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Brookhaven National Laboratory is using a Galil motion controller to control the velocity of a linear stage that moves a silicon substrate during the development of the Multilayer Laue Lens (MLL).

The lens is used to focus synchrotron X rays.

Working with CVD Equipment and Galil Motion Control, Brookhaven developed a magnetron sputtering system that deposits thousands of ultra-thin layers of two different materials (WSi2 and Si) onto silicon substrates to create the MLL.

Coating thicknesses range to 100um with up to 62,000 layers in a stack, with the thinnest layer measuring less than 1nm.

During production, the substrates are loaded onto a linear translation stage or a ‘transport car’ that rides on a stationary base and rail assembly and is controlled by Galil’s DMC-4020 two-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 23ft, ultra-high-vacuum chamber that contains nine magnetron sputtering guns and four cryogenic pumps.

The car travels at defined speeds from 0.01in/sec to 9in/sec, with maximum acceleration reaching and maintaining no less than 5in/sec2.

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 0.01 per cent ripple.

According to Galil, its controller beat the specification by four times thanks to its sinusoidal commutation mode, which ensured 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 per cent.

The engineers at Brookhaven appreciated the position mode of the Galil controller, which simplified the 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 20 seconds of each cycle to provide data logging and to check for system errors.

The National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory allows scientists to probe nanostructures as small as a few atoms in size using the powerful, fast and bright infrared, ultraviolet 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 – such as 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 MLL will be used to precisely steer and focus the X rays to about 1nm of the item being analysed.

Galil Motion Control

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