrication

The single crystal optics fabrication laboratory will be equipped with a precision slicing machine and a lapper-polisher. The three-axis CNC slicer specified in Appendix 2 has been installed at the APS for machining Si and Ge crystals. The lapper-polisher described in Appendix 3 is being installed at the APS. Note that it can handle samples up to 10" x 3" without compromising flatness.

X-ray Characterization Facility

The x-ray laboratories will be equipped with the following diffraction instruments:

Double-crystal goniometer for measuring rocking curves
Triple-axis, four-circle diffractometer
Back Laue camera for rough crystal orientation
Single-axis goniometer for precision crystal orientation
Crystal mounts to transfer oriented crystals to the slicer

These standard diffraction instruments will not be described in detail here.

Appendix 1

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WYKO - 6000PC Figure Interferometer Specifications

(Specifications from The WYKO 6000PC Interferometer)

System Performance

Calibrated accuracy:	Less than lambda/100 rms
System accuracy:	Dependent on reference optic quality
Repeatability of p-v:	Less than lambda/100 2 sigma deviation of 100 measurements, each averaging four sets of data
Repeatability of rms:	Less than lambda/1000 2 sigma deviation of 100 measurements, each averaging four sets of data
Measurement resolution:	lambda/1024
Data acquisition time:	Less than 167 ms
Measurement-to-measurement repeatability:	lambda/500 or better Max. rms deviation between any two consecutive measurments

Interferometer

Optical configuration:		Fizeau interferometer
Test beam diameter:		152.4 mm (6 in.)
Source:		Actively stabilized HeNe laser
Frequency stability:		± 0.5 Mhz/min., ± 2 Mhz/hour
Pupil imagining:		Continuous 6:1 zoom
Alignment FOV:		± 2 degrees
Fringe viewing:		TV monitor
Active pixels:		745 x 488
Digitized resolution:		256 x 240
Test beam height:		133.4 mm ± 2.5 mm

Appendix 2

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Meyer Burger - Slicing Machine Specifications

The slicing machine TS 121 is especially designed for the automatic slicing of hard and brittle materials (e.g., optical glass, ceramic materials, quartz, etc.) by means of diamond tools.

Some special features:

Non-corroding protection of the working area
Slide ways and limit switches outside the working area
Slide drives with DC-servomotors
Positioning of the longitudinal slide with incremental rotary encoder
Positioning of the cross and vertical slide with incremental linear transducers
CNC-continuous-path-control for 3 axes and CRT screen in the control cabinet next to the machine

Technical Data

(Note that all technical specifications are subject to change without notice according to the manufacturer.)

Slicing blade:	External diameter Bore Cutting speeds in range from Slicing blade flanges	250 - 400 32 10 - 75 dia. 100, 140, or 200	mm mm m/s mm
Tool spindle:	14 fixed spindle speeds in range from Spindle diameter Motor rating and speed of the three-phase AC motor	800 - 3550 32 4 kW/1500	rpm mm rpm
Longitudinal slide: (X axis)	Maximum travel path Cutting feed speed programmable from Longitudinal travel paths programmable from Rapid transverse Digital display of feed speed in Digital display of slide position	500 5 - 2000 0.001 - 500 2000 0.001	mm mm/min mm mm/min mm/min mm/min
Cross slide: (Y axis)	Maximum travel path Feed speed programmable from Feed step length programmable from Rapid transverse Digital display of feed speed in Digital display of slide position	320 5 - 2000 0.001 - 320 2000 0.001	mm mm/min mm mm/min mm/min mm
Vertical slide: (Z axis)	Maximum travel path Feed speed programmable from Vertical travel paths programmable from Rapid transverse Digital display of feed speed in Digital display of slide position	160 5 - 2000 0.001 - 160 2000 0.001	mm mm/min mm mm/min mm/min mm
Worktable: (Special accessory)	Rotary table Adjustment with hand wheel or DC-servomotor (C-axis) Rotary table turns With hand wheel: angle adjust to 1' = With servomotor: angle values programmable in 0.001° Quick adjustment (rapid traverse) with servomotor Distance spindle axis - rotary table	dia. 375 360 0.017 3.6 6 217 - 377	mm ° ° " rpm mm
Dimensions (WxDxH)	Machine Control cabinet	1300 x 1380 x 2230 600 x 1000 x 2000	mm mm
Weight:	Machine Control cabinet	1700 300	kg kg

Standard equipment for slicing machine TS 121

2 lever rods for transporting machine
1 spindle dia. 32 mm to hold slicing blade
2 spacers dia. 55 mm and groove nut
1 pair flanges dia. 100, 140, and 100 mm
1 spindle main bearing with or without driving notch
1 fixed spindle speed in range from 800 to 3550 rpm

