Xspress 3 mini is the new compact version of the popular high-speed fluorescence detector readout Xspress 3. It provides the same performance as a full sized Xspress 3 in a more compact enclosure. This means that Xspress 3 Mini is capable of readout at > 4Mcps count rates, allowing for more efficient use of available photons. Xspress 3 Mini also features a unique variable front end. This means the readout can be matched to the detector without the need for hardware intervention and in an automated fashion. This allows Xspress 3 Mini to be plug and play with multiple detectors.
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
- Max Output Count Rate >4 Mcps
- Max E Resolution (FWHM) 126eV at 70KHz at Mn (measured with Vortex ME4 at APS)
- Channels One to Four
- ROIs 16 / channel (software)
- Frames 16384
- Deadtime per event < 100ns
- Peaking Time Not applicable. Sampling time: 12.5ns to 12.5 X 1024 points (12.8µs)
- Peak Stability 30eV over a 3MHz 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 Xspress 3
Xspress 3 Mini is provided with a web based UI that can be used to configure, calibrate, and test the device. The web UI is run from the Xspress 3 Mini host computer and can be accessed from any computer on the same network. It provides a highly automated way for users to calibrate the system without manufacturer intervention. Firstly the detector is electronically matched to the readout system, and then the detector reset and event profiles are measured and automatically configured.
The software suite can then be used to collect MCAs and measure key metrics such as count rate, full width half max, peak position, and dead time. These results can be exported in csv format for further analysis.
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.
Two of the core fields that Xspress 3 Mini is applicable to are X-ray Fluorescence Mapping and EXAFS. Detailed below are two application notes from beamlines at international synchrotrons. For more information please see the full Xspress 3 Application Notes
Elemental mapping is one of the core fields that is significantly detector limited. Below is data from an experiment phosphorus mapping of leaves at SSRL, collected by Dr Sam Webb and Dr Courtney Roach.
Mono energy was 13.5 keV, dwell time of 30 ms per pixel, with 80×80 micron pixels. The detector was set to run pretty hot, so the [standard readouts] were definitely at their high end and probably above the nominal operating range — the ICR on the Xspress 3 was from 500 kHz to 2.5 MHz. These are plants that had been dosed with a substantial amount of Zn too.
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.
Proven to operate 10x faster than standard detectors
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
We are often presented with difficult situations in which the scientists are struggling to gather data as they would like. A common occurrence is a scientist trying to gather data on an element which is overshadowed by a close neighbouring fluorescence or scatter peak.
≈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.