1. GeoSoilEnviroCARS The University of Chicago
4,000 Spectra or 4,000,000 ROIs per Second: EPICS Support for High-Speed Digital X-ray Spectroscopy with the XIA xMap
Mark Rivers, Center for Advanced Radiation Sources
Motivation
Need a cost-effective way to collect XRF spectra from multi-element detector arrays
Modern detectors, particularly silicon drift diodes (SDD) can run at >250,000 cps per detector, or >1,000,000 cps for a 4-element array like the quad Vortex
Depending on the application, can thus get a usable signal (1,000 counts) in 1 ms.
Need to keep the overhead less than that!
EPICS Software
EPICS software allows complete control of the xMAP configuration and acquisition from any beamline control system.
DXP 3-0 is a complete rewrite of the EPICS support for XIA modules (Saturn, DXP2X, xMAP)
DXP parameter control no longer uses special DXP record, uses standard EPICS records (ao, ai, bo, bi, etc.)
Based on asynPortDriver, originally written for EPICS areaDetector module
Single driver that supports the MCA record, high-level and low-level DXP parameter control with standard EPICS records, and NDArray callbacks for file-saving plugins in mapping mode
MCA Record Support
Uses standard asyn device support for the MCA record, same as Canberra AIM, SIS multichannel scaler and other MCA/MCS hardware
Start and stop data acquisition, readout the spectra, and control and read the data acquisition time.
Supports up to 32 Regions of Interest (ROIs) for computing the net or total counts in each fluorescence peak.
MCA record ROIs can be defined graphically in IDL or Python clients, copied to the internal xMAP SCA definitions.
Used for individual spot analyses or slow mapping
DXP Parameters
The xMAP and other XIA modules have about 12 high-level parameters and nearly 200 low-level parameters.
High-level parameters including peaking time, MCA bin width, etc. EPICS software provides convenient methods to copy the values from detector 1 to all detectors, simplifying setup.
Read/write access is also provided to all low-level parameters, though this should be rarely used
Mapping Modes
MCA spectra mode. Collects complete XRF spectra for each detector at each pixel. xMAP buffer holds 128 pixels.
ROI (SCA) mapping mode. Collects total counts for each of 16 ROIs at each pixel. xMAP buffer holds 5457 pixels.
xMAP Hardware
4 channels per PXI module
4 MB of memory per module. Used to buffer spectra or ROIs for very fast data collection
Double-buffered to support simultaneous readout and acquisition
1 LEMO input for gate and trigger functions.
Peaking times down to 125ns
Supports both RC and reset preamps
4 data collection modes: MCA spectra, MCA mapping, ROI mapping, and List mode (List mode will be supported in the near future)
PXI/PCI interface which achieves ~20 MB/sec when reading out xMAP. More than 20 times faster than CAMAC
4 xMAP modules in a PXI crate with fiber-optic connection to a Windows control computer running EPICS IOC software
Performance
MCA spectra mode: >4, channel spectra per second, limited by readout rate of xMAP over PXI/PCI pixels/s for a 4-channel quad Vortex, 40 points/s for a 100-element EXAFS detector
ROI/SCAN mode: 10,000 pixels/second for any number of detectors, limited by xMAP overhead in pixel advance to about 100 µs/pixel. For 16 ROIs and 30 detectors=4.8M ROIs/s
First results
The images below are some of the first scans collected with the new EPICS xMAP software. They were all collected in on-the-fly scanning mode, collecting complete XRF spectra at each pixel, with pixel dwell times of 30 to 200 ms.
EPICS medm Control Screens
X-Y Scan of Alzheimer’s mouse brain
Fe (red), Cu (green), Zn (blue)
9-element Ge and 2 SDD detectors
1050x793 pixels
Pixel size=6x6µm
200ms per pixel
Total time=49 hours
Collected at NSLS X-26A
Thanks to Tony Lanzirotti (U. of Chicago), Lisa Miller and Megan Bourassa (Stony Brook/NSLS)
X-Y scan of Alyssum murale leaf
Ca (green), Mn (red), Zn (blue)
9-element Ge and 2 SDD detectors
463x179 pixels
Pixel size=7x7µm
100ms per pixel
Total time=138 minutes
Collected at NSLS X-26A
Thanks to Ryan Tappero (NSLS)
High-level parameter control
Top-level 16-element control
Mapping mode control
Zn Ka
Rb Ka
As Ka
Sr Ka
Fluorescence tomography of heavy metals in rice
Top images are sinograms, bottom images are reconstructed slices
4-element Vortex SDD detector
650 x 181 pixels
Pixel size=2µm x 1°
30ms per pixel
Total time=67 minutes
Collected at APS 13-ID-C
Thanks to Matt Newville (U. of Chicago), Anne-Marie Carey, (U. of Aberdeen), and Kirk Scheckel (US-EPA)
ROI and SCA control
netCDF file setup for saving mapping mode data
Rb: marks phloem transport Sr: marks xylem transport
Rb Ka
Zn Ka
As Ka
Sr Ka
Low-level parameter control
Pre-amp output trace
16-channel detector spectra