1 motor pulley, diameter depending on desired rpm
1 spindle pulley, diameter depending on desired rpm
spindle speeds possible with spindle motor 4 kW, 1500 rpm (50 Hz): 800, 900, 1000, 1120, 1250, 1400, 1600, 1800, 2000, 2240, 2500, 2800, 3150, and 3550 rpm

1 taper reduction for counter bearing and 2 draw-in screws for using the spindles of slicing machines TS 3, TS 33, TS 4, and the quartz cutting machine QS 3
2 movable coolant supply pipes with nozzles
1 set operating keys
1 operating instructions with wiring diagram, diagrams, and equipment list

Additional equipment necessary to operate the machine

Diamond slicing blade
Workpiece - worktable (rotary table or magnetic chuck)
Work holder plate 300 x 250 12 mm
Cement, e.g., A46 for fixing the workpieces
Sipport plate (made of, e.g., glass, ceramic, etc.) for cementing the workpieces
Coolant, e.g., Mill-Kut 12-CO
Coolant and grinding agent concentrate, e.g., OEST Meba SKNF
Dressing Stone for slicing blade, e.g., Abrafract BFR 200

Appendix 3

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Engis - HYPREZ Lapper-Polisher Specifications

HYPREZ Lapping System Model 28LMPV
(Pneumatic Pressure System with Variable Speed) Standard Features:

Microprocessor base touch control panel with large, easy-to-read L.E.D. displays mounted to a movable pendant for convenient access at each work station
Electronic variable speed drive (inverter) adjustable from 0 - 100 rpm, 5 HP, 230 VAC
3 Ring arms - roller yoke type
Each pneumatic station has a single lever control for both inboard and outboard adjustments
The complete pneumatic structure can be swung to the side of the machine for easy access to lap plate for removal or cleaning
3 HP - 3 phase drive (soft start drive)
Abrasive slurry pump system
Separate oversize tapered roller bearing
Spindle driven by a quiet antifriction gearbox and motor combination via a high torque belt and pulley system
Large-bore cylinders with double pistons and oversize piston rods for supporting greater lapping pressures and frictional drag
Air filter lubicator
35" work height for easy loading and unloading
48" diameter fully adjustable parts table
3 Natural iron conditioning rings (12" I.D.)
Flatness gauge for plate
NEMA 12 wiring
208 V, 3 phase electrics
500 Lbs. maximum load delivered per cylinder

Dimensions: 58" L x 48" W x 74" H

Shipping weight: 3,000 lbs. approx.

Return to list of TBs

Phase Shifting Optics
Mirau objectives	X 2.5 and X 100
Field of view	>2.5 mm x 2.5 mm minimum
Vertical resolution	<0.05 nm for all magnifications
Lateral resolution	<0.5 µm
Repeatability	<0.2 nm rms difference of 2 measurements <0.05 nm rms 16 averages w/ null <0.1 nm rms 16 averages w/ 5 fringes rms for 2 sigma of 100 sets of measurements, each set is the average of 16 profile measurements
Reproducibility	sigma of 20 measurements will be less than 0.15 Å, each measurement consists of 4 intensity averages with the instrument refocused between each measurement
Computer	HP 382/16+2 workstation or equivalent DOS floppy disk data transfer for compatibility with DOS PC Interferometer operation and analysis software

Phase Shifting Optics
Aperture	150 mm (6-inch aperture) [with the flexibility for larger aperture (e.g., 450 mm)]
Accuracy	better than lambda/100 peak-valley (P-V) at lambda =632.8 nm Value for accuracy reflects the overall accuracy for absolute testing. System accuracy for relative testing is dependent on the quality of the reference optic.
Precision	better than lambda/1300 rms (6-inch aperture) Instrument precision is the residual rms error that reflects the difference of two consecutive measurements, each consisting of an average of 16 sets of data. The specification is derived from a sample of 100 measurements and represents the mean value plus 2 sigma (98% confidence).
Repeatability	better than lambda/100 P-V (6-inch aperture) better than lambda/8000 rms (6-inch aperture) Repeatability of the quoted statistic for 100 measurements, in which each sample consists of an average of 16 sets of data. The specifications are for the 2 sigma (95%) repeatability of the data. P-V calculated over 97% clear aperture; rms calculated over 100% clear aperture.
Maximum Slope	better than 60 fringes
Zoom Range	6 X
Computer	IBM-compatible DOS 486 PC platform processor