Why use PMAC?

LNLS needed a controller capable of advanced multi-axis coordination, non-linear motion control algorithms, true synchronous motion, and compatibility with a wide range of encoder types including BiSS-C. After evaluation, they selected Faraday Motion Controls bespoke Power Brick LV, PMAC solution — supplied and supported by Faraday Motion Controls Ltd — as their standard platform for all complex beamline applications across the entire Sirius facility. This decision is documented in their own peer-reviewed literature, with Faraday Motion Controls named directly as supplier.

What Faraday Motion Controls delivered?

We didn't ship boxes of hardware. We delivered a complete, application-ready control and servo package: every unit configured to the application, servo loops tuned, and wired to LNLS's own customer-specific pinout requirements. Their engineers received systems ready to install and commission — not products requiring further bench setup at one of the world's most demanding research facilities.

The application: four-bounce crystal monochromator

One of the most challenging applications in the Sirius programme was the Four-Bounce Crystal Monochromator (4CM), developed for the CARNAÚBA and CATERETÊ beamlines — the two longest beamlines in the facility, dedicated to coherent X-ray nanoprobe and coherent scattering experiments.

The 4CM selects X-ray energy using two silicon crystal pairs, each positioned by a direct-drive rotary stage inside an ultra-high vacuum chamber. The two crystals must rotate in precise coordination to maintain energy selection — and the tolerance is unforgiving: coordination error must remain below 1 microradian throughout motion.

To put that in context: one microradian is the angle subtended by a millimetre at one kilometre distance. Holding two independent rotary axes to that level of agreement, continuously, while scanning through an angular range, is an extraordinary demand on any motion controller.

When the alternative fell short

LNLS evaluated a competing controller — the Aerotech Ensemble Epaq MR — for the crystal coordination task. In the recommended operating mode for this type of application, it produced coordination errors of approximately 210 microradians: 210 times over the acceptable limit. An alternative mode reduced the error but introduced operational constraints that were incompatible with the calibration workflow, and required a full system reset to toggle — causing loss of position reference each time.

What our PMAC solution achieved

Using the Power Brick LV IMS’s native kinematics scripting and a 20 kHz servo loop, LNLS achieved crystal coordination below 1 microradian throughout motion — meeting their specification where the competing system had failed by two orders of magnitude. Positional stability of the individual crystal stages measured between 20 and 40 nrad RMS across the full operating angle range.

The Power Brick LV IMS's ability to handle the direct-drive PMSM stages, decode dual-readhead BiSS-C encoders, and execute coordinated multi-axis kinematics within a single controller was central to achieving these results.

Independent validation

This work was not internal testing. The results were presented and published at ICALEPCS 2021 — the International Conference on Accelerator and Large Experimental Physics Control Systems — the leading peer-reviewed forum for exactly this class of problem. The numbers are not marketing claims. They are independently validated results from one of the world's foremost synchrotron facilities.

What this means for your project

If your application demands motion control at the nanoradian level — beamline optics, sample stages, monochromators, or any precision instrument where standard solutions have already fallen short — we can help. We supply the same platform, as a complete application-ready package, with the configuration, tuning, and wiring done before it reaches you.

Contact us to discuss your Motion Control requirements.