Instrument Control - Measurement
The heart of instrument is the instrument server, which handles the execution of the sample
measurement. Physically it is a powerful multicore server that is capable of:
• Communicating with the various instrument components such as
o the hardware directly controlling the detector
o the source and shutter hardware
o the motion controller for
- various pinholes
- stages and insertable items
- sample stage
• Broadcasting the images of the sample
• Storing and retrieving data
• Receiving instructions from a remote client
The control and communication is built on a SPEC backbone, drawing on years of synchrotron experience in instrument control.
The Instrument Control Client (ICC)
The Instrument Control Client (ICC) is the “remote” human interface to the Instrument server. It is a graphical user interface that runs on either a windows or linux computer different from the instrument server. The ICC requires only a good internet connection and a good graphics card. The ICC allows:
o Interactive Control of Instrument components, such as
- Shutter on/off
- Stages motion/sample alignment
- Measurement: Start/Stop/Save/Continue
- Setting measurement modes
- Providing background information on samples
o Script based control of Instrument components, such as
- All of the interactive commands
- Multiple Sample Measurements
- Sample parameter Scans (position, temperature etc)
o Results Display, such as
- Scan Plots
- 2D Detector Data
- Averages of 2D data (Radial, Azimuthal, Slice etc)
- Live image of sample
The measurement philosophy
Given the almost complete automation of SAXSLAB’s GANESHA and the wide range of scattering angles that the detector can collect (at various distances from the detector), we have had the opportunity to rethink how we do SAXS experiments in the laboratory. As a result we have developed at least two new unique - see note 1 - approaches to optimizing the performance of the SAXS system.
Automatic Multiconfigurational Measurements
Conventional SAXS systems all have the possibility of manually setting the instrument up in different configurations to obtain different combinations of q-range and intensity. Sometimes this is done by moving the detector closer or further away from the sample. And sometimes it even entails changing the aperture sizes.
Some users will even combine the data from these different settings. All conventional systems have this possibility, but in practice research groups rarely make these changes regularly since in the long run they are considered troublesome. Being fully motorized, the act of changing configuration with the GANESHA is a simple instruction to the instrument server, both a simple single change or a schedule of measurements in multiple configurations without human intervention.
Both the ICC and the data-reduction software handle the automated multi-configurational measurements.
Asymmetric Beam stop positioning for low-q data taking
For very high end systems one can consider three rectangular apertures for collimation, where the aperture size can be set to from 0 to 7 mm in increments of ½ microns. The number of combinations of pinhole configurations therefore borders infinite. To each pinhole configuration, there is one ideal beam stop size.
Unfortunately, we do not have an infinite number of beamstops automatically available to us…so at first glance we cannot make use of the vast number of aperture configurations. However, we have come up with a scheme that requires only a few beam stops, and still allows for an infinite number of aperture configurations. We have termed the scheme “Asymmetric Beamstop”
1 - At least unique among commercially available SAXS cameras