Synchrotron is a highly powerful source of X-ray, where the X-rays are created by highly accelerated electrons, releasing energy at X-ray wavelength when changing directions. These X-ray beams are guided with a beamline and steered to an experimental end-station. They interact with matter in the end-station, helping to study the properties of various materials. The much shorter wavelength of X-rays when compared to visible light makes it possible to probe much smaller structures (in nanometer range) compared to traditional microscopes. X-rays are quite often used in imaging because they have high penetration capabilities depending on their energies. Sample positioning is a central issue because the beams are highly focused. Hence, triggering, feedback and detection of the sample position should be well sustained and recorded.
BiSS-C, an open source interface, is based on the RS422 protocol supporting signal transmission of up to 10 MHz . The option for processing external trigger signals enables the synchronization for multiple devices and is also supported up to 10 MHz. To satisfy the need for synchronous data communication, attocube provides an IDS3010 with the BiSS-C interface to suit the standards of the Diamond Light Source and Omron/Delta Tau.
Vibration propagation and error motions are key information for the motion accuracy in high precision systems for moving objects in nanometer ranges. Due to this, synchrotron facilities regularly upgrade and develop different components to stay on track with the most recent technology. Of late, the beamline I08 upgraded the endstation using attocube interferometers IDS3010 with BiSS-C interface. An experimental setup at the Diamond Light Source is synchronously triggering and tracking the movement of eight different linear axes. The Delta Tau “GeoBrick” controller controls these eight axes. This ensures the accurate time stamped data from all eight axes, namely the three IDS3010 devices.
Figure 1 shows a simplified version of the setup. The setup consists of three motion modules: a manual positioner at the bottom, on top of it a stepper motor for more coarse adjustments, and finally on top of that a piezo-based positioner for fine motions. All three modules can move in X-, Y-, and Z-direction. The complete setup consists of nine linear movements and is tracked by 8-axes consisting of M12/C1.6 high vacuum compatible sensor heads. Every motion needs to be tracked as the sample’s position is relevant for each movement of the three modules. Two kinds of error motions (parasitic movements) are pertinent for the sample’s position: vibrations caused by moving the positioner that spread to connecting positioners and the sample, as well as uneven motions caused by non-parallel mountings between the positioners.
Figure 1. Rough sketch of the setup. The eight sensor heads M12/C1.6 are shown monitoring the 3 modules, each module consist of 3-dimentional X, Y, and Z movements. The complete setup is in high vacuum.
In Figure 2, a measurement example is shown. This example only involves the X, Y, and Z piezo-based positioners in the upper module. The two error motions are shown while moving the fine piezo positioner in the X-direction using 5 nm step sizes. X-axis (the red line) shows the positioner moving in one direction; after 10 steps, the positioner is moving back with one 50 nm step. Y-axis (the blue line) shows the error motions of the fine positioner orthogonal to the motion of the positioner in the horizontal level. The noised oscillations are caused by the vibration propagation emerging from the positioner’s motions.
This line shows a linear offset of 10 pm for every step. This offset originates from the not perfect parallel mounting between the X- and Y- positioners. Using the information for the other axes, this non orthogonal mount can be compensated. The vertical movements of the fine positioned is represented by Z-axis (the green line). Only the last step of 50 nm shows a significant change of the vertical position, apparently caused by a rapid vibration.
Figure 2. The blue curve shows the water surface and sensor head movements and the red curve represents the displacements measured on the side of the mirror after hitting the optical table with a hammer.
This synchronous motion capturing and data acquisition of different measurement axes was realized by the BiSS-C interface in addition to the picometer resolution provided by the IDS3010. This real-time interface aids the simultaneous triggering of multiple measurement axes. For synchronous data acquisition, eight axes of three IDS devices were triggered in this example. With the BiSS-C interface connected with the Master Control on the Delta Tau, one could read the eight incremental encoders from the positioners and the eight interferometer axes. Additionally, the absolute positioners need not cross any reference axis.
 Official BiSS-C website: http://www.biss-interface.com/
 IDS3010 interfaces description http://attocube.com/attosensorics/ids-sensors/ids3010/
This information has been sourced, reviewed and adapted from materials provided by Attocube Systems AG.
For more information on this source, please visit Attocube Systems AG.