Xspress 3 Mini
What is it? How does it work?
Xspress 3 Mini is also provided with an extensive software suite that allows the readout system to be commissioned and calibrated via a user friendly web based UI. It is also supported by drivers for the synchrotron industry standard control systems TANGO and EPICS.
Xspress 3 Mini is targeted at customers with low channel count detectors where Xspress 3 was historically outside of their price range. Xspress 3 Mini provides an opportunity for these customers to significantly improve throughput of their SDD or HPGe detectors at a reasonable cost. Xspress 3 Mini is available in one and two channel configurations
Specifications
- Max Output Count Rate > 4 Mcps
- Max E Resolution (FWHM) 125 eV at 35 KHz at Mn †
- Channels 1 or 2 per unit, 2+ or more units can be connected to create a 3+ channel system
- ROIs 16 / channel (software)
- Frames 12,000
- Deadtime per event < 80 ns (dependent on detector)
- Peaking Time Adaptive (≥12.5 ns)
- Peak Stability 30 eV over a 3 MHz range at Iron Foil. 0.4% ‡
- Pileup Inspection Effective input / output correction system
- Data Transfer Rate Gigabit Ethernet
- I/O 2x TTL in, 2x TTL out
- Detector Feedback Capacitive (Resistive not supported)
- Detector Calibration Easy to use Web UI; calibration only needs repeating for a change of detector
† Measured with Vortex ME4 at APS
‡ Measured with Xspress 3
Software
Xspress 3 Mini supports the two major controls system, with drivers available for both EPICS and TANGO. Both of these drivers are available as source code and pre-packaged as RPMs for enterprise Linux 7 systems.
Xspress 3 Mini supports the two major controls system, with drivers available for both EPICS and TANGO. Both of these drivers are available as source code and pre-packaged as RPMs for enterprise Linux 7 systems.
Application notes
SSRL
Elemental mapping is one of the core fields that is significantly detector limited. These figures show data from an experimental phosphorus mapping of leaves at SSRL, collected by Dr Sam Webb and Dr Courtney Roach.
EXAFS
Beamline I18, Diamond Light Source
Xspress 3 has become beneficial at EXAFS beamlines for its advanced detector readout rates, proven to operate 10x faster than standard readouts.
I18 at Diamond Light Source provides a world class microfocus beamline facility, using a high-brightness micron-sized X-ray beam for the study of complex inhomogeneous materials and systems under realistic conditions.
Xspress 3 is the default readout system on I18. In standard operation, Xspress 3 is connected to a Hitachi Vortex ME4 and an SGX Sensortech multi-element SDD detector, giving a total of 10 detector elements. I18 requires fast, accurate readout electronics to get the best performance from their detectors. Of particular importance to I18 is accurate dead time correction. Dead time correction is a critical factor when collecting EXAFS data as non-dead time corrected data is non linear which can result in attenuated oscillations in the resulting processed EXAFS signal.
This can have serious implications when modeling EXAFS data such as implying a lower coordination number than is actually present. The example below shows how Xspress 3 can be used to collect accurately dead time corrected data. Data were collected by Professor Fred Mosselmans on beamline I18 at Diamond Light Source using a 6 element SGX detector coupled with an Xspress 3 readout system. The sample geometry was kept constant while the beam intensity was varied. As can be seen in Figure 1 the ratio of pre-edge peak height to edge height is constant for all spectra indicating that Dead Time Correction (DTC) is operating as intended.
Figure 2 shows the extracted EXAFS signal from the edge scans collected in Figure 1. As can be seen in both Figure 1 and Figure 2 the spectra are virtually identical at count rates all the way from 17k counts per second, up to the maximum of 650k counts per second.
EXAFS in challenging scenarios
≈13 femtograms of Mo in the beam (5 kHz on a 1.2 MHz background)
Matt Newville took some data in such a situation at a GSECARS beamline at the APS with a 1mm Hitachi Vortex ME4.
The MCA of the NIST AXO-RF4 standard showed a visible molybdenum peak. The standard has 1.4ng / mm2 so with a 2 x 5 µm beam there was only ≈13 femtograms of Mo in the beam. The neighbouring scatter peak dwarfs the Mo peak with almost two orders of magnitude greater flux. 1.2 Mcps total count rate, Mo Kα ≈5khz net.
