Brookhaven National Laboratory: Controller helps development of lens to focus X-rays
Brookhaven National Laboratory uses a Galil motion controller to control the velocity of a linear stage that moves a silicon substrate during the development of a Multilayer Laue Lens (MLL), according to a release from Galil Motion Control of Rocklin, CA. The lens focuses synchrotron X-rays. Working with CVD Equipment Corp. of Ronkonkoma, NY, and Galil, Brookhaven developed a magnetron sputtering system that deposits thousands of ultra-thin layers of two materials (WSi2 and Si) onto silicon substrates to create the MLL. Coating thicknesses range to 100 micrometers with up to 62,000 layers in a stack, with the thinnest layer less than 1 nm.
During production, the substrates are loaded onto a linear-translation stage or “transport car” that rides on a stationary base and rail assembly, and is controlled by Galil’s DMC-4020 2-axis motion controller. The controller sends signals to a Trust Linear Amplifier and receives feedback from a high resolution encoder to move the car one-dimensionally back and forth throughout the 23-foot, ultra-high vacuum chamber that contains nine magnetron sputtering guns and four cryogenic pumps. The car travels at defined speeds from .01”/second to 9”/second, with maximum acceleration reaching and maintaining no less than 5”/second2.
Typically, the coating process involves the deposition of several thousands of layers over as many as 100,000 nonstop cycles over a period of six days. A critical specification of the MLL deposition system called for a smooth, reliable and repeatable velocity stability with less than .01% ripple. The Galil controller beat the specification by four times.
It did so with its sinusoidal commutation mode which assured that a smooth sinusoidal signal (resolved into a full 16-bits) was sent to the amplifier. This, plus the incorporation of a linear amplifier instead of a switching one, enabled the DMC-4020 to reduce the velocity ripple to 0.0025%.
The engineers at Brookhaven appreciated the position mode of the Galil controller which allowed for easy programming of the back and forth linear motion of the transport car.
Another key feature is that all communication between the DMC-4020 and the host computer is via Ethernet. This enabled the host computer to send commands to the controller to commence a new cycle the moment after receiving signals from the controller announcing the completion of a cycle.
To ensure accuracy and repeatability, the DMC-4020 recorded actual position, position error, velocity and torque every twenty seconds of each cycle to provide data logging and check for system errors.
The National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory is located in Upton, NY. It allows scientists to probe nanostructures as small as a few atoms using the powerful, fast and bright infrared, UV and x-ray light produced by a synchrotron.
The NSLS produces such light by accelerating electrons inside one of two football-field sized rings at close to the speed of light. When the light is focused on a specific sample—like a human cell or a speck of interplanetary dust—it produces an image of its most minute properties on a detector for analysis.
Brookhaven is building a new synchrotron, the NSLS-II which, when completed, will be capable of producing X-rays more than 10,000 times brighter than its cousin. To achieve this, the specially coated Multilayer Laue Lens will be used for precise steering and focusing of the X-rays to about 1 nm of the item being analyzed.
Galil said it is the first company to produce a microprocessor-based servo motor controller without tachometer feedback. More than 500,000 Galil controllers are installed in machines for the medical, semiconductor, machine tool, food processing, and textile industries, and other applications. Recent Galil introductions include motion and I/O controllers for the Ethernet including the high-speed Accelera motion controllers, lowest cost Econo motion controllers and the RIO Pocket PLC series.
National Synchrotron Light Source at Brookhaven National Laboratory, www.nsls.bnl.gov, in Upton, New York, is a national user research facility funded by the U.S. Department of Energy’s Office of Basic Energy Science. NSLS operates two electron storage rings: an X-Ray ring and a Vacuum Ultraviolet (VUV) ring which provide intense light spanning the electromagnetic spectrum from the infrared through x-rays. More than 2300 scientists from universities, industries and government labs perform research at the NSLS. In construction is the new NSLS-II, a medium-energy electron storage ring (3 billion electron-volts) designed to deliver world-leading intensity and brightness, and will produce x-rays more than 10,000 times brighter than the current NSLS. It is expected to be fully operational in 2015.
– Edited Mark T. Hoske, CFE Media, Control Engineering, www.controleng.com
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