Resources: Brookhaven National Laboratory
Galil Motion Control Inc.

Researchers at Brookhaven National Laboratory are using a Galil motion controller to handle positioning chores in a machine that builds multilayer Laue lenses. The lenses are used to focus X-rays from synchrotrons at the nanometer level. Lenses consist of up to 62,000 layers ranging in thickness from 1 nm to 100 microns.The layers are made up of two materials, WSi2 and Si.

The DMC-4020 controller positions a linear stage holding the silicon substrate upon which the lens will be built layer by layer. The linear stage moves through a 23-ft-long ultrahighvacuum chamber containing nine magnetron sputtering guns and four cryogenic pumps. The stage travels back and forth between the sputtering guns at 0.1 to 9 ips, with accelerations of up to 5 ips2. The entire process takes as many as 100,000 moves over six days as the layers are individually created.

One criteria for moving the substrate was that velocity had to be extremely stable — less than 0.01% ripple. The Galil controller’s sinusoidal commutation mode delivers a smooth sinusoidal signal, resolved into a full 16 bits, to the amplifier. This, plus the device’s use of a linear rather than a switching amplifier, lets the controller module limit velocity ripple to 0.0025%. The controller also communicates with the host computer via Ethernet so the host computer can command the controller to start a new cycle once notified that the previous cycle is over. The controller records position, position error, velocity, and torque every 20 sec to check for system errors and log data.

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